A mission in the Cretaceous of southern Israel

April 9th, 2014

Wadi Mishar viewMITZPE RAMON, ISRAEL–Today Yoav and I set out to solve a mapping dilemma concerning the boundaries of the Upper Cretaceous (Cenomanian) En Yorqe’am Formation in the Negev and, eventually, the Judean Desert to the north. It involved a bumpy ride deep into some of the most beautiful areas of the country, and it produced all sorts of delicious paleontological and sedimentological mysteries. I’ll talk more about this trip in later entires. Since it was 12 hours and I get up at 4:00 a.m. tomorrow, this is a truncated entry!

The setting is the stratigraphy of the En Yorqe’am and its bounding units: the Hevyon Formation below and the Zafit Formation above. Our job was to examine the contacts between these units and help come up with consistent definitions that can be used throughout the region. Right now there is considerable fuzziness as to where each formation begins and ends. Above is a labeled image showing the magnificent outcrop in Wadi Mishar (taken from our studied section at N 30.54899°, E 34.98843°).

Oysters En Yorqeam 040914In the process of sharpening the definition of the En Yorqe’am, we found some magnificent fossils. There are many paleontological and sedimentological projects possible in this unit. Oysters dominate the En Yorqe’am in most places we visited. Above is a close view of one outcrop (at N 30.65788°, E 35.08764°; Nahal Neqarot) showing that the sediment is almost entirely oyster. The shells are often beautifully bored, but strangely there are virtually no encrusters.

Stromatoporoid En Yorqeam 040914To our surprise, we found these large roundish objects that look very much like stromatoporoids (at N 30.65788°, E 35.08764°). The lack visible mamelons (or corallites, for that matter), but internally they appear to show the typical laminations and pillars of these calcareous sponges. I’ve never seen them in the Cretaceous before, which is at the end of their range. I could be wrong and these fossils are odd altered corals. Only cutting and polishing will tell.

Terebratulids En Yorqeam 040914Also unexpected was the prevalence of brachiopods in parts of the En Yorqe’am (at N 30.65788°, E 35.08764°). These are articulated terebratulid brachiopods. They look very Jurassic in their appearance, but here they are in the Upper Cretaceous.

I’m looking forward to working with Wooster students on these outcrops next year! More on the En Yorqe’am later this week.

Cretaceous echinoderms are today’s stars

April 8th, 2014

Zichor 040814MITZPE RAMON, ISRAEL–There’s a joke in the title, in case you didn’t notice! I was on my own for my second day of fieldwork in southern Israel. I revisited yesterday’s outcrops of the Upper Cretaceous (Coniacian) Zichor Formation, taking more time to plot out future section-measuring and fossil-collecting sites for students. I was also able to spend a lot of classic nose-on-the-ground time sorting out the fossils.

The outcrop above is about the top half of the Zichor Formation in this area (N 30.30587°, E 34.96543°). Note the cemented limestones near the top and the soft marls in the foreground. Both have plenty of fossils, but you can imagine which is easier to collect from.

Filograna? 040814One mystery of this unit is at the very top of the section in one of the last bedding planes. There are extensive amounts of a twisty worm-tube called Filograna (or at least something close to it). You can see it in the above image. I was told earlier it was a “mat”, but it appears to be instead broken fragments of tube accumulations scattered about. Strange critter, this worm.Echinoid tests 040814The marls of the Zichor have an impressive echinoderm content. Since they have calcitic tests, they are very well preserved. Above are five heart urchins showing their classic pentameral symmetry.

Echinoid test plates 040814Here are fragments of a cidaroid echinoid test. In the middle of each plate is a circle with a boss extending outwards. Spines were attached to these, one of which is included in the image. I hope on our later expedition we can find whole specimens. Students are always up for these discovery challenges.

Asteroid ray oral 040814This was a first find for me: an asteroid (sea star) ray fragment. I don’t think I’ve ever found a sea star fossil before. We are looking above at the oral side where tube feet would have extended.

Asteroid ray aboral 040814This is the other side of the fragment — the aboral side. Beyond being cool, I’m afraid there is not a lot of significance for this fossil unless I can identify it further. Sea stars are famous for living in all sorts of marine environments, from the intertidal to deep trenches.

Some future Wooster students are going to have a good time with this unit sorting out the paleontological, sedimentological and stratigraphic contexts and then comparing this tropical fauna to the better known assemblages in the temperate north.

A Triassic afternoon in southern Israel

April 8th, 2014

Mitzpe Ramon distant view 040814MITZPE RAMON, ISRAEL–This afternoon I walked through the spectacular Middle Triassic sections in Wadi Gevanim on the southern side of the Makhtesh Ramon structure. I will be on a fantastic trip this Thursday to a little-visited Triassic section farther south, so I wanted to refresh my memory of these units. The above image is looking north from Wadi Gevanim to Mitzpe Ramon just visible on the cliff edge of the makhtesh. (What a setting, eh?)

Nautiloids Ammonites 040814I found myself almost completely repeating an entry from last year on Wadi Gevanim (which had the added bonus of students in it). Today I gathered some impressive fossil cephalopods from the Saharonim Formation (Middle Triassic, Anisian-Ladinian) for a group photograph. I note only now that one of the nautiloids above appears last year as well! From the upper left going clockwise: nautiloid, ammonite, nautiloid, ammonite. All are internal molds (the outer shell has been removed).

Nautiloid 040814That upper left nautiloid is worth a closer look. The mold has been split down the middle showing the septa (internal walls dividing the chambers) and an impressive “beaded” siphuncle (connecting tube) running the length of the conch (shell).

Terebratulids 040814Finally, here is a handful of the common terebratulid brachiopods from the Saharonim. Speaking of which, have I mentioned the species Menathyris wilsoni from the Saharonim? You certainly must meet Menathyris wilsoni!

A Wooster Geologist is finally warm enough

April 7th, 2014

Yoav Zichor 040714MITZPE RAMON, ISRAEL–When I left Wooster on Saturday morning it was 34°F and overcast. It was sunny and an astonishing 84°F when I arrived in Tel Aviv on Sunday afternoon. That additional 50 degrees felt very good indeed after a winter of polar vortices and late-March snowstorms. I’m now based in the Ramon Suites Hotel in Mitzpe Ramon near the lip of the spectacular Makhtesh Ramon (N 30.60638°, E 34.80128°).

I’m back in Israel as part of my research leave from the College. This is my chance to explore new outcrops and ideas with my Israeli colleagues to prepare for the next generation of Independent Study students — and, of course, to do plenty of science for its own sake. I miss my students, though, for their companionship, sharp eyes, challenging questions, and navigation abilities (i.e., telling me when I’ve taken a wrong turn). This is how the leave system works so that we always have fresh projects with interesting and testable hypotheses. This is my 11th field season in Israel.

Today I met my long-time friend Yoav Avni of the Geological Survey of Israel, along with Zeev Lewy, a paleontologist retired from the Survey, to look at a fossiliferous unit Zeev discovered over two decades ago south of Mitzpe Ramon. We looked at the thickest section of the Zichor Formation (Late Cretaceous, Coniacian) to sort out a remarkably diverse set of silicified (silica-replaced) fossils associated with a mat of worm tubes (possibly of the genus Filograna). The top image shows the upper portion of the Zichor, with Yoav for scale (location: N 30.30587°, E 34.96543°). The image below is a view of the bedding plane with most (but not all) of the silicified fossils colored dark brown.

Zichor silcified fossils 040714One of the cool things about this layer is that the fossils are silicified, which is rare in this part of the Cretaceous section. Another is that aragonitic mollusks are preserved in this way (especially gastropods and bivalves), along with their calcitic cousins (like oysters and pectenids). The Filograna-like worm tube layer itself is fascinating since no one knows much about the paleoecology of this group, and we suspect it may have some significant evidence about the paleoenvironment encoded in its spaghetti-like appearance.

Zichor Menuha contact 040714The top of the Zichor meets the bottom of the Menuha Formation chalks (Late Cretaceous, Santonian). In this view, the yellow and brown Zichor is in the foreground and middle ground, with the whitish Menuha in the background.

Zichor Menuha close 040714Yoav and I visited the boundary between the Zichor (darker unit on the left) and Menuha (lighter on the right) to assess their relationship (N 30.30212°, E 34.95909°). At outcrops 30 km to the north this boundary is marked by a deep unconformity (eroded interval) and a layer of encrusted and bored cobbles. Here the boundary is flat and nearly continuous. The layer of silicified shells is just a few centimeters below the unconformity. This may not be by chance — units immediately below unconformities often have silicified zones.

Some of you may remember these unit names from previous expeditions. Micah Risacher (’11) worked on the Zichor Formation and its fossils in the Makhtesh Ramon area, and Andrew Retzler (’11) did his Independent Study research on the Menuha. We can now build on their excellent work as we develop additional outcrops and new questions.

Ordnance 040714Finally, it wouldn’t be the Negev if there wasn’t some ordnance on the outcrop. Can you tell what kind of bomb is shown above? The clues are in its current condition!

Wooster’s Fossil of the Week: An infected crinoid from the Middle Jurassic of southern Israel

July 28th, 2013

CrinoidGalls03 copyThis weathered beauty is a stem fragment of the articulate crinoid Apiocrinites negevensis from the Matmor Formation (Middle Jurassic, Callovian) of the Negev, southern Israel. The regular divisions you see making up the stem are the columnals, which look a bit like a stack of poker chips. You can even make out the crenulations on the articulating faces of the columnals, seen as tiny zig-zags. What is unusual about this stem, of course, are the large swellings with multiple holes. These appear to be something like the galls you sometimes see in plant stems formed when a parasite is surrounded by living plant tissue.
CrinoidGalls02 copySenior Independent Studies student Lizzie Reinthal (’14) is working on these odd structures (we have dozens of examples) as part of her investigation of the taphonomy of A. negevensis in the Matmor Formation. We know that the swellings were made by the interaction of some sort of organism with the living crinoid, but we don’t yet know the timing or mechanism. It could be that the holes were drilled first into the stem and the crinoid grew the extra skeletal tissue to essentially push them away, or the swellings could have been the equivalent of galls and some sort of enclosed animal bored its way out of the structure. (And an extra point to those of you who spotted the barnacle boring! Note that it has no swelling around it and thus was likely drilled after the death of the crinoid.)

These infected crinoid stems were first described from the Matmor by Feldman and Brett (1998). They suggested they were from parasitic myzostome worms, which are usually found on crinoid arms and have a long fossil record (see Meyer and Ausich, 1983, and Hess, 2010). They could also be from some sort of embedded organism like that represented by Phosphannulus on Paleozoic crinoid stems (Welch, 1976).

Lizzie will be pursuing the mystery by careful sectioning some of these swellings and seeing if she can relate the crinoid skeletal growth patterns to either a borer or an embedded parasite. Unfortunately that means we must destroy some specimens to better understand the phenomenon, a classic dilemma paleontologists sometimes face.

References:

Feldman, H.R. and Brett, C.E. 1998. Epi- and endobiontic organisms on Late Jurassic crinoid columns from the Negev Desert, Israel: Implications for co-evolution. Lethaia 31: 57–71.

Hess, H. 2010. Myzostome deformation on arms of the Early Jurassic crinoid Balanocrinus gracilis (Charlesworth). Journal of Paleontology 84: 1031-1034.

Meyer, D.L. and Ausich, W.I. 1983. Biotic interactions among recent and fossil crinoids, p. 377–427. In: Tevesz, M.J.S. and McCall, P.L., eds., Biotic interactions in recent and fossil benthic communities. Plenum Press, New York.

Welch, J.R. 1976. Phosphannulus on Paleozoic crinoid stems. Journal of Paleontology 50: 218-225.

An ancient Nabatean, Roman and Byzantine city in the northern Negev

July 12th, 2013

MamshitGuardhouseMansion071213MITZPE RAMON, ISRAEL–Our final stop of the final day: Mamshit. Above you see some of the ruins of this city east of Dimona and a short distance west of the descent into the Dead Sea Rift Valley. The highest structure is the “guardhouse” (which overlooked a reservoir) and the lower on the right is known as “the wealthy house”. All the other rocks you see are remnants of mostly homes and other dwellings.

Mamshit was established by the Nabateans as a station along the Incense Route around 50 CE. Most of the primary buildings were constructed in the Second Century after the Nabatean Kingdom became part of the Roman Empire. As a trading city it flourished until the Seventh Century when either the Persian (614 CE) or the Arab Invasion (636 CE) ended its importance and it faded away. Today we toured it for about an hour and we were the only people there.

MamshitDam071213From the Guardhouse one of the three Mamshit dams comes into view. These were the most critical structures in the settlement because they captured the winter runoff in reservoirs that could be used throughout the dry summers. The area behind this dam is now completely silted up. There was a British police post at this site in the 1930s and 1940s running a series of patrols on camels. The Brits rebuilt the dam for their own use.

MamshitWesternChurch071213This is a lavish church (the “western church” or “Church of St. Nilus”) in Mamshit. Beautiful mosaics are still preserved on the floors.

MamshitStudentsExploring071213The Wooster students are her exploring one of the grander houses built in the Second Century.

MamshitDoorways071213Steph and Lizzie are using the doorways to estimate the likely heights of the residents. Looks like they were more Lizzie size than Steph!

This was a suitable place to end the Team Israel 2013 expedition: a location where geology, archaeology, history and culture are combined in ruins still open for interpretation and study. Now we have one more night before departing early in the morning for the airport in Tel Aviv. We appreciate this opportunity for travel and research very much!

Last day of fieldwork for Team Israel 2013

July 11th, 2013

1_DragFoldOscar071113MITZPE RAMON, ISRAEL–We like to think that Dr. Shelley Judge would be proud of our fieldwork today. The Wooster Geologists returned to Wadi Hawarim to finish our fieldwork for Oscar Mmari’s project on synsedimentary faulting in the Mishash Formation (Campanian, Upper Cretaceous). We returned to the fault visible above just to the left of the dark outcrop of the lower Mishash. The left side is upthrown, the right downthrown, making this a very steep normal fault. the Mishash seen here is in a magnificent drag fold against the fault. The Mishash is eroded away on the upthrown block, so we could only climb to the top of the hill here and estimate the minimum displacement on the fault. The blocks are separated by at least 50 meters. The fault trace is almost exactly east-west. You can barely see Oscar in the lower right standing on the spot where the Mishash rocks fold more than 90° to become horizontal to the right. Oscar and I worked today to follow the fate of a conglomerate that is thickest at the fault where Oscar is standing (location 031 on the image at the end of this post), and then thins and becomes finer as we move away from the fault into the syncline to the south. We believe this indicates that the conglomerate came from the upthrown block and thus the fault formed while the Mishash was being deposited. (Lizzie Reinthal and Steph Bosch, in the meantime, collected more shark’s teeth for us and then explored the wadi system.)

2_HawarimPhosphorites071113This is the Mishash Formation phosphorite zone several hundred meters south of the fault (location 049 in the bottom image). It is much thicker than the section near the fault (see the top photo in this entry).

3_ThinConglomerates071113The conglomerate that is a meter thick near the fault is reduced to these two lensoidal coarse sandstones that Oscar found in this southernmost outcrop. The grain size and thickness reduces dramatically as we move away from the fault.

4_WadiHawarimSection071113This beautiful Wadi Hawarim section of the phosphorites gave us our final clues as to the relationship between the fault and the conglomerate. We also have a sealevel story here with shrimp burrows, but we’ll save that for a later post after Oscar has done some lab work.

5_Hawarim071113Here is a Google Earth view of Oscar’s collecting sites and measured sections. The fault shown in the top photo is at 031, with the photo taken from 047. The fault runs east-west, and Oscar’s sites are all to the south.

 

Return to the Ora Formation

July 9th, 2013

8_MudVolcano070913MITZPE RAMON, ISRAEL–The last location Wooster Geologists in Israel visited today was on the southern edge of the Makhtesh Ramon structure (N 30.58209°, E 34.89375°). Here are excellent exposures of the Ora Formation (Upper Cretaceous, Turonian). This curious feature was a challenge to the students to interpret. I also got it wrong in my explanation on the outcrop, so listen up Steph, Lizzie and Oscar! The students are standing in a portion of the outcrop that is mud with suspended blocks of limestone. This is a cross-section of a diapir, or body of sediment that has moved upwards through the rocks that cap it. This was caused by water-saturated sediment being compressed by the sediments above, forcing it upwards through cracks and crevices. What I got wrong was that the flat strata on top of the mud was present when the diapir formed. (I said it came later.) The mud never reached the surface to become a mud volcano. This is why the resistant beds below are bent downwards — the upward force of the mud flow was stopped by the capping rock, thus deflecting the edges of the units below. A complicated story — which is one of the many things that makes the Ora Formation interesting.

9_Oysters070913Also in the Ora Formation at this same site is a half-meter-thick unit composed entirely of oyster shells. Many of the oysters are encrusted with other oysters and, who knows, maybe bryozoans as well. (And no, Paul Taylor, I didn’t see any here yet!)

10_Hardground070913The Ora Formation also has a fabulous carbonate hardground, which was a cemented seafloor surface. We can tell this particular surface was hard rock on the Cretaceous seafloor because of all those little holes. These are the borings of bivalves known as Gastrochaenolites. They could only be made by grinding away at a cemented substrate.

Hardgrounds, oysters, odd diapirs … opportunities for future study! Israeli geologists have done fantastic work with this unit, so there are many collaborations possible here.

Adventures in the Triassic: Exploring the Gevanim Valley in Makhtesh Ramon, southern Israel

July 9th, 2013

2_NordmarkiteStock070913MITZPE RAMON, ISRAEL–The second visit of the day for Wooster’s Team Israel 2013 was to the Gevanim Valley on the south side of the Makhtesh Ramon structure. This is a fascinating place where Cretaceous intrusions formed an uplifted dome exposing Triassic sedimentary rocks. It is a rare place to see abundant Triassic marine fossils. Our first stop was a nordmarkite stock intruded into the Gevanim Formation (Middle Triassic, Anisian). We always dedicate this image to our own Dr. Meagen Pollock who knows what nordmarkite is without having to google it.

3_GevanimRamonalinidSite070913Our first task was to locate the Gevanim Formation and examine the many specimens of the large bivalve Ramonalina ramanensis to look for rare Triassic encrusters. Above is an outcrop of the part of the Gevanim which has large numbers of this dark-colored, shoe-shaped clam.

4_Ramonalina070913Here are two nearly complete specimens of Ramonalina ramanensis. Alas, we found not a single encruster. The rumor that there are microconchids on these shells seems to be false. Science marches on.

5_LizzieSaharonim070913Above the Gevanim Formation is the Saharonim Formation (Middle Triassic, Anisian-Ladinian). Lizzie Reinthal is here standing near the base of it exposed in the western part of the Gevanim Valley. This is a very fossiliferous limestone and marl that is extremely well exposed here.

6_CephalopodsSaharonim070913Nautiloids and ammonoids are very abundant in the Saharonim. In fact, just about every large object in this exposure of the unit is one or the other. The coin in the image above is sitting on an ammonoid (a ceratite). The other fossils are internal molds of nautiloids.

7_SaharonimBrachiopods070913Our goal today, though, was to find terebratulid bachiopods with original calcite still preserved. We found dozens, a few of which are shown above. These are mostly of the genus Coenothyris. These specimens are destined for isotopic analysis in the laboratory of Dr. Pedro Marenco at Bryn Mawr College. Mission accomplished.

“The Carpentry” in Makhtesh Ramon: Unexpected columnar jointing

July 9th, 2013

1_JointedSandstone070913MITZPE RAMON, ISRAEL–At first glance this rocky outcrop in the middle of Makhtesh Ramon appears to be a typical columnar-jointed basalt. We’ve seen this many times on our blog (for example here and here). However, these rocks are entirely a quartzose sandstone. They have the typical polygonal joints of a cooled lava flow, but the rock is an unmetamorphosed sedimentary unit. This remarkable site is known as “the carpentry” (Haminsara) in the park.

How did these joints form? It is not from the sandstone melting and then cooling, like you’ll see in some places on Wikipedia. (And some people think this is basalt, which is a good reason for more interpretive signs in this place.) Likely it was a hydrothermal process by which superheated water from nearby intrusions warmed up the sandstone until it expanded a bit, and then it cracked along these joints during cooling. The sandstone was never heated to temperatures that would turn it into quartzite, much less liquid. Columnar-jointed sandstone is rare but not unique, as you can see here and here.

This was the first stop for the Wooster Geologists in Israel today as we explored parts of Makhtesh Ramon to follow up on various small projects.

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