Reconstruction of Tertiary progradation and clinoform development on the New Jersey passive margin by 2-D backstripping

We have reconstructed the Oligocene to Middle Miocene paleobathymetry and s tratigraphy of the New Jersey margin using a modified backstripping techniq ue. By analyzing the geometry of the margin through time, we investigate it s response to fluctuating sea level, changing climate, and Variable sedimen t supply during the Tertiary. The reconstructions reveal a change in the ma rgin morphology from a more steeply dipping (1 :300 to 1 :500) carbonate ra mp in the Eocene to a flatter shelf with a sharp shelf edge at present. Thi s was accomplished by an increase in the terrigenous sediment supply that f illed available accommodation and caused progradation across the margin. We link the increase in sediment flux with climatic cooling rather than tecto nic processes. The progradation is evidenced by a series of clinoforms whos e formation was modulated by sea level and which extend over 100 km across the shelf. The height and dip of the clinoforms increased as they extended onto the deeper parts of the earlier ramp. The Miocene clinoform rollovers at the New Jersey margin had water depths of similar to 60-130 m and are in terpreted as the edge of a new continental shelf built over the older ramp. Sea-level fall was probably insufficient to drive the Miocene shorelines p ast the shelf breaks. Thus, measurements of sea-level amplitude based upon 'coastal' onlap over the clinoforms are not reliable. (C) 1999 Elsevier Sci ence B.V. All rights reserved.