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Complex oöids from Triassic lake deposit, Virginia

ContributorsCarozzi, Albert V.
Published inAmerican Journal of Science, vol. 262, no. 2, p. 231-241
Publication date1964
Abstract

Complex reworked oöids are described from a lacustrine limestone intercalated in the Manassas formation (Late Triassic) near Culpeper, Virginia. These oöids are characterized by several sets of concentric or non-concentric rings with intercalations of an argillaceous calcilutite which also builds their nuclei and the interstitial matrix of the deposit. The nuclei are simple or compound. In the first case, they consist of an irregular pellet probably generated by a process of aggregation of aragonite needles. Compound nuclei display two to sixteen oöids embedded in a variable amount of mud. Both types of reworked oöids result from the numerous repetition of phases of oölitization, deposition in a mud where pellets were formed by aggregation, and reworking. These processes must have taken place in the immediate vicinity of each other. Such conditions are actually very common in shallow water environments, lacustrine, lagoonal, or marine. Complex reworked oöids occur in small number in almost all oölitic limestones but have been frequently overlooked. Their abundance in the Triassic of Virginia is unusual for a carbonate rock. However it is comparable to the situation displayed in many oölitic iron ores where numerous complex oöids indicate reworking phenomena of high complexity.

Affiliation Not a UNIGE publication
Citation (ISO format)
CAROZZI, Albert V. Complex oöids from Triassic lake deposit, Virginia. In: American Journal of Science, 1964, vol. 262, n° 2, p. 231–241. doi: 10.2475/ajs.262.2.231
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ISSN of the journal0002-9599
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