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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 69 (1985)

Issue: 9. (September)

First Page: 1444

Last Page: 1444

Title: Significance of Great Lateral Extent of Thin Units in Newark Supergroup (Lower Mesozoic, Eastern North America): ABSTRACT

Author(s): Paul E. Previous HitOlsenTop

Article Type: Meeting abstract

Abstract:

The lacustrine sediments of the Newark Supergroup accumulated in rift valleys developed during the early phases of the fragmentation of Pangea. Analogy with modern rift valleys has led us to expect abrupt facies transitions and syndepositional structural complexity. However, in contrast to their supposed modern analogs, many thin (< 6 m) organic-rich lacustrine units within the Newark can be traced over large areas (+2,000 km2) with only gradual lateral changes in thickness and lithology.

Lateral correlation is afforded by: (1) detailed ecostratigraphic correlation of fossils in lacustrine cycles, (2) key marker beds such as earthquake-induced fluidized beds, (3) detailed paleomagnetic reversal stratigraphy (by others), and (4) matching of microlaminae and turbidites. These observations suggest that the lakes which produced the organic-rich units were very large (+2,000 km2) and deep (+100 m) while at their maximum extent.

The continuity of thin beds across the major intrabasin faults and the gradual lateral change in thickness over the basins show that these faults were not active during the deposition of the units and that the size of the subsiding blocks of these Mesozoic basins was much larger than is currently the case in the east African rifts. Simple analogy between Newark and African rift systems in structure and facies is not justified and obscures their real and important differences.

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