, , ,

Valles Caldera

Valles Caldera Scientific Core Drilling Services

Deep Coring of the Valles Caldera: Obtaining a Long-Term Paleoclimate Record from Northern New Mexico

Peter J. Fawcett and John W. Geissman University of New Mexico

Fraser Goff and Jeff Heikoop Los Alamos National Lab

Scott Anderson Northern Arizona University

Short History

The goal of this project was to obtain and analyze a deep (~100 m) sediment core from a lacustrine sequence in the Valles Caldera, northern New Mexico. Our work focused on determining the paleoenvironmental record of long-lived lakes in the caldera and developing a paleoclimatic record for this part of northern New Mexico for a substantial part of the middle Pleistocene. The core was drilled by DOSECC in May 2004 with the CS500 rig, and achieved a total depth of 82.1m. Most of this material was lacustrine clay with over 99% recovery. Recovery of the basal sands and gravels at the base of the core was significantly less, but we did capture a basal tephra that allowed for a constraining Ar-Ar age date. The core, VC-3, was archived at the LacCore Facility at the University of Minnesota and initial core description and sampling was conducted there.

Questions to be Answered

The questions we hoped to address with core VC-3 pertained to the paleoclimatic history of northern New Mexico over much longer time periods than the many late Pleistocene to Holocene records that are available in the area. In particular, we hoped to develop a long-term Pleistocene record that would span a significant portion of the middle Pleistocene, including some of the longer interglacials with a similar orbital forcing to today (e.g. MIS 11). The goal here was to examine natural climatic variability under such conditions as an analog for future climate change in the southwest.

What Samples were Collected?

We sampled the lacustrine mud portion of the core at a resolution of ~20 cm for a total of several hundred samples. The gravels were not sampled in detail, but the 3-cm thick basal tephra was sampled almost completely.

What Did We Do to the Samples?

An Ar-Ar age date of 552 ± 3 ka was obtained from the basal tephra, constraining the base of the core to the middle Pleistocene. To develop the paleoclimatic record, the lacustrine mud samples were split for a number of different analyses, conducted at multiple institutions (UNM, LacCore, LANL, NAU, UMN-Duluth). These analyses included organic carbon, C/N ratios, d13C, d15N, magnetic mineral properties (magnetic susceptibility MS, anisotropy of remanent magnetization, ARM), XRD of clay minerals, ICP OES (destructive elemental analysis) scanning XRF (non-destructive elemental analyses), compound specific dD, Methylated Branched Tetraether (MBT – a new paleotemperature analysis), pollen and charcoal content as well as a detailed sedimentologic description of the entire core.

What Did We Learn?

The 82-m deep lacustrine sediment core from the Valles Caldera, northern New Mexico reveals details of climate change over two glacial cycles in the middle Pleistocene. Core VC-3, taken from the Valle Grande, has a basal 40Ar/39Ar date of 552 ± 3 kyr from a tephra associated with the eruption of the South Mountain rhyolite which formed the lake. A variety of proxies including core sedimentology, organic carbon and carbon isotopic ratios, pollen, scanning XRF analysis and a new paleotemperature proxy, MBT (methylated branched tetraether) content of soil bacteria reveal two major warm periods above the basal tephra which we correlate with interglacials MIS 13 and MIS 11. This chronology is corroborated by the identification of two geomagnetic field ‘events’ which are correlated with globally recognized events (14α and 11α). The lacustrine record terminates at ~350 ka when the lake filled its available accommodation space behind the dam of rhyolite lava. Thus, the entire core spans two full glacial-interglacial cycles in the middle Pleistocene.

Valles Caldera Drilling

Figure 1: DOSECC CS500 rig operating in the Valle Grande, Valles Caldera, New Mexico

MBT temperature estimates show average glacial temperatures in core VC-3 of -4oC, and average interglacial temperatures of +4oC, and the general trends are well corroborated by multiple proxies including interglacial/glacial pollen ratios and lacustrine organic productivity estimates (organic carbon and Si/Ti ratios from the scanning XRF). A temperature increase of ~9oC occurs during Termination V, the largest glacial termination in the Pleistocene. Multiple proxies from VC-3 show significant structure during the two interglacials present in the core (MIS 13 and 11). Three warm substages (~ 2oC warmer) are recognized within MIS 11 based on organic productivity (Corg, Si/Ti ratios), pollen taxa, elevated charcoal from fires, and the MBT temperature estimates. These warm substages appear to be a strong response to precessional forcing in the SW continental interior even though the amplitude of eccentricity-modulated precession was at a minimum during MIS 11. These results suggest that future climate change in the SW may be characterized by similar natural temperature variability on precessional timescales, superimposed on future anthropogenic warming. Intervals of mudcrack facies representing significant drought conditions occur during or just after the warmest phases of the two interglacials. This past coupling between warm temperatures and extended drought in the SW as a natural feature of long interglacials is consistent with recent predictions of extended Dust-Bowl-like conditions in the SW as a response to global warming.

Where We Able to Answer These Questions & Why Should Society Care?

As a result of the multiple analyses and collaborations in this project, we were able to address the questions posed prior to the drilling project. We have generated a long, high-resolution terrestrial paleoclimate record for the middle Pleistocene, including important reconstructions of the variability within two long interglacials (MIS 11 and MIS 13). As these periods represent possible analogs for future climate change in the southwest, society should be very interested, particularly as the paleoclimate record appears to support the recent prediction of extended Dust-Bowl-like conditions in the SW as a response to global warming. The record also shows how vegetation and charcoal has changed in response to past climate change, potentially showing how vegetation and fire regimes might respond to future climate change.

Valles Caldera Drilling1

Figure 2: Representative core sections of glacials (MIS 14, MIS 12) and interglacials (MIS13).

 

References:

* denotes graduate student author

Fawcett, P.J., Heikoop, J., Goff, F., Anderson, R.S., Donohoo-Hurley, L., Geissman, J.W., WoldeGabriel, G., Allen, C.D., Johnson, C.M., Smith, S.J., and Fessenden-Rahn, J., 2007, Two Middle Pleistocene Glacial-Interglacial Cycles from the Valle Grande, Jemez Mountains, northern New Mexico; New Mexico Geological Society Guidebook, 58th Field Conference, Geology of the Jemez Mountains Region II, 2007, p. 409-417.

Johnson, C.M.*, Fawcett, P.J., and Ali, A.S., 2007, Geochemical Indicators of Redox Conditions as a Proxy for mid-Pleistocene Climate Change From a Lacustrine Sediment Core, Valles Caldera, New Mexico, New Mexico Geological Society Guidebook, 58th Field Conference, Geology of the Jemez Mountains Region II, 2007, p. 418-423.

Donohoo-Hurley, L.*, Geissman, J.W., Fawcett, P.J., Wawrzyniec, T., and Goff, F., 2007, A 200 kyr lacustrine record from the Valles Caldera: Insight from environmental magnetism and paleomagnetism, New Mexico Geological Society Guidebook, 58th Field Conference, Geology of the Jemez Mountains Region II, 2007, p. 424-432.

WoldeGabriel, G., Heikoop, J., Goff, F., Counce, D., Fawcett, P.J., and Fessenden-Rahn, J., 2007, Appraisal of post-South Mountain volcanism lacustrine sedimentation in the Valles Caldera using tephra units, New Mexico Geological Society Guidebook, 58th Field Conference, Geology of the Jemez Mountains Region II, 2007, p. 83-85.

 

Presentations

November 2008   Quaternary and Environmental Sciences and Department of Geology, Northern Arizona University (Fawcett)

March 2008 Valles Caldera Trust Public Forum, Albuquerque (Fawcett)

November 2007 IGPP Climate Study Group, LANL (Fawcett)

September 2007 Department of Geosciences, UNM (Fawcett)

September 2007 Fall Field Conference of the Geological Society of New Mexico, Jemez Mountains (Fawcett, Goff)

June 2007 IGPP Board Meeting, Santa Fe (Heikoop)

 

Presentation with Published Abstracts

Cisneros-Dozal, L, Heikoop, J., Fessenden, J., Fawcett, P., Kawka, O, and Sachs, J., 2007, Mid-Pleistocene lacustrine records of carbon and nitrogen elemental and isotopic data from Valles Caldera, New Mexico, USA, Eos Trans. AGU 88(52), Fall Meet. Suppl., Abstract PP43B-1253.

Dodd, J.P., Sharp, Z.D., Fawcett, P.J., Schiff, C., and Kaufman, D.S., 2007, A laser-extraction technique for oxygen isotope analysis of diatom frustules, Eos Trans. AGU 88(52), Fall Meet. Suppl., Abstract B13A-0893.

Donohoo-Hurley, L. L., Geissman, J.W., Fawcett, P. J., Wawrzniec, T. F., and Goff, F, 2005, Environmental magnetic record of lacustrine sediments of the Valles Caldera, New Mexico, New Mexico Geological Society Spring Meeting, Abstracts with Program

Donohoo-Hurley, L., Geissman, J.W., Fawcett, P.J., Wawrzyniec, T.F., and Goff, F., 2005, Preliminary results of the environmental magnetic record of Pleistocene Valles Caldera sediments, New Mexico, Geological Society of America Abstracts with Programs, Vol. 37, No. 7, p. 453

Donohoo-Hurley, L.L., Geissman, J.W., Fawcett, P.J., Wawrzyniec, T.F., and Goff, F, 2006, An environmental magnetism investigation of the Pleistocene lacustrine sediments from the Valle Grande, New Mexico, New Mexico Geological Society 2006 Spring Meeting, Socorro, NM, Abstract volume, p. 17.

Fawcett, P J., Goff, F., Heikoop, J.,Allen, C.D., Donohoo-Hurley, L., Geissman, J.W., Wawrzyniec, T.F., Johnson, C., Fessenden-Rahn,J., WoldeGabriel, G. and Schnurrenberger, D., 2005, Deep coring in the Valles Caldera, New Mexico to obtain a long-term paleoclimatic record, New Mexico Geological Society Spring Meeting, Abstracts with Program.

Fawcett, P.J. Fawcett, Werne, J., Anderson, R.S, Heikoop, J., Brown, E., Hurley, L, Smith, S., Berke, M., Soltow, H., Goff, F., Geissman, J., WoldeGabriel, G., Fessenden, J., Cisneros-Dozal, M., and Allen, C.D., 2008, Coupled Warming and Drought in the American Southwest During Long mid-Pleistocene Interglacials (MIS 11 and 13), AGU Fall Meeting, 2008.

Fawcett, P.J., Goff, F., Heikoop, J., Allen, C.D., Donohoo-Hurley, L., Geissman, J.W., Johnson, C., WoldeGabriel, G., and Fessenden-Rahn, J., 2005, Climate change over a glacial-interglacial cycle during the middle Pleistocene: A long term record from the Valles Caldera, New Mexico, Earth System Processes 2, Calgary, Alberta, GSA Specialty Meetings Abstracts with Programs No. 1, p. 33.

Fawcett, P.J., Goff, F., Heikoop, J., Allen, Craig D., , Donohoo-Hurley, L., Wawrzyniec, T.F., Geissman J.W., Fessenden-Rahn, J., WoldeGabriel, G., and Schnurrenberger, D., 2004, Deep Coring in the Valles Caldera, Northern New Mexico to Obtain a Long-Term Paleoclimatic Record, EOS Transactions, American Geophysical Union, v. 85 T43C-1346.

Fawcett, P.J., Heikoop, J., Anderson, R.S., Donohoo-Hurley, L., Goff, F., Geissman, J.W., Johnson, C., Allen, C.D., WoldeGabriel, G., and Fessenden-Rahn, J., 2006, Two mid-Pleistocene glacial cycles from the Valles Caldera, New Mexico, 10th International Paleolimnology Symposium June 25-29, 2006, Duluth, Minnesota, USA, Abstracts Volume, p. 32.

Fawcett, P.J., Heikoop, J., Anderson, R.S., Hurley, L., Goff, F. WoldeGabriel, G., Geissman, J., and Allen, C.D., 2007, A long middle Pleistocene climate record (MIS 14 to 9) from lacustrine sediments in the Valles Caldera, New Mexico, Geological Society of America Abstracts with Programs, Vol. 39, No. 6, p. 270.

Fawcett, P.J., Heikoop, J., Anderson, R.S., Hurley, L., Goff, F., Johnson, C., Geissman, J.W., and Allen, C.D., 2007, Two mid-Pleisocene glacial cycles (MIS 14 to 10) from lacustrine sediments in the Valles Caldera, northern New Mexico, Abstract XVII INQUA Congress Cairns Australia; Quaternary International v. 167-168, p. 114.

Fawcett, P.J., Heikoop, J., Anderson, R.S., Hurley, L., Goff, F., Geissman, J.W., Johnson, C., WoldeGabriel, G., Allen, C.D., and Fessendeh-Rahn, J., 2006, Two mid-Pleistocene glacial cycles (MIS 14 to 10) from lacustrine sediments in the Valles Caldera, New Mexico, EOS Trans, 87(52) AGU, Fall Meet. Suppl., Abstract PP51B-1137.

Fawcett, P.J., Heikoop, J., Goff, F., Allen, C.D., Anderson, R.S., Donohoo-Hurley, L., Geismman, J.W., Johnson, C., WoldeGabriel, G., and Fessenden-Rahn, J., 2005, Climate change over a glacial-interglacial cycle from the mid Pleistocene: A lacustrine record from the Valles Caldera, New Mexico, American Geophysical Union Annual Fall Meeting. Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract PP31A-1505

Fawcett, P.J., Heikoop, J., Goff, F., Anderson, R.S., Donohoo-Hurley, L., Geissman, J.W., Johnson, C., Allen, C.D., WoldeGabriel, G., and Fessenden-Rahn, J., 2006, A mid-Pleistocene glacial-interglacial cycle from the Valles Caldera, New Mexico, New Mexico Geological Society 2006 Spring Meeting, Socorro, NM, Abstract volume, p. 18.

Hurley, L., Geissman, J.W., Fawcett, P.J., Wawrzyniec, T., and Goff, F., 2006, An investigation of environmental magnetism of the Pleistoene Valle Grande lacustrine sediments, New Mexico, Geological Society of America Abstracts with Programs, Vol. 38, No. 7, p. 199

Hurley, L.L., Geissmann, J.W., Fawcett, P., Wawrzyniec, T., and Goff, F., 2007, Environmental magnetism of mid-Pleistocene lacustrine sediments of the Valles Caldera, New Mexico, Eos Trans. AGU 88(52), Fall Meet. Suppl., Abstract GP53B-1218.

Johnson, C.M., Fawcett, P.J., and Ali, A.S., 2006, Geochemical and mineralogical indicators of redox conditions of a mid-Pleistocene lake in the Valles Caldera, New Mexico, New Mexico Geological Society 2006 Spring Meeting, Socorro, NM, p. 23.

Johnson, C.M., Fawcett, P.J., and Ali, M., 2006, Geochemical Indicators of Redox Conditions as a Proxy for mid-Pleistocene Climate Change From a Lacustrine Sediment Core, Valles Caldera, New Mexico, EOS Trans, 87(52) AGU, Fall Meet. Suppl., Abstract PP51B-1143.

 

Valles Caldera Drilling2

Figure 3: Core VC-3 Stratigraphic section, Organic Carbon (%) in siderite free fraction, bulk magnetic susceptibility (SI x 10-6) and bulk sediment density (g/cm3). Age assignments are based on Ar-Ar dates, and correlation with geomagnetic field events and glacial terminations. MBT temperature estimates (in oC) and depths given in red, within the Organic Carbon plot.

, , ,

Lake Bosumtwi

Lake Bosumtwi Scientific Core Drilling Services Project

The 2004 ICDP Bosumtwi Impact Crater Drilling Project, Ghana

Christian Koeberl University of Vienna

Bernd Milkereit University of Toronto

Jonathan T. Overpeck University of Arizona

Christopher A. Scholz Syracuse University

The 10.5-km-diameter 1.07 Ma Bosumtwi impact crater was the subject of an interdisciplinary and international drilling effort of the International Continental Scientific Drilling Program (ICDP) from July to October 2004. Sixteen different cores were drilled by DOSECC at six locations within the lake, to a maximum depth of 540 m. A total of about 2.2 km of core material was obtained. 

Introduction and Geological Setting

Bosumtwi is one of only four known impact craters associated with a tektite strewn field. It is a well-preserved complex impact structure that displays a pronounced rim and is almost completely filled by the 8 km diameter Lake Bosumtwi. The crater is excavated in 2 Ga metamorphosed and crystalline rocks of the Birimian System; it is surrounded by a slight near-circular depression and an outer ring of minor topographic highs with a diameter about 20 km. The goal of the integrated drilling, rock property and surface geophysical study was to study the three-dimensional building blocks of the impact crater (delineate key lithological units, image fault patterns, and define alteration zones).

Lake Bosumtwi Drilling

Figure 1 – Location map with ICDP boreholes and seismic profile shown in Fig. 2.

Paleoclimatic Studies at Bosumtwi

Owing to its impact origin, Bosumtwi possesses several important characteristics that make it well suited to provide a record of tropical climate change. In order to gain greater insight into the role of the tropics in triggering, intensifying and propagating climate changes, scientific drilling for the recovery of long sediment records from Lake Bosumtwi was undertaken. Five drill sites (Fig. 1) were occupied along a water-depth transect in order to facilitate the reconstruction of the lake level history. At these five drill sites, a total of 14 separate holes were drilled. Total sediment recovery was 1,833 m. For the first time the GLAD lake drilling system (a system specifically constructed for drilling at lakes) cored an entire lacustrine sediment fill from lakefloor to bedrock.

 

The complete 1 Ma lacustrine sediment fill was recovered from the crater ending in impact-glass bearing, accretionary lapilli fallout. This accretionary lapilli unit represents the initial post-impact sedimentation and provides an important age constraint for the overlying sedimentary sequence. The initial lacustrine sediment is characterized by a bioturbated, light-gray mud with abundant gastropod shells suggesting that a shallow-water oxic lake environment was established in the crater. Future study of the earliest lacustrine sediment will address important questions related to the formation of the lake and the establishment of biologic communities following the impact. Most of the overlying 294 m of mud is laminated thus these sediment cores will provide a unique 1 million year record of tropical climate change in continental Africa at extremely high resolution. The shallow water drill sites consist of alternating laminated lacustrine mud (deepwater environment), moderately-sorted sand (nearshore beach environment) and sandy gravel (fluvial or lake marginal environments). These sediments preserve a record of major lake level variability that will greatly advance the present Bosumtwi lake level histories obtained from highstand terraces and shorter piston cores. All of the drill sites will be used to produce a basin-scale stratigraphic framework for the crater sediment fill.

Geophysics and Impact Results

The two impactite cores, LB-07A and LB-08A, were drilled into the deepest section of the annular moat (540 m) and the flank of the central uplift (450 m), respectively. Samples from these cores have been studied by more than a dozen different research teams from around the world. The first set of peer-reviewed papers resulting from this work has just been published in a special issue of the journal “Meteoritics and Planetary Science”, which contains 27 papers on various aspects of the impact and geophysical studies at Bosumtwi.

At both impactite holes, drilling progressed through the impact breccia layer into fractured bedrock. LB-07A comprises lithic (in the uppermost part) and suevitic impact breccias with appreciable amounts of impact melt fragments. The lithic clast content is dominated by graywacke, besides various metapelites, quartzite, and a carbonate target component. Shock deformation in the form of quartz grains with planar microdeformations is abundant. First chemical results indicate a number of suevite samples that are strongly enriched in siderophile elements and Mg, but the presence of a definite meteoritic component in these samples cannot be confirmed due to high indigenous values. Core LB-08A comprises suevitic breccia in the uppermost part, followed with depth by a thick sequence of graywacke-dominated metasediment with suevite and a few granitoid dike intercalations. It is assumed that the metasediment package represents bedrock intersected in the flank of the central uplift.

Major results include the complete petrographic and geochemical record of the impactite fill. Major surprises in this regard include the, in comparison to suevites outside of the crater, small impact melt component and the record of shock metamorphism in the clast content of suevites, which are both at variance with earlier numerical modeling results. Also, impact-related hydrothermal overprint seems to be limited. These examples suffice to illustrate that further research on impact structures, accompanied by numerical modeling, is required to solve these and other problematics. Impactite geochemistry has also revealed that the impact breccias and the Ivory Coast tektite compositions can be satisfactorily modeled as mixtures of the known Birimian-age target rocks (metasedimentary rocks and granitoids). The geophysical studies, calibrated against the petrophysical data retrieved from the drill cores, have allowed to develop much improved three-dimensional models for the crater volume.

Lake Bosumtwi Drilling1

Figure 2 – Seismic section with deep boreholes.

Deep drilling results confirmed the general structure of the crater as imaged by the pre-drilling seismic surveys. Borehole geophysical studies conducted in the two boreholes confirmed the low seismic velocities for the post-impact sediments (less than 1800 m/s) and the impactites (2600-3300 m/s). The impactites exhibit extremely high porosities (up to 30 vol%), which has important implications for mechanical rock stability.

The statistical analysis of the velocities and densities reveals a seismically transparent impactite sequence (free of prominent internal reflections). Petrophysical core analyses provide no support for the presence of a homogeneous magnetic unit (= melt breccia) within the center of the structure. Borehole vector-magnetic data point to a patchy distribution of highly magnetic rocks within the impactite sequence.

Prior to drilling, numerical modeling estimated melt and tektite production using different impact angles and projectile velocities. The most suitable conditions for the generation of tektites are high-velocity impacts (>20 km/s) with an impact angle between 30 and 50° from the horizontal. Not all the melt is deposited inside the crater. In the case of a vertical impact at 15 km/s, 68% of the melt is deposited inside the crater. Results of the numerical modeling agreed well with the then-available geophysical data, crater size, and the distribution of tektites and microtektites of the tektite strewn field. The now observed situation for breccias within and around the crater is very different from these model results. The predicted amount of melt is much higher than the meager amounts observed. Clearly, much more melt has been incorporated in the suevite ejected outside of the structure, in comparison with the low amounts measured in the within-crater suevite occurrences. The lack of a coherent melt sheet, or indeed of any significant amounts of melt rock in the crater fill, is thus in contrast to expectations from modeling and pre-drilling geophysics, and presents an interesting problem for comparative studies and requires re-evaluation of existing data from other terrestrial impact craters, as well as modeling parameters. This research project provided important new data and improved our understanding of global change and impact processes.

Lake Bosumtwi Drilling2

Figure 3 – Bosumtwi Project Coring Team aboard DOSECC’s GLAD800 drilling platform, R/V Kerry Kelts.

 

Read more about this scientific core drilling services project at ICDP.

Acknowledgments

This work was supported by the International Continental Drilling Program (ICDP), the U.S. NSF-Earth System History Program under Grant No. ATM-0402010, Austrian National Science Foundation (project P17194-N10), the Austrian Academy of Sciences, and by the Canadian National Science Foundation. Drilling was performed by DOSECC.

References:

Koeberl C., Milkereit B., Overpeck J.T., Scholz C.A., Amoako P.Y.O., Boamah D., Danuor S.K., Karp T., Kueck J., Hecky R.E., King J., and Peck J.A.

(2007) An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi impact crater, Ghana, drilling project – An overview. Meteoritics and Planetary Science 42, 483-511.

Ferrière, L., Koeberl, C., Ivanov, B.A., and Reimold, W.U. (2008) Shock metamorphism of Bosumtwi impact crater rocks, shock attenuation, and uplift formation. Science 322, 1678-1681.

Nowaczyk N.R., Melles, M. and Minyuk, P., 2007: A revised age model for core PG1351 from Lake El’gygytgyn, Chukotka, based on magnetic susceptibility variations correlated to northern hemisphere insolation variations, Journal of Paleolimnology, 37: 65-76.

Secondary References:

Asikainen, C.A., Francus, P. and Brigham-Grette, J., 2006: Sediment fabric, clay mineralogy, and grain-size as indicators of climate change since 65 ka at El’gygytgyn Crater Lake, Northeast Siberia, Journal of Paleolimnology, 37: 105-122.

Berger, A. and Loutre, M.F., 1991: Insolation values for the climate of the last 10 million of years, Quaternary Science Reviews, 10: 297-317.

Brigham-Grette, J. and Carter, L.D., 1992: Pliocene marine transgressions of northern Alaska: Circumarctic Correlations and Paleoclimate, Arctic, 43(4): 74-89.

Brigham-Grette, J., Melles, M., Minyuk, P. and Scientific Party, 2007: Overview and Significance of a 250 ka Paleoclimate Record from El’gygytgyn Crater Lake, NE Russia, Journal of Paleolimnology, 37: 1-16.

Cherapanov, M.V, Snyder, J.A. and Brigham-Grette, J., 2007: Diatom Stratigraphy of the last 250 ka at Lake El’gygytgyn, northeast Siberia, Journal of Paleolimnology, 37: 155-162.

Dowsett, H.J., 2007: The PRISM paleoclimate reconstruction and Pliocene sea-surface temperature. In: Williams, M., et al., (Eds.) Deep-Time Perspectives on Climate Change: Marrying the Signal from Computer Models and Biological Proxies: The Micropaleontological Society, Special Publications, The Geological Society, London, 459-480.

Forman S.L., Pierson J., Gomez J., Brigham-Grette J., Nowaczyk N.R. and Melles, M., 2007: Luminescence geochronology for sediments from Lake El´gygytgyn, northwest Siberia, Russia: Constraining the timing of paleoenvironmental events for the past 200 ka, Journal of Paleolimnology, 37: 77-88.

Gebhardt, A.C., Niessen, F. and Kopsch, C., 2006: Central ring structure identified in one of the world’s best-preserved impact craters, Geology, 34: 145-148.

Glushkova, O.Yu. and Smirnov, V.N., 2007: Pliocene to Holocene geomorphic evolution and paleogeography of the El’gygytgyn Lake region, NE Russia, Journal of Paleolimnology, 37, 37-47.

Haug, G.H., et al., 2005: North Pacific seasonality and the glaciation of North America 2.7 million years ago, Nature, doi:10.1038, 1-5.

Juschus O., Preusser F., Melles M. and Radtke U., 2007: Applying SAR-IRSL methodology for dating fine-grained sediments from Lake El´gygytgyn, north-eastern Siberia, Quaternary Geochronology, 2: 137-142.

Layer, P.W., 2000. Argon-40/argon-39 age of the El’gygytgyn impact event, Chukotka, Russia, Meteroitics and Planetary Science, 35: 591-599.

Lisiecki, L.E. and Raymo, M.E., 2005: A Pliocene-Pleistocene stack of 57 globally distributed benthic ∂18O records, Paleoceanography, 20: PA1003, doi:10.1029/2004PA001071

Lozhkin, A.V., Anderson, P.M., Matrosova, T.V. and Minyuk, P.S., 2007: The pollen record from El’gygytgyn Lake: implications for vegetation and climate histories of northern Chukokta since the late middle Pleistocene, Journal of Paleolimnology, 37: 135-153.

Melles, M., Brigham-Grette, J., Glushkova, O.Yu., Minyuk, P.S., Nowaczyk, N.R. and Hubberten, H.W., 2007: Sedimentary geochemistry of a pilot core from Lake El’gygytgyn – a sensitive record of climate variability in the East Siberian Arctic during the past three climate cycles, Journal of Paleolimnology, 37: 89-104.

Miller, G.H. and Brigham-Grette, J. (lead authors) and 17 contributing authors, in press: Temperature and Precipitation history of the Arctic, Chapter 4, IN, Past Climate Variability and change in the Arctic and High Latitudes, CCSP Synthesis and Assessment Product 1.2, US Govt Climate Change Program. 201 pgs.

Minyuk, P.S., Brigham-Grette, J., Melles, M.M., Borkhodovev, V.Yu., Glushkova, O.Yu., 2007: Inorganic geochemistry of El’gygytgyn Lake sediments (northeastern Russia) as an indicator of paleoclimatic change for the last 250 kyr, Journal of Paleolimnology, 37: 123-133

Niessen, F., Gebhardt, A.C. and Kopsch, C., 2007: Seismic investigation of the El’gygytgyn impact crater lake (Central Chukotka, NE Siberia): preliminary results, Journal of Paleolimnology, 37: 49-63.

Nolan, M. and Brigham-Grette, J., 2007: Basic Hydrology, Limnology, and meterology of modern Lake El’gygytgyn, Siberia, Journal of Paleolimnology, 37: 17-35.

Nolan, M., Liston, G., Prokein, P., Huntzinger, R., Brigham-Grette, J. and Sharpton, V., 2003: Analysis of Lake Ice Dynamics and Morphology on Lake El’gygytgyn, Siberia, using SAR and Landsat, Journal of Geophysical Research, 108(D2): 8162-8174.

Nowaczyk et al., 2002: Magnetostratigraphic results from impact crater Lake El’gygytgyn, northeastern Siberia: A 300 kyr long high resolution terrestrial paleoclimatic record from the Arctic, Geophysical Journal International, 150: 109-126.

Nowaczyk N.R., Melles, M. and Minyuk, P., 2007: A revised age model for core PG1351 from Lake El’gygytgyn, Chukotka, based on magnetic susceptibility variations correlated to northern hemisphere insolation variations, Journal of Paleolimnology, 37: 65-76.

Salzmann, U., Haywood, A.M., Lunt, D.J., Valdes, P.J. and Hill, D.J., 2008: A new global biome 4004 reconstruction and data-model comparison for the Middle Pliocene, Global Ecology and Biogeography, 17: 432-447.

, ,

Laguna Salada

Laguna Salada project, located in Mexico

Natural Variability and Climatic Change in the Delta of the Colorado River region

Laguna Salada project, located in Mexico

Juan Contreras, Arturo Martín-Barajas, and Juan Carlos Herguera Centro de Investigación Científica y de      Educación Superior de Ensenada

Ana Luisa Carreño Universidad Nacional Autónoma de México

The Salton Trough region of southern California and the Mexicali valley in north Mexico conforms the Delta of the Colorado. The delta of the Colorado provides with water to a population of more than 2.5 million inhabitants. The delta is so fertile that its agricultural output is the largest in Mexico; it also hosts the largest settlement of industrial complexes in the country. The combined production of those two economical sectors accounts for 1.5% of the gross domestic product of Mexico. Understanding of past climatic changes in the region is of vital importance because it can give us an idea of how the hydrological balance, specially the dynamics of the Colorado River, will be affected by global warming.

Colorado River Drilling

Figure 1 – Panoramic view of the drilling operations on the barren lakebed of Laguna Salada. The lake disappeared after the building and filling of the Hoover Dam in the 30’s.

Drilling in this basin also opens a window into the tectonic processes acting in the northern Gulf of California. Recovering sediment samples from the Laguna Salada basin will also help to characterize the mechanical response of the soil to shaking during earthquakes.

The delta of the Colorado River is an area of rapid subsidence due to extension along the San Andreas-Imperial fault system and high flux of sediments transported by the Colorado River. These areas, therefore, have a high preservation potential to store information of past climate events. In January 2004 DOSECC recovered 92 m of lacustrine sediments from two shallow boreholes drilled in Laguna Salada, and active sedimentary basin in northern Baja California, México. Laguna Salada occupies a semiclosed depression between the Sierra the Cucapá on the west and the Sierra de Juárez on the east. Our goal for drilling in this basin was threefold: (i) to document past climatic changes during the last glacial age and its transition to the present warmer climate, (ii) to document climate changes during the last two glacial cycles, and (iii) to document the vertical slip component of the Laguna Salada fault, which bounds the eastern margin of the basin.

Colorado River Drilling1

Figure 2 – Drillers emplacing downhole logging geophysical instruments. This picture, as well as brief note about the drilling operations, made into the Spanish edition of National Geographic Magazine.

Boreholes were drilled at the toe of the alluvial fans adjacent to the Sierra de Juárez and on dry lakebed close to the Sierra de Cucapá and the Laguna Salada fault. Recovery was in excess of 95%. Equipment used during the drilling operation included DOSECC Lake System (DLS) suite of coring tools and a modified CS-500 rig. The main tool employed for coring was a hydraulic piston core. The quality of the cores is excellent, being found millimeter-scale primary sedimentary structures preserved in the sequence.

Ten C14 dates in charred organic matter and plant remnants indicate the core spans ~50 Ka and sedimentation rates are in the order of ~0.7 mm/yr. We can resolve in the core, therefore, climatic variability at timescales ranging from Milankovitch forcing up to millennial to centennial periodicities imprinted at scales ranging from centimeters to meters. We have found, for example, that 0.7-2 mm-thick lamina group in bundles of 6, 25 and 50 cm. Intercalations of massive clay, gypsum and sand tend to form cycles of 50 cm and 100-120 cm. We also have identified evidences of abrupt climate changes.

At Milankovitch time scales we have identified cycles based on sedimentary facies in the core, color, granulometry, mineralogical composition and primary structures such as laminae, dissecation cracks, and bioturbation. Additionally, we obtained reflectivity of sediments every 5mm to 1 cm depending on the scale of the primary structures. The recovered stratigraphy consists of three sedimentary successions. The base of the core is characterized by laminae of silt and mud 5mm-1cm thick deposited during glacial stage 2 through the last glacial maximum. This ancient paleolake was characterized by moist conditions in which a water table prevailed year-round. Good preservation of laminae suggests that bottom anoxia was frequent phenomenon.

Colorado River Drilling2

Figure 3 – stratigraphic column of the LS04-1 core. It contains a description of the sedimentary facies recovered by the cores. Additionally, it shows the major climatic changes experienced in the region during the last 60 kyr.

During the last glacial maximum, moisture conditions changed drastically. Laminations are replaced by finely stratified sand and further upsection by repetitive packages 50cm-thick composed of coarse sand, brown mud, greenish silt and mud, caped by 5-10 cm of evaporites. These sediments were deposited in a continental sabka environment with intermittent freshwater input, as evidenced by the clear dissecation cycles.

The Holocene climate in the region also experienced major shifts. For instance, the Holocene thermal maximum is characterized by deposition of well-classified sand deposits with granulometry similar to that of modern dune fields. This is indicative of hyper-arid conditions. The second half of the Holocene, on the other hand, experienced a return to relatively more moist conditions. However, the hydraulic balance probably is close to null given the presence of evaporitic deposits intercalated with laminated mud and fine sand.

Laguna Salada project, located in Mexico, was a 2004 project that was CICESE-funded.

 

View related publication.

Colorado River Drilling3

Figure 4 – Core from Laguna Salada showing perturbed sediments by an earthquake of at least Mw 6.

 

, , ,

Hawaii Scientific Drilling Project

Hawaii Scientific Core Drilling Services

Hawaii Scientific Drilling Project (1991 – 2008)

D.J. DePaolo Lawrence Berkeley National Laboratory

E.M. Stolper California Institute of Technology

D.M. Thomas University of Hawai’i at Manoa

 

Hawaii Scientific DrillingThe Hawaii Scientific Drilling Project drilled and cored two holes in Hilo, Hawaii, the deeper reaching a depth of 3520 meters below sea level, and retrieved a total of 4600 meters of rock core; 525 meters from the Mauna Loa volcano and the remainder from the Mauna Kea volcano. The Mauna Loa core extends the continuous lava stratigraphy of that volcano back to 100 ka and reveals major changes in lava geochemistry over that time period. The Mauna Kea core spans an age range from about 200 to perhaps 700 ka and when combined with surface outcrops, provides a 700 ky record of the lava output from a single volcano. During the time covered by the lavas from the core the volcano drifted some 60 to 80 km across the melting region of the Hawaiian mantle plume, and therefore the HSDP rock core provides the first systematic cross-sectional sampling of a deep mantle plume. The geochemical characterization of the core, which involved an international team of 40 scientists over a period of 15 years, provides information about mantle plume structure and ultimately about the deepest parts of the Earth’s mantle. The study of the lava core, which still continues, has provided unprecedented information about the internal structure of a large oceanic volcano and the time scale over which volcanoes grow. The hole also provides an intriguing glimpse of a complex subsurface hydrological regime that differs greatly from the generalized view of ocean island hydrology.

Hawaii Scientific Drilling1Drilling conditions were favorable in the subaerial parts of the volcanic section, where coring was fast and efficient. The submarine part of the lava section, made up primarily of volcanogenic sediments and pillow lavas, proved considerably more difficult to drill. Some of the difficulties, and considerable additional expense, were due to pressurized aquifers at depth and a few critical mistakes made while setting casing. Even with the more difficult conditions, the project retrieved about 2400 meters of nearly continuous core from the submarine section of Mauna Kea. Overall the HSDP project was highly successful, even though the original target depth was about 20% deeper than the final hole depth. The project results answer important questions about oceanic volcanoes, mantle plumes, and ocean island water resources, but raise many more that might be addressed with further moderate-depth drilling in other Hawaiian volcanoes.

Read more about this scientific core drilling services project at ICDP.

Representative References:

Abouchami, W., Hofmann, A.W., Galer, S.J.G., Frey, F.A., Eisele. J., Feigenson, M. (2005): Lead isotopes reveal bilateral asymmetry and vertical continuity in the Hawaiian mantle plume. Nature 434:851-856 (14 April 2005); doi:10.1038/nature03402.

Büttner, G., Huenges, E. (2002): The heat transfer in the region of the Mauna Kea (Hawaii) – constraints from borehole temperature measurements and coupled thermo-hydraulic modelling. Tectonophysics, 371, 23-40.

DePaolo, D.J. and Weis, D. (2007): Hotspot volcanoes and Large Igneous Provinces. In Harms, U. et al., ed. Continental Scientific Drilling: A Decade of Progress and Challenges for the Future, Springer-Verlag, 366pp

DePaolo, D.J., Stolper, E.M. and Thomas, D.M. (2007): Scientific Drilling In Hotspot Volcanoes, McGraw-Hill Yearbook of Science and Technology, p. 203-205

Helm-Clark, C.M., Rodgers, D.W., Smith, R.P. (2004): Borehole geophysical techniques to define stratigraphy, alteration and aquifers in basalt. Journal of Applied Geophysics, 55(1-2):3-38.

Herzberg, C. (2006): Petrology and thermal structure of the Hawaiian plume from Mauna Kea volcano. Nature 444:605-609 (30 November 2006); doi:10.1038/nature05254.

Lassiter, J.C., Hauri, E.H. (1998): Osmium-isotope variations in Hawaiian lavas: evidence for recycled lithosphere in the Hawaiian plume. Earth Planet. Sci. Lett. 164, 483-496.

Li, X., Kind, R., Yuan, X., Wölbern, I., Hanka, W. (2004): Rejuvenation of the lithosphere by the Hawaiian plume. Nature 427:827-829 (26 February 2004) doi:10.1038/nature02349.

Lassiter, J.C., (2003) Rhenium volatility in subaerial lavas: constraints from subaerial and submarine portions of the HSDP-2 Mauna Kea drillcore. Earth Planet. Sci. Lett. V. 214, pp. 311-325.

Ren, Z-Y., Ingle, S., Takahashi, E., Hirano, N., Hirata, T. (2005): The chemical structure of the Hawaiian plume. Nature 436:837–840.

Ribe, N.M. (2004): Earth Science: Through Thick and Thin. Nature 427:793-795 (26 February 2004) doi:10.1038/427793a.

Sobolev, A.V. (2002): Hunting for Earth’s primary melts. Humboldt Kosmos 79/2002:19-20.

Sobolev, A.V., Hofmann, A.W., Nikogosian, I.K. (2000): Recycled oceanic crust observed in ‘ghost plagioclase’ within the source of Mauna Loa lavas. Nature 404:986-989.

Sobolev, A.V., Hofmann, A.W., Sobolev, S.V., Nikogosian, I.K. (2005): An olivine-free mantle source of Hawaiian shield basalts. Nature 434:590-597 (31 March 2005); doi:10.1038/nature03411.

Vahle, C., Kontny, A., (2005), The use of field dependence of AC susceptibility for the interpretation of magnetic mineralogy and magnetic fabrics in the HSDP-2 basalts, Hawaii. Earth Planet. Sci. Lett., V. 238, pp. 110– 129

Walton, A.W., (2008) Microtubules in basalt glass from Hawaii Scientific Drilling Project #2 phase 1 core and Hilina slope, Hawaii: evidence of the occurrence and behavior of endolithic microorganisms. Geobiology, 6, 351–364

Zimmermann, G., Burkhardt, H., Englehard, L., (2005): Scale dependence of hydraulic and structural parameters in fractured rock, from borehole data (KTB and HSDP). From: HARVEY, P. K., BREWER, T. S., PEZARD, P. A. and PETROV, V. A. (eds), Petrophysical Properties of Crystalline Rocks. Geological Society, London, Special Publications, 240, 39-45

HSDP2 Papers (G-Cubed):

Althaus, T., Niedermann, S., Erzinger, J. (2001): Noble gases in olivine phenocrysts from drill core samples of the Hawaii Scientific Drilling Project (HSDP) pilot and main holes (Mauna Loa and Mauna Kea, Hawaii). doi: 10.1029/2001GC000275.

Blichert-Toft, J., Weis, D., Maerschalk, C., Agranier, A., Albarède, F. (2003): Hawaiian hot spot dynamics as inferred from the Hf and Pb isotope evolution of Mauna Kea volcano. Geochem. Geophys. Geosyst. 4, doi: 10.1029/2002GC000340.

Bryce, J.G., DePaolo, D.J., Lassiter, J.C. (2004): Geochemical structure of the Hawaiian plume: Sr, Nd, and Os isotopes in the 2.8 km HSDP-2 section of Mauna Kea volcano. Geochem. Geophys. Geosyst., Vol. 6, Q09G18, doi: 10.1029/2004GC000809.

Chan, Lui-Heung, Frey, F.A. (2002): Lithium isotope geochemistry of the Hawaiian plume: Results from the Hawaii Scientific Drilling Project and Koolau Volcano. doi: 10.1029/2002GC000365.

Eisele, J., Abouchami, W., Galer, S.J.G., Hofmann, A.W. (2002): The 320 kyr Pb isotope evolution of Mauna Kea lavas recorded in the HSDP-2 drill core. doi: 10.1029/2002GC000339

Feigenson, M.D., Bolge, L.L., Carr, M.J., Herzberg, C.T. (2001): REE inverse modeling of HSDP2 basalts: Evidence for multiple sources in the Hawaiian plume. doi: 10.1029/2001GC000271.

Fisk, M.R., Storrie-Lombardi, M.C., Douglas, S., Popa, R., McDonald, G., Di Meo-Savoie, C., (2003), Evidence of biological activity in Hawaiian subsurface basalts. Geochem. Geophys. Geosyst. Volume 4, Number 12, 1103, doi:10.1029/2002GC000387.

Garcia, M.O., Haskins, E.H., Stolper, E.M., Baker, M., (2007), Stratigraphy of the Hawai‘i Scientific Drilling Project core (HSDP2): Anatomy of a Hawaiian shield volcano. Geochem. Geophys. Geosyst. Volume 8, Number 2, doi: 10.1029/2006GC001379

Stolper, E.M., DePaolo, D.J., Thomas, D.M. (1996): Introduction of special section: Hawaii Scientific Drilling Project. Journal of Geophysical Research, 101, B5, p. 11593-11598.

Walton, A.W. and Peter Schiffman, 2003, Alteration of hyaloclastites in the HSDP 2 Phase 1 Drill Core 1. Description and paragenesis: Geochemistry, Geophysics, and Geosystems, v. 4, # 5, Paper # 2002GC000368, 3I pp.

Walton, A.W., Schiffinan, Peter, and Macpherson, G.L., 2005, Alteration of hyaloclastites in the HSDP 2 Phase I Drill Core 2. Mass balance of the conversion of sideromelane to palagonite and chabazite, Geochemistry, Geophysics, and Geosystems, v, 6, #9 Paper #2004GC00903, 27 pp.

Walton, Anthony W., 2007, Formation, modification, and preservation of microbial endolithic borings in hyaloclastite from Hawaii: Clues for petrographic recognition of mictrorbial traces in basalt glass of any provenance and stage of alteration: Lunar and Planetary Science XXXVIII, 1975.

Walton, Anthony W., 2008, Petrographic examination of occurrence, associations, and behavior of microorganisms: Endolithic microborings in basalt glass from HSDP 2 Phase I Core, Hilo and Hilina Slope, Hawaii. Geobiology, v. 6, p. 351-364, DOl: 10.1 I I l/j.14724669.2008.00149.

Yang, H.-J., Frey, F.A., Rhodes, J.M., Garcia, M.O. (1996): Evolution of Mauna Kea volcano: Inferences from Lava compositions recovered in the Hawaii Scientific Drilling Project. Journal of Geophysical Research, 101, B5, p. 11747-11767.

Stolper, E.M., DePaolo, D.J., Thomas, D.M. (1996): Introduction of special section: Hawaii Scientific Drilling Project. Journal of Geophysical Research, 101, B5, p. 11593-11598.

Walton, A.W. and Peter Schiffman, 2003, Alteration of hyaloclastites in the HSDP 2 Phase 1 Drill Core 1. Description and paragenesis: Geochemistry, Geophysics, and Geosystems, v. 4, # 5, Paper # 2002GC000368, 3I pp.

Walton, A.W., Schiffinan, Peter, and Macpherson, G.L., 2005, Alteration of hyaloclastites in the HSDP 2 Phase I Drill Core 2. Mass balance of the conversion of sideromelane to palagonite and chabazite, Geochemistry, Geophysics, and Geosystems, v, 6, #9 Paper #2004GC00903, 27 pp.

Walton, Anthony W., 2007, Formation, modification, and preservation of microbial endolithic borings in hyaloclastite from Hawaii: Clues for petrographic recognition of mictrorbial traces in basalt glass of any provenance and stage of alteration: Lunar and Planetary Science XXXVIII, 1975.

Walton, Anthony W., 2008, Petrographic examination of occurrence, associations, and behavior of microorganisms: Endolithic microborings in basalt glass from HSDP 2 Phase I Core, Hilo and Hilina Slope, Hawaii. Geobiology, v. 6, p. 351-364, DOl: 10.1 I I l/j.14724669.2008.00149.

Yang, H.-J., Frey, F.A., Rhodes, J.M., Garcia, M.O. (1996): Evolution of Mauna Kea volcano: Inferences from Lava compositions recovered in the Hawaii Scientific Drilling Project. Journal of Geophysical Research, 101, B5, p. 11747-11767.

, , ,

Iceland Lakes

Iceland Lakes Scientific Core Drilling Services Project

Iceland Lakes Drilling Project

Gifford Miller University of Colorado

Aslaug Geirsdottir University of Iceland

DOSECC’s GLAD200 drilling system was used to target three Icelandic lakes, Hestvatn (HST), Hvítárvatn (HVT), and Haukadalsvatn (HAK), each with 10 to 12 ka years of sediment fill, averaging 1 to 2 m sediment per thousand years. From these collections, one PhD (J Black, Colorado HVT), and two MSc (H Hannesdottir, Iceland HST and Gudrun Eva Johannsdottir, tephra geochemistry) theses have been completed. Two additional theses (D Larson, Colorado HVT, PhD and K Olafsdottir, Iceland HAK, MSc) are in progress.

Major Findings

1) During the Holocene thermal maximum (9 to 5 ka) summer temperatures were up to 3 °C warmer than late 20th Century averages, and Iceland’s large ice caps were either absent (Langjokull), or greatly reduced (Vatnajokull).

2) Neoglaciation set in about 5 ka with the maximum snowline lowering during the Little Ice Age.

3) Summer temperature depression during the Little Ice Age was up to 1.5 °C below late 20th Century averages, producing the most expanded local glacier limits since regional deglaciation.

4) Laminations in the HVT sediment cores have been confirmed to be annual varves. Varve thicknesses have been determined in two cores back to 870 AD, and in one additional core back 3 ka BP, with confirmation from 5 historic tephras and one 14C-dated tephra (H3). Varve thickness provides proxies for glacier size (summer temperature) and precipitation at annual resolution over this time interval. Spectral analyses of these signals (Olafsdottir) is in progress.

5) A geochemical characterization of all major tephra deposited over the past 10 ka is nearing completion. Lake records provide a far more complete record of explosive volcanism in Iceland than does any other archive, especially for tephras older than about 6 ka.

 

Iceland Lakes Drilling

Figure 1 – GLAD200 drilling platform
being used to core Hvítárvatn.

Iceland Lakes Drilling1

 

, ,

Geoclutter

ONR Geoclutter Program

 

ONR Geoclutter Program: Final Analysis of Geophysical and Geological Data

James A. Austin, Jr. and John A. Goff University of Texas Institute for Geophysics

Long-Term Goals

The primary goal of the Geoclutter program is to assess geologic clutter/reverberation issues in a seismically and geologically well-characterized shallow-water environment. The mid-outer continental shelf off New Jersey provides such an opportunity, because both bathymetry (a known and prominent cause of backscatter) and portions of the shallow subsurface have been mapped in detail as a result of STRATAFORM. The Geoclutter program consists of three field program phases: (I) an acoustic reconnaissance survey utilizing Navy gray ships and assets to identify potential geoclutter hot spots; (II) a full bistatic acoustic experiment focusing on the chosen areas, and (III), the focus of the work described here, detailed geologic and geophysical surveys of the hot spots identified in Phases I and II.

Objectives

Our primary objective for this grant were to finalize analysis of geological and geophysical data collected as part of the ONR Geoclutter program. In particular, we intend to complete the interpretation of the 2001 and 2002 chirp seismic data in conjunction with the analysis of cores collected in the region. These products will provide critical constraints on geoacoustic modeling of the New Jersey shelf region, which continues to be a focus of ONR-sponsored acoustic field work.

Approach

We employed a variety of approaches in our work. Stratal horizons are interpreted from chirp seismic data using commercial seismic interpretation software. Seafloor measurements, including grain size, porosity, in situ velocity and attenuation, backscatter strength, and acoustic impedance, are compared with each other using correlation analyses. Cores have been both logged for geoacoustic properties, providing ground truth, and sampled, to corroborate geologic interpretation and provide age dating of the sedimentary strata evident in the chirp data.

Work Completed

Interpretation of the chirp data has continued with significant progress. The analysis of seafloor properties based on in situ acoustic data, grab samples, short cores and remote sensing data (chirp and backscatter) is complete. Three long cores, ranging in length from 4 to 13 m, were collected in 2002 aboard the R/V Knorr using the Active Heave Compensated AHC-800 system supplied and operated by DOSECC (Figs. 1 and 4). These cores are the longest high-quality cores collected from this part of the margin and represent a unique sample set to provide temporal, stratigraphic and environmental context both for seismic stratigraphic interpretation and future sampling efforts. Geotechnical measurements from these cores were logged at sea, and samples have recently been collected which have undergone detailed analyses for time stratigraphy, sediment texture and paleoenvironmental conditions.

ONR Geoclutter Program

Figure 1. Location of deep-towed chirp-sonar tracklines collected aboard R/V Endeavor (EN359 and EN370), superimposed on NOAA’s bathymetry of the New Jersey middle and outer continental shelf. The small inset locates our study area regionally. Drill sites 1-3 cored with DOSECC’s AHC-800 system aboard R/V Knorr in fall 2002 are marked as yellow stars.

Results

Previous progress reports have detailed our extensive results to date (Fulthorpe and Austin, 2004; Goff and Nordfjord, 2004; Goff et al., 2004; Nordfjord et al., 2005; Goff et al., 2005; Gulick et al., 2005). Here we focus on the latest results from an extensive analysis of the internal stratigraphy of fill units within the channel networks that are shallowly buried across most of the middle and outer shelf. These results are presented in a newly submitted manuscript (Nordfjord et al., in press).

The fill strata of incised valleys on the New Jersey outer shelf demonstrate an upward and landward progression of four sedimentary facies (Figure 2), as observed in 1-4 kHz deep-towed chirp seismic data. From oldest to youngest, these are interpreted as fluvial lags (SF1), estuarine mixed sand and muds (SF2), estuary central bay muds (SF3) and redistributed estuary mouth sands (SF4). These fill units are covered by a transgressive oceanic ravinement surface, “T”, and Holocene marine sand deposits. Seismic facies of the transgressive systems tract (SF2-SF4) are interpreted to represent fluvial, estuarine and shelf depositional systems that are bounded by seismic reflectors marking source diastems or unconformities.

ONR Geoclutter Program1

Figure 2. Representative collocated chirp images at crossing the edge of a buried fluvial channel. The 1-15 kHz data were used as a guide for interpreting significant seismic boundaries, while the 1-4 kHz data provided more detail of the seismic facies.

 

Transgressive paleovalley-fill Successions identified in the New Jersey outer shelf Quaternary section contain three transgressive surfaces identified best in the 1-15 kHz chirp data (Figure 2), B1-3, interpreted as bay ravinement, intermediate flooding surface and tidal ravinement, respectively, which are wholly or partly preserved in vertical succession. These incised-valley-confined diastems significantly modify the antecedent, regionally developed, fluvial erosion surfaces. This modification is affected by erosion accompanying submergence and hypsometric change as the paleo-river valley evolves into a paleo-estuary. The original fluvially-incised surface, “Channels”, is generally only preserved as a distinct surface within valley axes, beneath a partly preserved fluvial depositional system. The fluvial erosion surfaces have typically been modified by bay (B1) and tidal (B3) ravinements within incised valleys, which then becomes a composite erosional surfaces cut by fluvial, estuarine and shoreface-shelf processes. The regionally developed “T” horizon caps subjacent incised-valley fill successions and marks landward passage of an oceanic shoreface over the underlying infilled paleo-estuaries. Dipward changes in the thickness of the SF3 and SF4 units suggest either a stillstand in the passage of the shoreline, which allowed for variations in unit thicknesses, or that the valley shape controlled the hydrodynamic conditions for sediment transport and deposition. In particular, we suggest that narrower valleys will promote tidally-dominated, fine-grained deposition while broader valleys will attenuate tidal flow velocities, allow the estuary to be dominated by wave energy and promote coarse-grained deposition. Our study demonstrates wave- and tide- dominated facies can coexist within the fill strata. A model for the development of valley fill strata is presented in Figure 3.

Impact / Applications

The primary application of our geological and geophysical characterization is in the establishment of critical paleoenvironmental characteristics for the understanding of acoustic interactions with the seabed. For example, the model presented in Figure 3 can be used as a basis for predicting the geoacoustic properties of sediments within the buried channels, as well as predict physical property contrasts between those sediments and the host strata that could give rise to a significant acoustic response.

Related Projects

The ONR STRATAFORM program provided initial site characterization for the Geoclutter natural laboratory. The SWAT acoustic experiment was also carried out in this area, and the 2006 Shallow Water Acoustics experiment is now planned for this area.

ONR Geoclutter Program2

Figure 3. Schematic representations of the evolution of New Jersey outer shelf incised valley systems, including their stratigraphic boundaries and sedimentary facies, as they went from (A) fluvial systems with preserved fluvial lags to (B) more aggradational stage as the system started to get backfilled and finally to (C) a typically passive infilling stage with the central basin mud and estuary mouth complexes. Not shown is the formation of the transgressive oceanic ravinement, following infilling, which likely reworked and removed significant portions of the incised valley fill deposited.

ONR Geoclutter Program3

Figure 4. DOSECC’s Active Heave Compensated drilling rig aboard the R/V Knorr.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Publications

Fulthorpe, C.S., and J.A. Austin, Jr., 2004. Shallowly buried, enigmatic seismic stratigraphy on the New Jersey outer shelf: Evidence for latest Pleistocene catastrophic erosion? Geology 32, 1013–1016. [published, refereed]

Goff, J. A., and S. Nordfjord, 2004. Interpolation of fluvial morphology using channel-oriented coordinate transformation: A case study from the New Jersey Shelf. Math. Geol. 36, 643-658. [published, refereed]

Goff, J. A., B. J. Kraft, L. A. Mayer, S. G. Schock, C. K. Sommerfield, H. C. Olson, S. P. S. Gulick, and S. Nordfjord, 2004. Seabed characterization on the New Jersey middle and outer shelf: Correlability and spatial variability of seafloor sediment properties. Mar. Geol. 209, 147-172. [published, refereed]

Goff, J. A., J A. Austin, Jr., S. Gulick, S. Nordfjord, B. Christensen, C. Sommerfield, and H. Olson, C. Alexander, 2005. Recent and modern marine erosion on the New Jersey outer shelf, Mar. Geol. 216, 275-296. [published, refereed]

Gulick, S. P. S., J. A. Goff, J. A. Austin, Jr., C. R. Alexander, Jr., S. Nordfjord, and Craig S. Fulthorpe, 2005. Basal inflection-controlled shelf-edge wedges off New Jersey track sea-level fall. Geology 33, 429-432. [published, refereed]

Nordfjord, S., J. A. Goff, J. A. Austin, Jr., and C. K. Sommerfield, 2005. Seismic geomorphology of buried channel systems on the New Jersey outer shelf: Assessing past environmental conditions. Mar. Geol. 214, 339-364. [published, refereed]

Nordfjord, S., J. A. Goff, J. A. Austin, Jr., and S. P. S. Gulick, Seismic facies analysis of shallowly buried incised valleys, New Jersey continental shelf: understanding late Quaternary paleoenvironments during the last transgression, submitted to J. Sed. Res.

The Geoclutter Program was funded by the Office of Naval Research

, ,

Soufrière Hills Volcano

Soufriere Hill Volcano

The CALIPSO Project at Soufrière Hills Volcano, Montserrat, BWI: Using Integrated Deformation Data to Constrain Magmatic Processes

Glen Mattioli University of Arkansas, Fayetteville

Barry Voight, Derek Elsworth, Dannie Hidayat Pennsylvania State University

Alan Linde, Selwyn Sacks Carnegie Institution of Washington

Peter Malin Eylon Shalev Duke University

Jurgen Nueberg University of Leeds

Steve Sparks University of Bristol

 

The “Caribbean Andesite Lava Island Precision Seismo-geodetic Observatory,” (i.e. CALIPSO) has greatly enhanced the geophysical infrastructure at the Soufrière Hills Volcano (SHV), Montserrat with installation of an integrated array of borehole and surface instrumentation at four sites. Each site has a Sacks-Evertson dilatometer, a three-component seismometer (~Hz to 1 kHz), a Pinnacle Technologies tiltmeter, and an Ashtech u-Z CGPS receiver with choke ring antenna. This sensor package is similar to that being installed at volcanoes in western North America as part of EarthScope.

 

Soufriere Hill Volcano

Figure 1. Aerial photograph to the southwest showing the scar from the 2003 massive dome collapse of SHV and its pyroclastic flow-created delta deposits. Photo by B. Voight.

CALIPSO sensors recorded the collapse of the SHV lava dome on Montserrat in July 2003, the largest such event worldwide in the historical record (Mattioli et al., 2004). Dilatometer data show remarkable and unprecedented rapid (~600s) pressurization of a deep source. Voight et al. (2006) inferred an oblate spheriodal source with average radius ~1 km centered at 5.5 to 6 km depth. An overpressure of ~1 MPa, was attributed to growth of 1-3% of gas bubbles in supersaturated magma, triggered by the dynamics of dome unloading.

Pyroclastic flows entering the sea may cause tsunami generation at coastal volcanoes worldwide, but geophysically monitored field occurrences are very rare. Mattioli et al. (2007) reconstructed the process of tsunami generation and propagation during the prolonged, gigantic collapse of the SHV in 2003 using a combination of strain, seismic, and GPS data from the CALIPSO array.

Soufriere Hill Volcano1

Figure 2. DOSECC’s CS500 drilling rig on-site at Soufrière Hills Volcano.

Mattioli (2005) also reported that periods of surface uplift recorded by GPS at SHV correspond to an inflating, and subsidence, to a deflating Mogi source. Inverted depths are between 6 and 13 km, with the recent observations favoring a deeper source, supporting a temporal evolution of the mid-crustal pre-eruption storage zone from 1995 to 2005. Elsworth et al., 2008 modeled the surface deformation and surface efflux records from 1995 through 2007 assuming a vertically stacked array of two chambers at 6 and 12 km depth. They concluded that despite the episodic nature of the SHV eruption, melt was supplied to the base of the magmatic system at nearly constant rate and that the lower chamber was largely responsible for the surface deformation.

, ,

Englebright Reservior

Englebright Lake Drilling Project 3

Charles N. Alpers and Lorraine E. Flint  U.S. Geological Survey

Noah P. Snyder  Boston College

Englebright Lake Drilling Project 3

Figure 2 – GLAD200 drilling platform on Englebright Lake

During May-June 2002, DOSECC and the U.S. Geological Survey collaborated on research drilling at Englebright Lake, a 70,000 acre-foot reservoir built in 1941 on the Yuba River in the northwestern Sierra Nevada of California. The drilling at Englebright Lake was part of the Upper Yuba River Studies Program, a multi-disciplinary, multi-agency effort with the overall purpose of addressing the following question:

“To determine if the introduction of wild chinook salmon and steelhead to the Upper Yuba River watershed is biologically, environmentally, and socio-economically feasible over the long term.”

Specific to Englebright Lake, the main project goal was to characterize reservoir sediments with regard to grain-size distribution and mercury concentration so that the possible effects of dam removal and sediment release downstream could be assessed. The work was funded by the Resources Agency of the State of California under the California Bay-Delta Program (CALFED) and by the U.S. Geological Survey.

Englebright Lake Drilling Project 1

Figure 1 – Location map and sampling sites

In all, 335 meters of core were collected, primarily using hydraulic piston methods. Average recovery was 86%. Thirty holes were drilled at seven locations – at six of the locations, complete sections through the reservoir bed sediment deposits were achieved. Sediment thickness ranged from 6 m near Englebright Dam to 33 m in the mid-reservoir area. Before splitting, cores were analyzed for magnetic susceptibility, bulk density (neutron log), and gamma radiation. After splitting, digital photographs were taken and archived along with descriptive information.

One set of subsamples were taken immediately for analysis of methylmercury (frozen for preservation), moisture content, and loss on ignition (organic content). After all cores were logged and stratigraphic correlations were determined, a second, more detailed round of subsampling resulting in a vertically continuous section at each location was done, for analysis of grain-size distribution, total mercury, and other trace metals. Selected subsamples were used for geochronology (210Pb and 137Cs).

Results of grain-size distribution and loss on ignition for 561 samples were used to extrapolate from one-dimensional vertical sections of sediment sampled in cores to entire three dimensional volumes of the reservoir deposit. In this manner, the mass of the reservoir sediment deposit was estimated to be 26 x 106 metric tons of material, of which 64.7 to 68.5% was sand and gravel and the remainder was silt and clay.

Total mercury concentrations in unsieved sediment increased with decreasing distance from the dam, following a trend toward finer grained sediment. Average mercury concentrations of samples rich in silt and clay was about 300 nanograms per gram (ng/g, or parts per billion, ppb), whereas average Hg in sand-gravel-rich samples was about 12 ng/g (or ppb).

The successful drilling of complete post-reservoir sediment profiles at Englebright Lake allowed the USGS to make the first quantitative assessment of the total mass of mercury contained within a foothill reservoir in a watershed greatly impacted by historical gold mining. Based on available information, about 2.3×106 kg of mercury were lost to the environment in the Yuba River watershed in association with historical gold mining. The estimated total mass of mercury in Englebright lake sediments (accumulated from 1941 to 2002) is 2,500 to 2,800 kg, which represents about 0.1% of the total amount of Hg estimated to have been lost to the environment during historical gold mining in this watershed.

Results of this project will play a significant role in determining the potential impacts of the removal of Englebright Dam on downstream environments. Also, the core samples from Englebright Lake represent an archive of the history of sediment transport and deposition processes in the Yuba River watershed over more than six decades, and are a potential resource to future researchers investigating watershed transport processes.

References:

Alpers, C.N., Antweiler, R.A., Snyder, N.P., and Curtis, J.A., in review, Mercury transport and deposition in a watershed affected by historical gold mining: the upper Yuba River, California. Journal article for Water Resources Research.

Alpers, C.N., Hunerlach, M.P., Marvin-DiPasquale, M.C., Antweiler, R.C., Lasorsa, B.K., De Wild, J.F., and Snyder, N.P., 2006, Geochemical Data for Mercury, Methylmercury, and Other Constituents in Sediments from Englebright Lake, California, 2002: U.S. Geological Survey Data Series 151, 95 p. http://pubs.water.usgs.gov/ds151/

Snyder, N.P., and Hampton, M.A., 2003, Preliminary cross section of Englebright Lake sediments, U.S. Geological Survey Open-File Report 03-397, 1 plate. http://geopubs.wr.usgs.gov/open-file/of03-397/

Snyder, N.P., Alpers, C.N., Flint, L.E., Curtis, J.A., Hampton, M.A., Haskell, B.J., and Nielson, D.L., 2004a, Report on the May-June 2002 Englebright Lake deep coring campaign:  U.S. Geological Survey Open-File Report 2004-1061, 32 p. plus 10 plates. http://pubs.usgs.gov/of/2004/1061/

Snyder, N.P., Allen, J.R., Dare, C., Hampton, M.A., Schneider, G., Wooley, R.J., Alpers, C.N., and Marvin-DiPasquale, M.C., 2004b, Sediment grain-size and loss-on-ignition analyses from 2002 Englebright Lake coring and sampling campaigns:  U.S. Geological Survey Open-File Report 2004-1080, 46 p. http://pubs.usgs.gov/of/2004/1080/

Snyder, N.P., Rubin, D.M., Alpers, C.N., Childs, J.R., Curtis, J.A., Flint, L.E., and Wright, S.A., 2004c, Estimating rates and properties of sediment accumulation behind a dam: Englebright Lake, Yuba River, northern California, Water Resources Research, v. 40, W11301, doi:10.1029/2004WR003279 http://www2.bc.edu/~snyderno/snyder_etal_2004.pdf

Snyder, N.P., Wright, S.A., Alpers, C.N., Flint, L.E., Holmes, C.W., and Rubin, D.M., 2006, Reconstructing depositional processes and history from reservoir stratigraphy: Englebright Lake, Yuba River, northern California, Journal of Geophysical Research, v. 111, F04003, doi:10.1029/2005JF000451. http://www.agu.org/journals/jf/jf0604/2005JF000451/ http://www2.bc.edu/~snyderno/snyder_etal_2006.pdf

Englebright Lake Drilling Project 2

 

, ,

Lake Titicaca

Lake Titicaca Scientific Core Drilling Project

Lake Titicaca Drilling Project

P.A. Baker Duke University

S.C. Fritz University of Nebraska

G.O. Seltzer Syracuse University

 

Lake Titicaca is a high-elevation (3812 m) lake in the tropical Andes of Bolivia and Peru and was drilled in April/May 2001 using the GLAD 800 drilling platform and coring system (Figure 1). This site is critical for reconstructing the history of the South American summer monsoon system and how long-term variation in effective moisture in the tropical Andes is affected by variation of global-scale glacial boundary conditions, orbitally produced changes in seasonal insolation, and changes in tropical Pacific and/or Atlantic sea-surface temperature. Over 625 m of mud was recovered from paired overlapping holes in three locations. The longest recovered sequence spans 136 m and consists of alternations between two primary lithologic units, indicative of four major glacial stages and the intervening interglacials.

 

Lake Titicaca Drilling

Figure 1 – GLAD800 drilling platform on Lake Titicaca

Generally, the intervals of increased glaciation were periods when Lake Titicaca was deep and fresh and therefore times of high effective moisture and likely high precipitation (based on calcium carbonate concentrations, diatom stratigraphy, and d13C isotopic measurements on bulk organic carbon). A chronology based on radiocarbon, U-series ages on aragonite laminae, and tuning to the Vostok CO2 record suggests that the drilled sequence extends over approximately the last 370,000 years. Extrapolation of the radiocarbon chronology suggests that the most recent period of ice expansion in the cordillera surrounding the lake began approximately 60,000 14C yr BP, following a major dry interval. A series of U-series dates on discrete aragonite layers suggests that the penultimate low stand of Lake Titicaca, rather than dating to the last summer solar minimum (~32,000 yr BP), is coincident with MIS5e, the penultimate interglacial stage (~125,000 yr BP). This suggests that the water balance of the lake is as strongly influenced by global-scale (an tropical) temperature changes and boundary conditions as by precession forcing of the South American summer monsoon.

Lake Titicaca Drilling1

Figure 2 – Drilling log and lithology of Lake Titicaca borehole 2B.

Read more about this scientific core drilling services project at ICDP.

References:

Baker, P.A. and S.C. Fritz. High-resolution records and mechanisms of climate variability in tropical South America…and beyond. IODP-ICDP Workshop: Acquiring high to ultra-high resolution geological records of past climate change by scientific drilling, October 2008, Potsdam, Germany.

Baker, P.A., S.C. Fritz, C.A. Rigsby, S.A Burns, K.Coley, E. Ekdahl. “Millennial Climate Variability in Tropical South America”. American Geophysical Union, San Francisco, December 2005.

Baker, P.A., S.C. Fritz, G.O. Seltzer, & C. Rigsby. Tropical climate dynamics in the South American Altiplano. AGU Annual Meeting, San Francisco, December 2003.

Baker, P.A., S.C. Fritz, G.O. Seltzer, C. Rigsby, S. Cross, M. Grove, A. Ballantyne. “Climates of tropical South America: past, present, and future” European Geophysical Union, Vienna, April 2007.

Baker, P.A., S.C. Fritz, G.O. Seltzer, K. Arnold, & P. Tapia. Geochemical and diatom records of hydrologic variability in the tropical Andes during the late Quaternary from drill cores of Lake Titicaca. AGU, San Francisco, December 2002. EOS Trans. 83: F896.

Baker, PA, S C Fritz, G O Seltzer, A P Ballantyne, C A Rigsby. The Terrestrial Paleoclimatic Record of the Late Quaternary as Revealed by Drilling Lake Titicaca, Peru/Bolivia. American Geophysical Union, San Francisco, December 2004

Ekdahl, E J, S C Fritz, L R Stevens, P A Baker, G O Seltzer. A High-Resolution Biogenic Silica Record From Lake Titicaca, Peru-Bolivia: South American Millennial-Scale Climate Variability From 18-60 Kya. American Geophysical Union, San Francisco, December 2004.

Ekdahl, E., Fritz, S.C., Baker, P.A., Burns, S.A., Coley, K., Rigsby, C.A. “Multi-Decadal to Millennial Scale Holocene Hydrologic Variation in the Southern Hemisphere Tropics of South America”. American Geophysical Union, San Francisco, December 2005.

Fritz, S.C., P.A. Baker, E. Ekdahl, S. Burns, “Holocene multi-decadal to millennial-scale hydrologic variability on the South American Altiplano”, American Geophysical Union, San Francisco, December 2006.

Fritz, S.C., P.A. Baker, G.O. Seltzer, A. Ballantyne, P. Tapia, H. Cheng, R.L. Edwards. 2007. Quaternary glaciation and hydrologic variation in the South American tropics as reconstructed from the Lake Titicaca drilling project. Quaternary Research 68: 410-420.

Fritz, S.C., P.A. Baker, G.O. Seltzer, E. Ekdahl, “Glaciation and hydrologic variation in the South American tropics during the last 400,000 yr”. American Geophysical Union, San Francisco, December 2005.

Fritz, S.C., P.A.Baker, G.O. Seltzer. “Late Quaternary hydrologic variability in the southern tropical Andes and its relationship to the adjoining Amazon Basin and major climate drivers”, International Quaternary Association Congress, Cairns, Australia, August 2007.

Fritz, S.C., T. Johnson, P.A. Baker, S. Colman, W. Dean, J. Peck. 2006. Large-lake drilling projects supported by the US National Science Foundation Earth Systems History Program. PAGES News 14: 19-20.

Seltzer, G.O., P.A. Baker, S.C. Fritz, D. Rodbell, & B. Valero. The record of tropical glaciation from drill cores from Lake Titicaca, Bolivia/Peru. Geological Society of America, Seattle, November 2003.

Seltzer, G.O., P.A. Baker, S.C.Fritz, K. Arnold, A. Ballantine, P. Tapia, & C. Veliz. A long record of tropical glaciation and climate change in drill cores from Lake Titicaca. AGU, San Francisco, December 2001. EOS Trans. 82: F757.

Seltzer, G.O., S.C. Fritz, P.A. Baker. A >100 kyr record of glaciation from the southern tropical Andes. AGU San Francisco, December 2002. EOS Trans. 83: F896.

Partial listing of presentations:

Fritz, S.C. – Invited University presentations:

2008: Braunschweig University (Geology)

2007: Kansas State University (Geology), University of Adelaide, Australia (Geography), University of Edinburgh (Geosciences), CEREGE, Aix-en-Provence, France

2006: Queens University, Kingston, ON (Biological Sciences), University (Environmental Sciences), Louisiana State University (Geology)

2005: Lehigh University (Earth & Environmental Sciences), Iowa State University (Earth & Atmospheric Sciences)

University of Iowa (Geology), Geological Survey of Denmark and Greenland

Data are archived at http://www.ncdc.noaa.gov/paleo/data.html

, ,

Chicxulub Impact Structure 2001

Chixculub scientific core drilling project

Toward a Sequence Stratigraphy of the Chicxulub Impact Basin Infill

Michael T. Whalen and Zulmacristina F. Pearson  University of Alaska Fairbanks

Sean P. Gulick University of Texas at Austin

 

Co-PIs Michael Whalen and Sean Gulick were funded in 2005 under a pre-drilling activity proposal to conduct stratigraphic analysis of the Yaxcopoil-1 (Yax-1) core and investigate the relationship of the core to offshore 2D seismic data to provide insight into the Tertiary infilling history of the Chicxulub impact basin. High-resolution logging of approximately 400 m of Tertiary carbonate-dominated sedimentary rocks in Yax-1 (Dressler et al., 2003) provides details of the lithostratigraphy and biostratigraphy and permits a preliminary sequence stratigraphic analysis of the post-impact succession in the basin. Approximately 290 samples were collected for petrographic, x-ray diffraction and biostratigraphic analyses. Analysis of offshore 2D seismic data provides a broader view of the process of Tertiary basin infilling and the history of Yucatàn carbonate platform development.

Chicxulub Impact Basin

Figure 1. Interpreted seismic line from the northeast portion of the crater illustrating the position of the K/T boundary and six overlying seismic units. Note the two sets of prograding clinoforms in seismic Unit C. Inset is a photograph from sequence 3, ~640 m Yax-1 core, illustrating graded turbidites that may be similar to the deposits making up toes of prograding clinoforms in seismic Unit C. Modified from Pearson et al. (2006).

 

Ten lithofacies were categorized into two broad groups: redeposited and background facies that occur in 5 lithostratigraphic units. Redeposited facies include carbonate supportstones of a wide array of grain sizes and finer-grained facies with evidence of soft sediment deformation, all of which were deposited by a variety of gravity flow mechanisms. Background facies include fine-grained argillaceous and clean limestones that were deposited mainly from suspension, below storm wave base, at depths ranging from bathyal to neritic. Depositional environments range from a deep-water, steep slope inside the Chicxulub crater rim to outer carbonate ramp neritic environments that were established once the Yucatàn platform had prograded seaward.

Five depositional sequences were identified based on transgressive and maximum flooding surfaces and facies stacking patterns. Biostratigraphic data remains equivocal but indicate that the first 3 sequences range from Early Paleocene to Early Eocene in age. The base of sequences 1 through 4 contain coarse-grained redeposited carbonates interpreted as lowstand gravity-flow deposits, while the highstand of sequence 3 records the first evidence of relatively fine-grained turbidite deposits that we interpret as the initial record of Yucatàn platform progradation into the Chicxulub basin (Fig. 1). Sequences 4 and 5 consist mainly of background and fine-grained redeposited facies but by the top of sequence 4 indicate that the Yucatàn platform slope and outer ramp had prograded over the position of the Yax-1 core. The upper portion of sequence 3 and lower sequence 4 appear to straddle the Paleocene-Eocene boundary. A series of soft sediment deformed units in sequence 3 may have been deposited in response to events associated with the Paleocene-Eocene thermal maximum; however, better biostratigraphic control will be necessary to test this hypothesis.

Six seismic units were identified, the lower 5 of which appear to roughly correlate with the 5 sequences in the Yax-1 core (Fig. 1). The geometry and distribution of seismic units A and B are strongly controlled by the morphology of the crater. Unit C, with two sets of clinoforms, records a major progradational event in the eastern portion of the basin that may to be related to turbidite deposition in sequence 3 in Yax-1 (Fig. 1). The timing of significant platform progradation into the basin near Yax-1; however, appears to be during sequence 4, i.e. later than in the eastern part of the basin. Seismic units D and E display parallel reflectors indicating relatively level bottom conditions similar to the depositional environments indicated by lithofacies in upper sequence 4 and sequence 5. By the time of deposition of unit E, the western and central parts of the basin were mostly infilled. The top of units E and D, at the edges of the inner crater, is an erosional truncation surface that marks the base of unit F. Unit F, overlies an erosional truncation that cuts into units D and E, and is characterized by discontinuous reflectors that are restricted to the northeastern portion of the basin, the last part of the basin to be infilled during the Tertiary (Pearson et al., 2006; Whalen et al., 2007; Gulick et al., 2008).

Chicxulub Impact Basin1

Figure 2. DOSECC’s Hybrid Coring System installed on a rotary rig, drilling the Yax-1 core.

 

Chicxulub is the largest well-preserved impact structure on Earth. Analysis of the Yax-1 core and comparison with patterns of deposition revealed with 2D seismic data provide us with information about the post-impact history of Chicxulub and the history of infilling the impact basin. If Chicxulub is representative, large marine impacts in tectonically quiescent regions may dominate local depositional environments for millions to tens of millions of years post-impact before returning control to eustasy. Successions within impact basins will likely record shoaling and slope readjustment as the instantaneously created basin is filled on geologic timescales. Our understanding of the processes and consequences of large-scale impacts have been enhanced through study of the Chicxulub impact structure and sediment infill. The relatively rapid, post-impact recovery of the Yucatàn carbonate platform demonstrates the resiliency of the carbonate-producing systems to even the most catastrophic, mass-extinction inducing events.

 

 

 

 

Read more on this scientific core drilling services project at ICDP.

References

Dressler, B.O., Sharpton, V.L. Morgan, J.V., Buffler, R., Moran, D., Smit, J., Stöffler, D., and Urrutia, J., 2003, Investigating a 65-Ma-Old Smoking Gun: Deep Drilling of the Chicxulub Impact Structure. EOS, Transactions, American Geophysical Union v. 84, no. 14, p. 125-130.

Gulick, S. P. S., P. J. Barton, G. L. Christeson, J. V. Morgan, M. McDonald, K. Mendoza-Cervantes, Z. F. Pearson, A. Surendra, J. Urrutia-Fucugauchi, P. M. Vermeesch, and M. R. Warner (2008), Importance of pre-impact crustal structure for the asymmetry of the Chicxulub impact crater, Nature Geoscience, v. 1, p. 131-135.

Pearson, Z.F., Whalen, M.T., Gulick, S.P., and Norris, R., 2006, Annealing The Chicxulub Impact: Tertiary Yucatan Carbonate Platform Development and Basin Infilling, Geological Society of America Abstracts with Programs, v. 38, p. 297.

Whalen, M.T., Pearson, Z.F., and Gulick, S.S.P., 2007, Toward a Sequence Stratigraphy of the Chicxulub Impact Basin Infill: Integration of Lithostratigraphy, Biostratigraphy, and Seismic Stratigraphy: Final Report of Pre-drilling Activity Proposal to the Joint Oceanographic Institutions, 27 p.