Oxygen isotopic variations show that polar ice volume has changed markedly during the last 35 m.y. (the "Icehouse" interval), and perhaps longer (Miller et al., 1991a). As a result, global sea level has varied by many tens of meters, and such changes have had a profound impact on shallow-water deposition, nearshore ecosystems, particle and nutrient transfer to the deep sea, and other components of the ocean-atmosphere system. The primary goals of Leg 174A are to investigate the stratigraphic responses to sea-level change, and specifically to:

Seismic stratigraphic studies reveal a complex array of discontinuities within the mid-Atlantic continental margin. Leg 174A will provide new information about the arrangement of depositional facies that is needed to evaluate whether the surfaces provisionally interpreted as sequence boundaries are in fact related to the lowering of depositional base level. Leg 174A will also place constraints on the partitioning of unconformity-bounded sequences between so-called lowstand, transgressive, and highstand units. This is relevant to the controversial issue of how sequence boundary development is related to the time of most rapid sea-level fall.

To 174A Drilling Strategy and Proposed Sites

To 174A Table of Contents

ODP Publications Homepage

ODP Homepage