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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 65 (1981)

Issue: 5. (May)

First Page: 918

Last Page: 918

Title: Blake Escarpment Carbonate Platform Edge: Conclusions Based on Observations and Sampling from Research Submersible: ABSTRACT

Author(s): William P. Dillon, Charles K. Paull, Page C. Valentine

Article Type: Meeting abstract


Three continuous transects of the Blake Escarpment, east of Florida, were made during 10 dives in the submersible Alvin at depths from 1,400 to 4,000 m. We observed and sampled outcrops of horizontal strata known, from multichannel profiles across the dive sites, to extend westward beneath the Blake Plateau carbonate platform. The northern end of the Blake Escarpment, at the salient of the Blake Spur, is a nearly vertical limestone cliff, which is pitted and commonly fluted by vertical borings, coated by ferromanganese oxide, and heavily encrusted by organisms. Presumably, the cliff face is maintained by bioerosion and corrosion, and debris is removed by the strong turbulent currents (2 kn). Average slopes were less steep at transects 130 and 200 km south of the Blake Spu , but vertical cliffs as much as 450 m high exist. Talus slopes are common, and the large blocks and landward dips of beds suggest collapse of fragments at least several hundred meters across. On the southern transect are broad slopes of rippled pteropod sand between near-vertical outcrops; a vertical 160-m cliff of massive limestone at the top of the escarpment and rudists in talus blocks suggest the presence of a Mesozoic reef. Preliminary analysis of calcarenous nannofossils shows rocks as old as Early Cretaceous; identification of older rocks is anticipated. Sedimentary structures and components indicate deposition in shallow water. Thousands of meters of subsidence and extensive erosional retreat were required to create the escarpment's present configuration.

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