PALEOTEMPERATURES VERSUS SEA-LEVEL - OXYGEN-ISOTOPE SIGNAL FROM FISH BONE PHOSPHATE OF THE MIOCENE CALVERT CLIFFS, MARYLAND

The use of skeletal oxygen isotopic records for use in paleotemperatur e reconstruction has been hampered by the lack of independent evidence for ocean water oxygen isotopic composition. The delta(18)O record fr om homeothermic cetaceans has provided an independent estimate of ocea n delta(18)O values represented by the Calvert and Choptank formations of Maryland. Fish teeth and bones (especially shark and ray teeth) we re also collected from these sediments and provide the basis for paleo temperature estimates for represented time slices of the middle Miocen e. Trends in delta(18)O values of the fish phosphate throughout the Ca lvert Formation are of opposite polarity to the trends from the cetace an bone phosphate. Paleotemperatures calculated using the cetacean pro xies for ocean delta(18)O values sharpen the already present trend, in dicating that ocean temperatures increased during episodes of greater glaciation and decreased during periods of lesser or no glaciation. Wh en using modern average ocean values of 0 parts per thousand SMOW in t he paleotemperature calculation, however, corrected paleotemperatures for the Choptank Formation do not alter the existing pattern of temper atures