Wooster Geologists at GSA

November 2nd, 2012

Many of the Wooster Geologists have embarked on the journey to Charlotte, NC, for the 2012 National Meeting of GSA. If you’re attending the meeting, be sure to check out one of our presentations:

Don’t miss us at the Group Alumni Reception on Monday at 7 pm in the Westin Grand Ballroom CD. We’re taking our annual alumni photo at 8 pm. GSA President and Wooster Alum George Davis (’64) will also be joining us at 8 pm.

Real-life photos to come!

 

Upside-down and inside-out: Cryptic skeletobiont communities from the Late Ordovician of Ohio, Indiana, and Kentucky — An abstract submitted to the Geological Society of America for the 2012 annual meeting

August 14th, 2012

Editor’s note: The Wooster Geologists in Indiana this summer wrote an abstract for the Geological Society of America Annual Meeting in Charlotte, North Carolina, this November. The following is from student guest blogger Kit Price in the format required for GSA abstracts:

Upside-down and inside-out: Cryptic skeletobiont communities from the Late Ordovician of Ohio, Indiana, and Kentucky

PRICE, Katherine W. and WILSON, Mark A., Department of Geology, The College of Wooster, 944 College Mall, Wooster, OH 44691

In the majority of the studies in which skeletobiont communities are described, they are found on the exteriors of shell substrates. Skeletobiont communities that inhabited cryptic environments inside some of these same organisms are poorly known. In those instances where cryptic skeletobiont communities have been described, they are on a much larger scale (i.e., cavities in bryozoan reefs and under hardground ledges) and do not include smaller cryptic communities. The Cincinnatian Series of Ohio, Indiana, and Kentucky has many examples of these cryptic communities. Skeletobionts encrusted the interiors of gastropod, monoplacophoran, and nautiloid shells post-mortem, and are mostly made up of sheet and runner-type bryozoans and cornulitids, along with some craniid brachiopods and microconchids. Interestingly, in contrast to other studies on skeletobionts, the majority of the encrusters in our study do not appear to have been concerned with the location of the host aperture. Only the runner-type bryozoans (Cuffeyella and Corynotrypa) appear to have some directional preference, generally increasing their crypticity and branching away from the aperture. However, increasing crypticity is not always the case; sometimes the bryozoans branch parallel to the aperture or even grew towards it. Aside from shedding light on the life habits of these encrusters, these cryptic skeletobionts also inadvertently preserved their hosts through bioimmuration. Bioimmuration is a type of fossil preservation in which a skeletal organism overgrows another, preserving its negative relief. These cryptic communities not only tell us more about the organisms living in these isolated cavities, but they also have preserved detailed external and internal molds of their host aragonitic fauna. This provides information about shell morphology that would have otherwise been lost to dissolution. Because of the abundance of skeletal bioimmuration in the Cincinnatian, a comparison of cryptic to exposed skeletobionts living in the same environments can be made.

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The header photograph is of an internal mold of a monoplacophoran mollusk. At the left you can see the branching runners of the bryozoan Cuffeyella, shown in closer view below.

Above is a close-up of the monoplacophoran internal mold. This bryozoan (Cuffeyella) was growing on the inside of the monoplacophoran shell. That shell filled with sediment and then dissolved, leaving the cemented sediment and the underside of the encrusting bryozoan. (Thus the “upside-down and inside-out” preservation.)

This is a view of the underside of skeletobionts that grew inside a nautiloid conch. The conch dissolved, leaving the undersides of various encrusters. A = the inarticulate brachiopod Petrocrania; B = sheet-like bryozoan; C = a rare microconchid with an extended apertural tube; D = another sheet-like bryozoan; E = one of many Trypanites or Palaeosabella borings.

Kit Price (’13) on one of her outcrops in Indiana (C/W-149) on July 28, 2012.

Patchiness and ecological structure in a Middle Jurassic equatorial crinoid-brachiopod community (Matmor Formation, Callovian, southern Israel) — An abstract submitted to the Geological Society of America for the 2012 annual meeting

August 6th, 2012

Editor’s note: The Wooster Geologists in Israel this spring wrote abstracts for the Geological Society of America Annual Meeting in Charlotte, North Carolina, this November. The following is from student guest blogger Melissa Torma in the format required for GSA abstracts:

TORMA, Melissa, WILSON, Mark A., Department of Geology, The College of Wooster, Wooster, OH 44691 USA; FELDMAN, Howard R., Division of Paleontology (Invertebrates), American Museum of Natural History, New York, NY 10024

The Matmor Formation is a Middle-Upper Jurassic (Callovian-Oxfordian) marl and limestone unit entirely exposed in Hamakhtesh Hagadol in the Negev of southern Israel. It was deposited in shallow marine waters very close to the paleoequator in the Ethiopian Province of the Tethyan Faunal Realm. It is very fossiliferous throughout most of its 100 meters of thickness. The Matmor Formation has been well described stratigraphically, and several of its fossil groups have been taxonomically assessed (notably the brachiopods, ammonites, crinoids and sclerobionts), but there is yet no community-level analysis of the entire fauna. This work is part of that larger paleoecological project. We systematically collected from the most fossiliferous unit of the Matmor (SU 51 in the local stratigraphy; upper Callovian; Quenstedtoceras (Lamberticeras) lamberti Zone) over several kilometers. The community in this marl is dominated by abundant crinoids (a new species of Apiocrinites), rhynchonellid (Somalirhynchia and Burmirhynchia) and terebratulid (Bihenithyris and Digonella) brachiopods, echinoids (mostly rhabdocidarids), calcisponges and scleractinian corals. Mollusks, other than small attached oysters, are relatively rare, and bryozoans are represented by only a few encrusters. The fossils are concentrated in patches a few tens of meters in diameter separated from each other by featureless, unfossiliferous yellow marl. The patches share many of the same common taxa (especially the crinoids and brachiopods) but differ in the relative abundance of corals. No infauna has been found in this unit, either as trace or body fossils. The environment appears to have been a shallow water embayment with a muddy substrate. Patches of epifauna developed as shelly islands across this seafloor. Crinoids and small corals may have been the pioneers on this soft bottom, providing increasing amounts of skeletal debris to facilitate the settlement of brachiopods and other invertebrates. A periodic influx of fine sediment during storms limited the diversity of this assemblage by smothering patches under several centimeters of mud. This community was thus kept in its early successional stages by periodic disturbance.

Analysis of a Rhuddanian (Llandovery, Lower Silurian) sclerobiont community in the Hilliste Formation on Hiiumaa Island, Estonia: a hard substrate-dwelling recovery fauna — An abstract submitted to the Geological Society of America for the 2012 annual meeting

July 19th, 2012

Editor’s note: The Wooster Geologists in Estonia this summer wrote abstracts for posters at the Geological Society of America Annual Meeting in Charlotte, North Carolina, this November. The following is from student guest blogger Jonah Novek in the format required for GSA abstracts:

Analysis of a Rhuddanian (Llandovery, Lower Silurian) sclerobiont community in the Hilliste Formation on Hiiumaa Island, Estonia: a hard substrate-dwelling recovery fauna

NOVEK, Jonah M., WILSON, Mark A., EKKA, Richa N., Department of Geology, The College of Wooster, Wooster, OH 44691 USA; AUSICH, William I., School of Earth Sciences, The Ohio State University, Columbus, OH 43210 USA; VINN, Olev, Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia

The Hilliste Formation on the island of Hiiumaa, western Estonia, is a Rhuddanian (Llandovery, Lower Silurian) sequence of limestones and shales.  It represents some of the earliest Silurian rocks on the paleocontinent of Baltica. The depositional system was tropical and shallow marine with tempestites indicated by overturned and broken corals and stromatoporoids. This unit contains a recovery fauna from the Ordovician Mass Extinction. Major taxa in the Hilliste Formation include crinoids, trilobites, bryozoans, corals, stromatoporoids, gastropods, and brachiopods. Sclerobiont communities (organisms that lived on or within hard substrates) have not yet been described from Rhuddanian faunas. The Hilliste Formation contains many encrusters and a few borings on skeletal substrates (primarily corals and crinoid stems). These sclerobionts include at least three kinds of crinoid holdfasts, cornulitids, sheet-like bryozoans, runner-type bryozoans, erect bryozoan holdfasts, and auloporid corals. Most if not all of these sclerobionts inhabited dead substrates. We studied the Hilliste Formation in a small quarry near the village of Hilliste on Hiiumaa. Numerous encrusted and bored specimens were collected for analysis of sclerobiont occurrences in this rare example of a Rhuddanian hard substrate community. These encrusters and borings, along with the macrofauna, have a distinct Late Ordovician aspect.

Stratigraphy and paleoenvironment of the Soeginina Beds (Paadla Formation, Lower Ludlow, Upper Silurian) on Saaremaa Island, Estonia — An abstract submitted to the Geological Society of America for the 2012 annual meeting

July 19th, 2012

Editor’s note: The Wooster Geologists in Estonia this summer wrote abstracts for posters at the Geological Society of America Annual Meeting in Charlotte, North Carolina, this November. The following is from student guest blogger Richa Ekka in the format required for GSA abstracts:

Stratigraphy and paleoenvironment of the Soeginina Beds (Paadla Formation, Lower Ludlow, Upper Silurian) on Saaremaa Island, Estonia

EKKA, Richa N., WILSON, Mark A., NOVEK, Jonah M., Department of Geology, The College of Wooster, Wooster, OH 44691 USA; VINN, Olev, Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia

The Soeginina Beds in the Paadla Formation on the island of Saaremaa, western Estonia, are a Lower Ludlow (Upper Silurian) sequence of dolostones, marls, and stromatolites. They represent rocks just above the Wenlock/Ludlow boundary, which is distinguished by a major disconformity that can be correlated to a regional regression on the paleocontinent of Baltica. We interpret the depositional environment of the Soeginina Beds as having been a hypersaline lagoon. Our evidence includes halite crystal molds, oscillation ripples, eurypterid fragments, stromatolites, ostracods, gastropods, Chondrites trace fossils, intraclasts and oncoids. Nautiloid conchs are common, probably because storm currents washed them in. We measured two sections of the Soeginina Beds at Kübassaare, eastern Saaremaa, western Estonia. The beds in one section are virtually horizontal; in the second they are steeply dipping, probably because of Pleistocene glacial ice overpressure. The beds begin with fine-grained dolostone and end with large, well-preserved domical stromatolites. The equivalent section at Soeginina Pank in western Saaremaa (about 86 kilometers away) has larger oncoids, branching coral fragments, and smaller stromatolites. It is also more heavily dolomitized. We interpret these differences as showing the western Soeginina Beds were deposited in slightly deeper, less saline waters than those in the east at Kübassaare.

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