Source: https://geo-nsdi.er.usgs.gov/metadata/open-file/95-1/metadata.faq.html
Timestamp: 2019-04-20 06:41:34+00:00

Document:
The data contained in this report represent our preliminary findings of the analyses of two cores of Pliocene and early Pleistocene sediments from the eastern Great Basin. This is a collaborative project involving specialists from the USGS, Kansas State University, and the University of California-Davis in paleontology (Thompson, Buchner, Forester, Bradbury), stratigraphy and sedimentology (Oviatt, Kelsey, Bracht), and paleomagnetism and environmental magnetism (Roberts).
Thompson, Robert S., Oviatt, C.G., Roberts, A.P., Buchner, J., Kelsey, R., Bracht, C., Forester, R.M., and Bradbury, J.P., 1995, Stratigraphy, Sedimentology, Paleontology, and Paleomagnetism of Pliocene-Early Pleistocene Lacustrine Deposits in Two Cores from Western Utah: U.S. Geological Survey Open-File Report 95-1, U.S. Geological Survey, Denver, CO.
Locations of sites discussed in text. The shaded areas represent elevations above 6000 ft (1829 m). Woodland and forest vegetation generally occurs above this elevation, steppe and desert below.
Black Rock core stratigraphy plotted against the magnetostratigraphy, macrofossil occurrences, and magnetic susceptibility. BR = Brunhes, J = Jaramillo, C = Cobb Mountain, O = Olduvai, R = Reunion, X = Anomaly X, K = Kaena.
Pit of Death Stratigraphy. Br = Brunhes, J = Jaramillo, O = Olduvai, R = R&#233;union, X = Anomaly X.
Comparison of Black Rock and Pit of Death chronologies.
Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 1. Longitudes are given to the nearest 1. Latitude and longitude values are specified in Degrees, minutes, and decimal seconds.
Black Rock Core Log. Lithologic description containing information on grain size, color, bedding structures, sedimentary structures and occurance of plant-macrofossils.
Black Rock Core Paleomagnetic Data. Paleomagnetic inclination measured by either Alternating Field demagnetization method or thermal demagnetization method.
Black Rock Core Pollen Data. Counts of 57 pollen taxa from 159 samples from the Black Rock core.
Pit of Death Core Log. Lithologic description of the Pit of Death Core containing information on grain size, color, bedding structures, sedimentary structures and occurance of plant-macrofossils.
Pit of Death Core Paleomagnetic Data. Paleomagnetic inclination measured by either Alternating Field demagnetization method or thermal demagnetization method.
Vector component diagrams indicating representative demagnetizationbehavior of paleomagnetic samples.
Diagram showing paleomagnetic interpretation, lithology, occurance of seeds, occurance of root traces, occurance of leaf impressions and magnetic susceptibility in the Black Rock core.
Diagram showing the paleomagnetic inclination record of the Black Rock core.
Diagram showing age vs. depth relationship based on paleomagnetics and tephrochronology in the Black Rock Core.
Diagram showing paleomagnetic record and pollen percentages of 15 taxa in the Black Rock core.
Diagram of Three-level moving averages of conifer and steppe pollen from the Black Rock Core vs. time.
Diagram showing paleomagnetic interpretation, lithology, occurance of mud cracks and magnetic susceptibility in the Pit of Death core.
Diagram showing the paleomagnetic inclination record of the Pit of Death core.
Diagram showing age vs. depth relationship based on paleomagnetics and tephrochronology in the Pit of Death Core.
Diagram comparing the magnetic susceptibiliy records of the Black Rock and Pit of Death cores.
Diagram comparing the chronologies and depositional rates of the Black Rock and Pit of Death cores.
Diagram comparing the lacustrine histories of Pliocene through Pleistocene sites in western Utah.
Paleoenvironmental interpretations summarizing the analysis of approximately 900 ostracode samples from the Black Rock core.
Summary of results of analysis of 10 ostracode samples from the Pit of Death core.
This report is the preliminary result of a collaborative project involving specialists from the USGS, Kansas State University, and the University of California-Davis in paleontology (Robert S. Thompson, Jennifer Rose Buchner, R.M. Forester, J.P. Bradbury), stratigraphy and sedimentology (Charles G. Oviatt, Rachel Kelsey, Christopher Bracht), and paleomagnetism and environmental magnetism (Andrew P. Roberts).
We are investigating the paleoclimatic history of western Utah as part of the USGS Global Change and Climate History Program studies of long-term climatic changes in the western United States. Our initial objective is to document the environmental conditions during the mid-Pliocene period of warmer-than-modern global climates (the focus of the USGS Pliocene Research, Interpretation, and Synoptic Mapping [PRISM] project). We also seek to determine how and when these conditions gave way to the late Quaternary pattern of climatic variations (in which short periods of very moist climates have been separated by long periods of arid conditions).
Billings, W.D., 1949, The shadscale vegetation zone of Nevada and eastern California in relation to climate and soils: American Midland Naturalist v. 42, p. 87-109.
Cande, S.C., and Kent, D.V, 1992, A new geomagnetic polarity time scale for the Late Cretaceous and Cenozoic: Journal of Geophysical Research v. 97, p. 13, 917-13,951.
Canfield, D.E., and Berner, R.A., 1987, Dissolution and pyritization of magnetite in anoxic marine sediments: Geochimica et Cosmochimica Acta v. 51, p. 645-659..
Source_Contribution: Chemistry of magnetic minerals in reducing environments.
Condie, K.C., and Barsky, C.K., 1972, Origin of the Quaternary basalts from the Black Rock Desert region, Utah: Geological Society of America Bulletin v. 83, p. 333-352..
Crecraft, H. R., Nash, W. P., and Evans, S. H., Jr., 1981, Late Cenozoic volcanism at Twin Peaks, Utah - Geology and petrology: Journal of Geophysical Research v. 86: p. 10,303-10,320.
Cui, Y., Roberts, A.P, Verosub, K.L., Thompson, R.S., and Oviatt, C.G., 1994, A Study of the Matuyama-Brunhes Geomagnetic Polarity Transition From Sevier Lake, Utah [abs.]: EOS, Transactions of the American Geophysical Union v. 75, p. 194-195.
Davis, O.K., 1984, Pollen frequencies reflect vegetation patterns in a Great Basin (U.S.A.) mountain range: Review of Palaeobotany and Palynology v. 40, p. 295-315..
Davis, O.K., 1993, Preliminary pollen analysis of Neogene sediment of the Great Salt Lake, U.S.A [abs]: American Association of Stratigraphic Palynologists, Inc., Program and Abstracts 1993 Annual Meeting, Baton Rouge, LA, p. 20..
DeMenocal, P.B., Ruddiman, W.F., and Kent, D.V., 1990, Depth of post-depositional remanence acquisition in deep-sea sediments: a case study of the Brunhes-Matuyama reversal and oxygen isotope stage 19.1: Earth and Planetary Science Letters v. 99, p. 1-13.
Source_Contribution: Magnetic remanence acquisition in sediments.
Eardley, A.J., Shuey, R.T., Gvosdetsky, V., Nash, W.P., Picard, M.D., Grey, D.C., and Kukla, G.J., 1973, Lake cycles in the Bonneville Basin, Utah: Geological Society of America Bulletin v. 84, p. 211-216.
Machette, M. N., 1985, Late Cenozoic geology of the Beaver basin, southwestern Utah: Brigham Young University Geology Studies v. 32, pt. 1, p. 19-37..
Paleohydrology of the Beaver River and the Sevier River drainage systems.
Oviatt, C. G., 1991, Quaternary geology of the Black Rock Desert, Millard County, Utah: Utah Geological and Mineral Survey Special Studies 73, 23 p..
Oviatt, C. G., 1992, Quaternary geology of the Scipio Valley area, Millard and Juab Counties, Utah: Utah Geological Survey Special Study no. 79, 16 p..
Oviatt, C. G., 1994, Review of the Quaternary geology of the Sevier and Black Rock Deserts: Utah Geological Association Publication v. 23, p. 97-103..
Roberts, A.P., and Turner, G.M., 1993, Diagenetic formation of ferrimagnetic iron sulphide minerals in rapidly deposited marine sediments.: Earth and Planetary Science Letters v. 115, p. 257-273..
Thompson, Robert S., 1991, Pliocene environments and climates in the western United States: Quaternary Science Reviews v. 10, p. 115-132..
Thompson, R.S., 1996, Pliocene and early Pleistocene environments and climates of the western Snake River Plain, Idaho: Marine Micropaleontology 1996.
Vance, R.E., and Mathewes, R.W., 1994, Deposition of modern pollen and plant macrofossils in a hypersaline prairie lake basin: Canadian Journal of Botany v. 72, p. 539-548..
Verosub, K.L., and Roberts, A.P., 1996, Environmental magnetism: past, present, and future: Journal of Geophysical Research in press.
Source_Contribution: Magnetostratigraphic correlation of lake-catchment sediments.
Williams, S.K., 1994, Late Cenozoic tephrostratigraphy of deep sediment cores from the Bonneville Basin, northwest Utah: Geological Society of America Bulletin v. 105, p. 1517-1530..
Paleomagnetic Analysis. Oriented paleomagnetic samples were taken by carving pedestals into the cores and slipping plastic boxes (2.5 x 2.5 x 1.5 cm) over the pedestals. In general, samples were collected at 1 m (3.3 ft) intervals throughout the length of both cores.For paleomagnetic studies, 307 and 139 samples were analyzed from the Black Rock and Pit of Death cores respectively. The samples were stepwise demagnetized by either alternating field (AF) or thermal methods. AF demagnetization was generally carried out at successive peak fields of 0, 10, 20, 25, 40, and 60 mT, and in some cases, additional intermediate steps were included at peak fields of 5, 15, 30, and 50 mT. Thermal demagnetization was carried out at successive steps of 20, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, and 600 degrees C. Magnetic susceptibility was measured at each thermal demagnetization level to monitor for thermal alteration. Remanence measurements were made on a 2G Enterprises cryogenic magnetometer. AF demagnetization was carried out with a Schonstedt AF demagnetizer and thermal demagnetization was carried out with a Schonstedt thermal demagnetizing unit. Magnetic susceptibility was measured with a Bartington Instruments magnetic susceptibility meter.
Accuracy of measurements and processes is discussed in detail in the "Materials and Methods" section of the report.
The horizontal coordinates of the drilling sites are given in degrees, minutes and seconds of latitude and longitude. A second of longitude at 39 degrees latitude is approximately 19.45 meters. A second of latitude is approximately 30.92 meters. This suggests that the longitude of the sites is known to within 19.45 meters and the latitude of the sites is known to within 30.92 meters.
The elevation of the Black Rock site is given as 4930 feet and the elevation of the Pit of Death site is given as 4535 feet. This suggests that the measurements are accurate to within 5 vertical feet.
Core logs (Appendix 1, Appendix 4) indicate that the drilling machinery indicated drilling depth in increments of 1/100th of a foot.
Approximately 8 ft (2.4 m) of tan silt overlies 17 ft (5.2 m) of basalt at the Black Rock site. The coring process did not recover any of the silt or basalt (although some of the silt was recovered in Shelby tubes), nor was it possible to recover the uppermost few feet of sediment underlying the basalt. Core recovery began at 25.25 ft (7.7 m) and extended down to 896.83 ft (273.35 m). As shown in Appendix 1, core recovery was excellent throughout most of this depth range.
The only unrecovered section of significant thickness in the Pit of Death core is near the bottom. Pebbly mud in the interval between 428 and 431 ft overlies an interval of about 40 ft of sand and gravel, from which no core was recovered. From 472 ft to the base of the core at 512 ft, is a sequence of moderately cemented, poorly sorted, tuffaceous sand.
Of the 159 samples processed from the Black Rock site, 142 contained sufficient pollen for analysis. Ten samples were processed from the Pit of Death core, and all were barren of pollen.
The occurrences of these plant macrofossils has been recorded during the sediment descriptions and by examination of slides prepared for ostracode analysis.
Approximately 920 samples have been prepared from the Black Rock core, and 10 from the Pit of Death Core.
Twenty-four samples have been analyzed from the Black Rock core and 10 from the Pit of Death core.
Coring equipment and original logs record core depths for both cores in the English units of "decimal feet". The depths recorded in the Metric units of "meters" were calculated from the English measurements.
Both alternating-field and thermal methods were used for demagnetization of paleomagnetic samples. When the thermal method was used, magnetic susceptibility was measured at each demagnetization step to monitor for thermal alteration.

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