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Great Salt Lake Scientific Drilling

Bonneville Basin scientific drilling

Ecosystem and Paleohydrological Response to Quaternary Climate Change in the Bonneville Basin, Utah

Scientific Drilling Project by DOSECC Core Drilling Services

Deborah P. Balch, Andrew S. Cohen and J. Warren Beck University of Arizona

Douglas W. Schnurrenberger University of Minnesota (currently at DOSECC)

Brian J. Haskell, Hai Cheng and R. Lawrence Edwards University of Minnesota

Blas L. Valero Garces Pyrenean Institute of Ecology

We report the results of a detailed paleoecological study of the Bonneville basin covering the last ~280,000 yr. Our study used fossil ostracodes and a sedimentological record obtained from the August 2000 GLAD800 drilling operation at Great Salt Lake. We analyzed 125 samples, taken at ~1 m intervals from Site 4 (GSL00-4), for ostracodes and other paleoecologic and sedimentologic indicators of environmental change. Multivariate analyses applied to the ostracode data and qualitative analyses of fossil and sedimentological data indicate an alternation between three major environments at the core site over the cored interval: (1) shallow saline or hypersaline lakes; (2) salt or freshwater marshes; and (3) occasional deep freshwater lakes. These environmental changes are consistent with shoreline studies of regional lake level fluctuations, but provide considerable new detail on both the timing and environmental conditions associated with the various lake phases. Our age model (using 14C, U-Series, tephra and biostratigraphic chronologies) allowed us to associate the core’s record of regional paleohydrology with the marine oxygen isotope stages of global climate change. The core contains continuous records for the last four glacial/interglacial sequences. Salt/freshwater marshes were common during the interglacials and deep freshwater conditions correspond with maximum global ice volume in OIS 2, and before a maximum in global ice during OIS 6. Immediately following deep lake phases, crashes in lake level from rapid desiccation resulted in the deposition of thick evaporite units. Our study suggests that the climate of the Great Salt Lake catchment appears to have been drier during OIS 6 than during OIS 2.We compare our record of environmental change during OIS 6 glaciation with other records from western United States and find that the overall pattern of climate was similar throughout the West, but differences in the timing of climate change (i.e. when a region became drier or moister) are common.

Bonneville Basin Drilling

Figure 1 – GLAD800 drilling barge on the Great Salt Lake

In the late 1990s, the International Continental Drilling Program (ICDP) provided funds for DOSECC (the US nonprofit research consortium for continental scientific drilling) to develop a dedicated lake drilling system, designated the GLAD800 system. The intent of this grant was to jump start scientific drilling in lakes around the world with an inexpensive and modular system that would be easily transported between sites, and would be broadly accessible to the scientific community. This system, including a barge platform, drill rig and coring tool kit, was first tested with NSF support at the Great Salt Lake and Bear Lake in August 2000. The mandate from NSF was that all engineering tests of the GLAD-800 system be coupled to significant scientific questions, so that the testing would also yield scientific benefits. The long history of scientific (and specifically paleoclimate) research on the Great Salt Lake, coupled with DOSECC’s location in Salt Lake City, made the Great Salt Lake and Bear Lake natural targets for this testing.

Bonneville Basin Drilling1

Figure 2 – Drilling locations

The drilling campaign collected four long cores from the Great Salt Lake and obtained a total of 371 m of sediment with 96% recovery. One site in particular, GSL00-4 (also known as Site 4), reached 121 m below lake floor (mblf) and provides the longest continuous record of the lake’s history ever collected from a drilling operation. Drilling took place in the hanging wall of the Carrington Fault, which is located along the southeast margin of the lake’s northern basin (Fig. 1). The primary objective for drilling at this site was to obtain a detailed basinal history extending back to Oxygen Isotope Stage (OIS) 6 and to use its paleontological and sedimentological contents to address questions related to paleoclimate. A preliminary study of the core, based on core catcher samples taken every 3 m (ca. 6000 yr resolution), suggested that Site 4 contains a high- resolution paleoecological record extending back ~250,000 yr BP based on tephra correlation and preliminary U-series dating (Dean et al., 2002). Paleoecological analyses of its ostracode assemblages, in particular, have shown that the lake levels have fluctuated over time giving rise to both marsh conditions and saline, open water conditions at the core site (Kowalewska and Cohen, 1998; Dean et al., 2002). Up to this point, we did not have detailed knowledge about these environmental fluctuations because the previous studies were at too low of a resolution. The goal of this current study was to explain these patterns in greater detail by accomplishing the following: (i) increase sampling frequency to improve resolution; (ii) resolve the chronological sequence of paleoecological and paleolimnological change through the acquisition of a reliable age model; and (iii) determine if these changes are correlated with changes in regional or global climate change, particularly at the glacial/interglacial time scale.

Bonneville Basin Drilling2

Figure 1 – Site 4 composite density and susceptibility graph

 

Site 4 contains a highly continuous paleoecological archive of Quaternary environmental and climate change. Our intermediate resolution sampling (~2,000 yr) is too coarse to capture the finer environmental fluctuations preserved in the core, however this study is a first step in unlocking the rich paleoenvironmental story of the Bonneville basin preserved at Site 4. Its paleoecological and sedimentological indicators show that the core site has fluctuated over time mostly between marsh and saline to hypersaline open-water conditions, but has, on occasion, been submerged in deep, freshwater. These local environmental changes can be understood in terms of oscillating lake levels. Our study confirms that climate forcing has played a major role in these lake level fluctuations and some, though not all, of the climatic fluctuations can be associated with changes in global ice volume. Overall, we see low to very low lake levels during the interglacial cycles (OIS 7, 5, 3 and 1). The lowest lake levels coincide with the presence of marsh indicators in the core’s sedimentary and paleoecological record. Saline/hypersaline conditions at the core site indicate regional lake levels higher than during marsh phases, but significantly lower than open freshwater conditions, such as the Little Valley cycle (mid OIS 6) and the Lake Bonneville cycle (late OIS 2). However, the climate of the Great Salt Lake catchment appears to have been drier during OIS 6 than during OIS 2. Thus, the high-resolution records and climate models from the last glacial advance may not serve as a good analog for the older glacial cycles. Many smaller lake level oscillations are recorded in Site 4, and with higher resolution sampling and a more robust age model, we may find that these smaller oscillations are sensitive to climate changes on millennial or shorter time scales. Oviatt (1997) found that some of the lake fluctuations associated with Lake Bonneville coincided with millennial scale Heinrich events. The sediments contained in Site 4 provide a detailed natural archive of (1) local environmental and ecological change at the core site (2) fluctuations in regional paleohydrology and (3) climate change over the last four glacial/interglacial sequences. This long, continuous record provides important insights into the paleoecology, paleohydrology and paleoclimate of the northeastern Great Basin, and will allow us the unique opportunity to link these insights into an interdisciplinary framework of past global change.

View the proposal for this scientific drilling project at ICDP.

Representative References:

Antevs, E., 1948. Climatic changes and pre-white man. The Great Basin, with Emphasis on Glacial and Postglacial Times, Bulletin of the University of Utah, vol. 38, pp. 167– 191.

Beck, W.J., Richards, D.A., Edwards, R.J., Silverman, B.W., Smart, P.L., Donahue, D.J., Hererra-Osterheld, S.H., Burr, G.S., Calsoyas, L., Jull, A.J.T., Biddulph, D., 2001. Extremely large variations of atmospheric 14C concentration during the last glacial period. Science, 292, 2453– 2458.

Cheng, Hai, Edwards, R. Lawrence, And Dettman, David L., 2005. A ~280ka Paleoecologic and Paleoclimatic Record for the Bonneville Basin derived from the GLAD800 Drilling Campaign at Great Salt Lake, Utah: oral presentation given at GSA Annual Meeting, Salt Lake City, UT

Cohen, A.S., Palacios_Fest, M.R., Negrini, R.M., Wigand, P.E., Erbes, D.B., 2000. A paleoclimate record for the past 250,000 years from Summer Lake, Orgeon, USA: II. Sedimentology, paleontology and geochemistry. J. Paleolimnol., 24, 151– 182.

Cohen, Andrew S., Balch, Deborah P., Helfrich, L. Cody Schnurrenberger, Douglas W., Haskell, Brian J., Valero-Garcés, Blas L., Beck, J. Warren, COHMAP, 1988. Climate changes in the last 18,000 years: observations and simulations. Science, 241, 1043– 1052.

Currey, D.R., 1990. Quaternary palaeolakes in the evolution of semidesert basins, with Special emphasis on Lake Bonneville and the Great Basin, USA. Palaeogeogr. Palaeoclimatol. Palaeoecol.,76, 189–214.

Currey, D.R., Oviatt, C.G., 1985. Durations, average rates, and probable causes of Lake Bonneville expansions, still-stands, and contractions during the last deep-lake cycle, 32,000 to 10,000 years ago. In: Kay, P.A., Diaz, H.F. (Eds.), Problems of and Prospects for Predicting Great Salt Lake Level. Cent. Publ. Affairs Admin. Univ. Utah, pp. 9 –24.

Davis, O.K., 1998. Palynological evidence for vegetation cycles in a 1.5 million year pollen record from the Great Salt Lake, Utah, USA. Palaeogeogr. Palaeoclimatol. Palaeoecol., 138, 175–185.

Davis, O.K., Moutoux, T.E., 1998. Tertiary and Quaternary vegetation history of the Great Salt Lake. J. Paleolimnol., 19, 417–427.

Dean, W., Rosenbaum, J., Haskell, B., Kelts, K., Schnurrenberger, D., Valero-Garces, Blas, Cohen, A., Davis, O., Dinter, D., Nielson, D., 2002. Progress in global lake drilling holds potential for global change research. Trans.-Am. Geophys. Union, 83 (85), 90– 91.

Hostetler, S.W., Giorgi, F., Bates, G.T., Bartlein, P.J., 1994. Lake–atmosphere feedbacks associated with paleolakes Bonneville and Lahontan. Science, 263, 665– 668.

Kaufman, D.S., Forman, S.L., Bright, J., 2001. Age of the Cutler Dam Alloformation (late Pleistocene), Bonneville basin, Utah. Quat. Res., 56, 322– 334.

Kowalewska, A., Cohen, A.S., 1998. Reconstruction of paleoenvironments of the Great Salt Lake Basin during the late Cenozoic. J. Paleolimnol., 20, 381– 407.

Kutzbach, J.E., Guetter, P.J., Behling, P.J., Selin, R., 1994. Simulated climatic changes: results of the COHMAP climate model experiments. In: Wright Jr., H.E., Kutzbach, J.E., Webb, T.I., Ruddiman, W.T., Street-Perrott, F.A., Bartlein, P.J. (Eds.), Global Climates Since the Last Glacial Maximum. University of Minnesota, Minneapolis, pp. 24– 93.

Oviatt, Charles G., And Thompson, Robert S., 2005. Late Quaternary History of Great Salt Lake and Lake Bonneville from Sediment Cores: oral presentation given at GSA Annual Meeting, Salt Lake City, UT

Oviatt, C.G., 1997. Lake Bonneville fluctuations and global climate change. Geology, 25, 155– 158.

Oviatt, C.G., 2002. Bonneville basin lacustrine history: thecontributions of G.K. Gilbert and Ernst Antevs. In: Hershler, R., Madsen, D.B., Currey, D.R. (Eds.), Great Basin Aquatic Systems History. Smithsonian Contributions to the Earth Sciences, vol. 33. Smithsonian Institution Press, Washington, DC, pp. 121–129.

Oviatt, C.G., McCoy, W.D., Reider, R.G., 1987. Evidence for a shallow Early or Middle Wisconsin-age lake in the Bonneville basin, Utah. Quat. Res., 2, 248–262.

Oviatt, C.G., Currey, D.R., Miller, D.M., 1990. Age and paleoclimatic significance of the Stansbury shoreline of Lake Bonneville, northeastern Great Basin. Quat. Res., 33, 291–305.

Oviatt, C.G., Currey, D.R., Sack, D., 1992. Radiocarbon chronology of Lake Bonneville, Eastern Great Basin, USA. Palaeogeogr. Palaeoclimatol. Palaeoecol., 99, 225–241.

Oviatt, C.G., Thompson, R.S., Kaufman, D.S., Bright, J., Forester, R.M., 1999. Reinterpretation of the Burmester Core, Bonneville Basin, Utah. Quat. Res., 52, 180– 184.

Palacios, M., Cohen, A., Haskell, B., Valero-Garces, B., Schnurrenberger, D., Heil, C., Dean, W., Davis, O., Kruger, N., Dinter, D., 2001. GLAD 1, GSL Site 4. In: Schnurrenberger, D., Haskell, B. (Eds), Initial Reports of Global Lakes Drilling Program Volume 1. Glad 1: Great Salt Lake, Utah and Bear

Lake, Utah, Idaho. Limnological Research Center CDROM, University of Minnesota, Minneapolis, Minnesota, pp. 37–46; 271–315.

Schnurrenberger, D., Russell, J., Kelts, K., 2003. Classification of lacustrine sediments based on sedimentary components. J. Paleolimnol., 29, 141–154.

Scott, W.E., McCoy, W.D., Shroba, R.R., Rubin, M., 1983. Reinterpretation of the exposed record of the last two cycles of Lake Bonneville, western United States. Quat. Res., 20, 261– 285.

Spencer, R.J., Baedecker, M.J., Eugster, H.P., Forester, R.M., Goldhaber, M.B., Jones, B.F., Kelts, K., Mckenzie, J., Madsen, D.B., Rettig, S.L., Rubin, M., Bowser, C.J., 1984. Great Salt Lake, and precursors, Utah: the last 30,000 years. Contrib. Mineral. Petrol., 86, 321– 334.

Thompson, R.S., Toolin, L.J., Forester, R.M., Spencer, R.J., 1990. Accelerator-mass spectrometer (AMS) radiocarbon dating of Pleistocene lake sediments in the Great Basin. Palaeogeogr. Palaeoclimatol. Palaeoecol., 78, 301– 313.

Thompson, R.S., Whitlock, C., Bartlein, P.J., Harrison, S.P., Spaulding, W.G., 1993. Climatic changes in the western United States since 18,000 yr B.P. In: Wright Jr., H.E., Kutzbach, J.E., Webb, T.I., Ruddiman, W.T., Street-Perrott, F.A., Bartlein, P.J. (Eds.), Global Climates Since the Last Glacial Maximum. University of Minnesota, Minneapolis, pp. 468–513.

Whitlock, C., Sarna-Wojcicki, A.M., Bartlein, P.J., Nickmann, R.J., 2000. Environmental history and tephrostratigraphy at Carp Lake, southwestern Columbia basin, Washington, USA. Palaeogeogr. Palaeoclimatol. Palaeoecol., 155, 7 –29.

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Bear Lake Scientific Drilling Project

Bear Lake Drilling scientific drilling

Paleoenvironments of Bear Lake, Utah and Idaho

Scientific Drilling Project by DOSECC Core Drilling Services

Joseph G. Rosenbaum, Walter E. Dean, and Marith C. Reheis USGS, Denver, CO

Jordon Bright, Darrell S. Kaufman, R. Scott Anderson, and Gonzalo Jiménez-Moreno Northern Arizona University

Steven M. Colman Large Lakes Observatory, University of Minnesota, Duluth

Clifford W. Heil, Jr. University of Rhode Island

Joseph P. Smoot USGS, Reston, VA

Lisa A. Doner Plymouth State University

Katrina Moser University of Western Ontario 

Bear Lake is located 100 km northeast of Salt Lake City and lies along the course of the Bear River, the largest river in the Great Basin. The lake, which is one of the oldest extant lakes in North America, occupies a tectonically active half-graben and contains hundreds of meters of Quaternary sediment. In 1996 a group led by the late Kerry Kelts (University of Minnesota) and Robert Thompson (U.S. Geological Survey) acquired three Kullenburg piston cores (4 to 5 m long) from Bear Lake. The coring arose from their recognition of Bear Lake as a potential repository of long records of paleoenvironmental change. They recognized that the lake is located in an area that is sensitive to changes in regional climate patterns, that the lake basin is long lived, and that, unlike many lakes in the Great Basin, Bear Lake was never dry during warm dry periods.

Bear Lake Drilling

Figure 1 – Comparison of carbonate-mineral content in the 120-m section of Bear Lake sediments penetrated by GLAD800 coring and oxygen isotope values (δ18O) based on SPECMAP. Weight % CaCO3 is based on total inorganic carbon and the proportion of calcite and aragonite is based on X-ray diffraction peak heights. δ18O values are in standard deviation units.

Paleoenvironmental studies of the Bear Lake sediment were conducted under the Western Lake/Catchment Systems Project of the USGS (funded by the USGS Earth Surface Dynamics Program). Initially, paleoenvironmental studies of Bear Lake focused on the three Kullenburg cores, which spanned the last ~30,000 years. Additional coring was conducted to elucidate the spatial distribution of sedimentary units. The study was also expanded to include extensive study of the catchment, including the properties of catchment materials and the processes that could potentially affect the delivery of catchment materials to the lake.

During 2000, DOSECC needed to test the newly developed GLAD800 drilling platform on suitable sites in the vicinity of Salt Lake City prior to shipping the platform to remote locations. Following initial testing in the shallow waters of Great Salt Lake, the GLAD800 platform was transported to Bear Lake where it was tested in deeper water (>50 m). The cost of drilling on Bear Lake was split equally between the USGS and NSF. Coring was extremely successful with nearly 100% recovery. Two cores, acquired near the lake’s depocenter (100 m and 120 m in length), extend the Bear Lake record over three glacial/interglacial cycles (about a quarter-million years).

Responses of the lake and catchment to climate change include intermittent disconnection from the Bear River, alternation between siliciclastic sedimentation (including glacial flour) and endogenic carbonate sedimentation (with aragonite forming during the driest intervals), and changes in stable isotopes, diatoms, and pollen. Although the lake underwent major changes in lake level, it did not dry out or become highly saline over the last several hundred thousand years. As a consequence of its relatively stable hydrology, the lake developed endemic populations of fish and ostracodes. Many of the results of this study are presented in Geological Society of America Special Paper 450, “Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment”.

Bear Lake Drilling1

Figure 2 – Bear Lake, Utah

References (*indicates that report contains information from GLAD800 core)

*Initial Reports of the Global Lake Drilling Program, Volume 1: GLAD1: Great Salt Lake, Utah, and Bear Lake, Utah/Idaho – Edited by D. Schnurrenberger and B. Haskell. (NOTE: This is a CD put out by the Limnological Research Center, University of Minnesota.)

*Dean, W.E, Rosenbaum, J.G, Haskell, B., Kelts, K., Schnurrenberger, D.,Valero-Garcés, B., Cohen, A., Davis, O., Dinter, D., and Nielson, D., 2002, Progress in Global Lake Drilling holds potential for Global Change research, EOS (Trans. American Geophysical Union), v. 83, p. 85, 90, 91.

*Colman, S.M., 2006, Acoustic stratigraphy of Bear Lake, Utah-Idaho—Late Quaternary sedimentation in a simple half-graben: Sedimentary Geology, v. 185, p. 113–125.

*Bright, J., Kaufman, D.S., Forester, R.M., and Dean, W.E., 2006, A continuous 250,000 yr record of oxygen and carbon isotopes in ostracode and bulk-sediment carbonate from Bear Lake, Utah-Idaho: Quaternary Science Reviews, v. 25, no. 17-18, p. 2258–2270.

*Colman, S.M, Kaufman, D.S., Bright, J., Heil, C., King, J.W., Dean, W.E., Rosenbaum, J.G., R.M. Forester, R.M., Bischoff, J.L., Perkins, M., McGeehin, J.P., 2006, Age model for a continuous, ca 250-kyr Quaternary lacustrine record from Bear Lake, Utah-Idaho, USA: Quaternary Science Reviews.

*Jiménez-Moreno, G., Anderson, R.S., and Fawcett, P.J., 2007, Orbital- and millennial-scale vegetation and climate changes of the past 225 ka from Bear Lake, Utah-Idaho (USA): Quaternary Science Reviews, v. 26, p. 1713–1724.

*Rosenbaum, J.G. and Kaufman, D.S., 2009, Introduction to Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment, in Rosenbaum, J.G., and Kaufman, D.S., eds., Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment: Geological Society of America Special Paper 450, pp. v – xiii.

*Dean, W.E.,, 2009, Endogenic carbonate sedimentation in Bear Lake, Utah and Idaho, over the last two glacial-interglacial cycles, in Rosenbaum, J.G., and Kaufman, D.S., eds., Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment: Geological Society of America Special Paper 450, pp. 169 – 196.

*Rosenbaum, J.G., and Heil Jr, C.W., 2009, The glacial/deglacial history of sedimentation in Bear Lake, Utah and Idaho, in Rosenbaum, J.G., and Kaufman, D.S., eds., Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment: Geological Society of America Special Paper 450, pp. 247 – 262.

*Heil Jr., C.W., King, J.W., Rosenbaum, J.G., Reynolds, R.L., and Steven M. Colman, S.M., 2009, Paleomagnetism and environmental magnetism of GLAD800 sediment cores from Bear Lake, Utah and Idaho, in Rosenbaum, J.G., and Kaufman, D.S., eds., Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment: Geological Society of America Special Paper 450, pp. 291 – 310.

*Kaufman, D.S., Bright, J., Dean, W.E., Rosenbaum, J.G., Moser, K., Anderson, R.S., Colman, S.M., Heil Jr., C.W., Gonzalo Jiménez-Moreno, G., Reheis, M.C., and Simmons, K.R., 2009, A quarter-million years of paleoenvironmental change at Bear Lake, Utah and Idaho, in Rosenbaum, J.G., and Kaufman, D.S., eds., Paleoenvironments of Bear Lake, Utah and Idaho, and its catchment: Geological Society of America Special Paper 450, pp. 311 – 351.

Abstracts:

*Rosenbaum, J., Dean, W., Honke, J., Skipp, G., Haskell, B., Schnurrenberger, D., Kelts, K., Palacios-Fest, M., Nielson, D., 2000, GLAD800 Drilling in Bear Lake, Utah/Idaho, Eos, v. 81, p. F709.

*Rosenbaum, J.G., Dean, W.E., Bright, J., Colman, S.M., Bischoff, J.L., Anderson, S.R., Forester, R.M., Kaufman, D.S., 2001, Climate record in a 240 kyr sediment core from Bear Lake, Utah/Idaho, Eos, v. 82, F756.

*Heil, C.W., King, J.W., Rosenbaum, J.G., 2001, Paleomagnetic chronology and mineral magnetic proxies of lake level for Bear Lake, Utah/Idaho, Eos, v. 82, F336-337.

*Dean, W.E., Bischoff, J.L., Forester, R.M., Rosenbaum, J.G., Simmons, K.R., and Skipp, G.L., Glacial-interglacial contrasts in carbonate sedimentation in Bear Lake Utah/Idaho – downstream recorder of Pacific climate, 2002, Geological Society of America Annual Meeting, Abstracts with Programs, p. 292.

*Dean, W.E., and Rosenbaum, J.G., 2003, GLAD800 coring on Bear Lake, Utah/Idaho, Third Annual Limnogeology Congress Abstract Volume, p. 71.

Rosenbaum, J.G., Dean, W.E., and S M Colman 2003, The glacial to Holocene transition in sediments from Bear Lake, Utah/Idaho, XVI INQUA Congress Programs with Abstracts, p. 163.

*Colman, S.M., Kaufman, D.S., Bright, J., Heil, C., King, J.W., Dean, W.E., Rosenbaum, J.G., Forester, R.M., Bischoff, J.L., Perkins, M., McGeehin, J.P., 2004, Age Model for a continuous 250-kyr Quaternary lacustrine record from Bear Lake, Utah-Idaho, Eos v. 85, abstract PP33B-0929.

*Kaufman, D.S., Anderson, R.S., Bright, J., Colman, S. M., Dean, W.E., Forester, R.M., Heil, C. W., Moser, K., Rosenbaum, J.G., and Simmons, K.R., 2005, Multi-proxy evidence for environmental change during the last two glacial-interglacial cycles from core BL00-1, Bear Lake, Utah-Idaho, Geological Society of America Abstracts with Programs, Vol. 37, No. 7, p. 336.

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Long Valley Exploratory Well

LONG VALLEY DEEP DRILLING scientific drilling project

Scientific Drilling Project by DOSECC Core Drilling Services

The Long Valley Exploratory Well (LVEW) is situated on the resurgent dome of Long Valley Caldera, at the boundary of the Sierra Nevada and the Basin and Range Province in eastern California (Figure 1). Long Valley Caldera was created by a catastrophic, voluminous eruption of high-silica rhyolite, approximately 760,000 years ago. Since that time, minor volcanic activity in the area has recurred every few hundred years and major volcanic episodes associated with the caldera magma system occur at a frequency of about every 200,000 years (Bailey, 1989). LVEW was drilled to assess the potential of a deep geothermal resource beneath the resurgent dome, help improve assessments of volcanic risk from major or minor volcanic eruptions emanating from the central caldera, and provide a “hole of opportunity” for testing drilling instruments and technology (Figure 2).

LVEW began in 1989 as an engineering and scientific research well for the U. S. Department of Energy’s Magma Energy Program. Original plans called for drilling to a total depth of 18,000 feet to be accomplished in four phases. Phase I was completed in 1989 to a depth of 2650 feet. In 1991, Phase II deepened the hole to 7200 feet, with emphasis on exploring the geothermal energy potential of a deep magmatic source. Data from Phase II suggested that downhole temperatures, which reached 100¡C at the bottom of the well, were too cool for geothermal development (Sass and others, 1991), although, mineralogical evidence suggested that, in the past, the temperatures had been as high as 350¡C for the same depth (McConnell and others, 1997).

LONG VALLEY DEEP DRILLING 2

Figure 1 – Long Valley location map.

The Long Valley Coring Project (LVCP), operated during July through September 1998, was the third phase of drilling at LVEW. This phase deepened the existing hole from 7180 feet to a final depth of 9831 feet (2188 to 2996 meters) during the summer of 1998. Unlike the previous two phases of drilling in which core was recovered only at specific intervals, LVCP recovered continuous core throughout the entire section. LVCP was initiated to obtain additional information on magmatic processes both past and present in the caldera. It was envisioned that by deepening the preexisting borehole it would be possible to gain information about the presence of small magmatic intrusions, the brittle-ductile transition above the inferred magma body, the nature of the temperature gradient, and perhaps the presence of a magma chamber or neogranite. In addition, drilling was expected to provide more details about geothermal energy potential, volcanic hazards and the stratigraphy of Long Valley Caldera, as well as to field-test a newly developed hybrid drilling unit (Sass and others, 1998). To achieve these goals, LVCP was slated to deepen the existing hole to a depth between 11,500 and 13,000 feet. However, unexpected delays and short bit runs, attributed to thick layers of metaquartzite, decreased daily recovered footage and cost precious drilling time and money. The final depth achieved was 9831 feet. Nevertheless, the retrieval of over 2500 feet of continuous core provided geologists with a wealth of new data and material for further research efforts.

LVEW Stratigraphy

During Phases I and II, LVEW passed through the volcanic caldera fill and into the metamorphosed intrusions and metasedimentary basement rock. LVCP continued to drill through a thick sequence of metasedimentary rocks (Figure 3). The metamorphic material is correlative with the Mt Morrison roof pendant which is intruded by Sierra Nevada granites to the west and south of the drillsite. Specifically, graphitic, banded metapelites, metaquartzites, calcareous sandstones, and calc-silicate rocks most resembles the sequence of metamorphic rocks that make up the nearby Ordovician Mt. Aggie Formation (McConnell and others, 1998). Metamorphic patterns in the recovered core are indicative of several episodes of deformation suggesting that multiple processes of metamorphism were active, either simultaneously or sequentially, in the area. Indeed, an increase in contact metamorphic grade in the deepest portion of the core suggests that drilling approached the contact aureole of an intrusive body. Possible sources include Cretaceous age Sierra Nevada granite or neogranite representing the chilled margin from the Long Valley Caldera magma chamber.

LVCP drilling intersected several igneous intrusions in the metamorphic rocks. Their chemistry and alteration vary greatly, suggesting intrusion at different times or multiple episodes of emplacement and magmatic activity in the caldera. Several intrusions are petrographically similar to hypabyssal sills in the overlying volcanic fill found during the earlier phases of drilling. Their cumulative thickness and presence is suggested to account for much of the elevation of the resurgent dome (McConnell and others, 1995). These intrusions may ultimately provide information about the underlying magma chamber.

The presence or absence of geothermal potential should be reflected in changes of temperature with depth. Temperature’s in LVEW are unexpectedly low (Figure 4). The last kilometer in the well is isothermal and the bottomhole temperature remains just above 100 ¡C. Despite these anomalously low temperatures, the core provides abundant evidence of deep hot water circulation. Thick zones of hydrothermal alteration and open veins of pristine crystals of hydrothermal minerals, such as quartz, epidote, chlorite, sulfide minerals, and blade calcite at depths of 8500-8550 and 9100 feet, suggest that vigorous hot water circulation was present in the recent past

LONG VALLEY DEEP DRILLING 2

Figure 2 – Long Valley cross section

In addition to locally stretched and ductilely deformed metasedimentary rocks, the core contains lithologic and structural evidence of recent faulting. Faulting is indicated by fresh fault gouge, open vein brecciation, and open fractures. Two sections show the most significant evidence for recent faulting. Thick fault gauges occur between 8630 and 8910, presumable indicating the largest and most active faults. A deeper sequence stretches from approximately 9420 to 9800 feet, repeating the package of faulted rocks many times; suggesting an active extensional fault zone. This depth coincides with the calculated hypocenters of the Long Valley Caldera seismic swarm from September 1997 to January 1998 (oral communication, Steve Hickman). This intriguing evidence for young and contemporaneous faulting may allow for interpretations of the state of stress in the area of the resurgent dome.

Future plans for the wellsite include continued temperature logging and the emplacement of a package of instruments including seismometers and flow meters to increase the monitoring capabilities of the Long Valley Observatory. A series of add-on science research projects are also underway including detailing geochemistry of fluid inclusions within the hydrothermal minerals, Alpha recoil track age determinations of volcanic rocks, and geophysical modeling of the thermal regime of the caldera.

[The above project summary was modified from Sacket et al., 1999.]

LONG VALLEY DEEP DRILLING 2

Related Publications

Bender-Lamb, Sylvia, Magma energy exploratory well, Long Valley Caldera, California Geology, 44 (4), p. 85-92, 1991.

Hill, David P., Sorey, Michael L., Ellsworth, William L., Sass, John H., Scientific drilling continues in Long Valley Caldera, California, Eos, Transactions, American Geophysical Union, 79 (36), p. 429, 432, 1998.

Martini, B. A., Cochran, S. A., Potts, D. C., Silver, E. A., Pickles, W. L., Carter, M. R., Priest, R. E., Wayne, B. M., White, W. T., III, Geobotanical characterization of a geothermal system using hyperspectral imagery; Long Valley Caldera, CA, USA, Anonymous, Proceedings of the thirteenth international conference; applied geologic remote sensing, Proceedings of the Thematic Conference on Geologic Remote Sensing, 13 (1), p. 337-341, 1999. Meeting: Thirteenth international conference on Applied geologic remote sensing, Vancouver, BC, Canada, March 1-3, 1999.

Sackett, Penelope C., McConnell, Vicki S., Roach, Angela L., Priest, Susan S., Sass, John H., Long Valley Coring Project, Inyo County, California, 1998; preliminary stratigraphy and images of recovered core, Open-File Report – U. S. Geological Survey , OF 99-0158, p. (1 disc), 1999.

Sass, John H., Finger, John T., McConnel, Vicki, The Long Valley coring project, Bulletin – Geothermal Resources Council, 27 (2), p. 44-46, 1997.

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LA Blind Thrusts

LA Blind Thrusts scientific drilling project, located in California, a current project that is institutionally-funded

Los Angeles Blind Thrusts

Scientific Drilling Project by DOSECC Core Drilling Services

LA Blind Thrusts project, located in California, a current project that is institutionally-funded.

This scientific drilling project was conducted in 1997 by DOSECC core drilling services.  Southern California is home to several blind thrust systems and other principal faults, some of which are exposed at the surface and vary in slip rates and earthquake recurrence intervals. Read more about the ramifications of this study in this NSF publication.

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Bass River Scientific Drilling Project

Bass River project, located in New Jersey, scientific drilling project

Bass River, New Jersey

Scientific Drilling Project by DOSECC Core Drilling Services

Bass River project, located in New JerseyBass River project, located in New Jersey, a 1996 project that was NSF (EAR and OCE), NJ Geological Survey, DE Geological Survey, USGS-funded.