Fossils in life position (Part 2)

One valve (half-shell) of a typical Miocene Pycnodonte oyster from Bed 4 of the Calvert Formation, Calvert Cliffs, Maryland. An old individual showing many growth lines that was collected from the reef shown in the previous post.

The presence of the fossil oysters that I described and illustrated in my previous post demonstrates several things.

• Like living oysters, they formed reefs—vast concentrations of individuals belonging to the same species.

• Before the oyster reef formed, about 2600 feet of sediment had already been deposited in this place.

• This prehistoric reef began when, at some point in time, environmental and substrate conditions were just right for baby oysters (larvae) to settle to the sea floor and begin growing shells. The oysters began to grow on blue marl, i.e., a clay layer that had been previously compacted and then extensively burrowed by marine invertebrates (mostly crustaceans). They did not begin to grow here during Noah’s Flood, which, as characterized by young-Earth creationists, was global and catastrophic, during which sediments that were tens to hundreds to thousands of feet thick were being deposited daily; sessile organisms (or any organisms for that matter) do not live in those kinds of conditions. None of the sediments along Calvert Cliffs show any evidence of having come about through catastrophic flood-like conditions.

• Once baby oysters begin growing on the sea floor, they are incapable of moving from that spot for the rest of their life (their shell is just too heavy).

• These large and thick-shelled oysters lived for many years in the same spot (or within inches) in which they are now preserved. One of the ways that you can know that these oysters lived here is that they are so well preserved with many shells preserving both valves intact. This is an observation that Thomas Say made back in 1824 of other fossil clams from Maryland. He wrote: “Many of these shells appear to the eye nearly perfect, in every respect, with the exception of color, as the recent ones of the coast, and not a few of the bivalves have both bivalves attached . . . circumstances which indicate an undisturbed deposition in the waters in which they lived.”

• And so these oysters did not live somewhere else on Earth and then were moved to this new spot as a result of Noah’s Flood. We know this because there are so many heavy shells of the same species present in one place. After 2600 feet of sediment had already been deposited in this place, Noah’s Flood could not have picked up these oysters from another intact oyster reef hundreds or thousands of miles away, transporting them together to then be dropped here, giving every indication that this is where multiple generations of shells spent all of their post-larval life. Nothing about these oysters lends any support to the suggestion that they never lived here but were only deposited here during Noah’s Flood.

• This oyster reef survived for at least as long as the age of its oldest member. That would be the minimum age for the age of this reef. Knowing exactly how long this reef survived here is not as important as recognizing that the individual filter-feeding oysters lived here for a length of time much longer than the duration of Noah’s Flood. Consequently, neither the sediments above or below these oysters could have come about as a result of this purported deluge. If these oysters represent a reef that existed prior to Noah’s Flood, then one must explain the origin of all the fossils in the 2600 feet of sediment below the reef. Alternatively, if this reef formed after Noah’s Flood, one has the burden of explaining when and how the 70 feet of sediments that now cover these oysters were deposited. There has been neither enough time nor the existence of environmental conditions suitable to accumulate the sediments lying above the reef (not to mention that all the other fossils above the oyster reef that are also in life position; they too demand slow rates of sediment accumulation).

• Oysters cannot survive if they are buried by sediment, so they were not living while buried in the sediment that now covers this extinct reef. Oysters don’t have long siphons (a fleshy tube allowing them to become buried in sediment and yet reach up through it to draw in water from the ocean bottom) and therefore don’t tolerate burial. Indeed, sediments were being laid down during the time that the oysters lived here; it’s just that the rate of accumulation was so slow that it did not interfere with the long life of these heavy-shelled oysters.

• This reef persisted at this precise stratigraphic level and in this exact geographic location for as long as environmental conditions were favorable for the growth and reproduction of the oysters. That the layer of fossil oysters is not really thick is clear indication that at some point, environmental conditions changed sufficiently to make it impossible for the reef to survive. Just like any other marine setting, environmental conditions did not remain the same forever, and eventually the water became too deep, which spelled doom for this reef.

• Sediments continued to accumulate slowly around the shells until they were completely buried.

I’ll conclude this series by discussing in my next post what implications  these facts about the oyster reef have for the claims of creationism and flood geology.

3 thoughts on “Fossils in life position (Part 2)”

    1. Dr. Stephen Godfrey replies:

      Thanks for your question about the pycnodontid oysters. The identification that I used was taken from Ward (1992; reference cited below). Dr. Lauck Ward reviewed the article that I posted and did not object to the identification that I provided. More recently though, Kidwell et al. (2015) identified these heavy pycnodontid oysters as “Ostrea” percrassa. So obviously, there is some question as to their generic identity. Perhaps a systematic review is in order. However, I have not found any reference identifying them to the genus “Crassostrea”. The Worldwide Mollusc Species Data Base lists the name as Ostrea percrassa Conrad, 1840 † – a synonym of: Pycnodonte percrassa (Conrad, 1840).

      Kidwell, S.M., Powars, D.S., Edwards, L.E., and Vogt, P.R. 2015. Miocene stratigraphy and paleoenvironments of the Calvert Cliffs, Maryland, in Brezinski, D.K.,

      Halka, J.P., and Ortt, R.A., Jr., eds., Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015: Geological Society of America

      Field Guide 40, p. 231–279, doi:10.1130/2015.0040(08).

      Ward, L. W. 1992. Molluscan Biostratigraphy of the Miocene, Middle Atlantic Coastal Plain of North America. Virginia Museum of Natural History Memoir, 2, 159 pp., 26 plates. Martinsville: Virginia Museum of Natural History.

      Stephen Godfrey


  1. Respected Dr. Stephen Godfrey ,
    Thank you very much for your informative reply. These oysters have thick foliated calcite shells and well developed chondraphore.
    2.AN ANALYSIS ON PREDATORY SIGNATURES ON MIOCENE OYSTERS OF CRASSOSTREA SP. FROM EAST COAST OF SOUTHERN INDIA (GSA Annual Meeting in Denver, Colorado, USA – 2016,Volume 48,Issue 7, Session No. 76,Booth 319,Paper .76-17Pages
    doi: 10.1130/abs/2016AM-285113


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