Mark Wilson May 23rd, 2011
MITZPE RAMON, ISRAEL–Today Will Cary, Yoav Avni (our friend from the Geological Survey of Israel) and I worked in the northern end of Makhtesh Gadol (“the large crater”). This geomorphic feature looks a bit like an oblong impact crater, but it is actually a kind of breached anticline known as a makhtesh.
We are interested in the Matmor Formation, a series of Middle Jurassic marls and limestones in the center of the structure. Our special interest is a fossiliferous unit in the Matmor Formation that is found throughout the exposure. It is very rich in crinoids, echinoids, corals and sponges, with a few brachiopods, ammonites and bivalves as well. We want to understand the distribution of this unit and its fossils.
If we saw this formation in only two dimensions, as in a typical roadcut, it would be easy to interpret. However, we have it exposed in 3-D because it is heavily dissected by small wadis. More data this way, and far more complications. We learned today that there are distinct facies (rock types characterized by fossils and/or sediments indicating a particular depositional environment) found in very close relationships. The rock units are patchy and the fossils patchy within the lithological patchiness. The number of variables used to predict fossil occurrences is now very large!
Mark Wilson May 22nd, 2011
We have written many times about the geology of southern Israel in our blog posts over the past two years, and there is plenty more to come this week. We haven’t discussed the little town we stay in during our expeditions. So I’m starting with an image of Will Cary overlooking the Makhtesh Ramon for the geological context, but it is the community behind him that interests us today.
Mitzpe Ramon was established on the northern edge of the makhtesh in 1951 as a way station and workers’ village on the road to the southern city of Eilat. It has a magnificent perspective on the makhtesh, and thus the Hebrew name means “Ramon view”. The first permanent residents came in the 1960s as refugees from northern Africa and central Europe. Later immigrants came primarily from the United States and Russia.
This mix of heritages gives this little town a unique community unlike any other in Israel. Large numbers of Black Hebrew Israelites left the United States in the 1960s and 1970s to settle in Israel. This group believes, essentially, that they are a “lost tribe” of Israel, some maintaining they are the only true Israelites remaining. You can imagine the controversies they stirred in Israel with such claims, so many began to settle in the more distant Negev development towns where they would be out of the mainstream of Israeli national life. Now a generation later they are full Israeli citizens and integrated enough into Israeli society to serve in the military and hold political offices. The Black Hebrew Israelites in Mitzpe Ramon wear knitted kippot (head coverings) and a colorful style of dress that looks to me right out of 1970 Harlem. They speak English among themselves (and to us), and they’ve established American jazz clubs in this little desert town.
Walking through the neighborhoods of Mitzpe Ramon you see a complex mix of cultures, from old Russian men sitting on benches with suit jackets and tightly buttoned shirts (regardless of the temperature) through fresh-faced (and always well-armed) soldiers the age of my students to African-American-Israeli children singing in the playgrounds in Hebrew while their parents converse in English. Above it all a bright blue desert sky, and below some of the most fascinating rocks in the world.
Mark Wilson May 15th, 2011
In advance of my next field trip to Israel (watch this space!), our highlighted fossil this week is the scleractinian coral Microsolena, a genus named by the French naturalist Jean Vincent Félix Lamouroux in 1821. The specimen above was collected from the Matmor Formation in Hamakhtesh Hagadol in the Negev Desert. It is Callovian in age, specifically the athleta Zone. (I know a lot of details about this area!) This coral is thus roughly 160-165 million years old.
Scleractinian corals appeared first in the Triassic and are the primary coral in today’s oceans. Unlike their extinct Paleozoic cousins, scleractinians have skeletons made of aragonite rather than calcite. Aragonite is relatively unstable and easily dissolves over geological time. Our specimen above has been replaced with the more stable calcite. This means that the exterior is preserved well enough to identify to the genus level, but details in the interior necessary for species determination have been recrystallized beyond recognition.
A nice oyster is still attached to the coral surface. Oyster shells are made of calcite and so are usually preserved very well. You can also see holes in the coral made by boring bivalves and given the name Gastrochaenolites. One of the bivalve borings is in a raised lump of the coral (center top of the image). This is reaction tissue built by the coral in response to the invading bivalve, a clear indication that some of the boring took place while the coral was alive. Most of the corals in the Matmor Formation are heavily bored by bivalves.
The Matmor Formation is exposed only in the cavity of Hamakhtesh Hagadol. Here it is about 100 meters thick and consists mostly fossiliferous marls and sponge-coral patch reefs. (One of the previous Fossils of the Week is a thecideide brachiopod attached to corals like the one above.) The Matmor sediments were deposited on a shallow marine ramp near the Middle Jurassic equator. It is this equatorial deposition that makes the Matmor such an interesting subject for paleoecological analysis. Most other described Jurassic faunas are in Europe and North America, and they were all formed under more temperate conditions.
Pandey, D.K., Ahmad, F. and Fürsich, F.T. 2000. Middle Jurassic scleractinian corals from northwestern Jordan. Beringeria 27: 3-29.
Wilson, M.A., Feldman, H.R., Bowen, J.C., and Avni, Y. 2008. A new equatorial, very shallow marine sclerozoan fauna from the Middle Jurassic (late Callovian) of southern Israel. Palaeogeography, Palaeoclimatology, Palaeoecology 263: 24-29.
Wilson, M.A., Feldman, H.R. and Krivicich, E.B. 2010. Bioerosion in an equatorial Middle Jurassic coral-sponge reef community (Callovian, Matmor Formation, southern Israel). Palaeogeography, Palaeoclimatology, Palaeoecology 289: 93-101.
Mark Wilson October 31st, 2010
DENVER, COLORADO — How I very much enjoy those few minutes AFTER giving a presentation, especially a Geological Society of America talk. That sense of renewed life, the rush of completing a task which was months in preparation, and the step back into the inviting shadows of the lecture room. I’ll just repeat my first and last slides below, and then link to the abstract. You will, I hope, see the joke in my blog post title!
Mark Wilson September 21st, 2010
WOOSTER, OHIO–That may not be the most exciting title I could choose, but it was a fun project nonetheless. My Estonian colleague Olev Vinn and I have a paper in the latest issue of Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen describing an assemblage of sabellid and polychaete tubeworms from the Middle Jurassic (Callovian) of the Negev in southern Israel. This tubeworm fauna is the first described from equatorial waters in the Jurassic, and there is none like it in the modern world. Our work here is part of a larger project to understand the evolution of tube-dwelling invertebrates.
Introducing a new species to the world through the paleontological literature is a privilege and pleasure. Inconsequential it may be in a larger frame, but a fragment of nature has been brought to the light for the first time since it left the stage millions of years ago. What we know about life has been increased a tiny bit, and there is a new creature to enjoy.
Mark Wilson June 15th, 2010
MITZPE RAMON, ISRAEL — Today we traveled northeast of Mitzpe Ramon to Makhtesh Gadol (“The Large Crater”) to look at some Jurassic fossils in the Matmor Formation. I had to take a few photographs and collect some cool crinoids there, but otherwise it was a kind of busman’s holiday for us. The Matmor Formation preserves a tropical marine fauna with loads of mollusks, echinoderms, brachiopods, sponges and corals. Several sets of Wooster students have worked here, and our friend Yoav still refers to stratigraphic sections by Wooster student names: Jeff, Elyssa, Sophie and Meredith. In fact the most important stratigraphic unit in the Matmor we know as “Meredith-1″. It was a fitting place to end our Wooster 2010 Israel fieldwork.
Mark Wilson June 14th, 2010
MITZPE RAMON, ISRAEL — We spent our last Cretaceous field day in our section of the Zihor and Menuha Formations just south of Makhtesh Ramon. It is a complicated place because of tectonic activity from the Late Cretaceous on, so we spent a lot of time tossing measuring tape off cliff edges to calculate unit thicknesses. The most exciting moment was when two Israeli fighter jets flew very low through a little pass in which we were working. The sudden noise and blast of air nearly knocked us down.
We finished our sections, collected our last samples, and headed back to our little house in the afternoon. Tomorrow we will visit Makhtesh Gadol to the northeast to look at Jurassic rocks which have been studied by previous sets of Wooster students.