Holocene paleohydrology of Little Salt Spring, Florida, based on ostracod assemblages and stable isotopes
Holocene paleohydrology of Little Salt Spring, Florida, based on ostracod assemblages and stable isotopes
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DOI：
10.1016/j.palaeo.2004.01.023
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
C. Zarikian;P. Swart;J. Gifford;P. Blackwelder
中科院分区：
文献类型：
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作者：
C. Zarikian;P. Swart;J. Gifford;P. Blackwelder
介形类组合和Cytheridella ilosvayi的δ 18 O和δ 13 C记录提供了佛罗里达中西部的一个天坑湖和水下考古保护区小盐泉12,000年的古水文重建。介形虫记录记录了水温和湖泊系统水文特征的相对变化，这些变化是气温升高、输入沃茨（浅层地下水与深层地下水）相对贡献的变化、降雨模式和全新世期间相对海平面上升的结果。数据表明，LSS最初提供了相对较低的直接降雨量和地表径流的春天的位置是更接近的补给区，远离淡水/盐水界面。在大约11，000年BP，LSS成为地下水的支持，最初由一个浅的淡水含水层与低δ 18 O组成，直到15700年BP，并在此之后的时间由18 O富集和日益矿化的地下水来自更深的，碳酸盐含水层的区域水位上升，使盐水界面更接近LSS的位置，在这个时候成为地下水排放区。数据还表明，最突然和最显著的水文变化发生在晚全新世，在2700 - 2000年BP之间的δ 18 O值较低（δ-2.86 ‰），随后δ 18 O组成呈阶梯状增加，在1100 - 900年BP之间达到最大值（δ-1.46 ‰）。在这些时期到现在的介形类组合的特点是咸水物种（Cyprideis spp.）。和佛罗里达湖花介（Limnocythere florangensis）。据推测，同位素值下降的间隔表明在干燥的气候条件下与盐水混合，而同位素值更富集的间隔表明在海平面高位期间盐水入侵。虽然在晚全新世干旱和随后降雨条件增加的确切时间方面，来自北方加勒比地区的其他记录与来自LSS的记录之间存在一些差异，但记录之间的差异可能是由于大陆对佛罗里达半岛海洋-大气相互作用的影响更大，LSS的地下水混合平衡非常复杂，以及在其他记录中的更好的约束年龄模型。
Ostracod assemblages and the δ18O and δ13C records of Cytheridella ilosvayi provide a ∼12,000 yr paleohydrological reconstruction of Little Salt Spring, a sinkhole lake and underwater archaeological preserve in west central Florida. The ostracod record documents relative changes in water temperature and hydrologic characteristics of the lacustrine system that are the result of warming air temperatures, changes in the relative contributions of input waters (shallow vs. deep groundwater), rainfall patterns and relative sea level rise during the Holocene. The data indicate that LSS was initially supplied by relatively low amounts of direct rainfall and surface runoff as the spring's location was closer to the recharge area and far from the freshwater/saltwater interface. At about 11,000 yr BP, LSS became groundwater supported, initially by a shallow freshwater aquifer with low δ18O composition until ∼5700 yr BP, and after that time by18O-enriched and increasingly mineralized groundwater originating from a deeper, carbonate aquifer as the regional water table rose bringing the saltwater interface closer to the location of LSS which at this time was becoming a groundwater discharge area. The data also shows that the most abrupt and pronounced hydrologic changes occurred during the Late Holocene with an interval of low δ18O values (∼−2.86‰) between 2700 and 2000 yr BP, followed by a stepped increase in δ18O composition with maximum values (∼−1.46‰) between 1100 and 900 yr BP. Over these periods to the present time the ostracod assemblage is characterized by brackish species (Cyprideis spp. and Limnocythere floridensis). It is inferred that the interval of decreased isotopic values indicates mixing with saline water during dry climatic conditions, while the interval of more enriched isotopic values suggest saltwater intrusion during a period of, presumably, a sea level highstand. Although some discrepancies exist between other records from the northern Caribbean region and the one from LSS with regards to the exact timing for the Late Holocene drying and subsequent increase in rainfall conditions, the differences between the records may be explained by greater continental influences on ocean–atmosphere interactions on the Florida peninsula, a highly complex groundwater mixing balance in LSS, and by a better constrained age-model in the other records.