Paleoclimatic Reconstruction Using the Correlation in δ18O of Hackberry Carbonate and Environmental Water, North America
Paleoclimatic Reconstruction Using the Correlation in δ18O of Hackberry Carbonate and Environmental Water, North America
复制标题
利用北美朴树碳酸盐 δ18O 与环境水的相关性重建古气候
作者：
A. Jahren;R. Amundson;C. Kendall;P. Wigand
摘要1979-1994年，从北美13个州和加拿大一个省的101个地点采集朴树果实。朴树是大平原第四纪沉积物中常见的植物化石，其生物矿化碳酸盐内果皮的δ 18 O值进行了分析，并与现场环境水的δ 18 O值作图，以证明朴树作为古气候指示剂的潜力。通过对科罗拉多斯特林三种树木的组织水δ 18 O值和朴树内果皮碳酸盐δ 18 O值的深入研究，进一步证实了这种相关性。朴树内果皮碳酸盐δ 18 O值与环境水之间的相关系数为[内果皮δ 18 O =38.56+0.69×环境水δ 18 O]（R=0.88; R2 =0.78; p值<0.0001）。大平原朴树碳酸盐与温度的关系为：（日平均最高生长季温度[°C]）=6.33+0.67（内果皮碳酸盐δ 18 O）（R=0.73; R2 =0.54; p值=0.0133）。在内华达州南部的平沃特洞穴（Pintwater Cave）发现的早全新世朴树碳酸盐化石的δ 18 O值表明，当时的降水δ 18 O值比现在的要高（早全新世为1.4 ‰，而今天为1.9 ‰至1.0 ‰）。这种转变，结合古植物学数据，表明夏季季风水分涌入这一地区在全新世早期。另外，更积极的δ 18 O值可以被视为暗示温度更高，虽然直接使用大平原朴树/温度关系到大盆地是有争议的价值。
Abstract Celtis sp. (commonly known as “hackberry”) fruits were collected from 101 North American sites located in 13 states and one Canadian province between the years of 1979–1994. The biomineralized carbonate endocarp of the hackberry, which is a common botanical fossil found throughout the Quaternary sediments of the Great Plains, was analyzed for its δ18O value and plotted against the δ18O value of site environmental water to demonstrate the potential of the hackberry as a paleoclimate indicator. This correlation was reinforced by intensive studies on extracted tissue-water δ18O value and hackberry endocarp carbonate δ18O value from three trees in Sterling, Colorado. The observed correlation in the large data set between hackberry endocarp carbonate δ18O value and environmental water is [endocarp δ18O=38.56+0.69×environmental water δ18O] (R=0.88; R 2=0.78; p value<0.0001). The relation of the hackberry carbonate to temperature in the Great Plains was the following: (average daily-maximum growing season temperature [°C])=6.33+0.67 (δ18O of endocarp carbonate) (R=0.73; R 2=0.54; p value=0.0133). The δ18O value of early Holocene fossil hackberry carbonate in the Pintwater Cave, southern Nevada, suggested precipitation δ18O values more positive than today (∼−4‰ early Holocene vs ∼−9 to −10‰ today). This shift, combined with paleobotanical data, suggests an influx of summer monsoonal moisture to this region in the early Holocene. Alternatively, the more positive δ18O values could be viewed as suggestive of warmer temperatures, although the direct use of Great Plains hackberry/temperature relationships to the Great Basin is of debatable value.