--> ABSTRACT: Topographically Restricted Deep-Sea Fan Deposits, Inglewood Field, Los Angeles Basin, by W. J. Schweller, J. Gidman, A. A. Reed, and C. W. Grant; #91038 (2010)

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Topographically Restricted Deep-Sea Fan Deposits, Inglewood Field, Los Angeles Basin

W. J. Schweller, J. Gidman, A. A. Reed, C. W. Grant

Pliocene deep marine sandstones and mudstones from the Inglewood field of the Los Angeles basin represent unusual deep-sea fan deposits that do not fit most published models. A 1,400-ft continuously cored interval consists of alternating sandstones and mudstones that represent turbidites and other types of deposits. Individual sandstone beds range from 0.1 ft to over 10 ft (2 cm to 3 m) thick and show differences in sedimentary features and grain-size distribution that correlate with bed thickness. Log correlations across the field show that most individual sandstone beds are laterally continuous across much of the field, indicating deposition in broad, flat lobes rather than in narrow channels.

Five lithofacies were identified. These can be related to depositional subenvironments such as lobes and overbanks (levees). However, the cored interval lacks the vertical sequences expected in a typical sand-rich fan prograding across an unrestricted basin. Markov sequence analysis shows nearly equal alternations of thinning-up and thickening-up sequences, rather than the small-scale thinning-up (channel abandonment) sequences superimposed on larger scale thickening-up (lobe progradation) sequences predicted by most deep-sea fan models.

The unusual vertical sequences probably result from topographic restriction of a turbidite-fed deep-sea fan developed in a deep, confined basin. The resultant geometry of sandstone beds implies a different strategy for field development than for fields that contain channelized deep-sea sands.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.