Stratigraphy and structure along a continuous seismic reflection profile from Cape Hatteras, North Carolina, to the Bermuda Rise

Abstract

A continuous seismic reflection profile extends from the continental slope off Cape Hatteras to the Bermuda Rise with sub-bottom penetration to about 2.0 sec (≈2.0 km). Each physiographic province is underlain by distinctive patterns of reflection interfaces which may correspond to sequences of well-stratified sediment. The continental slope is underlain by strata with low seaward gradients (< 0.9 × 10−2 radian SE) which are consistent with seaward projections of Cretaceous through Cenozoic coastal plain strata. The strata terminate against a thin mantle of sediment draped with a gradient of 10.5 × 10−2 radian SE nearly parallel to the sediment-water interface. The stratal terminations appear to have resulted from rotational slumping and retreat of the continental slope at least 5 km. The continental rise does not fit previous concepts that it is underlain either by unstratified sediment or by homogeneously stratified sediment. The continental rise is underlain to at least 0.5-sec two-way travel time (450 meters) primarily by extensive sedimentary strata with about 1.0 × 10−2 radian SE seaward gradients nearly parallel to the sediment-water interface. The strata are divided into a mosaic of units. Each unit is tens of kilometers wide (NW-SE) by hundreds of meters thick, contains a uniform pattern of strata, and is bounded by discontinuities. The discontinuities are interpreted as products of erosional and lateral gravitational displacement processes including, in particular, gravitational gliding. Gravitational gliding of units would explain the observed configuration of strata on the lower continental rise and is consistent with values of shear stress calculated for glide units buoyed by interstitial fluid pressure and with measured sediment shear strength. The continental rise may have extended primarily by gravitational gliding for a distance of the order of tens of kilometers over the margin of the Hatteras abyssal plain. A possible relict continental rise extends at least 150 km over a relict abyssal plain (horizon A). It is inferred from the configuration of the stratigraphic boundary that continental rise extension and abyssal plain formation may have alternated in time. The post-Late Cretaceous evolution of the continental margin has apparently involved tilting of the continental terrace including the coastal plain and two major extensions of the continental rise over two abyssal plains.