Archive for January 19th, 2014

Experiential Learning on Ice (with some water)

January 19th, 2014

Tom Lowell, Aaron Diefendorf and four students from the University of Cincinnati met up with the Wooster Geologists to core Browns Lake. We thank Marvin Sandy, who manages the bog for the Nature Conservancy for guidance and permission to do this work.
coresite

Coring Browns Lake from an ice platform on a winters day in Northeast Ohio. Four cores were taken – the longest of which was 17 meters. The mud in the cores is a record of 15,000 years of environmental change since the last Ice Age.
Browns Lake Bog is own by the Ohio Department of Natural Resources and managed by the Nature Conservancy.

Browns Lake Bog is owned by the Ohio Department of Natural Resources and managed by the Nature Conservancy.

pitcher

Pitcher plants are among the special biology of the bog. Note the ice forming within the pitcher.

auger

First a hole is augured to determine water depth in the basin. It is about 5 feet deep with 4-6 inches of ice.

A look at the drilling rig - anchored in the ice, tied down with ice screws.

A look at the drilling rig – anchored in the ice, tied down with ice screws and straps.

 

pipe

A look down the long axis of the drill pipe – note the corer sticking out of the ice stored in the lake to prevent it from freezing. The water is the warmest place on the site.

Tom explains the theory and Doug and Nick move into the practice phase.

Tom, the core boss,  explains the theory and Doug and Nick move into the practice phase.

humor

Tom and Michael share a coring joke – it help to have a sense of humor standing on ice for 6 hours at 15 degrees F with a breeze.

meter

Another meter of core is brought up – ready to be described, wrapped and archived. About half of the 40 meters of core went to Cincinnati for further analyses.

Lunch on the boardwalk

Lunch on the boardwalk

oscar_andy

Oscar and Andy take a break from the core archiving. Note the water that moves up through the hole in the ice. The weight of the rig and crew cause elastic and some plastic deformation to occur – after the rig is removed the ice slowly pops back into shape.

The last of the gear moves to the parking lot.

The last of the gear moves to the parking lot.

Thanks to Jesse Wiles for the photography.

The geese point the way back to Wooster. Thanks to Jesse Wiles for the photography.

 

 

 

 

 

 

Wooster’s Fossil of the Week: A crinoid-rich Lower Carboniferous siderite concretion (part III — those crinoids had company)

January 19th, 2014

Crinoid with platyceratid (cross-section) 585The last installment of our analysis of a Lower Carboniferous fossiliferous siderite concretion given to the department by Sam Root. In part I we looked at the crinoid stems and calices on the outside and discuss the formation of siderite concretions and the preservation of this particular assemblage. In part II we had our first look at polished sections of the concretion, taking special note of the crinoid stem morphology and its replacement by the mineral marcasite. For part III you were promised a molluscan surprise.

In the top view you can see that we have a section that fortuitously cut right through the center of a crinoid head. The stem is visible at the bottom, with the calyx and attached arms above. Crowning the calyx is a thin semi-circle of shell nestled open-side-down across the crinoid oral surface. This we can tell from the shell morphology is a parasitic platyceratid gastropod caught in place on its crinoid host. Nice.
Platyceratid Lower Carboniferous 585 annotatedThree years ago we received a fossil donation from the Calhoun family of local Lower Carboniferous fossils, including this beauty pictured above. It is a crinoid calyx (you can tell by the polygonal plates) with a cap-shaped platyceratid gastropod (Palaeocapulus acutirostre) preserved in place on top of it between the arms (now missing). I drew a line across the image to indicate the likely plane of section through a similar pair in our siderite concretion. In section the platyceratid would be recorded as a thin shelly top on the calyx.

Platyceratids have long been known as Paleozoic associates of crinoids. For many years we thought of them as simply coprophagous, meaning they were consuming crinoid feces as they exited the anus. (Awkward conversation, I know.) Careful work by Tom Baumiller (1990) showed that this arrangement (which would not have directly harmed the crinoid because it was, after all, done with the food) was likely not the case. He found trace fossil evidence that the platyceratids were likely accessing crinoid stomach contents directly through some sort of proboscis, and that these parasitized crinoids were stunted in their growth and thus directly harmed (but not killed — no good parasite wants to lose its meal ticket). Our new specimen was thus likely a miserable little crinoid, even if it didn’t have a brain to sort out its feelings.
Stem Calyx 121413As one last view of our crinoids in the concretion, look at the detail in the crinoid stem just below the calyx. The lumen is visible in the center of the stem, as well as the alternating ornaments on the columnals.

This has been a fun specimen to examine. Thanks, Sam!

References:

Baumiller, T.K. 1990. Non-predatory drilling of Mississippian crinoids by platyceratid gastropods. Palaeontology 33: 743-748.

Donovan, S.K., and Webster, G.D. 2013. Platyceratid gastropod infestations of Neoplatycrinus Wanner (Crinoidea) from the Permian of West Timor: speculations on thecal modifications. Proceedings of the Geologists’ Association 124: 988–993.