Paleodepth distribution of Neocene deep‐sea hiatuses

The depth of formation of Miocene to middle Pliocene deep‐sea hiatuses (NH1 to NH8)has been determined using 152 Deep Sea Drilling Project sites in the Atlantic, Pacific and Indian oceans. Megahiatuses representing maxima in deep‐sea erosion, occur at three water depths: below 3800 m, at intermediate depths between about 2000 and 3000 m, and in shallower waters above 1500 m paleodepth. Both the paleodepths and distribution of these hiatus maxima suggest that flow of Antarctic Bottom Water, Antarctic Intermediate Water, and North Atlantic Deep Water masses largely caused this erosion. Correlation of the hiatuses with oxygen isotope, carbonate and sea level records indicates that prior to 11 Ma, brief hiatuses including those resulting from nondeposition in high‐productivity equatorial regions largely correlate with global cooling episodes, high‐carbonate content, and lowstands of sea level. During the last 11 m.y., hiatuses also seem to correlate with cooling episodes, but carbonate dissolution is characteristic and sea levels may have been rising or at a lowstand. During the NH4, NH7, and NH8 intervals, it is possible that a rise in sea level corresponds with polar cooling, but there is uncertainty in correlation. Brief hiatuses during rising sea levels can be explained by basin‐shelf fractionation of carbonates. Hiatuses during sea level lowstands and cooling episodes may result from intensified bottom water circulation and increased corrosiveness of bottom water due to higher levels of CO₂ and increased productivity during increased upwelling. Supplement (Appendix 1) is availablewith entire article on microfiche. Orderfrom American Geophysical Union, 2000Florida Avenue, N.W., Washington, DC20009. Document P87001; $2.50. Paymentmust accompany order.