Team Minnesota visits the Upper Ordovician of Iowa

July 27th, 2016

1 Decorah Bruening QuarryRochester, Minnesota — Team Minnesota traveled south today to visit exposures of our three favorite formations: the Platteville Limestone, Decorah Shale, and Cummingsville Limestone. Where best to see the Decorah Shale than in Decorah, Iowa? Above the crew is scattered in the abandoned Decorah Bruening Quarry. They are walkinng on top of the Carimona Member of the Decorah, with the shaley units above topped by the Cummingsville Limestone.

2 Team with Deicke at Decorah BrueningWe began at the bottom with the Platteville and a bit of rare shade. Nikki Bell and Etienne Fang have their hands on the iconic Deicke Bentonite. A very handy time indicator, that volcanic ash deposit.

3 Andrew Decorah Cummingsville contactOur excellent guide Andrew Retzler of the Minnesota Geological Survey is examining the contact between the upper Decorah Shale and Lower Cummingsville Limestone. We found here several specimens of the “gumdrop” bryozoan Prasopora.

4 Rachel CummingsvilleRachel Wetzel gets a bit too close to the crumbly cliff of Cummingsville Limestone at the Decorah Bruening  Quarry.

5 Cummingsville limestoneWhere freshly exposed, the Cummingsville reveals itself to be a fascinating unit with alternating limestone lithologies. The darker layer here is a packstone with fine fossil debris. It is almost certainly a storm deposit.

6 Cummingsville ChondritesThis slab of Cummingsville is covered with beautiful Chondrites trace fossils.

7 Team at Golden HillIn the afternoon we returned to Minnesota and explored a very overgrown exposure of the Decorah Shale at the Golden Hill abandoned quarry along US 52 near Rochester. The main attraction here for us is the abundance of “iron ooids”, small spheres of iron oxides. Etienne Fang is studying their composition and origin for her Independent Study thesis. It’s a steep and muddy slope after a journey through head-high brush, but the bags full of samples made it worthwhile.

8 Golden Hill slabThe fossils here are gorgeous. This is the base of a crinoid calyx surrounded by brachiopod, crinoid and bryozoan debris.

It was a great day of exploration. Tomorrow we examine localities north of Rochester.

Wooster’s Fossil of the Week: A bored rhynchonellid brachiopod from the Middle Jurassic of France

July 22nd, 2016

1 Kutchi dorsal 585Another beautiful brachiopod this week from our friend Mr. Clive Champion in England. His donations to our collections have considerably enriched our teaching program, especially for brachiopods! This specimen is the rhynchonellid Kutchirhynchia morieri (Davidson, 1852) from the Middle Jurassic (Upper Bathonian) of Luc-sur-Mer, France. This is a view of the dorsal side with the dorsal valve on top with the ventral valve (containing the round opening from which the stalk-like pedicle extended) seen below it. Like most rhynchonellids, the valves have distinct plicae (thick ridges) where the shell is tightly folded.
2 Kutchi ventral 585This is the ventral view showing only the exterior of the ventral valve. Note the curved serpulid worm tube attached near the center, and the squiggly borings. These were likely sclerobionts (hard substrate dwellers) that occupied the brachiopod shell when the animal was still alive, since the dorsal and ventral valves are still articulated. The borings are probably of the ichnogenus Talpina, but I would have to grind down the shell to know for certain.
SSBuckmanThe genus Kutchirhynchia was named by Sydney Savory Buckman (1860-1929) in 1917. We met Buckman earlier in this blog when looking at another of his Jurassic rhynchonellid genera, Burmirhynchia. We learned a lot more about Buckman this summer during our expedition to the Jurassic of Dorset, where he did much of his work. He is best known there as an ammonite worker and stratigrapher (and massive taxonomic splitter).
3 Thomas DavidsonThe species Kutchirhynchia morieri was named by the Scottish paleontologist Thomas Davidson (1817-1885), who originally placed it in the large genus Rhynchonella. Buckman acknowledges Davidson in an ammonite monographs as one of his “earliest geological friends”. (Davidson was 43 years older than Buckman.) Davidson was born in Edinburgh to wealthy parents. He studied at the University of Edinburgh and then in France, Italy and Switzerland, where he made many long geological tours. He was convinced by the German paleontologist Christian Leopold von Buch (1774-1853) to work on fossil brachiopods. (Von Buch was 43 years older than Davidson. Nice to see the older generation having an effect on those kids!) Davidson stayed with brachiopods his entire career, producing massive monographs on both fossil and recent forms. He engraved his own plates on stone, and there are more than 200 of them. Davidson was elected a fellow of the Geological Society of London in 1852, awarded the Wollaston medal in 1865. In 1857 he was elected a Fellow of the Royal Society, receiving their Royal medal in 1870. Upon his death in Brighton, England, in 1885, his entire collection of fossil and recent brachiopods went to the British Museum.
4 Elizabeth GrayThis is a good place to mention Elizabeth Anderson Gray (1831-1924), an important fossil collector in Scotland who supplied Thomas Davidson and many other paleontologists with critical specimens for their work. She is one of the many unnoticed heroes of paleontology, being rarely acknowledged publicly and then overshadowed by her husband. She worked primarily in the Ordovician and Silurian and so did not give Davidson Jurassic rhynchonellids, but she provided hundreds of brachiopods from the early Paleozoic. I love this image of her knocking out fossils with a hammer, just like we do today. Trowelblazers has an excellent biographical page on Elizabeth Anderson Gray.

References:

Buckman, S.S. 1917. The Brachiopoda of the Namyau Beds, Northern Shan States, Burma. Palaeontologia lndica 3(2): 1-254.

Gilman, D.C., Thurston, H.T. and Colby, F.M., eds. 1905. Davidson, Thomas (paleontologist). New International Encyclopedia (1st ed.). New York: Dodd, Mead.

Shi, X. and Grant, R.E. 1993. Jurassic rhynchonellids: internal structures and taxonomic revisions. Smithsonian Contributions to Paleobiology, Number 73, 190 pages.

Wooster’s Fossils of the Week: A molluscan assemblage from the Miocene of Maryland

July 15th, 2016

1 Calvert Zone 10 Calvert Co MD 585Earlier this month a gentleman stopped by The Department of Geology and donated the above beautiful slab of fossils to our program. Dale Chadwick of Lancaster, Pennsylvania, is an avid amateur fossil collector with a very useful website and considerable generosity. His gift to the department makes an excellent Fossils of the Week entry. Later I’ll show you the equally-impressive other side of this specimen!

We have here a fine sandstone from the famous Calvert Formation (lower to middle Miocene) exposed at the Calvert Cliffs, Plum Point, Calvert County, Maryland, in the stratigraphic Shattuck Zone 10. As you can see, some horizons are densely fossiliferous with large numbers of gastropods and bivalves. This is what we refer to us a death assemblage, meaning these shells are not preserved in their life positions but how they accumulated just before final burial. These rocks and their fossils were the initial basis of Susan Kidwell’s important work on taphonomic feedback, or how shell accumulations affect the succeeding living communities.

So what are the prominent fossils in this slab? Dale has the answers on his website. I’ve annotated the image and made a list below:

2 Calvert Zone 10 Calvert Co MD 585 labeledA Turretilla variabilis (a turritellid gastropod)
B Stewartia sp. (a lucinid bivalve)
C Turritella plebia (a turritellid gastropod)
D Cardium laqueatum (a carditid bivalve)
E Siphonalia devexa (a buccinid gastropod)

So how did several of these animals die on that seafloor long ago? You’ve probably guessed predation by looking at that round hole in specimen B, a lucinid bivalve.

3 Naticid borehole Calvert 585The beveled nature of this round drillhole tells us it was made by a predatory naticid gastropod, which used its radula (a tongue-like device with sharp teeth) to penetrate the calcareous shell and damage the muscles holding it tight against the attack. About half the specimens in this slab show similar predatory penetrations. Wooster alumna Tricia Kelley did critical work on predation styles, intensities and evolutionary patterns with Calvert specimens like these.

Thank you again to Dale Chadwick for his gift!

References:

Kelley, P.H., 1983, Evolutionary patterns of eight Chesapeake Group molluscs: Evidence for the model of punctuated equilibria: Journal of Paleontology 57: 581–598.

Kelley, P.H. 1988. Predation by Miocene gastropods of the Chesapeake Group: stereotyped and predictable. Palaios 3: 436-448.

Kidwell, S.M. 1986. Taphonomic feedback in Miocene assemblages: Testing the role of dead hardparts in benthic communities: Palaios 1: 239–255.

Kidwell, S.M., Powars, D.S., Edwards, L.E. and Vogt, P.R. 2015. Miocene stratigraphy and paleoenvironments of the Calvert Cliffs, Maryland, in Brezinski, D.K., Halka, J.P. and Ortt, R.A., Jr., eds., Tripping from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 2015: Geological Society of America Field Guide 40, p. 231–279.

Wooster’s Fossil of the Week: An ammonite from the Middle Jurassic of southern England

July 8th, 2016

Leptosphinctes microconch Jurassic Dorset 585We’re featuring just a workaday fossil this week because of other summer activities. This is the ammonite Leptosphinctes Buckman 1929 from the Inferior Oolite (Middle Jurassic) at Coombe Quarry, Mapperton, Dorset, southern England. Cassidy Jester (’17) and I collected it last month during our 2016 England research expedition. Our friend Bob Chandler generously identified it. It popped out of a rock we were pounding into submission, providing a direct application of ammonite biostratigraphy to our work. As with many ammonites, the group is well known but the names are still a bit dodgy.

This specimen is a microconch, meaning it is the smaller version of a species pair, the larger being the macroconch. It is presumed that this is sexual dimorphism and that the microconch is the male because it didn’t need to carry resources for egg-laying. This is one reason why the taxonomy of these ammonites is in perpetual revision.

References:

Buckman, S.S. 1909–1930. Yorkshire Type Ammonites & Type Ammonites. Wesley & Son, Wheldon & Wesley, London, 790 pl.

Chandler, R B., Whicher, J., Dodge, M. and Dietze, V. 2014. Revision of the stratigraphy of the Inferior Oolite at Frogden Quarry, Oborne, Dorset, UK. Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen 274: 133-148.

Galácz, A. 2012. Early perisphinctid ammonites from the early/late Bajocian boundary interval (Middle Jurassic) from Lókút, Hungary. Geobios 45: 285-295.

Pavia, G. and Zunino, M. 2012. Ammonite assemblages and biostratigraphy at the Lower to Upper Bajocian boundary in the Digne area (SE France). Implications for the definition of the Late Bajocian GSSP. Revue de Paléobiologie, Vol. spéc, 11: 205-227.

Wooster’s Fossils of the Week: Iron-oxide oncoids (“snuff-boxes”) from the Middle Jurassic of southern England

July 1st, 2016

1 Snuffbox colection BBThese fossils (in the broad sense!) are inevitable for our weekly feature considering how much time we spent studying and collecting them during last month’s fieldwork in Dorset, southern England. “Snuff-boxes” are the subject of Cassidy Jester’s (’17) Senior Independent Study project, so here we’ll just broadly cover what we think we know about them.

These discoidal objects are called “snuff-boxes” because their carbonate centers (usually a bit of limestone or shell) often erode faster than their iron-oxide exteriors, making them weather a bit like boxes with lids.
2 Quote from Buckman 1910 67This quote from Buckman (1910, p. 67) is the earliest reference I can find to the snuff-box term. Snuff-boxes were sometimes works of art in the 18th and 19th centuries, although quarrymen probably had more homespun varieties in mind.
1 Snuffbox serpulidssWe’re counting these snuff-boxes as fossils here because they formed through biotic and physical processes. The cortex of a snuff-box has layers of serpulid worm tubes, as shown above.
4 Palmer Wilson Fig 3There are also cyclostome bryozoans embedded within the iron-oxide layers, as shown in this image from Palmer and Wilson (1990, fig. 3).
3 Snuff-box horn 061716We believe the snuff-boxes grew by accretion of microbially-induced layers of iron-oxide formed on their undersides, which would have been gloomy caverns on the seafloor. They then would have occasionally turned over and grew layers on the other side. Many snuff-boxes have extensions on their peripheries that look in cross-sections like horns, as seen above. The layers are separate from those that formed around the nucleus. They may have grown after the snuff-box became too big to be overturned by currents or animals.
6 Platy minerals pdt19573Paul Taylor and I looked at the cortex of a snuff-box with Scanning Electron Microscopy (SEM) and had the above surprising view. The odd platy materials may be limonite, an iron-oxide that is amorphous (non-crystalline).
7 Hebrew letters pdt19572Sometimes the plates look like they’ve partially evaporated, leaving remnants that resemble Hebrew letters!
8 iron ooid pdt19576Associated with the snuff-boxes are small “iron ooids” that are about sand-size. They too have the platy materials, and so their origin may be similar to that of the snuff-boxes.

Cassidy has an interesting project ahead of her testing various origin hypotheses and sorting out the paleontology, mineralogy and geochemistry.

References:

Buckman, S.S. 1910. Certain Jurassic (Lias-Oolite) strata of south Dorset and their correlation. Quarterly Journal of the Geological Society 66: 52-89.

Burkhalter, R.M. 1995. Ooidal ironstones and ferruginous microbialites: origin and relation to sequence stratigraphy (Aalenian and Bajocian, Swiss Jura mountains). Sedimentology 42: 57-74.

Gatrall, M., Jenkyns, H.C. and Parsons, C.F. 1972. Limonitic concretions from the European Jurassic, with particular reference to the “snuff-boxes” of southern England. Sedimentology 18: 79-103.

Palmer, T.J. and Wilson, M.A. 1990. Growth of ferruginous oncoliths in the Bajocian (Middle Jurassic) of Europe. Terra Nova 2: 142-147.

Wooster’s Fossils of the Week: Encrusting cyanobacteria from the Upper Ordovician of the Cincinnati region

June 24th, 2016

1 pdt19598 D1253Deep in the basement of the Natural History Museum in London, Paul Taylor and I were examining cyclostome bryozoans encrusting an Upper Ordovician brachiopod with a Scanning Electron Microscope (SEM). This is one of our favorite activities, as the SEM always reveals tiny surprises about our specimens. That day the surprises were the smallest yet – fossils we had never seen before.

2 Infected brachWe were studying the dorsal exterior surface of this beat-up brachiopod from a 19th Century collection labelled “Cincinnati Group”. (Image by Harry Taylor.) We knew it was the strophomenid Rafinesquina ponderosa, and that the tiny chains of bryozoans encrusting it were of the species Corynotrypa inflata. We’ve seen this scene a thousand times. But when we positioned the SEM beam near the center of the shell where there was a brown film …

3 pdt16920 D1253… we saw that the bryozoans were themselves encrusted with little pyritic squiggles. These were new to us.

4 pdt19580 D7139In some places there were thick, intertwining mats of these squiggles. We later found these fossils on two other brachiopod specimens, both also Rafinesquina ponderosa and from 19th Century collections with no further locality or stratigraphic information.

5 pdt19578 D7139Last week Paul and I scanned these specimens again and began to put together an analysis. We believe these are fossil cyanobacteria. They are uniserial, unbranching strands of cells that range from 5 to 9 microns in length and width. Some of individual strands are up to 700 microns long and many are sinuous. The cells are uniform in size and shape along the strands; there are no apparent heterocysts. They appear very similar in form to members of the Order Oscillatoriales.

6 CyanobacteriaCyanobacteria are among the oldest forms of life, dating back at least 2.1 billion years, and they are still abundant today. The fossils are nearly identical to extant forms, as seen above (image from: http://www.hfmagazineonline.com/cyanobacteria-worlds-smallest-oldest-eyeball/).

7 pdt19599 D1253Paul made this remarkable image, at 9000x his personal record for high magnification, showing the reticulate structure preserved on some of the fossil surfaces. Note that the scale bar is just 2 microns long. These are beautiful fossils in their tiny, tiny ways.

We have not seen these cyanobacteria fossils before on shell surfaces, so we submitted an abstract describing them for the Geological Society of America annual meeting in Denver this September. We are, of course, not experts on bacteria, so we are offering our observations to the scientific community for further discussion. Here is the conclusion of our abstract —

“We suggest the cyanobacterial mats developed shortly before final burial of the brachiopod shells. Since the cyanobacteria were photosynthetic, the shells are inferred to have rested with their dorsal valve exteriors upwards in the photic zone. That Cincinnatian brachiopod shells were occupied by cyanobacteria has been previously well demonstrated by their microborings but this is the first direct evidence of surface microbial mats on the shells. The mats no doubt played a role in the paleoecology of the sclerobiont communities on the brachiopods, and they may have influenced preservation of the shell surfaces by the “death mask” effect. The pyritized cyanobacteria can be detected with a handlens by dark squiggles on the brachiopod shells, but must be confirmed with SEM. We encourage researchers to examine the surfaces of shells from the Cincinnatian and elsewhere to find additional evidence of fossilized bacterial mats.”

References:

Noffke, N., Decho, A.W. and Stoodle, P. 2013. Slime through time: the fossil record of prokaryote evolution. Palaios 28: 1-5.

Tomescu, A. M., Klymiuk, A.A., Matsunaga, K.K., Bippus, A.C. and Shelton, G.W. 2016. Microbes and the Fossil Record: Selected Topics in Paleomicrobiology. In: Their World: A Diversity of Microbial Environments (pp. 69-169). Springer International Publishing.

Vogel, K. and Brett, C.E. 2009. Record of microendoliths in different facies of the Upper Ordovician in the Cincinnati Arch region USA: the early history of light-related microendolithic zonation. Palaeogeography, Palaeoclimatology, Palaeoecology 281: 1-24.

Final day at The Natural History Museum … and one more Jurassic snuff-box

June 17th, 2016

1 Chandler snuff-box cutLondon, England — My last day in London was spent working on GSA abstracts and examining one last ferruginous oncoid (“snuff-box”) from the Jurassic (Bajocian) of southern England. Bob Chandler donated to the cause a large discoidal snuff-box. We cut it (cross-section through the center shown above) and revealed its intricate internal structure.

2 Chandler snuff-box nucleusThe typical limestone nucleus is smaller than I expected, but it still shows typical features such as bioerosion.

3 Snuff-box horn 061716This specimen has beautifully-developed “horns” around the periphery. They are made of laminae not connected to the central cortex. Paul Taylor suggested that they form when the snuff-box is no long being moved about. Nice specimen. Cassidy Jester (’17) will have much to figure out in her Independent Study focused on these objects.

I’ve had a great and productive time on this expedition to England. Thank you again to my amigos Tim Palmer and Paul Taylor, as well as John Whicher, Bob Chandler and Consuelo Sendino. Science marches on.

Addendum: This is the way I like my Tube stations — empty! Take me home, District Line to Paddington. Saturday, June 18, 5:08 a.m.

Fulham Broadway tube station at 0508

Wooster’s Fossils of the Week: Symbiotic interactions in the Silurian of Baltica

June 17th, 2016

EcclimadictyonThis week’s fossils are from work Olev Vinn (University of Tartu, Estonia) and I did last summer that is soon to appear in the journal Lethaia. (An early electronic version of the manuscript has been available since November.) After numerous smaller studies describing symbiotic relationships recorded in Silurian fossils in the paleocontinent Baltica, we wrote a summary paper under Olev’s leadership. All the images are take by Olev and in the paper itself. I love this kind of study because it is about fossils as living, interacting organisms, not just static sets of characteristics.

For example, the top image is of the stromatoporoid Ecclimadictyon astrolaxum (a kind of hard sponge) with embedded rugosan corals (Palaeophyllum, with arrows) from the Jaagarahu Formation (Sheinwoodian) exposed at Abula cliff, Saaremaa Island, Estonia. The stromatoporoid and corals were growing together, each having their particular needs met and maybe even enhanced by the other.
syringoporidThe network of holes in this stromatoporoid from the Paadla Formation (Ludfordian) of Katri cliff, Saaremaa, represent the corallites of a syringoporid coral. Again, the coral and sponge formed an intergrown association.
ChaetosalpinxThis is a thin-section view of what was likely a soft-bodied worm (represented by Chaetosalpinx sibiriensis, noted by a white arrow) embedded in the tabulate coral Paleofavosites cf. collatatus from the Muksha Subformation (Homerian), Bagovitsa A, Podolia, Ukraine. Again, the worm was embedded in the living tissues of the host.

We found 13 such symbiotic associations in the Silurian of Baltica. Most of these interactions involved large skeletal organisms like stromatoporoids and corals, which provided stable hosts for smaller sessile filter-feeders and micro-predators. This work is part of a larger study looking at evolutionary trends in symbiotic associations during the Paleozoic.

References:

Tapanila, L. 2005. Palaeoecology and diversity of endosymbionts in Palaeozoic marine invertebrates: trace fossil evidence. Lethaia 38: 89–99.

Vinn, O. and Wilson, M.A. 2016. Symbiotic interactions in the Silurian of Baltica. Lethaia 49: 413–420.

Vinn, O., Wilson, M.A. and Motus, M.-A. 2014. Symbiotic endobiont biofacies in the Silurian of Baltica. Palaeogeography, Palaeoclimatology, Palaeoecology 404: 24–29.

Research in a paleontological paradise

June 16th, 2016

1 NHM front 061616London, England — If any center of scientific research can be sacred, the Natural History Museum of London is a holy of holies for paleontology. Its deep history, highly skilled researchers and staff, and magnificent architecture makes it a very special place. As I wrote before, it is a secular cathedral of science, particularly life science.

2 NHM cathedral of scienceIt is no accident the design of this building reflects a place of worship. Who do you think the white figure on the raised platform in the center is? He might as well be sitting on the altar.

3 Darwin presidingOf course! A portrait on Darwin’s upper left, not visible here and probably rarely noticed, is of his colleague Alfred Russel Wallace.

4 Darwin's NHM viewThis is Darwin’s view of the main hall and entrance of the museum. Six million visitors per year pass under his gaze.

5 Paul and SEM 061616This morning Paul and I worked with a scanning electron microscope to study particular fossils we had set aside for closer examination. Paul is the best scanning electron microscopist I have met.

6 SEM stageThis is the open stage and chamber of the SEM, with a brachiopod fixed in place by Paul for scanning. It is a complicated apparatus that can move the specimen in almost all directions in a vacuum under the electron beam.

7 Cortex pdt19574The first specimen we worked with was one of the Jurassic snuff-boxes. This is part of Cassidy Jester’s Independent Study project and her continuing research with Tim Palmer and me. Paul and I are mystified by the pattern we see here in the cortex of the snuff-box.

8 Ooid pdt19575These are two ferruginous ooids embedded in the cortex of the snuff-box. They show exactly the same mysterious irregular platy objects. Tim Palmer suggests they may be limonite, which is amorphous (without crystals). We’ll test that idea later with mineralogical and elemental analysis.

9 Jeffrey Thompson at NHM 061616I was delighted to see my friend Jeffrey Thompson in the palaeontology section doing research for his dissertation at the University of Southern California. He made an earlier appearance in this blog when he was just a kid.

10 Oscar Mmari and Jubilate Lema in LondonFor lunch I met my former student and veteran of an Independent Study field trip to Israel Oscar Mmari (on the left) and fellow Wooster graduate Jubilate Lema on the right. Both of these young Tanzanians are now making their way in the world. Oscar starts this fall at Imperial College, and Jubilate is an economist working with an investment firm in Johannesburg, South Africa. We had a delightful meal and walk around the museum neighborhood.

11 Dinner view 061616My long day ended with an excellent dinner with Paul and Patricia Taylor at the Swan Restaurant along the Thames River. This was our view from the table. This will all seem a dream in just two days time.

 

Another day of research at The Natural History Museum, London

June 15th, 2016

1 Mapped brach 061516London, England — I spent most of my museum time today at a keyboard, but in a splendid and collegial setting. Very productive and stimulating conversations with Paul Taylor and Consuelo Sendino, but mostly screen time. I drew little map boxes on a brachiopod, for example, as shown above.

2 Screen Shot 2016-06-15 at 2.23.30 PMI also used Image J to measure cell sizes, as shown in the above screen shot. More on what this is about tomorrow.

3 Winchendon Road viewFinally, I thought I’d share the view from my attic window of Winchendon Street. I think I hear and see every flight in and out of Heathrow!

4 London helicopterIncluding police helicopters. Often.

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