Goodbye, Makhtesh Gadol (for now)

July 7th, 2013

GoodbyeMakhteshGadol070713MITZPE RAMON, ISRAEL–Today Team Israel 2013 had its last visit to Makhtesh Gadol, marking the end of Lizzie Reinthal’s and Steph Bosch’s fieldwork. We collected our last specimens from the Matmor Formation, which is exposed only in the center of this magnificent structure. The students above are looking down into the northern part of the makhtesh from the viewpoint at Mount Avnon.

MakhteshGadol070713This is a view from the same spot looking south along the western wall of the makhtesh. You can see a bit of the curvy, narrow road below that we used to enter and exit the makhtesh. This road was built by the British during World War II when they thought there might be oil underneath this breached anticline.

MG_BronzeAgeStructure070713This ring of stones is the remnant of a Bronze Age livestock pen, along with a probable small shelter for the shepherd in the lower left. This features are found throughout Makhtesh Gadol, usually up on the flanks of the walls or the Matmor Hills. I happened to come across this one in today’s walkabout.

LastCollecting070713Finally, here are students collecting at our last site — the southernmost exposure of the echinoderm-rich subunit we’ve found to be so productive. This morning we found … wait for it … two more bryozoans! This is usually not big news in most of the places I’ve worked, but it sure is here. They are again runner-types, but not Stomatopora. Much more to report on these after we get back home with them.

We still have five more working days in Israel. One will be devoted to finishing Oscar’s fieldwork, one to finishing smaller projects in the Makhtesh Ramon area, one to exploration of geological sites Yoav has chosen for us, one for a trip to Jerusalem and the headquarters of the Geological Survey of Israel, and a final day to make sure we’ve done all we came to do.

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!

Phosphate success while Jurassic bryozoans remain elusive

July 4th, 2013

OscarOZsection070413MITZPE RAMON, ISRAEL–Oscar Mmari celebrated on his second outcrop today the completion of his stratigraphic columns for his project on the phosphate-bearing portions of the Mishash Formation in the Negev of southern Israel. It is certainly the least pretty section we’ve worked with because it is in the industrialized mining zone near the eastern outlet of Makhtesh Gadol, but we got the work done. This particular place is at N 30.94072°, E 35.03784° (for those of you following along). Look at this place on Google Earth and you’ll see how extensive the phosphate mines are here. Oscar is not yet done with fieldwork because we will come back to his sections for further observations and collecting.

LizzieStephMatmor070413Later in the afternoon we visited outcrops of the Matmor Formation in the northern part of Makhtesh Gadol. Just above Lizzie Reinthal’s right shoulder above (she’s in the center) the outlet from the makhtesh is visible as a break in the surrounding walls. Steph Bosch on the right is bravely hiding her disappointment because after lots of careful peering at the encrusted undersides of beautiful fossil corals, the four of us failed to come up with a single bryozoan. This is curious in itself. The encrusters are well preserved and diverse. (Olev Vinn and I wrote a paper on the various serpulid and sabellid worm tubes; Cezary Krawczynski and I have a paper on the thecideide brachiopods from here.) Every place we think we will see bryozoans we find instead worm tubes and calcisponges. The few Matmor bryozoans collected on previous field trips have been on echinoderm ossicles and holdfasts. Since echinoderms are common where corals are not, and vice versa, it may be that the bryozoans preferred the same conditions the crinoids and echinoids did. Later on this trip we will thus have a full-court press in the crinoid thickets and echinoid-rich beds.

PrettyCorals070413Still, the corals here are gorgeous. Here are two varieties of typical colonial scleractinians we saw today. The one on the right has all sorts of encrusters in the nooks and crannies between its corallites. The corals here are remarkably well preserved considering that their original aragonitic skeletons have been replaced by calcite. These are a bit of consolation for the missing bryozoans!

Fossil collecting under a desert sun

July 2nd, 2013

GroupCollecting070213MITZPE RAMON, ISRAEL–Today the Wooster Geologists in Israel collected fossils from the Matmor Formation in Makhtesh Gadol. It was time to begin assembling data for Lizzie Reinthal’s and Steph Bosch’s Independent Study projects, and to follow up on some projects I have going in this Middle Jurassic set of fossiliferous marls and limestones. We do all our work as a team so that everyone is helping with everyone else’s project at some point. In the image above we have everyone at work picking up fossils at one outcrop near the center of the makhtesh (N 30.93369°, E 34.97588°, to be exact).

LizzieCollecting070213Lizzie is working on crinoid taphonomy, which we’re approaching in a very systematic way. She laid out individual square-meter boundaries on her fossiliferous exposures and collected every bit of crinoid present, from single columnals (the disks that make up a crinoid stem) to partial calices (the crowns or “heads” where the feeding arms were attached). She even seived the sediment to get a sample of small fragments like those from the arms. This way we can assess how the crinoids were disarticulated and tossed about on the seafloor, and whether their stems had some characteristic detachment horizons.

MatmorMakhteshGadol070213_585We are here in the Matmor Hills looking south towards the distant wall of the makhtesh. Two geologists are collecting from a yellowish marl. What do you think that small red dot is in the center?

OscarCollecting070213Why it is Oscar Mmari showing his flair for innovation! He brought the umbrella not for rain (that’s not going to happen here in July, for sure) but just for this. He isn’t much for hats, and we all must admit he had the best shade all day.

StephCollecting070213And here is Steph Bosch carefully collecting tiny little specimens — hoping, hoping some will be encrusted by bryozoans. (None yet, but the best sites are yet to come.)

BittenSpines070213So what did we find? I can show you only a few things because fossil photography in a hotel room is more difficult than you might imagine. (Can you guess what background I’m using?) At one location in the Matmor Formation we collected every exposed echinoid spine in an attempt to statistically determine how many were bitten by some sort of predator. You can see that the spines displayed above have been chomped, probably by some sort of fish. Spines like these were part of an earlier Fossil of the Week post.

Nautiloid070213Yoav found this  nautiloid in subunit 52 of the Matmor Formation. The entire shell, including the septa (walls dividing the chambers), has been replaced with a fine-grained calcite. What are the two holes apparently punched through the shell? They could be just erosion, but I like to think they’re bite marks from some toothy reptile! [Added note: I think I've just identified this nautiloid. It has a distinctive groove on the venter (not visible here) which may place it in the genus Cymatonautilus. This genus lived only a short time (latest early to middle Callovian Stage of the Jurassic Period) and is found along the shallow shelf of the Tethys. Right interval, right place.]

Field reconnaissance in the northern Negev of Israel

July 1st, 2013

1FoldedPhosphates070113MITZPE RAMON, ISRAEL–This morning Team Israel 2013 met our friend Yoav Avni, a geologist with the Geological Survey of Israel (GSI), and we traveled north to our field localities. We did a survey of the sites so that we could put together an efficient schedule for our work over the next two weeks. We had a four-wheel drive vehicle from the GSI so we could get to places our little Budget rental car could only have nightmares about.

The first locations were for Oscar Mmari’s Cretaceous phosphorite work. The outcrop pictured at the top of this entry is on the east side of Makhtesh Gadol (N 30.93657°, E 035.03312°). We are looking toward the west at an incredibly asymmetric limb of a syncline. In the upper part of the exposure you can see the rocks dipping almost vertically, yet in the foreground they are nearly horizontal. They make an almost 90° bend. The Mishash Formation phosphatic zone is partly exposed as the white rocks along the side of the wadi. The phosphorites here are very thick and chalky.

2MishhashPhosphates070113A second phosphorite exposure for Oscar is in Wadi Havarim (N 30.84269°, E 34.75509°) not too far north of Mitzpe Ramon. The top of the cherty portion of the Mishash Formation is on the left in the middle; the light-colored units above are phosphorites. In the background is Nahal Zin, a deep valley formed by water draining north into the Dead Sea. The base level of the Dead Sea is so low that the wadis leading to it are rapidly downcut.

3OscarPhosphorite070113Here is Oscar getting is first look at the phosphorites at Wadi Havarim. Later this week we will measure at least one section at each locality and take plenty of samples for thin-sectioning and scanning electron microscopy.

4TraceFossil070113Steph Bosch’s hand gives us a scale for a nice set of trace fossils found in the phosphorite at Wadi Havarim. These look like callianassid shrimp burrows to me. We found some preserved as burrow-fills with apparent fecal pellets forming the outer walls. If true then the trace fossil ichnogenus is Ophiomorpha. This is a good indicator of shallow water.

5PhosphateSign070113We also briefly visited two phosphate mining sites east of Makhtesh Gadol. One has this helpful sign outside describing the geology of these deposits. The phosphorites are shown in yellow. Note that they formed in two synclines, both highly asymmetrical (as shown in our top photo).

6PhosphateMinedValleyWe viewed one phosphate mine where virtually the whole valley has been quarried, producing enormous piles of waste materials. Reclaiming mined terrain like this is especially difficult in this arid climate. Oscar will not only be looking at the geology of these phosphate deposits, but also the economics of mining, which now includes remediation and controls on emissions and water pollution.

7MatmorCollectingFirstDay070113After lunch we drove down into the center of Makhtesh Gadol and plotted out future localities for Steph and Lizzie to do their work in the Matmor Formation. (The above site is at N 30.93837°, E 34.97907°.) I’ve been to these sites many times with students, so it was relatively easy to make our plan for collecting crinoids and encrusting bryozoans tomorrow and next week.

8NabateanCistern070113Finally, no fieldwork in Israel is complete without a touch of archaeology. Yoav took us into a Nabatean cistern and showed us the clever engineering (and strategic plastering) necessary to make this hand-cut cavern into a water trapping and storage facility. This cistern is cut into the Menuha Formation, a chalk unit very familiar to Andrew Retzler (’11). This cistern was originally made sometime between 100 BCE and 100 CE. After the nabateans it was used by the Romans, Byzantines and Arabs. It was last used by Israeli pioneers over 60 years ago.

Tomorrow we return to Makhtesh Gadol and work in the hot sunlight filling collecting bags with tiny bits of crinoids and assorted encrusters. We’ve had a very good start.

Wooster’s Fossil of the Week: A barnacle-bored belemnite from the Jurassic of Spain

June 23rd, 2013

Hibolites_barnacle_borings585Two subjects of previous Fossil of the Week posts are combined together here: a belemnite (the elegant Hibolites hastatus) and barnacle borings (the ichnofossil Rogerella). This specimen is from the Jurassic of Moneva Teruel, Spain.

(Living belemnites reconstructed by Bogdanov on Wikipedia)

(Living belemnites reconstructed by Bogdanov on Wikipedia)

Belemnites are extinct cephalopods, oddly enough. The specimen is the guard or rostrum — a calcitic internal skeleton that gave the squid-like animal rigidity. Because they are made of solid, stable calcite, these guards can be extremely common in the fossil record, especially in the Jurassic and Cretaceous. Some people call these “belemnite battlefields”, probably because the fossils look so much like bullets.

de_BlainvilleHibolites hastatus was named by Henri Marie Ducrotay de Blainville (1777-1850) in 1827. He was a French naturalist with many accomplishments, especially in anatomy and systematics. He spent most of his career in the Faculty of Sciences at Paris, where he was a colleague (and eventual ideological enemy) of the epic Georges Cuvier. In 1830 he took over from the “father of invertebrate zoology” Jean-Baptiste Lamarck as the chair of natural history. Clearly he ran in powerful circles.

The yellow features in this close-up above are holes drilled by acrothoracic barnacles, which were then filled with fine-grained dolomite. The trace fossil thus formed is known as Rogerella. It is found from the Devonian all the way to today. Its presence on these belemnite guards shows that these structures laid for enough time on the seafloor that they could be colonized by barnacles. They are thus an indicator of the taphonomy (or history from death to discovery) of these fossils.

References:

Doyle, P. and MacDonald, D.I.M. 1993. Belemnite battlefields. Lethaia 26: 65-80.

Lambers, P. and Boekschoten, G.J. 1986. On fossil and recent borings produced by acrothoracic cirripeds. Geologie en Mijnbouw 65: 257–268.

Mariotti, N. 2002. Systematics and taphonomy of an Early Kimmeridgian belemnite fauna from the Mediterranean Tethys (Monte Nerone, Central Apennines, Italy). Geobios 35: 213-232.

Wooster’s Fossil of the Week: A shrimp from the Upper Jurassic of Bavaria, Germany

June 2nd, 2013

Aeger_tipularis_SolnhofenThe beautiful fossil shrimp above is Aeger tipularis (Schlotheim, 1822), and it comes from one of the most famous rock units: the Solnhofen Plattenkalk (Tithonian, Upper Jurassic) of Germany. (The Solnhofen is well known for its extraordinary fossils, including the fossil bird Archaeopteryx.) This shrimp is yet another generous gift to the Department of Geology from George Chambers (’79).

The shrimp in the Solnhofen are very well preserved. Note the long, long antennae and the tiny spines on the carapace. (I suspect, though, that parts of this specimen have been enhanced with ink by a commercial collector, especially the legs.)

SchlotheimFigure051813

Aeger tipularis was described in 1822 by Ernst Friedrich, Baron von Schlotheim (1764-1832), a prolific German paleontologist we profiled earlier. The drawing above is the original reconstruction by Schlotheim (1822, pl. 2, fig. 1; Solnhofen Lithographic Limestone, Solnhofen area; Lower Tithonian, Hybonotum Zone; width of figure 23.7 cm.)

References:

Garassino, A. and Teruzzi, G. 1990. The genus Aeger MÜNSTER, 1839 in the Sinemurian of Osteno in Lombardy (Crustacea, Decapoda). Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano 131: 105-136.

Schlotheim, E.F. von. 1822. Nachträge zur Petrefactenkunde (Addenda al Petrefactenkunde). Gotha, Beckersche Buchhandlung.

Schweigert, G. 2001. The late Jurassic decapod species Aeger tipularius (Schlotheim, 1822) (Crustacea: Decapoda: Aegeridae). Stuttgarter Beiträge zur Naturkunde, Series B, 309: 1-10.

Wooster’s Fossil of the Week: A grazed oyster from the Middle Jurassic of Gloucestershire, England

March 24th, 2013

Praeexogyra_acuminata_585This small oyster is not in itself unusual. In fact, it is one of the most common fossils in the Jurassic of western Europe: Praeexogyra acuminata (Sowerby, 1816). It may be better known by its older name: Ostrea acuminata. Local collectors call it the “sickle oyster” because of its curved shape. This specimen is from the Sharp’s Hill Formation (Middle Bathonian) exposed in the Snowshill Quarry near Moreton-in-Marsh, Gloucestershire, England. I collected it on my first trip to England in 1985.
Praeexogyra_acuminata_closerWhat attracted me to this particular shell can be seen in the above close-up: lots of little straight lines incised across its outer surface (along with a serpulid worm tube). The lines were scraped by the Aristotle’s Lantern of one or more regular echinoids (sea urchins). This is the trace fossil Gnathichnus pentax Bromley, 1975. We met this fossil last month cut into a Cretaceous oyster from Israel. One or more echinoids grazed over this Jurassic oyster, probably consuming algae and other organic materials.

Praeexogyra acuminata was an epifaunal filter-feeder, meaning it lived on the substrate sucking in seawater and sorting from it organic material for food. During the Middle Jurassic these oysters were so common that their shells formed thick deposits. It is possible that some deposits rich in these shells were formed in brackish waters rather than under fully marine conditions.

Ostrea acuminata was named by by the enthusiastic English natural historian James Sowerby (1757-1822). We met him earlier as the author of a Cretaceous bivalve genus.

References:

Bernard-Dumanois, A. and Delance, J-H. 1983. Microperforations par algues et champignons sur les coquilles des «Marnes à Ostrea acuminata (Bajocien supérieur) de Bourgogne (France), relations avec le milieu et utilisation paléobathymétrique. Geobios 16: 419-429.

Bernard-Dumanois, A. and Rat, P. 1983. Etagement des milieux sédimentaires marins. Paléoécologie des Huîtres dans les “Marnes à Ostrea acuminata” du Bajocien de Bourgogne (France). Comptes rendus de l’Académie des sciences Paris 296: 733-737.

Hudson, J.D. and Palmer, T.J. 1976. A euryhaline oyster from the Middle Jurassic and the origin of true oysters. Palaeontology 19: 79-93.

Wooster’s Fossil of the Week: A brittle star from the Upper Jurassic of Germany

March 10th, 2013

Ophiopetra lithographica aboral larger 010813_585Wooster geologists have again greatly benefited from the donation of a collection by an alumnus. George Chambers (’79), a successful professional photographer, sent us several boxes of minerals, rocks and fossils he had acquired in his lifelong passion for geology. (George was a geology major at Wooster in the class just after mine.) Among the many world-class specimens he gave us are two fossil ophiuroids (brittle stars). They are Ophiopetra lithographica Enay and Hess, 1962, from the Lower Hienheim Beds (Lower Tithonian, Upper Jurassic) near Regensburg, Germany. They are part of the “Fossillagerstätte Hienheim“, a preserved brittle star ecosystem in a lagoon at the edge of a Late Jurassic sea. This is the same set of lithographic limestones in which the famous bird fossil Archaeopteryx was found.
Ophiopetra lithographica 010813_585In both these images you see the spiny arms of the brittle stars twisted about. It is their flexibility and snake-like movements in life that provoked the scientific name ophiuroids (serpent-forms) for the brittle stars. The “brittle” term comes from their ability to autotomize (spontaneously detach) their arms when threatened, leaving a squirming distraction for a predator as they escape.
Ophiopetra lithographica aboral 010813_585Ophiopetra lithographica is probably the most common fossil brittle star known. It was preserved by the countless millions in these Jurassic lagoons in Germany. Most geologists believe they were buried by fine-grained carbonate sediment suspended by sudden storms. As you can see in the above close-up, the preservation of the plates and spines is remarkable.

Most brittle stars are suspension feeders (sorting out food particles from the water), deposit feeders (eating organic material in the sediment) or scavengers. Ophiopetra lithographica may have been a carnivore with its heavily-spined arms and strong jaws. It likely ate small arthropods on the seafloor.

The evolution of brittle stars is interesting and controversial. They were relatively common in the Paleozoic and then just barely survived the Permian extinctions. Their rapid evolution into a variety of taxa in the Mesozoic and Cenozoic has led to many debates about their phylogeny. Even the placement of Ophiopetra into a family is a problem. Does it belong to the Family Aplocomidae where it was originally placed or to the older Family Ophiolepididae as has been recently suggested?

Our students will enjoy these fine fossils in the invertebrate paleontology course. They have doubled our collection of brittle stars! Thank you again to George Chambers for his thoughtfulness and generosity.

References:

Enay, R. and Hess, H. 1962. Sur la découvertes d’Ophiures (Ophiopetra lithographica n.g. n.sp.) dans le Jurassique supérieur du Haut-Valromey (Jura méridional). Eclogae geologicae Helvetiae 55: 657-678.

Hess, H. and Meyer, C.A. 2008. A new ophiuroid (Geocoma schoentalensis sp. nov.) from the Middle Jurassic of northeastern Switzerland and remarks on the Family Aplocomidae Hess 1965. Swiss Journal of Geosciences 101: 29-40.

Röper, M. and Rothgänger, M. 1998. Die Plattenkalke von Hienheim (Landkreis Kelheim) – Echinodermen-Biotope im Südfränkischen Jura. Eichendorf (Eichendorf Verlag), 110 S.

Stöhr, S. 2012. Ophiuroid (Echinodermata) systematics—where do we come from, where do we stand and where should we go? In: Kroh, A. and Reich, M. (Eds.) Echinoderm Research 2010: Proceedings of the Seventh European Conference on Echinoderms, Göttingen, Germany, 2–9 October 2010. Zoosymposia, 7: 147-161.

Thuy, B., Klompmaker, A.A. and Jagt, J.W.M. 2012. Late Triassic (Rhaetian) ophiuroids from Winterswijk, the Netherlands; with comments on the systematic position of Aplocoma (Echinodermata, Ophiolepididae). In: Kroh, A. and Reich, M. (Eds.) Echinoderm Research 2010: Proceedings of the Seventh European Conference on Echinoderms, Göttingen, Germany, 2–9 October 2010. Zoosymposia, 7: 163-172.

Wooster’s Pseudofossil of the Week: Manganese dendrites from Germany

January 20th, 2013

We haven’t had a pseudofossil in this space for awhile. A pseudofossil is an object that is often mistaken for a fossil but is actually inorganic. The above may look like  fossil fern, but it is instead a set of beautiful manganese dendrites in the Solnhofen Limestone (Jurassic) of Germany (scale in millimeters). I put this photo on Wikipedia a long time ago as manganese dendrites. That didn’t stop one website from still using it as an example of a fossil.

Manganese dendrites are thin, branching crystals that grew over a surface in a rock or mineral. Often they are found in cracks or along bedding planes (as in the above example). These dendrites are usually some variety of manganese oxide. The minerals represented can include hollandite, coronadite, and cryptomelane. Apparently they are never pyrolusite, despite what you may see in textbooks. It is also impossible to tell the mineralogy from the shape of the dendrites alone.

How can you tell this is not a fossil plant? For one, the branches are too perfect: none overlap or are folded over or broken as you would expect in a buried three-dimensional plant. Next you’ll notice that all the branches extend from a line at the bottom of the image rather than from a single branching point. Finally, there is no distinction between branch, stem or leaf; instead it is a fractal-like distribution of tiny sharp-edged crystals.

As a bonus, check out this benefit you get from having manganese dendrites:

“Metaphysically, stones with dendrites resonate with blood vessels and nerves. They help heal the nervous system and conditions such as neuralgia. Dendrites can help with skeletal disorders, reverse capillary degeneration and stimulate the circulatory system. It is the stone of plenitude; it also helps create a peaceful environment and encourage the enjoyment of each moment. Dendrites deepen your connection to the earth and can bring stability in times of strife or confusion.”

The Stone of Plenitude! (I hope you do see my sarcasm here …)

This post, by the way, marks the completion of the second year of Wooster’s Fossils of the Week. So far we’ve had 104 posts. Check out our very first edition about a sweet auloporid coral!

References:

Potter, R.M. and Rossman, G.R. 1979. The mineralogy of manganese dendrites and coatings. American Mineralogist 64: 1219-1226.

Post, J.E. and McKeown, D.A. 2001. Characterization of manganese oxide mineralogy in rock varnish and dendrites using X-ray absorption spectroscopy. American Mineralogist 86: 701-713.

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