. Maryland geological survey. deposits consist very largely of redeposited Piedmontcrystallines, and. to a less extent of Appalachian strata, is what mightbe expected, but the circumstance that no clearly defined trace of re-deposited Newark materials has been found in the Potomac deposits ofMaryland is somewhat surprising. From this we must infer either thatthe Newark was not to any great extent exposed to Potomac erosion, orthat its materials were not sufficiently consolidated to permit of trans-portation, except in so finely divided a condition as to be is quite certain th
. Maryland geological survey. deposits consist very largely of redeposited Piedmontcrystallines, and. to a less extent of Appalachian strata, is what mightbe expected, but the circumstance that no clearly defined trace of re-deposited Newark materials has been found in the Potomac deposits ofMaryland is somewhat surprising. From this we must infer either thatthe Newark was not to any great extent exposed to Potomac erosion, orthat its materials were not sufficiently consolidated to permit of trans-portation, except in so finely divided a condition as to be is quite certain that during maximum Potomac subsidence a largebody of Newark materials, especially beyond the limits of Maryland,was beneath tide level, and therefore not exposed to subaerial as the Potomac beds themselves, particularly the basal ones,have since that date undergone considerable induration, often without * See list of species in Tables of Distribution. MARYLAND GEOLOGICAL SURVEY. LOWER CRETACEOUS. PLATE NEAR VIEW OF LAYERS OF CARBONATE OF IRON NODULES IN THE ARUNDEL CLAYS, REYNOLDS IRON MINE, I MILE SOUTH OF HANOVER, ANNE ARUNDEL COUNTY. Maryland Geological Survey 81 the agency of iron oxide, we may suppose that the subaerial Newarksandstones of that date, if consolidated at all, were considerably lessresistant than, for example, during the early Pleistocene, in the depositsof which the Newark materials are abundantly represented. The basal deposits of the Potomac Group, produced by the initial warp-ing of the continental border and described as the Patuxent formationindicate in their arkosic character their proximity to the source of supply,which was the extensively disintegrated Piedmont crystallines. It isassumed that the Weverton peneplain, upon which the oldest knownCoastal Plain sediments were deposited, extended as a land surface tothe eastward of the present coast line. The epeirogenic movement, whichstimulated erosion and inaugurated the Potomac
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