TRAINOR, DWIGHT M., Mobil Oil Company, New Orleans, LA; and D. F. Williams, Univ. of South Carolina, Columbia, SC

ABSTRACT: Oxygen Isotopic Evidence for Surface Water Salinity Changes in the Gulf of Mexico During the Late Neogene

Evidence is presented from oxygen isotopic measurements of planktonic foraminifera from wells in blocks: South Timbalier, Ewing Bank, and Green Canyon, for substantial negative isotope{18}O excursions in the surface waters of the north central Gulf of Mexico (GOM). These anomalous negative events extend from the late Pleistocene into the early Pliocene, as early as 4.1 million years before present (Ma). Isotopically negative meltwater is inferred to be the cause of a large proportion of the isotope{18}O excursions during the late Pliocene-Pleistocene period due to the establishment of ice conditions in the Northern Hemisphere. Negative isotope{18}O excursions in the north central GOM in the early Pliocene, documented in these wells, predate the currently accepted ages (between 3.2 and 2.4 Ma) for the initiation and establishment of glacial conditions in the Northern Hemisphere. This important new evidence indicates that continental ice may have existed on the North American continent prior to 3.2 Ma.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.