Wooster’s Fossil of the Week: An early bryozoan on a Middle Ordovician hardground from Utah

October 10th, 2014

ORBIPORA UTAHENSIS (Hinds, 1970) 072014Last week I presented eocrinoid holdfasts on carbonate hardgrounds from the Kanosh Formation (Middle Ordovician) in west-central Utah. This week we have a thick and strangely featureless bryozoan from the same hardgrounds. It is very common on these surfaces, forming gray, perforate masses that look stuck on like silly putty. Above you see one on the left end of this hardground fragment. (The circular object to the right is another eocrinoid holdfast.)
Kanosh bryo eo 072014Here is a closer view of the bryozoan, again with one of those ubiquitous eocrinoids encrusting it. The holes are the zooecial apertures. Each zooecium is the skeletal component of a living bryozoan individual (zooid). Note that the walls are thick and granular between the zooecia. All the zooecia look pretty much the same, and there are no other structures like spines, pillars or maculae. This is about as simple as a bryozoan gets.

It is impossible to be certain without a thin-section or acetate peel showing the interior, but I’m pretty sure this Kanosh bryozoan is Orbipora utahensis (Hinds, 1970). It matches fairly well the description in Hinds (1970), who named it Dianulites utahensis, and it fits within the redescription by Ernst et al. (2007).

Several years ago we would have called this a trepostome bryozoan and left it at that. These are, after all, the “stony bryozoans” with thick calcite skeletons and long zooecia. However, the group to which Orbipora belongs is unusual because they have no polymorphs (small zooecia different from the primary zooecia) and have granular skeletal textures rather than laminated. We think the granular walls may be because the original skeletons were made of high-magnesium calcite that later altered to low-magnesium calcite and dolomite, losing details of the microstructure. Orbipora is thus in an as yet undescribed new order of bryozoans. [Update: See comment below from Paul Taylor.]

The Kanosh hardgrounds and their attaching faunas are important in geological and biological history because they are telling us something about the geochemical conditions of the seawater when they formed. We think this was a peak time of Calcite Seas, when low-magnesium calcite was a primary marine precipitate and carbon dioxide levels were high in the atmosphere and seawater. Hardgrounds would have formed rapidly because of early cementation, and aragonite and high-magnesium skeletons would have altered soon after death. The abundant Kanosh communities and substrates are critical evidence for these conditions that were superimposed on the Great Ordovician Biodiversification Event (GOBE). We thus have a delightful combination of seawater geochemistry (and, ultimately, the tectonics that controls it) and evolution intertwined in the history of these rocks and fossils.

References:

Ernst, A., Taylor, P.D. and Wilson, M.A. 2007. Ordovician bryozoans from the Kanosh Formation (Whiterockian) of Utah, USA. Journal of Paleontology 81: 998-1008.

Hinds, R.W. 1970. Ordovician Bryozoa from the Pogonip Group of Millard County, western Utah. Brigham Young University Research Studies, Geology Series 17: 19–40.

Marenco, P.J., Marenco, K.N., Lubitz, R.L. and Niu, D. 2013. Contrasting long-term global and short-term local redox proxies during the Great Ordovician Biodiversification Event: A case study from Fossil Mountain, Utah, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 377: 45-51.

Wilson, M.A., Palmer, T.J., Guensburg, T.E., Finton, C.D. and Kaufman, L.E. 1992. The development of an Early Ordovician hardground community in response to rapid sea-floor calcite precipitation. Lethaia 25: 19-34.

Wooster’s Fossils of the Week: Eocrinoid holdfasts on a Middle Ordovician hardground from Utah

October 3rd, 2014

Kanosh Hardground 072014 smBack in the late 1980s and early 1990s, several students and I did fieldwork in the Middle Ordovician Kanosh Formation in west-central Utah. One year we were joined by my friend Tim Palmer of the University of Aberystwyth. Together, Chris Finton (’91), Lewis Kaufman (’91), Tim and I put together a paper describing the carbonate hardground communities in this remarkable formation (Wilson et al., 1992). At top is an image of one of the surface of one of these hardgrounds. It is covered with holdfasts of rhipidocystid eocrinoids, a kind of primitive echinoderm.
Fossil Mountain UtahMost of the hardgrounds we studied in the Kanosh Formation were found here at Fossil Mountain near Ibex, Utah. (If you want to consider Ibex a place, at least.) It was a beautiful place to work, and it is still highly productive for geologists and paleontologists (see Marenco et al., 2013, for the latest investigation).

Kanosh eocrinoid 2The encrusters on the Kanosh hardgrounds are dominated by two groups: bryozoans (which we’ll highlight next week) and stemmed echinoderms (this week’s subject). The echinoderms are represented by thousands of these small attachment structures called holdfasts. The stem of the echinoderm was attached here to the hardground. The entire skeleton of the echinoderm, including the hardground, is made of low-magnesium calcite, so they are very well preserved. Surprisingly, the hardground communities in the Kanosh have very few sponges or borings.

Kanosh eocrinoid 3 072014The holdfasts come in a few varieties with subtle morphological differences. Here we have one with a tri-radiate center.

Kanosh eocrinoids 1Sometimes the holdfasts blended together on the hardground surface, which was probably the result of competition for attachment space. Note the tri-radiate centers.

Mandalacystis diagramFrom a few plates we found, it appears that the rhipidocystid eocrinoid holdfasts are from a creature like Mandalacystis, which is pictured above from Figure 1 of Lewis et al. (1987). We can’t tell for certain without more of the skeleton, but the holdfasts are very similar to what has been described for the genus.

These Middle Ordovician hardgrounds were formed at an interesting time in the chemistry of the oceans and the development of marine invertebrate faunas. More on that next week!

References:

Ernst, A., Taylor, P.D. and Wilson, M.A. 2007. Ordovician bryozoans from the Kanosh Formation (Whiterockian) of Utah, USA. Journal of Paleontology 81: 998-1008.

Lewis, R.D., Sprinkle, J., Bailey, J.B., Moffit, J. and Parsley, R.L. 1987. Mandalacystis, a new rhipidocystid eocrinoid from the Whiterockian Stage (Ordovician) in Oklahoma and Nevada. Journal of Paleontology 61: 1222-1235.

Marenco, P.J., Marenco, K.N., Lubitz, R.L. and Niu, D. 2013. Contrasting long-term global and short-term local redox proxies during the Great Ordovician Biodiversification Event: A case study from Fossil Mountain, Utah, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 377: 45-51.

Wilson, M.A., Palmer, T.J., Guensburg, T.E., Finton, C.D. and Kaufman, L.E. 1992. The development of an Early Ordovician hardground community in response to rapid sea-floor calcite precipitation. Lethaia 25: 19-34.

Wooster’s Fossil of the Week: A faulted oyster ball from the Middle Jurassic of Utah

July 25th, 2014

Split oyster ball 062914I’m returning this week to one of my favorite fossil types: the ostreolith, popularly known as the “oyster ball”. These were lovingly described in a previous blog entry, so please click there to see how they were formed and some additional images. They are found almost exclusively in the Carmel Formation (Middle Jurassic) of southwestern Utah.They are circumrotatory (a fancy word for “rolling around while forming”) accumulations of small cup-like oysters along with minor numbers of plicatulid bivalves, disciniscid brachiopods, cyclostome bryozoans (see Taylor & Wilson, 1999), and mytilid bivalves that drilled borings known as Gastrochaenolites. They are nice little hard-substrate communities originally nucleated on bivalve shells (Wilson et al., 1998).

oyster ball close 062914Here is a close view of the oyster valves on the outside of the ostreolith. They are attached to similar valves below them, and it is oysters all the way to the center.

What is special about our specimen here is that it managed to obtain a fault right through its center! The chances of this happening are slim, given that they are relatively rare in the rock matrix. The faulting was probably during the Miocene related to a “left-lateral transfer zone that displaces north-south–trending crustal blocks of the eastern Basin and Range Province to the west” (Petronis et al., 2014, p. 534). This is an interesting tectonic region between the Basin and Range Province and the Colorado Plateau.

Slickenfibers 062914A close view of the fault surface shows it is a striated slickenside. The striations (called slickenlines) are parallel to the direction of movement, not that we have to guess when we look at the ostreolith itself. There are also calcitic deposits here formed during faulting called slickenfibres. These elongated crystals have tiny step-like breaks in them that show the actual direction of movement.

Another nice specimen combining paleontology and structural geology.

References:

Petronis, M.S., Holm, D.K., Geissman, J.W., Hacker, D.B. and Arnold, B.J. 2014. Paleomagnetic results from the eastern Caliente-Enterprise zone, southwestern Utah: Implications for initiation of a major Miocene transfer zone. Geosphere 10: 534-563.

Taylor, P.D. and Wilson, M.A. 1999. Middle Jurassic bryozoans from the Carmel Formation of southwestern Utah. Journal of Paleontology 73: 816-830.

Wilson, M.A., Ozanne, C.R. and Palmer, T.J. 1998. Origin and paleoecology of free-rolling oyster accumulations (ostreoliths) in the Middle Jurassic of southwestern Utah, USA. Palaios 13: 70-78.

Iron Flows and Camera Blows

July 21st, 2014

Guest Bloggers:  Sarah McGrath (’17) and Chloe Wallace (’17), both members of Team Utah 2014

 

EPHRAIM, UTAH — No longer rookie bloggers Chloe and Sarah here, coming at you from the sweet comfort of our couch in Utah. Before collecting pounds of oncolites and encountering countless kill sites, we were just two inexperienced field geologists spending our long days becoming pros with the Trimble. The Trimble is a survey grade GPS unit. We used it to map the many iron concretions throughout the Six-Mile Canyon Formation. Over the course of a day and a half we were able to map over 200 points on one single rib of the outcrop.

As you will see below it takes a truly skilled and brave geologist to be worthy of the power that is the Trimble. Lesson learned: do not forget to zip the pocket that is holding your camera as you lean over a steep cliff just to collect a single data point. Thankfully, Sarah’s camera survived the fall and still works somehow. Nikons, people! Also as Sarah was retrieving her camera she came upon some lovely iron staining that otherwise would not have been discovered. There’s always an upside!

picture 6 - 585

How to Trimble 101: This isn’t your basic car GPS.

picture 7 - 585

Seconds before Sarah dropped her camera down the side of the cliff. All in the name of science!

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The iron staining Sarah came upon while retrieving her camera at the bottom of the cliff.

picture 9 - 585

We’ve gotten too used to this view. We’re going to miss Utah! Thanks for an amazing two weeks full of scalding heat, accessibility to more Peace Tea than one human should consume, and unforgettable geology.

 

 

Oncolites and Kill Sites

July 21st, 2014

Guest Bloggers:  Sarah McGrath (’17) and Chloe Wallace (’17), both members of Team Utah 2014

 

EPHRAIM, UTAH –  Rookie bloggers, Sarah and Chloe, coming at you from beautiful Ephraim, Utah! We’ll admit early on that are blogging skills are not the most proficient, but we’re giving it a shot (mostly because we are being “strongly encouraged”). We figure plenty of enticing pictures will make up for what we are lacking.

We began a new project in the field on Thursday. We gathered data and collected oncolites in the North Horn Formation. We measured over 50 oncolites within the rock face and collected about a dozen float samples. The following day we did more oncolite work, collecting at least 150 float samples, in the Flagstaff at “Snake Ridge,” which was cleverly named by Dr. Judge after countless rattlesnake sightings. Luckily for us, we have yet to see a single snake the entire trip. Knock on wood; still one day left in the field.

Although we haven’t seen any rattlesnakes, we’ve encountered enough kill sites to last us a lifetime. At our first sighting we ran away in disgust, but by our most recent kill site we were taking creative photos with them. We suspect our friend Freddy the mountain lion may be at fault.

picture 1 - 585

The view from the North Horn Formation.

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One bag out of many of the collected oncolites at the infamous “Snake Ledge.”  Note the medical tape holding one of the oncolites together!!

picture 3 - killsite

Most recent kill site shot. Maggots don’t scare us.

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More wildlife encountered in the field. This jackrabbit kept us quite entertained for at least thirty minutes.

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Possible homestead of the one and only Freddy the mountain lion.

 

 

Hot Springs and I.S. Frenzy

July 17th, 2014

Guest Blogger:  Kelli Baxstrom (’16), member of Team Utah 2014

 

EPHRAIM, UTAH –  A week into Utah, and feelings are mixed between slight hysteria for those who continue to fall off the couch in the evening due to exhaustion and an ongoing sense of awe of the beautiful world that exists outside Ohio.

Sunday was a day off for us, and so the four of us hopped in a van with some of the OSU field camp students – including recent CoW graduate Tricia Hall – and headed to some hot springs near Spanish Fork. We smelled like sulfur the rest of the day, but the waterfall and pools were worth it!

hotspring

​Wednesday was very I.S. focused for Michael and myself. For my part, I am a double major in Religious Studies as well as Geology. So in order to meld my I.S., Dr. Judge drove me to Nephi to meet the Chairwoman of the Paiute Indian Tribe of Utah. It was very enlightening to talk to a native and political spokeswoman of the tribe, and I learned so much of political, historical and socioeconomic activity of the Paiutes for the last millennia. Dr. Judge also enjoyed the meeting - possibly more than myself – in learning all the ways that the Paiutes have lived and prospered in the areas where she has worked and researched for several years.

After Dr. Judge and I got back from Nephi, Michael and I spread out on the floor with a multitude of topographic maps of Utah trying to decide what we would like to do for I.S. At the moment, that is a prospect Michael and I irrationally believe is completely​ unattainable. But Dr. Judge has faith in us.

Hey, Team British Columbia, here’s proof that there’s some real wildlife out here in Utah…

moose

Brain-melting Heat in the Sanpete Valley

July 16th, 2014

Guest Blogger:  Michael Williams (’16), member of Team Utah 2014

 

EPHRAIM, UTAH –Team Utah 2014 is now approaching the one-week mark of being in the field. For the past four days we’ve been working on one of Dr. Judge’s pet projects: deformation bands and fluid flow in the Sixmile Canyon Formation. This Cretaceous sandstone underwent some serious deformation during the building of the Rocky Mountains, and this strain reveals itself in several remarkable features, including jointing, deformation bands, and bizarre outcroppings of iron. Team Utah has been working hard to measure, categorize, date, and record these features, all while enduring non-stop, brain-melting heat.

We agreed early on that work would begin every morning at 8:00am, so naturally we don’t actually make it out in the field until 9:00am or later. It’s a short drive followed by an even shorter hike to our field site, so it’s typically still mid-morning as we begin the day’s work. Each day has had us focusing on different features in our area. Our most productive days involve measuring the orientations of joints. Other days we hike for hours, looking for the perfect outcrop of deformation bands. No matter our mission, the charge is led by Measurement Machine Shelley Judge, Brunton in hand and field notebook at the ready.

joints

Some nice sets of joints in a nearly horizontal wall of sandstone. On our first day alone we managed to measure just over 200 individual joints.  Brunton Compass for scale.

kelli

Kelli examines some bizarre iron fins protruding from the rock face. We suspect that these were caused by fluid flow through the porous rock.

reidel ladder

A beautiful example of deformation bands forming Riedel ladders. Unfortunately, this particular rock had fallen off the outcrop, and so it couldn’t be included in our data.

michael below

Michael down below (bottom center), measuring orientations of deformation bands, while Kelli records from above (top right).

falling

Sometimes, when the heat starts getting to us, we decompress by falling off of cliffs.

sanpete

You can’t help but occasionally stop to admire the postcard-like beauty of the Sanpete Valley.

WOO

Even temperatures upward of 100 degrees can’t stop the Scott spirit.

Meet Team Utah 2014

July 15th, 2014

EPHRAIM, UTAH — On July 9, four Wooster students traveled to Utah to begin structural and stratigraphic research with me.  They will be out here until July 22, when we will all fly back to Ohio together.  I’d like to introduce these students to you!!

Team Utah

Above is a great picture of Team Utah on the morning of their first day in the field.  From L to R, the students are:  Michael Williams (’16), Kelli Baxstrom (’16), Sarah McGrath (’17), and Chloe Wallace (’17).  Don’t they look enthused, happy, and eager?  (At this point, they do not actually realize that impact of desert heat:  temperatures will soon be 95-100 degrees by noon each day!!  Utah at the end of July can definitely be hot, making field work strenuous.)

During our time in Utah, we have 3 projects that require our attention.  Our primary objective will be to collect data for the deformation band work that I have been doing for a few years.  We will take a comprehensive look at some additional Cretaceous units that may contain deformation bands.  Also, we want to undertake two reconnaissance projects for future I.S. research.  One involves the Cretaceous to Paleogene North Horn Formation, and the other involves the Paleogene Colton Formation.  If there is time left, we will undertake more reconnaissance work in the Jurassic Arapien Formation, which is the core of an amazing diapir in the Sanpete Valley.  Because Mark Wilson has also been interested in the Jurassic of Utah for several years, I’m hoping that I can convince Mark to join forces with me one summer for a joint I.S. research project in Utah.  I really love the stratigraphy of central Utah, so I want to incorporate more I.S. research on the units out here (which have experienced the spectrum of Sevier orogenesis to Basin and Range extension.)

In the coming days, I’m going to ask each of the students to blog in order to reflect on their time in Utah thus far.  They have nearly been here for one week, so stay tuned for some additional news from Ephraim!!

After 5 weeks in the field…my first blog!!

July 15th, 2014

EPHRAIM, UTAH — My apologies for not blogging sooner, but things have been very, very busy out here in the Sanpete Valley.  I spent the first 4 weeks doing my usual summer teaching at Ohio State’s Geology Field Camp.  This summer, we have 22 students — one of whom is Tricia Hall (’14).  During her time at Wooster, Tricia spent 2 summers with me in Utah doing research that eventually culminated in her I.S. on deformation bands within the Sixmile Canyon Formation.  She decided to pursue graduate studies at Ohio State, and her new advisor (Terry Wilson) is the director of the field camp.  So, Tricia is currently completing field camp this summer before beginning her M.S. research in the fall.  It has been wonderful for me to continue to teach her about the joys of Utah geology!!

I’ve been teaching with a great cast of characters:  Terry (OSU), Cristina Millan (OSU), and Dan Kelley (BGSU).  We have had rotating faculty the past 5 weeks, and I have enjoyed every minute of teaching with them this summer.  I always cherish these summer nights in Ephraim, because although they are filled with work, they are also filled with a ton of laughter.  Days are long (6 am to 10+pm with students), so making sure that you are enjoying the teaching is paramount.

Below is a photo that I took from an overlook of Palisade State Park, with its golf course and swimming hole in view.  One of our field camp exercises involves a cross-section W-E across the Sanpete Valley.  This view to the SW encompasses much of the cross-section transect.  Although I cannot give away any field camp secrets for next year’s class, I will say that there is some amazing geology here, with spectacular faults, folds, and unconformities.

Palisade Overlook

One of the most exciting evenings at field camp this year began as a very typical night after dinner.  Students were all extremely busy, diligently trying to finish an assignment by 10 pm.  All of a sudden, there was a low “roar”, and the apartment building began to shake.  We were actually experiencing a nearby earthquake!!  How cool is that?  Needless to say, myself and Cristina (co-instructor) quickly exited our apartment — only to witness all of the other geologists racing out of their rooms in excitement.  You can read about all of the details of the Spring City 4.2 earthquake (which was only about 10 miles to the NE) at: http://earthquake.usgs.gov/earthquakes/pager/events/uu/60075207/index.html

I was exceptionally excited, because its epicenter was on the flanks of the Wasatch monocline, where I did much of my dissertation research.  Although we had several aftershocks, field campers only felt the one episode of shaking.  It was a great educational moment, because Ephraim lies in the transition zone between the Colorado Plateau and the Basin and Range Province.  This region exhibits some of the easternmost normal faulting associated with Basin and Range extension in Utah.

Please look for additional blogs in the very near future.  I currently am working with 4 Wooster students since finishing my teaching duties at field camp.

 

 

Wooster’s Fossils of the Week: “Star-rock” crinoids from the Middle Jurassic of Utah

May 18th, 2014

Isocrinus_nicoleti_Encrinite_Mt_Carmel_585This little slab of crinoid stem fragments comes from the Co-op Creek Member of the Carmel Formation (Middle Jurassic) exposed in northwestern Kane County, Utah. I collected it with my friend Carol Tang as we explored a beautiful encrinite (a rock dominated by crinoid skeletal debris) exposed near Mount Carmel Junction. In 2000, Carol and her colleagues published a description and analysis of this unit and its characteristic crinoid, Isocrinus nicoleti (Desor, 1845). This piece sits on a shelf in my office because it is so ethereal with its star-shaped columnals (stem sections). In fact, the local people in the area collect pieces of the encrinite and sell them as “star rocks“. As I recall, some folks were rather territorial about the outcrops!

Isocrinus nicoleti is one of only three crinoid species known in the Jurassic of North America. (The others are I. wyomingensis and Seirocrinus subangularis.) Tang et al. (2000) showed that this species migrated into southwestern North America by moving southward through a very narrow seaway for thousands of kilometers. I. nicoleti had long stems and relatively small crowns, so it left us zillions of the columnals and very few calices. These washed into large subtidal dunes creating the cross-bedded encrinite.
Isocrinus asteriaThe genus Isocrinus is still alive, most notably in the deep waters around Barbados in the Caribbean. Above is a diagram of Isocrinus asteria originally published by Jean-Étienne Guettard in 1761. The long stem is star-shaped in cross-section.
Pierre Jean Edouard DesorThis gentleman is Professor Pierre Jean Édouard Desor (1811-1882), who named Isocrinus nicoleti in 1845. He is shown here 20 years later. Desor was a German-Swiss geologist who studied two very disparate subjects: glaciers and Jurassic echinoderms. He trained as a lawyer in Germany, but got caught up in the democratic German unity movement of 1832-1833 and had to flee to Paris. In 1837 he met Louis Agassiz and began to collaborate with him on a variety of projects paleontological and glaciological. He even had a trip to the United States where he helped survey the coast of Lake Superior. He took a position as professor of geology at the academy of Neuchâtel, Switzerland, in 1852, eventually retiring in genteel affluence. (This is not how these geological biographies usually end!)

References:

Ausich, W.I. 1997. Regional encrinites: a vanished lithofacies. In: Brett, C.E. and Baird, G.C. (eds.): Paleontological Events, p. 509-519. Columbia University Press, New York.

Baumiller, T.K., Llewellyn, G., Messing, C.G. and Ausich, W.I. 1995. Taphonomy of isocrinid stalks: influence of decay and autotomy. Palaios 10: 87-95.

Desor, É. 1845 Résumé de ses études sur les crinoides fossilies de la Suisse. Bulletin de la Societe Neuchateloise des Sciences Naturelles 1: 211-222.

Hall, R.L. 1991. Seirocrinus subangularis (Miller, 1821), a Pliensbachian (Lower Jurassic) crinoid from the Fernie Formation, Alberta, Canada. Journal of Paleontology 65: 300-307.

Peterson, F. 1994. Sand dunes, sabkhas, streams, and shallow seas: Jurassic paleogeography in the southern part of the western interior basin. In: Caputo, M.V., Peterson, J.A. and Franczyk, K.J. (eds.): Mesozoic Systems of the Rocky Mountain Region, USA, p. 233-272. Rocky Mountain Section-SEPM, Denver, Colorado.

Tang, C.M., Bottjer, D.J. and Simms, M.J. 2000. Stalked crinoids from a Jurassic tidal deposit in western North America. Lethaia 33: 46-54.

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