Archive for August, 2014

Stuck in Girdwood

August 9th, 2014

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Kaitlin, Nick and Dr. Wiles.

GIRDWOOD, ALASKA – The College of Wooster Tree Ring team set off for Columbia Bay Glacier this past wednesday. After arriving in Anchorage with no troubles we drove down to Girdwood to hopefully catch a helicopter with a company called Alpine Air. Unfortunately for us the Alaskan weather had some other plans in mind. Due to a storm in the Prince Williams Sound area the rain and high winds made it impossible to fly to the glacier and forced us to be grounded in Girdwood. Thanks to the hospitallity of USGS glaciologist Shad O’Neel the College of Wooster Tree Ring team was able to stay in a condo owned by his family at the base of the local ski resort in town. The group is currently on standby waiting for any break in the weather to fly to Columbia Glacier.

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Devils Club along the trail in Girdwood.

The storm may have prevented us from traveling to Columbia via helicopter but it did not slow us down from collecting samples. Yesterday the group hiked up in the surrounding trails around Girdwood testing out our rain gear, exploring the beautiful Alaskan area and most importantly collecting some living tree ring samples. The group plans to travel to the intertidal later today to collect some samples from  the 1964 Great Alaskan Earthquake.

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Kaitlin extracting a core sample from a Mountain Hemlock in Girdwood.

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Girdwood, Alaska.

Wooster’s Fossil of the Week: An Early Cretaceous cobble-dwelling bryozoan

August 8th, 2014

Faringdon quartz 071714One of my formative experiences as a young paleontologist was working in the Faringdon Sponge Gravels (Lower Cretaceous, Upper Aptian) of south-central England while on my first research leave in 1985. (I was just a kid!) These gravels are extraordinarily fossiliferous with sponges, brachiopods, corals, vertebrate bones, and a variety of cobbles, both calcareous and siliceous. These coarse sediments were deposited in narrow channels dominated by tidal currents with significant energy reworking and sorting the fossil and rock debris. Above is a cobble of very hard vein quartz from the Sponge Gravels. On the left end you see an encrusting bryozoan with an unusual morphology.
LhwydThe fossils of the Faringdon Sponge Gravels have been studied for a very long time. The first formal notice of them is a museum catalogue compiled by Edward Lhwyd (image above) and published in 1699. Lhwyd (1660-1709) was a Welsh natural philosopher better known by his Latinized name Eduardus Luidus. He had an unfortunate childhood being the illegitimate son of what has been reported as a “dissolute and impractical” (and poor) father. Still, he was better off than most and had schooling all the way up to Oxford (but he could not afford to graduate). In 1684 he became an assistant to Robert Plot, the Keeper of the Ashmolean Museum in Oxford. He became a great scientific traveler and collector, specializing in plants and fossils and (eventually) ancient languages of Britain. In 1691 he was appointed Keeper at the Ashmolean. His book detailing fossils of Britain (Lithophylacii Britannici Ichnographia) was published with financial assistant from his good friend Isaac Newton.
Corynella in Lhwyd plate 18This is plate 18 from Lhwyd (1699). The fossil in the upper right is the sponge Corynella from the Faringdon Sponge Gravels.

Lhwyd’s views on the origin of fossils are with describing. This is a summary from Edmonds (1973, p. 307-308):

He suggested a sequence in which mists and vapours over the sea were impregnated with the ‘seed’ of marine animals. These were raised and carried for considerable distances before they descended over land in rain and fog. The ‘invisible animacula’ then penetrated deep into the earth and there germinated; and in this way complete replicas of sea organisms, or sometimes only parts of individuals, were reproduced in stone. Lhwyd also suggests that fossil plants known to him only as resembling leaves of ferns and mosses which have minute ‘seed’, were formed in the same manner. He claimed that this theory explained a number of features about fossils in a satisfactory manner: the presence in England of nautiluses and exotic shells which were no longer found in neighbouring seas; the absence of birds and viviparous animals not found by Lhwyd as fossils; the varying and often quite large size of the forms, not usual in present oceans; and the variation in preservation from perfect replica to vague representation, which was thought to represent degeneration with time.

What is most interesting about these ideas is that they have no reference to Noah’s Flood or other divine interventions.

In 1708, Lhwyd was elected a Fellow of the Royal Society in 1708. He didn’t enjoy this privilege long for he died of pleurisy the next year at age 49.
Reptoclausa hagenowi Cretaceous England 071714Now back to the bryozoan on the Faringdon cobble. It is the cyclostome Reptoclausa hagenowi (Sharpe, 1854). It has an odd form of irregularly radiating ridges of feeding zooids (autozooids) separated from each other by structural zooids (kenozooids). I like to think (although I have no evidence) that this morphology was resistant to abrasion in the rough-and-tumble life of living on a cobble in a high-energy channel. There are few other encrusters on the outer surfaces of the Faringdon cobbles.

The next two Fossils of the Week will also be from the fascinating Faringdon Sponge Gravels.

References:

Edmonds, J.M. 1973. Lhwyd, Edward, p. 307-308. In: Gillespie, C.C. (ed.). Dictionary of Scientific Biography, 8. Charles Scribner’s Sons, New York, 620 pp.

Lhwyd, E. 1699. Lithophylacii Britannici Ichnographia. London, 139 pages.

Meyer, C.J.A. 1864. I. Notes on Brachiopoda from the Pebble-bed of the Lower Greensand of Surrey; with Descriptions of the New Species, and Remarks on the Correlation of the Greensand Beds of Kent, Surrey, and Berks, and of the Farringdon Sponge-gravel and the Tourtia of Belgium. Geological Magazine 1(06): 249-257.

Pitt L.J. and Taylor P.D. 1990. Cretaceous Bryozoa from the Faringdon Sponge Gravel (Aptian) of Oxfordshire. Bulletin of the British Museum (Natural History), Geology Series, 46: 61–152.

Wells, M.R., Allison, P.A., Piggott, M.D., Hampson, G.J., Pain, C.C. and Gorman, G.J. 2010. Tidal modeling of an ancient tide-dominated seaway, part 2: the Aptian Lower Greensand Seaway of Northwest Europe. Journal of Sedimentary Research 80: 411-439.

Wilson, M.A. 1986. Coelobites and spatial refuges in a Lower Cretaceous cobble-dwelling hardground fauna. Palaeontology 29: 691-703.

Wooster’s Fossils of the Week: An Ordovician hardground with a bryozoan and borings — and an unexpected twist

August 1st, 2014

1 Hardground Bryo Large 071514aThe view above, one quite familiar to me, is of a carbonate hardground from the Upper Ordovician Corryville Formation exposed near Washington, Mason County, Kentucky. We are looking directly at the bedding plane of this limestone. The lumpy, spotted fossil covering about half the surface is a trepostome bryozoan. It looks like a dollop of thick pudding plopped on the rock. In the upper left are round holes that are openings of the trace fossil Trypanites, a common boring in carbonate hard substrates.
2 Closer hdgd bryo 071514bThis closer view shows the bryozoan details in the right half. You can barely pick out the tiny pin holes of the zooecia (the tubes that contained the individual zooids) and see the raised areas called maculae, which may have assisted in directing water currents for these colonial filter-feeders. Without a thin-section or peel I can’t identify the bryozoan beyond trepostome. The Trypanites borings in the hardground surface are also visible.
3 Hardground oblique Ordovician sm 071514cThis oblique view brings all the elements together. The bryozoan has closely encrusted the microtopography of the hardground surface. The Trypanites borings are shown cutting directly through the limestone of the hardground. Both of these observations confirm that the hardground was cemented seafloor sediment when the encrusters and borers occupied it.
4 Cross section hdgd 071514dHere is a full cross-section view showing the borings and the draping nature of the bryozoan. Now for the twist — I’m showing the specimen upside-down! It was actually found in place with the bryozoan down, not up. This is the roof of a small cave on the Ordovician seafloor. The bryozoan was hanging down from the ceiling, and the boring organisms were drilling upwards. The true orientation of this specimen is thus —
5 Cross section hdgd right side up 071514dThe cave was apparently formed after the carbonate hardground was cemented on the seafloor. Currents may have washed away unconsolidated muds underneath the hardground, forming a small cavity then occupied by the borers and the bryozoan: an ancient cave fauna. Brett & Liddell (1978) showed similar cavity encrustation in the Middle Ordovician, and I recorded a nearly identical situation in the Middle Jurassic of Utah (Wilson, 1998). Other detailed fossil marine caves are described from the Jurassic by Palmer & Fürsich (1974) and Taylor & Palmer (1994).

I should write up this Ordovician story someday!

References:

Brett, C.E. and Liddell, W.D. 1978. Preservation and paleoecology of a Middle Ordovician hardground community. Paleobiology 4: 329– 348.

Bromley, R.G. 1972. On some ichnotaxa in hard substrates, with a redefinition of Trypanites Mägdefrau. Paläontologische Zeitschrift 46: 93–98.

Palmer, T.J. 1982. Cambrian to Cretaceous changes in hardground communities. Lethaia 15: 309–323.

Palmer, T.J. and Fürsich, F.T. 1974. The ecology of a Middle Jurassic hardground and crevice fauna. Palaeontology 17: 507–524.

Taylor, P.D. and Palmer, T.J. 1994. Submarine caves in a Jurassic reef (La Rochelle, France) and the evolution of cave biotas. Naturwissenschaften 81: 357-360.

Taylor, P.D. and Wilson. M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1–103.

Wilson, M.A. 1998. Succession in a Jurassic marine cavity community and the evolution of cryptic marine faunas. Geology 26: 379-381.

Wilson, M.A. and Palmer, T.J. 1992. Hardgrounds and hardground faunas. University of Wales, Aberystwyth, Institute of Earth Studies Publications 9: 1–131.

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