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Harold A. Hubbard

Publications and source records attributed to Harold A. Hubbard.

5 recordsLinked to original sources
USGS1975

Geology of Porcupine Mountains in Carp River and White Pine Quadrangles, Michigan

The Porcupine Mountains are the eroded remnants of the upper limb of an anticline that is faulted along most of its southern, overturned, limb. The exposed rocks include about 5,000 ft (1,525 m) of middle Keweenawan intermediate to mafic lava flows interbedded with subordinate lithic sedimentary rocks and also include about 3,000 ft (915 m) of overlying middle and upper Keweenawan sedimentary rocks. The sediments are derived from lower Keweenawan and older rocks. The structural relief is at least 8,000 ft (2,440 m) between the crest of the Porcupine Mountains anticline and the trough of the Iron River syncline about 5 mi (8 km) to the south. The reverse fault along the southern, overturned, limb of the anticline has a displacement of about 5,000 ft (1,525 m).

Michigan↗
USGS1975

Lower Keweenawan volcanic rocks of Michigan and Wisconsin

Unconformable sequences of Keweenawan volcanic rocks occur in Michigan and adjacent Wisconsin. The sequences differ in types of rocks, magnetic properties, metamorphic grade, and pattern of structural deformation; they had different vent areas and were deposited in basins that were only partly overlapping. The older sequence includes the Bessemer Quartzite and two newly named formations that are here assigned to the lower Keweenawan. The younger sequence includes the well-known Portage Lake Volcanics and a younger unnamed formation, both of middle Keweenawan age. Formerly the older rocks were interpreted as a fault-repeated part of the Portage Lake Volcanics, but new evidence indicates that these older rocks had been metamorphosed and tilted and were being eroded in middle Keeweenawan time.

Michigan, Wisconsin↗