Lithic Type Specimen: OJCU-4 (Ordovician Jefferson City-Cotter Undifferentiated, Variety 4)

Object Details

Notes: OJCU-4 (Ordovician Jefferson City-Cotter Undifferentiated, Variety 4): Found in the Mountain Home area of Arkansas. A dark gray to almost black ground is streaked in places with lighter medium gray. Texture varies from fine and vitreous (in the almost black areas) to medium coarse (in the banded or streaked). Some of the black or dark gray resembles Pitkin chert. The streaked portions tend to be more fractured than the solid dark dolomite. Weathers to a tan or brown. A fairly scarce variety.; JEFFERSON CITY. The Jefferson City formation is found on the surface throughout the southern half of Missouri, except in the extreme southeast and in the western counties (except McDonald & Barry, where limited amounts occurr). Over much of this area the Jefferson City and Cotter are not differentiated because the lithiologies are similar and often thin. In many cases the mottled and irregularly banded Jefferson City dolomite cannot be separated from from similarly marked Cotter. A careful microscopic examination reveals few distinguishing differences, so these are best left undifferentiated. The following two varieties seem to be clearly associated with the Jefferson City formation.; Jefferson City-Cotter
Record Last Modified: 22 Jun 2022
Specimen Count: 1