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The Oriskany sandstone of New York is known in the central Appalachian region as the Ridgeley, overlying a lower member, called the Shriver. The topmost part of the Oriskany formation is generally bestrewn by round or elliptical black nodules described by modern stratigraphers as "chert nodules." These "chert nodules" were studied by the writer; they are phosphatic, the phosphate occurring in the form of collophane. X-ray diffraction pattern of the collophane is essentially the same as that of apatite.
Phosphates in the Oriskany formation are the result of complex factors prevailing in the Oriskany and Onondaga seas. The "chert nodules in the Oriskany" of New York were deposited in the westward-transgressing Onondaga sea, hence they occur in basal Onondaga. It is improbable that the genesis of phosphatic nodules is due to catastrophic events.
The Huntersville chert contains phosphatic nodules associated with glauconite and is not due to "chertification" of Onondaga shale.
Phosphate is found in abundance at many places in the Paleozoic column where it is certain that there is no unconformity, hence phosphate in itself is not a reliable criterion of unconformity. Since at some point of the phosphorus cycle there is an intimate connection between this element and organic matter, and since it is conceded today that oil and gas are derived from organic material, it is highly desirable to establish the exact connection existing between phosphates on the one hand and the source material of oil and gas on the other.
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