A late Holocene palaeoenvironmental record from Altona Bay, St. Croix, US Virgin Islands

Abstract

Geografisk Tidsskrift, Danish Journal of Geography 108(2):59–70, 2008 A reconstruction of the palaeoenvironmental development of Altona Bay, St. Croix, northeastern Caribbean, has been made based on the sedimentological, geochemical and pollen analyses of a 1.83 m long vibracore. For chronological control, AMS 14C measurements were made at 5 levels downcore. The sedimentary sequence covers the last c. 4,700 years, containing both (mangrove) peat and fine-grained clastic sediment units. Comparison with regional Holocene sea level data demonstrates a gradual marine flooding of a mangrove environment around 3,500 cal BP was presumably related to a regional late Holocene sea-level rise, from a position, c. 2 m lower than present. After a c. 1,000 year period of marine sedimentation lasting until c. 2,500 cal BP, renewed formation of tropical wetland occurred at the site. This development may be attributed to the increased isolation of the shallow Altona Bay, most likely due to sea- ward formation of a well-developed spit system and possibly under the influence of enhanced storm-wave action in the period between c. 4,000 and 2,200 cal BP. Since the 1960's the repeated passage of severe hurricanes (e.g. Hugo, 1989) has had a significant impact on the sedimentation pattern of the bay and has caused a major hiatus and the recent deposition of sediments immediately overlying the c. 2,500 year old peat.