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The AAPG/Datapages Combined Publications Database

CSPG Special Publications


The Mesozoic of Middle North America: A Selection of Papers from the Symposium on the Mesozoic of Middle North America, Calgary, Alberta, Canada — Memoir 9, 1984
Pages 569-569
Symposium Abstracts

Barrier Island, Tidal Inlet and Previous HitFloodNext Hit Tidal Delta Deposits of the Upper Cretaceous Spring Canyon Member, Blackhawk Formation: Abstract

D. L. Kamola1, J. D. Howard2


Beach-to-offshore sequences in the Spring Canyon Member of the Upper Cretaceous Blackhawk Formation have previously been identified as mainland beach or wave-dominated deltaic deposits. The identification of Previous HitfloodNext Hit tidal deltas and tidal inlets in the Helper, Utah area suggest these marine sequences are actually barrier island deposits.

An erosional contact, marking the removal of the foreshore and part of the upper shoreface, exists between Previous HitfloodNext Hit tidal delta and beach deposits. Truncated trough crossbeds of the upper shoreface are overlain by thin, landward-dipping, imbricated sheets of the Previous HitfloodNext Hit tidal delta. These sheets, each burrowed and/or rooted, indicate episodic pulses of sand entering a lagoonal system. Lateral to the Previous HitfloodNext Hit tidal delta, burrowed siltstones, interpreted as lagoonal deposits, overlie burrowed tops of trough cross-bedded upper shoreface sandstone.

A sheet-sand deposit of channel-fill, trough crossbedded sandstone, interpreted as tidal inlet facies, replaces the foreshore and part of the upper shoreface of the corresponding beach sequence. This sandstone separates coastal plain and shoreface deposits. Current ripples, convolute bedding, reactivation surfaces, and intensely bioturbated beds are common in the tidal inlet facies. Trough crossbeds vary from a predominantly NW (landward) orientation, to a combination of NW, SW and NE orientations. Trace fossils include Ophiomorpha, Teredolites, and ?ray-hole structures. Landward-imbricated sandstone sheets of the Previous HitfloodNext Hit tidal delta occur updip from the tidal inlet facies.

Smaller, tidally influenced channel-fill deposits (15 -20′, 5 - 6 m thick), landward of the tidal inlet facies, are characterized by landward oriented (Previous HitfloodNext Hit dominated) paleocurrent directions, brackish-water bivalves, Ophiomorpha, Thalassinoides, and Teredolites. Collectively, this indicates a Previous HitfloodTop dominated, marginal marine environment landward of the barriers.

No major distributary channel system exists landward of the tidal inlet facies. Because of this, the tidal inlet cannot be misidentified as a distributary channel deposit.


Acknowledgments and Associated Footnotes

1 Exxon Production Research Co., Box 2189, Houston, Texas 77001

2 Skidaway Institute of Oceanography, Savannah, Georgia

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