noaa-other-11200 Chinese Loess Plateau 700KYr Amino Acid Racemization Data Oches, E.A.; McCoy, W.D. Chinese Loess Plateau 700KYr Amino Acid Racemization Data 2011-06-01 NCDC-Paleoclimatology ONLINE Files Pending https://www.ncdc.noaa.gov/paleo/study/11200 Investigator E.A. Oches Investigator W.D. McCoy earth science paleoclimate others geoscientificInformation 700000 cal yr BP 0 cal yr BP Complete 35.7 35.7 109.4 109.4 Continent Asia Eastern Asia China Luochuan>LATITUDE 35.7>LONGITUDE 109.4 None Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site. English DOC/NOAA/NESDIS/NCEI National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce https://www.ncdc.noaa.gov/data-access/paleoclimatology-data DATA Center Contact Bruce Bauer bruce.a.bauer@noaa.gov paleo@noaa.gov 303-497-6280 303-497-6513

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Boulder CO 80305-3328 USA online ASCII Oches, E.A. and W.D. McCoy. 2001. Historical developments and recent advances in amino acid geochronology applied to loess research: examples from North America, Europe, and China. Earth-Science Reviews, Vol. 54, Issues 1-3, June 2001, pp. 173-192. doi:10.1016/S0012-8252(01)00047-2

Amino acid geochronology provides important chronostratigraphic insight in the regional correlation and paleoclimatic evaluation of loess-paleosol sequences in the midwestern US, throughout western, central, and eastern Europe, and in China. In general, loess of the last four glacial cycles, corresponding to marine oxygen-isotope stages (OIS) 2-4, 6, 8, and 10, respectively, can be distinguished on the basis of alloisoleucine/isoleucine (A/I) ratios measured in fossil gastropod shells preserved in the loess. The racemization reaction is much slower in older samples, resulting in decreased temporal resolution. In the midwestern US and Europe, it is not possible to confidently subdivide the last glacial cycle on the basis of aminostratigraphic data. However, in China, where effective temperatures were higher during the Late Pleistocene, loess above and below L1SS1, the OIS-3 interstadial paleosol, can be distinguished using amino acid racemization data. With improvements in analytical methods, multiple amino acid D/L enantiomers are now being measured using reverse-phase liquid chromatography. Aspartic acid racemizes at a higher rate than the traditionally measured alloisoleucine/isoleucine diastereomers and can be measured more rapidly. This development offers hope for better temporal resolution and enhanced stratigraphic subdivision of loess units than has been achieved previously. STUDY NOTES: Alloisoleucine/isoleucine data from fossil snail shells recovered from loess strata of the Chinese loess plateau in the region near Luochuan, Shaanxi Province, China. Fossil gastropod shells collected from large exposures of stratified loess and paleosols in the vicinity of Luochuan, Shaanxi Province, China, are analyzed by cation-exchange HPLC to determine the extent of isoleucine epimerization. Three of the sample sites (Lower Heimu, Upper Heimu and Potou) are within about three kilometers of the village of Luochuan and are near branches of a large, deep gully system (Heimugou). The fourth site is at an excavation for a railroad grade about 20 km southwest of Luochuan and close to the city of Huangling. The ratio of D-alloisoleucine/L-isoleucine (AI) progressively increases in shells from strata of increasing stratigraphic age over several loess (glacial) cycles from L1 (youngest) to L5 (oldest sampled for this report). The AI values provide clear discrimination of loess stratigraphic units L1, L2 and L3. Although AI values continue to increase in units older than L3, resolution decreases. Confounding the inevitable reduction of resolution with increasing age is the fact that shells are much less abundant in the older strata and, therefore, few shell samples were recovered. Due to this scarcity of data, the extent of isoleucine epimerization in shells from these older units remains poorly characterized. On the other hand, the resolution in the youngest loess, L1, is good enough that it appears possible to discriminate between the two loess strata within it, L1LL1 and L1LL2.

GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/aar/oches2001loess/oches2001loess.xls GET DATA https://www1.ncdc.noaa.gov/pub/data/paleo/aar/oches2001loess/oches2001loess.txt USA/NOAA DIF Version 9.8.4 2018-12-11 2018-12-11