The basal member of the Zechstein (Permian) carbonate rock sequence of southeastern Durham is considered the product of accumulation of carbonates and/or mud alternating withaccumulation of bituminous matter during a long slow process of sedimentation. The distribution of most minor elements reflects normal weathering of the land surface, but the contents of zinc, lead, barium, and, in places, copper exhibit a variation that does not conform to any pattern that could be related primarily to rate of sedimentation. Intermittent introduction of the anomalously distributed elements by submarine springs into the lagoonal environment of the depositional basin is probably the most satisfactory of three possible explanations of the source of the abnormally distributed elements.

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