Collaborative Research: (ESH) Late Paleocene and Early Eocene Nonmarine Climates in the Gulf of Mexico Basin, Texas

合作研究：（ESH）德克萨斯州墨西哥湾盆地晚古新世和早始新世非海洋气候

• 批准号: 9631188
• 负责人: Jack Wolfe
• 金额: $ 13.09万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-09-01 至 2001-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9631188&HistoricalAwards=false
• 关键词: Collaborative; Research; ESH; Late; Paleocene

9631188 Wolfe This project aims to develop an initial framework for nonmarine climates from the mid-Paleocene (ca. 60 Ma) through the end of the early Eocene (ca. 49 Ma). The early Eocene (ca. 49-53/54 Ma) was by consensus the warmest period during the Tertiary, except possibly for a brief period after the Cretaceous-Tertiary boundary. The climatic developments preceding the early Eocene thermal optimum need to be studied in order to understand whether the optimum represented an abrupt change in climate or was a culmination of previously established trends. Further, unlike the marine records of climate change, the nonmarine record provides evidence of changes in seasonal temperatures and changes in precipitation regimes. Such data are necessary to fully evaluate predictions based on General Circulation Models, especially if, as has been suggested, the early Eocene thermal optimum resulted from high amounts of atmospheric CO2. Some assemblages of fossil leaves have been previously reported from the Wilcox Group (ca. 49-60 Ma) of the Texas part of the Gulf of Mexico (Mississippi) Embayment, but many more have been observed in the field and remain to be collected. These leaf assemblages can be related strategically to the intertonguing marine planktic sequence and, as well, related to the generally accepted sea-level curves. In some instances, palynological correlations will need to be made between nonmarine sections that cannot be directly traced into marine sections. The Texas Wilcox vegetation was a paleolatitude of ~30oN and will provide the first long record of nonmarine climate and climatic change during the Paleocene and early Eocene at such a low latitude. The vegetation represented is that of a floodplain. The assemblages all represent low altitude vegetation, and thus the variable of paleoaltitude is held constant. Further, rain shadows, which are problematic in leaf assemblages from the Western Interior, would not have been a factor. Traditional methods of pale obotanical/palynological analyses for paleoenvironmental interpretations involve determination of fossils in terms of their nearest living relatives and the questionable assumption of unchanging climatic tolerances for plants through time. This procedure would represent a very time-consuming effort of many years' duration, and, even then, the inferences could be questioned on a theoretical basis. In contrast, collection, curation, and assignment of the Wilcox leaves to individual species can be done in a comparatively short time. Instead of using the nearest living relative method of paleoclimatic inferences, the leaf assemblages will be analyzed by means of CLAMP (Climate-Leaf Analysis Multivariate Program). This method was first proposed in 1990 and is, in some respects, still in a developmental stage, to which the proposed research will contribute. The method analyzes 31 rigorously defined physiognomic character states of leaves by means of Canonical Correspondence Analysis (CCA), a multivariate program increasingly and widely employed in ecological studies. Analysis of modern samples collected proximal to stations where meteorological data have been recorded allows estimates derived from CLAMP to be calibrated with various meteorological parameters, including mean annual temperature, mean cold-month and warm-month temperatures, growing season length, growing season precipitation, relative humidity, and seasonal drought. Preliminary analyses suggest that mean annual temperatures in the Texas Wilcox showed an increase during the mid- to late Paleocene. The analyses also indicated that, whereas the mid- to late Paleocene in Texas was characterized by very abundant precipitation, by the end of the early Eocene thermal optimum the climatic regime had pronounced seasonal drought. ??

小行星9631188 该项目的目的是为古新世中期（约2000年）的非海洋气候建立一个初步框架。60 Ma）至始新世早期（约60 Ma）。49 Ma）。 早始新世（Eocene）49-53/54 Ma）是公认的第三纪最温暖的时期，除了可能是一个短暂的时期后，第三纪的边界。 需要研究始新世早期热最适期之前的气候发展，以了解最适期是否代表气候的突然变化，或者是先前确定的趋势的顶点。 此外，与海洋气候变化记录不同，非海洋记录提供了季节温度变化和降水变化的证据。 这些数据是必要的，以充分评估预测的基础上，一般环流模式，特别是如果，如已建议，始新世早期的热最佳导致大量的大气CO2。 一些化石叶的组合以前曾在威尔科克斯群（Wilcox Group）中报道过。49-60 Ma）的墨西哥湾（密西西比）Embayment的得克萨斯州的一部分，但更多的已被观察到在外地和仍然有待收集。 这些叶组合可以与战略intertonguing海洋南极序列，以及，有关的普遍接受的海平面曲线。 在某些情况下，孢粉学的相关性将需要作出之间的非海相部分，不能直接追溯到海相部分。 得克萨斯州威尔科克斯植被是一个古纬度约30 oN，将提供第一个长期的记录，非海洋气候和气候变化在古新世和始新世早期在这样一个低纬度。 图中的植被是河漫滩。 这些组合都代表低海拔植被，因此古海拔变量保持不变。 此外，雨的阴影，这是有问题的叶片组合从西部内陆，不会是一个因素。 传统的古环境解释的古植物学/孢粉学分析方法涉及确定化石的最近的生活亲属和植物的气候耐受性随着时间的推移不变的可疑假设。 这一程序将是一个非常耗时的努力，需要多年的时间，而且，即使这样，推论也可能在理论基础上受到质疑。 相比之下，收集，策展和分配威尔考克斯叶到个别物种可以在相对较短的时间内完成。 本文将用CLAMP（Climate-Leaf Analysis Multivariate Program）程序分析叶组合，而不是用古气候推断中的最近生存亲缘关系法。 该方法于1990年首次提出，在某些方面仍处于发展阶段，拟议的研究将有助于这一发展。 该方法分析了31个严格定义的外貌特征的状态，通过典型对应分析（CCA），一个多变量的程序越来越广泛地应用于生态学研究。 现代样本收集近站的气象数据已记录的分析，使CLAMP得出的估计与各种气象参数，包括平均年温度，平均冷月和暖月温度，生长季节长度，生长季节降水，相对湿度和季节性干旱进行校准。 初步分析表明，德克萨斯州威尔科克斯的年平均气温在古新世中期至晚期有所上升。 分析还表明，虽然中晚古新世在得克萨斯州的特点是非常丰富的降水，到始新世早期的热最佳结束的气候制度有明显的季节性干旱。 ??