The Waccamaw formation is directly on top of the Peedee in that area, with the intervening layers all eroded away, so that the Exogyras probably were washed out of the Cretaceous sediment by the late Pliocene ocean.  It is possible that some of them had ben washed out of Cretaceous sediment by previous incursions of the ocean and then remobilized by the Waccamaw ocean, which also washed away almost all trace of the intervening layers.  Different units within the Waccamaw and possibly older Pliocene material are also mixed in at this locality, so a lot of reworking was going on.  Not too far away, I found a single Cubitostrea sellaeformis, a distinctive large mid-Eocene oyster, where older Pliocene deposits lie directly on the Cretaceous Peedee.  All the rest of the Eocene had been washed away.

Thus, the "Waccamaw" Exogyras are probably only washed into the immediately overlying layer, but we do not generally have as neat a succession of layers as the Gulf Coast.

    Dr. David Campbell
    "Old Seashells"
    Biology Department
    Saint Mary's College of Maryland
    18952 E. Fisher Road
    St. Mary's City, MD  20686-3001 USA
    [log in to unmask], 301 862-0372 Fax: 301 862-0996
"Mollusks murmured 'Morning!'.  And salmon chanted 'Evening!'."-Frank Muir, Oh My Word!