Holocene Changes in Sea Level: Evidence in Micronesia
F. P. Shepard 1,
J. R. Curray 1,
W. A. Newman 1,
A. L. Bloom 2,
N. D. Newell 3,
J. I. Tracey Jr. 4, and
H. H. Veeh 5
1 Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92037
2 Department of Geology, Cornell University, Ithaca, New York 14850
3 American Museum of Natural History, New York 10024
4 U.S. Geological Survey, Washington, D.C. 20242
5 Department of Geology, Yale University, New Haven, Connecticut 06520
Investigation of 33 islands, scattered widely across the Caroline and Marshall Island groups in the Central Pacific revealed no emerged reefs in which corals had unquestionably formed in situ, or other direct evidence of postglacial high stands of sea level. Low unconsolidated rock terraces and ridges of reefflat islands, mostly lying between tide levels, were composed of rubble conglomerates; carbon-14 dating of 11 samples from the conglomerates so far may suggest a former slightly higher sea level (nine samples range between 1890 and 3450 and one approaches 4500 years ago). However, recent hurricanes have produced ridges of comparable height and material, and in the same areas relics from World War II have been found cemented in place. Thus these datings do not in themselves necessarily indicate formerly higher sea levels. Rubble tracts are produced by storms under present conditions without any change in datum, and there seems to be no compelling evidence that they were not so developed during various periods in the past.
