Palaeohydrological significance of late Quaternary strontium isotope ratios in a tropical lake |
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| Institution: | 1. State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;2. MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;3. Department of Geoscience, University of Wisconsin, 1215 West Dayton Street, Madison, WI 53706, USA;4. Oil and Gas Survey, China Geological Survey, Beijing 100029, China;1. Laboratory for Paleoclimatology and Climatology, Department of Geography, University of Ottawa, Ottawa, ON K1N 6N5, Canada;2. Research and Collections, Archaeology and History, Canadian Museum of Civilization, 100 Laurier Street, Gatineau, QC K1A 0M8, Canada;1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, China;2. School of Earth, Atmosphere & Environment, Monash University, Melbourne, VIC 3800, Australia;3. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China;4. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China |
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| Abstract: | Ostracods preserved in late Quaternary sediments of Wallywash Great Pond, a fresh coastal lake in SW Jamaica, record temporal variations in the strontium-isotope composition of lake water. Oxygen-isotope and Sr/Ca ratios in ostracods reveal temporal variations in the lake's hydrology, related to effective precipitation, and in its salinity related to varying marine-saline groundwater input from changes in relative sea level. Evaluation of isotopic and trace-element data indicates that the stratigraphic variations in 87Sr/86Sr ratios during the late Quaternary are best explained by climatically-controlled hydrological changes. During wetter periods, the lake's Sr budget was dominated by springwater input with relatively low 87Sr/86Sr ratio, whereas during drier times reduced springflow, possibly coupled with input of more-radiogenic Sr from other sources, such as sea-spray aerosols and perhaps Saharan dust, led to an increase in the Sr-isotope ratio of the lake water. Despite proximity of the lake to the sea and evidence for slight intrusion of marine saline groundwater in the past, however, the extent of marine input appears to have had limited influence on the lake's Sr-isotope ratios. Whereas the 87Sr/86Sr ratios cannot be used as a palaeosalinity proxy in this particular lake, they do provide valuable information about the mechanisms underlying hydrological change. |
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