Depositional environments, diagenesis, hydrocarbons: Codell and Juana Lopez members of Carlile shale (upper Cretaceous), Canon City-Raton basins, south-central Colorado

Conference · Fri Sep 01 00:00:00 EDT 1989 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:5630613

Krutak, P R ^[1]

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1. Louisiana State Univ., Baton Rouge (USA)

Codell and Juana Lopez strata in the Canon City and northern Raton basins comprise a nearshore marine system which was deposited in a series of barrier islands, lagoon fills, tidal deltas, and offshore bars. Codell thicknesses vary but average 6 m (20 ft). Three areally significant Codell paleoenvironments occur: barrier island, lagoonal, and offshore bar. Juana Lopez rocks are thinner, usually less than 1.8 m (6 ft). Five distinctive lithofacies/paleoenvironments occur in the Juana Lopez: (1) a calcarenite or limy sandstone (tidal flat); (2) a sandstone with limonitized borings (offshore bar complex); (3) a shaly to massive sandstone sequence (subaerial beach/dune ); (4) a sandy limestone or biosparite (lagoonal/bay molluscan biostromes); and (5) a sandy shale (offshore bar sequence). These deposits accumulated along a northeastward-trending coast that prograded southeastward in response to a gradual drop in sea level. Petrographic and scanning electron microscopy study reveals the following diagenetic sequence in the Codell Sandstone: (1) modification by authigenic, syntaxial quartz overgrowths; (2) chert cementation; (3) dissolution episodes causing corrosion of quartz, chert, and feldspar; (4) calcite cementation; (5) late-stage limonitization; and, in rare instances, (6) dehydration of limonite to hematite. Diagenetic changes in the Juana Lopez Member involve minor dolomitization, precipitation of calcite rim cement, and limonitic staining. Stratigraphically trapped hydrocarbons occur in bioturbated, relict shelf Codell sandstones in the west-central portion of the Denver basin. Valley-fill( ) Codell sandstones of the northern Denver basin are generally tight but do produce. Juana Lopez calcarenites and fetid biosparities may lack commercial hydrocarbons.

• OSTI ID: 5630613
• Report Number(s): CONF-8910195-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 73:9; Conference: AAPG Rocky Mountain Section meeting, Albuquerque, NM (USA), 1-4 Oct 1989; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

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