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.

A day at the Natural History Museum in London

June 14th, 2016

1 Drawer of brachiopodsLondon, England — My first full day at The Natural History Museum in London was interesting and inspiring as always, but it did have its tedium. This drawer of Ordovician brachiopods, for example. I scanned each with my handlens in the dim lighting looking for a particular kind of encruster.

2 Drawers of brachiopodsDrawer after drawer. Saw many curious fossils, but not one example of what I was looking for. Not an uncommon experience!

3 Harry photographing 061416One of the best parts of a museum visit is meeting skilled staff. Harry Taylor is a master photographer of fossils. Paul Taylor and I took him a fossil this morning and he immediately created a superb image for our work. In my inexpert photograph above, what looks like a blast furnace behind the camera is his lighting and flash system.

4 Harry Paul photographyHarry and Paul discuss the image on screen.

5 Bryo copyHere is a small version of the final result of Harry’s artistry. The original file is 111 megabytes! This is a brachiopod (Rafinesquina ponderosa) from the Cincinnatian rocks of southern Ohio. It is encrusted with something special I’ll describe in a later post. We’ll use this high-resolution image for detailed mapping of this surface.

6 Emanuela Di Martino SEM 061416Paul and I visited our colleague Emanuela Di Martino to congratulate her on Italy’s recent win in the Euro 2016 football tournament. She is operating the Scanning Electron Microscope (SEM) Paul and I will be using in two days. I’ve sat here for many hours scanning specimens with Paul.

7 Tony Wighton cuttingPaul and I had a bryozoan we wanted to cut in half to study its interior. Tony Wighton immediately sliced it for us.

8 Tony Wighton polishingTony then gave each half a mirror finish, producing spectacular specimens that considerably enhance the value of the collections.

It was a good day at the museum. The rain stopped long enough for us to get fresh hamburgers at the nearby open market for lunch, and then we had drinks at the Victoria & Albert Museum next door. I don’t take any of this for granted!

Wooster Geologists in Bristol, England

June 11th, 2016

1 Bristol Museum and UniversityBristol, England — Cassidy Jester (’17) and I are spending the weekend in Bristol after finishing our fieldwork in Dorset this week. Our travel and lodging arrangements required a couple of days here before we go to London on Monday and then our separate ways. We’ll continue to sort out our specimens, work on a GSA abstract, and explore the city. This afternoon, while waiting for our hotel rooms to open, we walked through the central part of the city to the Bristol City Museum and Art Gallery. It is the building with the pillars on the left. The magnificent tall building on the right is part of the University of Bristol — the part that houses the Earth Sciences Department.

2 Bristol City Museum and Art GalleryThis museum is a wonderful combination of art, history and science, with considerable space devoted to geology and paleontology.

3 Bristol pregnant ichthyosaurAmong the many exhibits, I picked one to share: a pregnant ichthyosaur from the local Jurassic. Note the tiny arrow in the lower left of the skeleton.

4 Bristol ichthyosaur fetusAt the arrow, among the bones of this female ichthyosaur is this hand-sized skeleton of a fetus, direct evidence that ichthyosaurs, though reptiles, gave live birth. Paleontology is so cool.

Team Dorset finishes its fieldwork

June 10th, 2016

1 Snuffbox serpulidssSherborne, England — Cassidy Jester (’17), Tim Palmer and I today finished our fieldwork. Cassidy is now set for her Senior Independent Study project with plenty of specimens, observations, photographs and ideas to last the next 10 months. This morning we visited the Burton Bradstock beach exposure of the snuffboxes, meeting our great colleague Caroline Buttler (Department of Natural Sciences, Amgueddfa Cymru – National Museum Wales, Cardiff) and her husband Simon for lunch on the outcrop. It was great fun, and Caroline had additional discoveries for us, including the exfoliated snuffbox layer shown above with serpulid worm tubes.

2 Ammonite gastropod snuffboxesWe had time to look for more fossils associated with the snuffboxes. Above you see a gastropod on the left and an ammonite on the right, with snuffbox bits scattered about.

3 Burton Bradstock pendentWe also found many examples of burrow systems with cryptic pendent iron-rich layers, including those shown above. (I rotated the image 180° because the block we studied on the beach is upside-down.)

4 Maiden Castle rampartsOn the way back to our lodgings near Sherborne we stopped by the Iron Age hill fort Maiden Castle, a portion of the massive earthen ramparts of which are shown above.

Our collecting, measuring and describing is done. Most of the work for this project, of course, will be in the Wooster geology labs. We will have delightful memories of our sunny days in Dorset, and the invaluable assistance of our colleagues Bob Chandler and John Whicher. I am personally most grateful for the geological and navigational skills of Tim Palmer, our wonderful companion and astute advisor. Without him none of this could be done.

Crew in Whicher MuseumThe Dorset crew in the Whicher Museum. From the left, Bob Chandler, Mark Wilson, Tim Palmer, John Whicher, and Cassidy Jester (’17).

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