Abstract

Fault trough deposition during the Late Devonian in the Perry Formation of Maine and Canada produced texturally and mineralogically immature red and green sandstones as well as conglomerates and mudstones containing angular clasts and hematite and calcite cement. Deposition occurred in two separate basins, each with different source areas. The origin of the red color of the Perry Formation is two fold. Some of the red pigment is primary, derived from underlying older lithologic units. Secondly, mafic minerals such as magnetite and hornblende, were altered and partially removed by intrastratal solutions providing in situ alteration to form additional hematite. Calcareous crusts associated with these sediments indicate they probably were formed in an arid setting. Once formed, these crusts impeded upward migrating iron-laden groundwater, trapping some iron in cracks and fractures below the crusts. Migration and deposition of iron in solution by groundwaters is suggested as an agent which aided in the formation of the red beds. The iron in solution might have been derived from an external source in the groundwater recharge area to supplement iron formed by in situ alternation of mafic minerals.

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