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Wooster’s Fossils of the Week: A Jurassic seafloor assemblage
Images from fieldwork this week. These are all fossils exposed on a single bedding plane in the Matmor Formation (Middle Jurassic, Callovian) exposed in Makhtesh Gadol. I found them many years ago while working through the stratigraphy near the top of the formation. They present a vignette of life in a shallow carbonate Jurassic sea. They are so well preserved you can almost feel the gentle waves and hear the squawks of the pterosaurs wheeling above. In the top image we have my favorite of the set: A gastropod shell in the middle surrounded by mytilid bivalves. The bivalves were no doubt attached to the gastropod by their thin byssal threads, holding them in place in the choppy waters. The preservation is remarkable. All these shells are calcitized, but retain their ornamentation. They are exposed on a bank of a wadi, and so they have been lightly etched from the matrix by sandy water during floods.
Just to show the gastropod-bivalve association is not a fluke of preservation, here’s another set. On this bedding plane are four such assemblages.
Here’s another gastropod, this one with heavy spines.
A high-spired gastropod is on the left, with a mytilid in side-view on the right.
Another gastropod to end the set. These are just a few of the many such fossils exposed on this bedding plane of the Matmor Formation.
Source: http://woostergeologists.scotblogs.wooster.edu/2016/03/18/woosters-fossils-of-the-week-a-jurassic-seafloor-assemblage/
