Archive for July, 2013

Wooster’s Fossils of the Week: Dinosaur footprints of unknown provenance

July 14th, 2013

DinosaurFootprintConcaveEpireliefThese are the only fossils in the Wooster collection I feel some shame about. They are tridactyl theropod dinosaur footprints. They are not spectacular, but they do the job for classes and visits by schoolchildren. I regret that we have them, frankly, because it means at some time in the distant past (well before me) someone chopped them out of a red sandstone, losing in the process all context including location and age. Footprints like these are most valuable, both scientifically and aesthetically, in their original places alongside the rest of the trackway. Now I can only guess that these footprints came from the Jurassic of the southwest, probably Arizona or Utah.

At least we can use them for some trace fossil terminology. (A trace fossil is evidence of organism behavior, such as a trail, burrow, boring or scratch marks.) The top image is what we expect from a fossil footprint: an indentation in the top of the sandy bed now turned to stone. It extends into the rock and is on the surface, so we call it a concave epirelief. (“Epi-” means surface.) The footprint below is also of a three-toed theropod dinosaur, but it extends out of the rock and is on the underside of the bed. We thus call it convex hyporelief. (“Hypo-” means underneath.)
DinosaurFootprintConvexHyporelief

WaterFilledFootprintOne quick way to see the outlines of an indistinct footprint is to fill a concave epirelief with water, as above. This provides much more contrast.
WilsonBoysFootprintThis is how dinosaur footprints should be appreciated: in the field as part of trackways. The kids above are three of my brothers a long, long time ago. I think this is near Tuba City, Arizona, and these are Jurassic theropod footprints like the Wooster specimens. Note that to increase contrast the footprint is filled with … let’s just say “water”.

References:

Miller, W.E., Britt, B.B. and Stadtman, K. 1989. Tridactyl tracks from the Moenave Formation of southwestern Utah (pp. 209-215). Gillette, D.D., and Lockley, M..G, eds., Dinosaur tracks and traces: Cambridge, Cambridge University Press.

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!

Wooster Geologists in the Dead Sea

July 12th, 2013

LizzieStephDeadSea071213MITZPE RAMON, ISRAEL–The Wooster Geologists in Israel spent their last full day in the country visiting the Dead Sea Rift Valley and an archaeological site. It feels very good to have packed our hiking boots away for the season. Above, of course, is Lizzie Reinthal and Steph Bosch floating in the hypersaline waters of the Dead Sea at an almost deserted Ein Gedi beach. The surface of the water here is at -427 meters, or about 1400 feet below sealevel, making it the lowest point on land. The water Lizzie and Steph are floating in is 8.6 times saltier than typical seawater. This means I don’t have to worry about anyone drowning here. (Swallowing the water and getting it in eyes and ears is another story!)

OscarDeadSea071213Oscar Mmari was there as well. His style was a bit more relaxed. He was no doubt pondering that the amount of bromine in these waters (at 4.2 g/kg) is the highest anywhere on Earth.

SodomSaltStudents071213On the way to Ein Gedi we stopped by the famous Mount Sodom — a mountain of salt. This is a famous salt diapir, or a salt dome that has reached the surface. The layers of salt here are vertical because of deformation caused by the upward movement of the material. The salt, mostly halite, moves up because it is less dense and more plastic than the overlying sediments.

SodomSalt071213This is a close view of the salt layers. It is very difficult to distinguish original sedimentary layers from planes developed by shear stress.

LotWifeSodomSalt071213The spot we briefly explored is underneath a jointed block of salt referred to as “Lot’s Wife”. Remember her? In Genesis she looked back at the destruction of Sodom and was turned into a pillar of salt. If this is her she was about 60 feet tall.

 

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.

 

Meeting a group of excellent young Israeli geologists

July 11th, 2013

OlympiadStudents071113MITZPE RAMON, ISRAEL–Today I had the pleasure of talking with four excellent Israeli students who form their nation’s team in the upcoming 7th International Earth Science Olympiad. Their advisor and coach, Hanan Ginat (on the far right), invited me to speak to these young adults about paleontology as they study for the competition to be held in India this September. I was amazed at how hard these students are working for this event, and how much will be required of them during the Olympiad. They will have ten days of tests and practical exercises. In past events these contests have included interpreting core samples, assessing building stones, and even planning dam sites. In the written tests there are questions not only about geology and paleontology, but also oceanography, atmospheric sciences, and astronomy. Wow. Most of it in English, too.

The students had excellent questions and quickly responded to puzzles about various fossil specimens you can see scattered on the table above. It was so much fun — the time just flew by. Good luck to them in the tournament and in their future endeavors. These are very bright students who know the value of learning and persistence.

Wooster Geologists in Jerusalem

July 10th, 2013

1_JerusalemWalls071013MITZPE RAMON, ISRAEL–This is the beautiful 400-year-old Turkish wall surrounding Jerusalem. It and virtually all the buildings in Jerusalem is made of “Jerusalem Stone” (a set of Cretaceous micritic limestones, to be pedantic). When the sun rises or sets on them they turn the city into the fabled “Jerusalem of Gold”.

Team Israel 2013 made the long drive up to Jerusalem with our colleague Yoav Avni to meet with geologists at the Geological Survey of Israel, and then visit Hebrew University and the National Natural History Collections. Of course, I also gave the students a tour of the Old City with its incredible history and multi-dimensional culture.

2_YoavOffice071013Had to show an image of Yoav in his office. Typical geologist’s office, I’d say. The Geological Survey of Israel is housed in a century-old complex built as a school by Germans and then occupied by the British Army from 1918 to 1948. It is incredibly cramped so they are moving to new facilities in a few years.

3_FossilSnake071013We saw many, many fossils and modern bones at the National Natural History Museum collections on the campus of Hebrew University. The staff was very generous with their time, and their enthusiasm was inspiring. Our token image: a Cretaceous snake with tiny legs just barely visible.

4_StudentsChurchSepulchre071013Our journey through the Old City was so much fun, even though we had to move relatively quickly. We walked here from the Survey buildings through diverse neighborhoods and then down the newly-renovated Jaffa Street. Here you might be able to make out the three Wooster students in front of the Church of the Holy Sepulchre.

5_WesternWall071013We also went to the Western Wall of the Temple Mount complex, a treasured site in Judaism.

6_Dome071013We couldn’t visit the Temple Mount because it was closed, but we did get this excellent view of the Dome of the Rock, an iconic Islamic shrine.

7_ZionGate071013This is the outside of Zion Gate in the Jerusalem Old City walls. The innumerable bullet holes are a reminder of the violence this city has seen over the centuries. Most of these are from the War of Independence (1948-1949) and the Six-Day War (1967).

8_GroupGSI071013Finally, here is our last group photo: Steph Bosch, Lizzie Reinthal, Oscar Mmari, me, and Yoav Avni. Yoav is leaving for Jordan tomorrow so this is the last day he is with us. The photo was taken by my long-time friend, Israeli geologist Amihai Sneh.

What a day in such a place.

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.

A day of geological exploration in the Negev: the En Yorqeam Formation (Upper Cretaceous) at Makhtesh Ramon

July 8th, 2013

12_EnYorqeamView070813MITZPE RAMON, ISRAEL–Our final stop on our geological tour today was close to our temporary home: on the northern rim of Makhtesh Ramon (N 30.62831°, E 34.81759). Exposed here is the En Yorqeam Formation (Upper Cretaceous, Cenomanian), seen above as the less resistant marly unit between two resistant limestones. I did my first presentation on Israeli geology with bored and encrusted oysters from the En Yorqeam, which were also the subjects of a Fossil of the Week post.

We visited this outcrop today because there are some stratigraphic questions about its thickness and distribution. Its rich fossil fauna has also not been described in detail. This would be an ideal Independent Study project someday, especially with one large outcrop so close to our headquarters.

13_Echinoids070813Echinoids are the stars of the fossil fauna in the En Yorqeam. In just ten minutes we picked up over a dozen well preserved specimens. The large ones at the top are Heterodiadema lybicum. I don’t know the identity of the two in the bottom row. I bet some sharp student, though, can come up with the names quickly!

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