Archive for July 5th, 2013

Bryozoans finally make an appearance in the Jurassic of southern Israel

July 5th, 2013

MatmorCollecting070513MITZPE RAMON, ISRAEL–The concentrated effort of all four Wooster Geologists in Israel finally paid off in fossil bryozoans today. Steph Bosch (center) is studying the bryozoans of the Matmor Formation (Middle Jurassic) in Makhtesh Gadol for her Independent Study project. We have bryozoan specimens collected on earlier expeditions to the Matmor, but on this trip have been stymied in our efforts to add to the meager collection. Bryozoans are rare in these equatorial sediments, even though the diversity of other fossils here is very high. We want to describe this fauna for the first time and place it in its environmental and evolutionary context.

This afternoon we visited a site at the far northeastern end of the makhtesh where we knew lots of crinoids were preserved. (The locality is creatively known as “GPS 004″; N 30.94916°, E 35.01110°.) Our working hypothesis is that bryozoans preferred the same conditions as echinoderms in the Matmor Sea. The strategy worked: we found two runner-type bryozoans on crinoid columns. They are the stomatoporid-type of uniserial runner, giving us at least two different species of bryozoan now from the Matmor. Undoubtedly there are more such specimens on the many crinoid ossicles we collected to wash and examine later in the Wooster lab. They are far too small to photograph here in my hotel room!

Steph, appropriately, found the first specimen. Oscar Mmari (on the left) found the second just as we were leaving. Lizzie Reinthal (on the right) is actually working on crinoid taphonomy, so she was very pleased by all the specimens we collected today.

MatmorCollectingView070513A wider view of our collecting site in the Matmor Formation, with the northeastern wall of Makhtesh Gadol in the background.

It feels good to now have all three Wooster seniors with materials they’ve collected for their Independent Study projects. A nice way to end our first week of work in Israel!

An outcrop Dr. Judge would love (Upper Cretaceous of southern Israel)

July 5th, 2013

WadiHavarimDragFold070513MITZPE RAMON, ISRAEL–Wooster Geologists Oscar Mmari’s Independent Study project on the Late Cretaceous phosphorites in the Negev has become multidimensional. His most interesting section is in Wadi Hawarim, where we returned today with Yoav Avni for additional observations and measurements. We are now doing a bit of structural geology that Dr. Shelley Judge would appreciate. In this view above, the dark resistant unit on the left is the lower silicified portion of the Mishash Formation (Upper Cretaceous). Even though it looks like an igneous intrusion, these are sedimentary beds folded so that they are vertical in attitude. On the right you may be able to make out Oscar standing on Mishash beds that are almost horizontal. How does this make sense?

What happened was faulting on the farthest left in this view above. A normal fault perpendicular to this screen has its upthrown block on the left and downthrown block on the right (where Oscar is standing). The Mishash silicified rocks are part of a drag fold as the blocks moved against each other. It appears that this faulting took place while the rest of the Mishash was still accumulating because debris from the silicified layers was spread over the phosphorites as they developed. There may also have been a shallowing of sealevel indicated by a layer colonized by shrimp who made Thalassinoides burrow systems that became inundated with siliciclastic sediment likely derived from the fault scarp.

OscarWadiHavarim070513In this view into Wadi Havarim, the whitish phosphorite beds of the Mishash Formation are in the center above a dark conglomerate and below the yellowish Ghareb Formation.

OscarAtWork070513Oscar is sitting on Mishash conglomerate taking careful notes on this complex geological scenario. He’s going to need his skills in structural geology, sedimentology, stratigraphy and paleontology for this project!