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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 5. (May)

First Page: 543

Last Page: 543

Title: Pennsylvanian Shelf Carbonates, Madera Formation, Taos Trough, Northern New Mexico: ABSTRACT

Author(s): Janice L. Alsop

Article Type: Meeting abstract

Abstract:

The sandy limestones of the Madera Formation differ significantly from shelf carbonates described in other southwestern late Paleozoic basins in that: (1) they were deposited adjacent to an active uplift that provided terrigenous clastics; and (2) no large scale phylloid algal mounds were developed. Prior to deposition of the Madera limestones, early to middle Desmoinesian deltaic deposits derived from the Uncompaghre uplift prograded eastward into the basin. Carbonate deposition was locally initiated on abandoned deltaic platforms, where low relief blue-green algal mudbanks and bryozoan mounds developed.

Carbonate deposition became widespread during a middle Desmoinesian transgression. Hummocky to cross-bedded crinoid grainstone shoals formed on and seaward of the algal mudbanks. These initial crinoid shoals were small and laterally discontinuous. As the shoals prograded and evolved into wave resistant barriers, extensive lagoonal and channeled tidal-flat deposits developed behind them. These low-energy lagoonal facies are characterized by small, low relief phylloid algal bars separated by bioturbated sandy siltstones. Fusulinid packstones filled tidal channels which graded laterally into dasycladacean algal flats. Progradation of the shoals also caused steepening of the platform margin, which led to restricted circulation in the slope/basinal depression. Anoxic conditions developed, nd thick black, calcareous shaly siltstones were deposited in the basin. Carbonate deposition on the shelf was then terminated by renewed fluvial activity.

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