Wooster’s Fossils of the Week: A Jurassic seafloor assemblage

March 18th, 2016

1 DSC_0184 copyImages 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.

2 DSC_0180 copyJust to show the gastropod-bivalve association is not a fluke of preservation, here’s another set. On this bedding plane are four such assemblages.

3 DSC_0178 copyHere’s another gastropod, this one with heavy spines.

4 DSC_0179 copyA high-spired gastropod is on the left, with a mytilid in side-view on the right.

5 DSC_0181 copyAnother gastropod to end the set. These are just a few of the many such fossils exposed on this bedding plane of the Matmor Formation.

2 Responses to “Wooster’s Fossils of the Week: A Jurassic seafloor assemblage”

  1. Bill Reinthalon 19 Mar 2016 at 10:13 am

    How big is that 10 sheqalim coin, Mark? Is a shekel divided into so many sheqalim? Why the difference in spelling–just because it’s a phonetic translation (shekel = sheqal?)? I had to look it up, but I couldn’t figure out how big it was….

    Israel has some really cool coin designs!

    Sorry…just curious!

  2. Mark Wilsonon 19 Mar 2016 at 11:25 am

    Hello Bill! That 10 shekel coin is 23 mm in diameter. The spelling is indeed phonetic. I’ve actually not dealt with coins less than 1/2 shekel. They are indeed cool designs, especially the bimetallic ones.

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