DOI: 10.25921/9jrb-yd12
title: NOAA/WDS Paleoclimatology - Wallywash Great Pond, Jamaica 125 KYr Multiproxy Sediment Data

description: 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.
description: We reconstruct the late Quaternary palaeolimnology of Wallywash Great Pond, a small, fault-bounded lake in the southwestern part of Jamaica, in order to infer changes of effective moisture. Our study is based on the 9.23-metre-long core WGP2, which consists of pure marls, organic marls and muds, organic mud and peat and earthy calcareous muds. We use the facies changes, ostracod faunal assemblages, sediment geochemistry, ostracod shell chemistry and stable-isotope variations in order to infer changes in lake level, evaporative enrichment and effective moisture change. The chronology of the core is based on radiocarbon and uranium-series dates. The core covers the past ~125 ka BP and is reasonably well dated for the Holocene, although chronological uncertainties increase further back in time. Three major lake highstands with slightly elevated salinity occurred during marine isotope stage 5, under elevated sea level and a humid climate. There is evidence of minor marine saline intrusion into the lake during the earliest of these highstands. The lake dried out ~93.5 ka BP as sea level fell and the climate became drier. It refilled around 10.7 ka BP. Three separate highstands during the Holocene were sustained by humid conditions and high relative sea level. Although there were small increases in salinity during the Holocene when sea level was close to the deepest part of the lake, significant saltwater intrusion appears to have been prevented by freshwater discharge from inland. The long-term trends in lake level reflect both orbitally-induced changes in insolation and eustatic sea level. Water-level fluctuations during the Holocene, however, reflect climatic changes on the millennial timescale rather than orbital forcing or sea-level change.  

The data from core WGP2 are presented against core depth, as in the original publications. Chronological information are presented below and in file wallywash2007age.txt.

In addition, we present ancillary information (A1-A5) relating to the modern water chemistry and water isotope composition and modern ostracod fauna of Wallywash Great Pond and other lakes in Western Jamaica: this information has been used to help us interpret the data from core WGP2.