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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 5. (May)

First Page: 603

Last Page: 604

Title: Recognition of High Gradient Braided Stream Deposits, Sespe Formation (Tertiary), Ventura Basin, California: ABSTRACT

Author(s): Willard A. McCracken

Article Type: Meeting abstract

Abstract:

Lower Sespe arkosic sandstones and petromictic conglomerates of late Eocene and Oligocene age rim the Ventura basin in California and are interpreted as high-gradient, braided river deposits. Lower Sespe deposits contain a high ratio (over 20/1) of bedload/suspended load. Lenticular, poorly sorted, imbricated, bar-shaped conglomerate units interbedded with graded to parallel-laminated sandstone beds are typical of lower Sespe deposits. Graded and reverse graded conglomerate units, graded

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sets of avalanche cross-stratification, cuspate cut-and-fill structures, and antidune cross-stratification also characterize the lower Sespe conglomerate facies. These features all indicate a braided stream model for lower Sespe deposits.

Steep gradients during lower Sespe deposition are suggested by: (1) clast size data (average maximum clast size = 41 cm), (2) a predominance of upper flow regime structures (85% of all structures measured), and (3) high consistency ratios (mean consistency ratio = 0.78) of paleocurrent data.

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Copyright 1997 American Association of Petroleum Geologists