Characteristics of deltaic deposits in the Cretaceous Pierre shale. Trinidad sandstone, and Vermejo formation. Raton Basin, Colorado

Journal Article · Thu Apr 01 04:00:00 EST 1982 · Mt. Geol.; (United States)

OSTI ID:6356678

Flores, R M ^[1]; Tur, S M

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1. U.S. Geological Survey, Denver, CO

The depositional models previously described for the regressive sequence of Upper Cretaceous Pierre Shale, Trinidad Sandstone, and Vermejo Formation lithologies in the Raton Basin, Colorado, indicate to some degree the constructional--and destructional--deltaic characteristics of the sequence. However, the relationships of specific deltaic environments and deltaic abandonment phases to coal accumulation and distribution in the Vermejo Formation are not well understood. Detailed facies analyses of closely spaced measured surface sections in the Trinidad and adjacent areas of Colorado reflect deposition in the river-influenced delta. That this deltaic system was accompanied by abandonment of subdeltas is indicated by a destructional-deltaic facies of heavily bioturbated, carbonaceous sandstones, siltstones, and shales best recorded in the delta front deposits of the Trinidad Sandstone. This destructional-deltaic facies commonly separates overlapped distributary mouth-bar sandstones. Like their modern counterparts in the Mississippi delta system, the abandoned delta-front deposits are affected by wave reworking, as indicated by their mature and clean characteristics, although associated offshore barrier islands apparently were not formed. Perhaps the difference between these modern and ancient deltaic deposits is related to associated basinal processes attendant to a uniformly subsiding system in the highly muddy prodeltaic depositional environment in the Raton Basin. Although abandonment of subdeltas had a limited influence on the characteristics of the Vermejo coal deposits, coal accumulation nevertheless remained primarily controlled by persistent organic sedimentation in interdistributary backswamps.

• OSTI ID: 6356678
• Journal Information: Mt. Geol.; (United States), Journal Name: Mt. Geol.; (United States) Vol. 19:2; ISSN MOGEA
• Country of Publication: United States
• Language: English

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