Technical Note 20/4

LEG 171C
Blake Nose:
Paleogene and Cretaceous Intermediate Water History

Modified from Proposal 462 Submitted By
Richard D. Norris
Staff Scientist: Adam Klaus
Co-Chief Scientists: Richard D. Norris & Dick Kroon
Abstract

Sediments on the Blake Plateau and Blake Nose in the western North Atlantic offer an ideal record for reconstructing water mass chemistry and circulation in the Cretaceous and early Cenozoic. The plateau's location in the northern hemisphere, proximal to the western end of the Tethys Seaway, makes the deposited sediments ideal for determining northern sources of deep and intermediate waters. Leg 171C will drill three shallow holes (170-450 m deep) at each of five sites in a transect from the margin of the Blake Plateau to the edge of the Blake Escarpment.

The proposed transect of cores will be used to: (1) interpret the vertical structure of the Paleogene and Cretaceous oceans and test the 'warm saline deep water' hypothesis near the proposed source areas; (2) provide critically needed low latitude sediments for interpreting tropical SST and climate cyclicity in the Cretaceous and Paleogene; (3) provide well preserved planktic microfossils for refinement of low latitude Paleogene and Cretaceous chronologies and evolutionary dynamics; (4) recover a complete Cretaceous/Paleogene boundary along a depth transect to describe the events surrounding the boundary and water depth-related changes in sedimentation of the boundary beds; (5) recover sections suitable for magnetic stratigraphy so that low latitude biochronologies may be tied directly to the magnetic reversal record; (6) interpret the thermocline and intermediate water structure of low latitude, Lower Cretaceous oceans and refine the biochronology of this period.

To Leg 171C Proposed Site Information