--> --> A Reevaluation of the Silurian Burnt Bluff Group, Michigan Basin through Sedimentologic and Paleoecologic analysis Voice, P.J., Harrison, W.B. III , and Grammer, G.M. #90044 (2005).

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A Reevaluation of the Silurian Burnt Bluff Group, Michigan Basin through Sedimentologic and Paleoecologic analysis

 

Voice, P.J. 1, Harrison, W.B. III 2, and Grammer, G.M. 2

1Present address: Virginia Tech University, Blacksburg, VA

2Western Michigan University and the Michigan Basin Core Research Laboratory, Kalamazoo, MI

 

The Middle Silurian Burnt Bluff Group has produced over 50 BCF of Natural Gas from several isolated fields in the northeastern and western-central portions of the Michigan Basin.  Very limited geological studies exist for these potentially significant hydrocarbon producing strata.

The Burnt Bluff Group was deposited as a shallow carbonate ramp during the Early Middle Silurian in the Michigan Basin.  The Burnt Bluff Group is composed of three formal Formations: the older Lime Island Formation, the Byron Formation and the younger Hendricks Formation.  The Burnt Bluff Group thins to the south of the outcrop belt and pinches out in the subsurface near the midline of the Lower Peninsula. 

The Lime Island formation was deposited above effective storm wave base with graded skeletal storm beds interbedded with bioturbated, skeletal wackestones.  Fossils include pentamerids, favositids and stromatoporoids, representing normal open marine conditions.  The Byron Formation consists of restricted lagoonal deposits containing ostracodes and gastropods and humid tidal flat deposits.  The Hendricks Formation has local tabulate-stromatoporoid patch reefs with background deposition of bioturbated, skeletal, mud-rich packstones of the mid-shelf environment.  Patch reefs of the Hendricks Formation are natural gas reservoirs in the northeastern Lower Peninsula, although most production is from the deeper water facies in the mid-basin open-shelf deposits similar to the overlying Manistique Group.  More basinward Burnt Bluff lithologies consist of bioturbated skeletal wackestones with skeletal storm lags and have been extensively dolomitized.  

Diverse floral and faunal elements suggest open marine conditions were prevalent over most of  Burnt Bluff Group time.  In addition, isotopic data from pentamerid brachiopods are similar to values derived from brachiopod material of other portions of the Silurian world and confirm that the Burnt Bluff Group was deposited under normal marine conditions.