Occurrence of hiatuses PH and NH 1 through NH 7 in DSDP holes

• Main Authors: Keller, Gerta, Barron, John A
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1983
• Subjects: 10-90; 10-97; 11-101; 11-102; 11-103; 11-104; 12-111; 12-116; 12-119; 14-141; 14-142; 15-149; 15-150; 15-151; 15-153; 15-154; 16-155; 16-157; 16-158; 16-159; 16-160; 16-161; 16-162; 16-163; 17-164; 17-165; 17-166; 17-168; 17-170; 17-171; 18-172; 18-173; 19-183; 19-192; 20-199; 20-200; 20-202; 21-205; 21-206; 21-207; 21-208; 21-209; 21-210; 22-212; 22-213; 22-214; 22-215; 22-216; 22-218; 23-220; Antarctic; Drake Passage; Pacific; Antarc*; Antarctica; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.719185; https://doi.org/10.1594/PANGAEA.719185

Miocene paleoceanographic evolution exhibits major changes resulting from the opening and closing of passages, the subsequent changes in oceanic circulation, and development of major Antarctic glaciation. The consequences and timing of these events can be observed in variations in the distribution of deep-sea hiatuses, sedimentation patterns, and biogeographic distribution of planktic organisms. The opening of the Drake Passage in the latest Oligocene to early Miocene (25-20 Ma) resulted in the establishment of the deep circumpolar current, which led to thermal isolation of Antarctica and increased global cooling. This development was associated with a major turnover in planktic organisms, resulting in the evolution of Neogene assemblages and the eventual extinction of Paleogene assemblages. The erosive patterns of two widespread hiatuses (PH, 23.0-22.5 Ma; and NH 1, 20-18 Ma) indicate that a deep circumequatorial circulation existed at this time, characterized by a broad band of carbonate-ooze deposition. Siliceous sedimentation was restricted to the North Atlantic and a narrow band around Antarctica. A major reorganization in deep-sea sedimentation and hiatus distribution patterns occurred near the early/middle Miocene boundary, apparently resulting from changes in oceanic circulation. Beginning at this time, deep-sea erosion occurred throughout the Caribbean (hiatus NH 2, 16-15 Ma), suggesting disruption of the deep circumequatorial circulation and northward deflection of deep currents, and/or intensification of the Gulf Stream. Sediment distribution patterns changed dramatically with the sudden appearance of siliceous-ooze deposition in the marginal and east equatorial North Pacific by 16.0 to 15.5 Ma, coincident with the decline of siliceous sedimentation in the North Atlantic. This silica switch may have been caused by the introduction of Norwegian Overflow Water into the North Atlantic acting as a barrier to outcropping of silica-rich Antarctic Bottom Water. The main aspects of the present oceanic ...