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P10. GALATHEA3 – LEG 16 ’WINMARGIN’ PROJECT Results from Marine
Geoscience Investigations in the former Danish West Indies
A. Kuijpers 1 , J. Bartholdy 2 , A. Fischel 3 S. Raussen 4 , H. Lykke Andersen 3 and M.-S. Seidenkrantz 3
1
Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen, aku@geus.dk
2
Institute of Geography and Geology, University of Copenhagen, 1350 Copenhagen jb@geo.ku.dk
3
Department of Geoscience, Aarhus University, 8000 Aarhus C andrea.fischel@geo.au.dk,
hla@geo.au.dk, mss@geo.au.dk
4
Maersk Oil & Gas, 1263 Copenhagen sara.raussen@maerskoil.com
Results are presented from marine geological and geophysical investigations in the Anegada-
Jungfern Passage (AJP) between St. Thomas and St. Croix, where maximum water depth is in
excess of 4000 m. The work was carried out within the framework of the Galathea3
‘WINMARGIN’ (West Indies Marine Geoscience Investigations) project 1 , March 2007. In addition,
palaeo-environmental studies were also carried out in shallow waters of Altona Bay on the north
coast of St. Croix. The main objectives of the project have been 1) to improve our knowledge of the
regional tectonic setting at this active Caribbean plate boundary ( tsunami risk !) and 2) to trace
possible links between changes in Caribbean ocean and atmospheric circulation ( hurricanes !) and
North Atlantic climate at higher latitudes.
Using high-resolution multi-channel seismic data and multi-beam echo-sounder information a
regional tectonic model has been proposed showing, amongst others, that the Puerto Rico – Virgin
Islands microplate is moving towards NNE with respect to the North American Plate at a slower
rate than the larger, stable part of the Caribbean Plate 2 . This implies steadily growing regional
tectonic stress and thus increasing earthquake and tsunami risk. Foraminiferal-based analysis of
sediment cores retrieved from deep-water sites in the AJP has revealed a marked tri-partition in the
oceanographic record of the past 10,000 years 3 . This is presumably due to a gradual southward
migration of the Inter-tropical Convergence Zone (ITCZ). Initially, prior to 6300 years ago, a more
northerly (summer) ITCZ position favored a more northward extension of the SE trade wind belt
and thereby an enhanced advection of Southern Hemisphere-derived water masses. The period
between about 6300 and 3700 years ago was characterized by high sea surface temperatures and a
weaker trade wind regime, whereas during the past 3700 years NE trade winds became stronger,
while sea surface temperatures became cooler and more variable. The palaeo-environmental record
from Altona Bay on St. Croix demonstrates a gradual flooding of an originally mangrove
environment around 3500 years ago, followed by marine sedimentation, and renewed formation of
tropical wetland starting about 2500 years ago 4 . Storm-wave action seems to have been particularly
enhanced between ca. 4000 and 2200 years ago, whereas also since the 1960’s the repeated passage
of severe hurricanes (e.g. Hugo, 1989) has resulted in significant erosion and sediment
redistribution in the bay.
1) A. Kuijpers & Project Group, 2007. Galathea3 – Leg 16 WINMARGIN project. Geological Survey of
Denmark and Greenland Report 2007/44, 1-24
2) S. Raussen, H.L. Andersen, A. Kuijpers, 2012. Tectonics of the Virgin Islands Basin, northeastern
Caribbean. Terra Nova (in revision)
3) A. Fischel, M.-S. Seidenkrantz, M. Kucera, A. Kuijpers, 2012. Holocene climate variability in the tropics
– A10,000 year record from the Anegada Jungfern Passage, NE Caribbean. Marine Micropaleontology
(submitted)
4) C.A. Jessen, J.B.T. Pedersen, J. Bartholdy, M.-S. Seidenkrantz, A. Kuijpers, 2008. A late Holocene
palaeoenvironmental record from Altona Bay, St. Croix, US Virgin Islands. Geografisk Tidsskrift 108 (2),
59-70
Program 17. danske havforskermøde, 127