Late Quaternary palaeolimnology of a tropical marl lake: Wallywash Great Pond,Jamaica |
| |
| Authors: | F A Street-Perrott P E Hales R A Perrott J C Fontes V R Switsur A Pearson |
| |
| Institution: | (1) Environmental Change Unit, 1A, Mansfield Rd., OX1 3TB Oxford, UK;(2) Tropical Palaeoenvironments Research Group, School of Geography, Mansfield Rd., OX1 3TB Oxford, UK;(3) Laboratoire d'Hydrologie et de Géochimie Isotopique, Université de Paris-Sud, Bâtiment 504, 91405 Orsay Cedex, France;(4) The Godwin Laboratory, Free School Lane, CB2 3RS Cambridge, UK;(5) Department of Biochemistry, University of the West Indies, Mona, Kingston 7, Jamaica |
| |
| Abstract: | Wallywash Great Pond (17° 57 N, 77° 48 W, 7 m a.s.l.) is the largest perennial lake in Jamaica. It occupies a fault trough within the karstic White Limestone. The Great Pond is a hardwater lake with a pH of 8.2–8.6 and an alkalinity of 3.6–3.9 meq 1–1. Its chemistry is strongly influenced by the spring discharge from the limestone. The lake water is subject to degassing, evaporation and bicarbonate assimilation by submerged plants and algae, resulting in marl precipitation. A 9.23 m core (WGP2), taken from a water depth of 2.8 m, was analysed for magnetic susceptibility, loss-on-ignition, carbonate content, mole % MgCO3 in calcite, and stable isotopes in the fine carbonate fraction. The chronology is based on ten14C and four U/Th dates. Four main sediment types alternate in the core: marl; organic, calcareous mud; organic mud or peat; and earthy, brown, calcareous mud. The marls represent periods of wet/warm climate during sea-level highstands and the organic deposits, shallower, swampy conditions. In contrast, the brown, calcareous muds were laid down when the lake was dry or ephemeral. The last interglacial (120 000-  106 000 yr BP) is represented by three distinct marl units. After a dry interval, stable, wet/warm conditions set in from 106 000 to 93 000 yr BP. A dry/cool climate prevailed between 93 000 and at least 9500 yr BP. Three subsequent cycles of alternating wet and dry conditions culminated in flooding of the basin by the Black River during the late Holocene. These recent events cannot be accurately dated by14C due to significant and temporally-variable inputs of  dead carbon from the springs. |
| |
| Keywords: | Jamaica Late Quaternary palaeolimnology marl stratigraphy stable isotopes harwater lake |
| 本文献已被 SpringerLink 等数据库收录！ |
|
