MESOZOIC-CENOZOIC SEDIMENTATION IN THE KANE FRACTURE-ZONE, WESTERN NORTH-ATLANTIC, AND UPLIFT HISTORY OF THE BERMUDA RISE

Seismic reflection profiles, basement structure-contour maps, and bath ymetric data are used to analyze sedimentation patterns over a distanc e of approximately 2,300 km along the Kane Fracture Zone and to interp ret uplift history of the Bermuda Rise. Sediments within the fracture valley thin seaward on younger crust and with distance from continenta l sources. Superposed on this pattern are the effects of local and reg ional basement structure, variations in surface-water productivity, in fluence of bottom currents, and local effects of sediment redistributi on. Preservation of a thicker and more complete sedimentary record wit hin the Kane fracture valley facilitates identification and eastward c orrelation of seismic reflections, and we have cross-correlated these reflections to synthesize an along-axis transect of the fracture zone. Stratigraphic correlations of key reflections to Deep Sea Drilling Pr oject drill sites determine the composition and ages of the lithologic sequences. Observed pinch-outs of seismic horizons J1, beta, and A o n fracture-valley crust extend significantly seaward of previously map ped limits, and the younger pinch-out ages accord better with ages def ined by deep-sea drilling. Paleosedimentation patterns in successive s tratigraphic intervals document the growth of the continental margin/b asin sedimentary prism from Late Jurassic time and the uplift of the B ermuda Rise beginning in middle Eocene time. Middle Eocene cessation o f turbidite deposition atop the Rise, as identified by Horizon A(t), m arks initiation of regional uplift. A seismic discontinuity in turbidi te ponds east of the Rise records a probable pulse of uplift during ea rly Oligocene time. Structure of the overlying seismic reflection sequ ence suggests continued uplift, albeit at decreasing rates, through th e late Oligocene and possibly through Miocene time. The anomalous elev ation of the Rise subsequently has been maintained, but there is no cl ear stratigraphic evidence for further growth. Turbidite ponds fill th e Kane fracture valley east of the Bermuda Rise and terminate against a prominent structural dam at 55-degrees 20'W. These ponds began to fi ll with turbidites in middle Eocene to early Olgocene time, and the se diments were derived from local sources. Within the past 10-12 m.y., t urbidity currents began to enter the ponds through connections with th e encroaching Nares Abyssal Plain, and they probably now constitute th e dominant sediment source for the fracture valley.