BARRIER AND B ACK-BARRIER ENVIRONMENTS OF DEPOSITION OF THE UPPER- CRETACEOUS ALMOND FORMATION, ROCK SPRINGS UPLIFT, WYOMING
1978; Rocky Mountain Association of Geologists; Linguagem: Inglês
ISSN
2327-2945
Autores Tópico(s)Geological formations and processes
ResumoDetailed analysis of t he detrital rocks associated with coal deposits in the upper part of t he Upper Cretaceous Almond Formation of the Mesaverde Group has resulted in the identification of coal depositional settings. The several lithofacies indicate t hat depositional environments of this interval in the upper part of the Almond Formation include shoreface, barrier island, tidal inlet, tidal delta, washover fan, tidal f lat, lagoon, tidal creek, overbank, pond, and marsh. Tidal delta, tidal-inlet-chan nel, washover-fan, and tidal-creek deposits signif- icantly affected back-barrier accretion and lagoon filling. The complete filling of the lagoon led to coalescing of marsh on the back side of the barrier island with the marsh on the landward side of the lagoon. Thin, dis- continuous c oal beds which rapidly prade into carbonaceous shale formed in t6e marsh in close proximity to the barrier island. Thin to thick, lateral l y extensive coal beds t:mt Ic~cal iv graJe into carbonaceo~~s shale formed in the marsh on emergent levee, overbank, and bayfill deposits at the landward side of the lagoon. Deposition of the above detrital Seposits as well as tidal-creek chanrlel sandstones caused splittino and merging of the c oal beds. The depositional process and rate of sedimentation aod subsidence in the d epositional basin influenced to some degree the lateral variation of t he coal beds. tiinability and resource potential of coal beds in the Almond Formation can be better assessed if the precise distribution of the sedimentary environments is recognized.
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