Mark Wilson November 15th, 2009
COLLEGE STATION, TEXAS–I never get tired of that too-obvious joke. I found the above productid brachiopod on the last outcrop of our little Texas expedition. It has been drilled by barnacles, which leave a distinctive slit-shaped hole with a tiny little comma shape at one end. It may not look special here photographed on my backpack in the sunlight, but it is. Hard substrate communities in the Permian are still poorly known. This specimen tells us that a future trip may reveal many more such specimens.
Paleontologists (and anyone else) should be able to tell me whether these borings were produced during the life of the brachiopod or after its death. Your determination can be posted in the comments below!
Mark Wilson November 15th, 2009
COLLEGE STATION, TEXAS–The upper one is the base of the Valera Formation on US Highway 84 (N31.88196°, W99.47115°) and the lower one is the lower Bead Mountain Formation on Route 6 near Albany; both are Permian and both have delicious microconchid fossils along with much else. You can imagine which is the more pleasant to work on.
I have been very impressed with the Permian geology of this part of Texas. The fossils and sedimentary rocks are very accessible and sufficiently mysterious to generate at least two paleontology and sedimentology projects, including future Independent Study work by Wooster students. Sure there are fire ants, rattlesnakes, and very fast country road driving, but it wouldn’t be Texas without them! (And the barbecue … all beef, dry-rubbed barbecue …)
Mark Wilson November 15th, 2009
Our Permian sections on this Texas trip have had thick beds of gypsum only a meter or three beneath our fossiliferous limestones and shales.
An outcrop of sedimentary gypsum below the Valera Formation (Permian).
Gypsum (calcium sulfate) is an evaporite mineral, indicating when the Permian shallow sea in this case was much saltier than normal (hypersaline). Our fossils show a restricted nature (lower diversity than normal, and generally smaller shells), but they were still living in at least close to normal salinities. This is especially the case with our numerous echinoids. We even have evidence of some evaporites within our fossiliferous limestones. It is a curious juxtaposition of deposition al environments.
Mark Wilson November 15th, 2009
The latest issue of the journal Palaeontology has an article describing a new family of large clams from the Triassic of southern Israel. The authors include Allison Mione (’05), who pursued this project as part of her geology Independent Study.
A specimen of the new clam family Ramonalinidae from the Triassic of southern Israel in Makhtesh Ramon.
The Ramonalinids: a new family of mound-building bivalves of the Early Middle Triassic
by Thomas E. Yancey, Mark A. Wilson and Allison C.S. Mione
Abstract: Ramonalina n. gen. is a large thick-shelled bivalve abundant in mounds preserved in the Gevanim Formation (late Anisian, Middle Triassic) of southern Israel. This bivalve was an edgewise-recliner with a flattened anteroventral (functionally basal) surface and partially fused valves. It is the basis of a new family, the Ramonalinidae, which is descended from the myalinids through adaptation to edgewise positioning. Ligamental attachment was inadequate to hold valves together on large adults, resulting in valve displacement followed by shell secretion in the apical area that fused valves together and caused irregular growth on abapical areas. The ramonalinids formed large, nearly monospecific mounds on firm mud substrates in shallow marine waters. These are the largest Middle Triassic bivalve mounds known.
(I am very proud!)
Mark Wilson November 13th, 2009
BROWNWOOD, TEXAS–It was nearly a five hour drive from College Station, Texas, through the Hill Country to our first Permian exposure in West Texas. (We passed, by the way, through Killeen and Fort Hood.) It was worth the trip for all the strange features we found on this outcrop of the Valera Formation.
Tom Yancey, a paleontologist at Texas A&M University, seated on our little outcrop of the Valera Formation in West Texas (N31.48454°, W99.69368°).
We spent several hours measuring, describing and sampling this outcrop in ideal weather. We found plenty of examples of what we came here for: fossil microconchids, otherwise known as “worm tubes”.
Microconchid tubes from the Valera Formation at the above outcrop.
We were surprised to also find abundant sea urchin (echinoid) spines in one of the limestone units here. These usually indicate normal marine salinity, but they are unaccompanied by other indicators such as brachiopods and bryozoans. A thick gypsum below our exposed rocks shows that we are likely dealing with elevated seawater salinity during the Permian in this area. A mystery. (And we love mysteries in this business.)
A barbed echinoid spine from the Valera Formation (Permian). In the lower left with the apparent hole in it is an echinoid test plate.
Tomorrow we visit a similar outcrop with microconchids. Now we have some hypotheses to test. Fieldwork is such a joy!
Mark Wilson October 19th, 2009
PORTLAND, OREGON–By now I’ve given over 35 talks at annual Geological Society of America meetings, but I still get as nervous as I did as a graduate student. The cavernous room, the high quality of the previous presentations, the people coming in and sitting expectantly — it all comes to an exquisite tension as I hear the speaker before me say, “And in conclusion …”. We don’t read from a text or even use notes in these 15-minute sessions. It all comes from the slides and our desperate hope that we remember what to say at each. Somehow the adrenaline kicks in as you step up to the podium. The words flow and the slides become old friends with stories which must be told.
I’m in that magical post-talk phase of the meeting this evening with no more performance pressure. I can now happily share a few slides from our presentation, along with happy memories of the field and lab work:
Mark Wilson October 18th, 2009
Elyssa Belding Krivicich (’09) and Sophie Lehman (’08) cheerfully presenting their poster on Jurassic marine paleoecology in Israel at the Geological Society of America meeting in Portland.
Mark Wilson October 18th, 2009
PORTLAND, OREGON–The Paleontological Society has a free short course program it runs on the day before the GSA meeting officially begins. When I began my career the topics were always about some taxonomic group such as “Brachiopods”, “Mollusks”, “Plants” and the like. The purpose was to gather a dozen or so experts on the topic and bring the participating paleontologists up to speed on the latest ideas and discoveries. As you might imagine, as useful as these sessions were, they often became dull recitations of anatomy and classification schemes.
This began to change about a decade ago with short course topics which were more interdisciplinary and not taxa-specific. We began to talk about issues such as predation, paleoecology, preservation, evolution — subjects which appealed to all paleontologists by cutting across differences within the field and foregoing systematic details. These sessions have been very successful, keeping hyperactive paleontologists in their seats most of the day. (As with all geologists, they would rather be in the lobby telling stories and making summer field plans.)
Yesterday’s short course was titled “Conservation Paleobiology”. There was some confusion as to what this title meant before it started (is it about preserving specimens in collections? saving paleontological localities from destruction?), but once it began it was clear this would be a different course from all those which preceded it. Karl Flessa of the University of Arizona (and one of the short course leaders) invented the term for the “application of paleoecological and geochemical techniques to the analysis of the prehistoric and historic skeletal remains of species threatened with extinction.” In other words, the concept is to make paleontology and paleontologists important players in the attempts to limit environmental degradation and preserve ecosystems in this time of climate change, overuse of resources, pollution and overpopulation. Those who study the history of life have much to contribute to understanding current extinctions and other ecological changes. In the more irreverent words of Karl: “Let’s put the dead to work”.
The presentation I found most impressive was by Jeremy Jackson of Scripps Institution of Oceanography (and a bryozozoologist of great note, I might add!). In his talk entitled “Historical ecology for the paleontologist”, he emphasized how much our baselines of what we expect to be “normal” for an ecosystem have shifted “beyond recognition from their formerly pristine state”. This shifting began with the first human interactions with the environment. The only way to deduce what “natural” ecosystems really were is through the fossil record. We have altered every environment on Earth to extraordinary degrees, each time shifting our baselines of what we thought it was like in some Edenic past. It was not a happy talk, that’s certain, but it did clearly lay out what contributions paleontologists must make to pull us back from the brink.
Mark Wilson September 9th, 2009
MAKHTESH RAMON, ISRAEL–On my last day of fieldwork Yoav took me to some wonderfully complex exposures of Cretaceous and Tertiary rocks just north of Makhtesh Ramon. They tell a story of the origins of the Makhtesh anticlinal structure, especially the date it appeared and whether it was ever exposed as an island before its center was eroded away. Part of the debate comes down to the depth at which certain Santonian (Cretaceous) sediments were deposited. These sediments contain oysters and exquisite shark’s teeth. We collected a nice set (see below) which I will attempt to identify to see if we can use what we may know about these sharks to determine the depth of deposition.
Cretaceous shark teeth collected from just north of Makhtesh Ramon (N30.56235°, E34.64876°).
Mark Wilson September 9th, 2009
Another indication of how shallow the seas were in the Middle Jurassic of southern Israel. This bedding plane in the Matmor Formation of Makhtesh Gadol has a gastropod (snail) fossil in the center of the image surrounded by angular shells of fossil mytilids (clams commonly called mussels today). In life the mytilids had attached to the gastropod and each other by fine yet strong byssal thread produced by a special gland. This kind of relationship is very common in tidal pools and other shallow areas where wave action is strong.