Date of Award
Master of Science
Geological and Environmental Sciences
Dr. W. David Kuenzi
Dr. William Harrison III
Dr. Gifford Kessler II
Masters Thesis-Open Access
A 5,000 ft (1,538 m) pre-Mt. Simon (Upper Cambrian) red-bed sequence, encountered in the Gratiot County deep borehole (Sparks et al. #1-8) and herein named the North Star Formation, consists of undeformed recurring beds of immature arkosic sandstone 2 to 34 in (5 to 85 cm) thick. These beds grade upward from erosional basal contacts into mudstone units 1 in to 12 ft (3 cm to 3.8 m) thick. Within the sandstones, grading, horizontal lamination, and crossstratification define Bouma intervals "a", "b", and "c", which combine to form incomplete Bouma sequences. Mudstones exhibit abundant horizontal laminations. Secondary sedimentary structures (load casts within mudstones and at sandstone-mudstone contacts, and abundant fluid escape structures) are indicative of the rapid accumulation of water-saturated sediment.
Modal and textural analysis reveals that the sandstone beds are composed of coarse- to fine-grained, quartz overgrowth- and calcitecemented, immature arkoses that average 57% framework grains, 9% mudstone rip-up clasts derived from underlying mudstones, 27% pseudomatrix and protomatrix, and 3% cement. Essential framework grains average 60% quartz, 37% potassium feldspar, 3% plagioclase, and 0.5% plutonic rock fragments, and indicate derivation either from granitic or gneissic source terranes. The roundness of the quartz and feldspar grains indicates prolonged abrasion in high-energy (near shore or eolian) environments before final deposition. During burial, precipitation of quartz overgrowth cement, before squashing of mudstone clasts to produce pseudomatrix, suggests that the rocks were at one time overpressured (undercompacted for the depth).
Pre-Mt. Simon facies similar to those from the Sparks et al. #1-8 are observed in a red-bed sequence penetrated in a well on Beaver Island, 160 mi (260 km) to the north. Both sequences occur within the Mid-Michigan gravity high, and are the result of penecontemporaneous deposition within submarine fan systems by sediment gravity flows, low-velocity tractive currents, and pelagic fallout. These fans formed in an elongate, broadly subsiding protoceanic basin which foundered isostatically following arrestment of Keweenawan rifting and production of oceanic lithosphere. It is further suggested that protoceanic rifting in the Lake Superior region and along the Mid- Michigan gravity anomaly was approximately contemporaneous, and that both areas underwent a similar sequence of thermotectonic volcanism, deformation, and sedimentation, followed by passive foundering and shallow marine and basinal turbidite sedimentation.
Fowler, "Analysis and Interpretation of the 5,000 ft (1,538 M) Red-Bed Sequence Encountered in the Sparks et al. #1-8 (Michigan Basin Deep Borehole)" (1979). Master's Theses. 1974.