Archive for the 'Uncategorized' Category
Mark Wilson October 23rd, 2015
While hiking through the Niagara Gorge on a field trip in August, my friend Andrej Ernst of the University of Kiel found the above block of siltstone from the Grimsby Formation (Silurian) with unusual small-scale ripples in a patch. Carl Brett (University of Cincinnati) immediately identified it as a sedimentary structure/fossil known since 1914 as Kinneyia. This name was new to me. I had long called such features “elephant skin”, but I’ve now learned that these “sedimentary wrinkles” have a long and sometimes contentious history of study, and they have significant variability (see references).
Charles Doolittle Walcott (1850-1927) was one of the best known and productive invertebrate paleontologists. An American, he most famously discovered the Cambrian Burgess Shale in western Canada with its fantastic soft-tissue preservation. Walcott was especially fascinated with finding the earliest evidence of life, so he intently studied rocks older than the Cambrian (an interval we used to call the Precambrian). In 1914 he published a compendium of what we considered to be fossil algae, including Kinneyia. Below is his original description followed by his photographic image.
We now know that these curious structures are not fossilized algae, hence the name Kinneyia no longer has any biological use. (You may note that most authors do not italicize the name, emphasizing that it is no longer a valid taxon. I keep the style as a reminder of the name’s history.) These are ripples with sinuous, bifurcating, flat-topped crests. They are sometimes very complicated when the crests interfere with each other. Their flat tops (when well-preserved) suggest that there was something lying above them. Most workers on Kinneyia conclude that this was a microbial mat, so Walcott would be at least satisfied that life was involved. Did the Kinneyia ripples form as gas built up underneath a decaying mat? Are they made when the mat shrinks through desiccation? Experimental physicists have even gotten involved in the interpretations. Thomas et al. (2013) write: “Microbial mats behave like viscoelastic fluids. We propose that the key mechanism involved in the formation of Kinneyia is a Kelvin-Helmholtz type instability induced in a viscoelastic film under flowing water. A ripple corrugation is spontaneously induced in the film and grows in amplitude over time.”
Kinneyia is thus a sedimentary feature formed by physical processes mediated by life in the form of a microbial mat. What those processes were is the most interesting question now.
Gerdes, G., Klenke, T. and Noffke, N. 2000. Microbial signatures in peritidal siliciclastic sediments: a catalogue. Sedimentology 47: 279-308.
Hagadorn, J.W. and Bottjer, D.J. 1997. Wrinkle structures: Microbially mediated sedimentary structures common in subtidal siliciclastic settings at the Proterozoic-Phanerozoic transition. Geology 25: 1047-1050.
Noffke, N., Gerdes, G., Klenke, T., Krumbein, W.E. 2001. Microbially induced sedimentary structures — a new category within the classification of primary sedimentary structures. Journal of Sedimentary Research A71: 649-656.
Porada, H., Ghergut, J. and Bouougri, E.H. 2008. Kinneyia-type wrinkle structures—critical review and model of formation. Palaios 23: 65-77.
Thomas, K., Herminghaus, S., Porada, H. and Goehring, L. 2013. Formation of Kinneyia via shear-induced instabilities in microbial mats. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 371(2004), 20120362.
Walcott, C.D. 1914. Cambrian geology and palaeontology III No.2 – Precambrian, Algonkian algal flora. Smithsonian Miscellaneous Collections 64: 77-156.
Mark Wilson October 18th, 2015
Annette Hilton (’17) is having a great time in Scotland, where she is spending a semester abroad. She had a chance to go on a geography field trip recently to the Isle of Kerrera, in the Inner Hebrides off the west coast of Scotland (near Oban). She sends her greetings with this photo in front of a famous unconformity with a 200 million year hiatus. The rocks below are Precambrian (Dalradian) slates and the rocks above are Devonian alluvial conglomerates that are part of the Old Red Sandstone complex. We’re glad to see it isn’t raining. Annette is in a fantastic place to study geology.
Mark Wilson October 16th, 2015
This lump of a fossil in Wooster’s teaching collection requires some explanation. It is not particularly well preserved, but it is our only representative of an interesting group of nautiloid cephalopods. The label that came with it says it is Poterioceras calvini, but I see no reason to believe it. There are simply not enough characters visible to identify it to the genus level, let alone the species. We should confine it to a higher taxon: Order Oncocerida Flower in Flower and Kummel, 1950. It comes from the Wisconsin Dolomite (Devonian) exposed in the city of Milwaukee.
On the left-hand side (with the scale) of each image you may barely make out vertical partitions, shown as faint lines. These are sutures, which represent the junction between internal septal walls and the outer shell. The shell has dissolved (since it was made of more soluble aragonite), leaving this internal mold fossil. The right side of the fossil shows no such partitions because it is where the large body chamber was located. The nautiloid animal lived in the body chamber, with the septal walls (and the chambers they delineated) behind it as the phragmocone.
This diagram from Wikipedia may make sense of this anatomy. The chambered phragmocone is shown in the top left, colored yellow; the body hangs below it in the body chamber. The phragmocone was filled with a mixture of gases and liquids, giving it positive buoyancy relative to the negatively-buoyant body chamber. The nautiloid thus in life hung upside-down facing the seafloor as it floated about. The cartoons on the right show the shell itself, including the keyhole aperture that kept the body from falling out.
Compare this to the typical orientation of a Paleozoic nautiloid (above). Both of these nautiloid types were nektic (swimming) predators. The oncocerid just did it by hanging upside-down!
The Order Oncocerida was named and described by one of the 20th Century’s most eccentric paleontologists, Rousseau Hayner Flower (1913-1988). I never met Dr. Flower, but I stumbled into a memorial session for him at the 1988 annual Geological Society of America meeting, which was held that year in Denver. Some people were barely holding back tears, others were laughing, and one crusty old paleontologist stormed out muttering “He was a bastard!”. I knew then that Flower was a character. (The photograph is from Wolberg, 1988, inside front cover.)
Rousseau Flower was born in a small town in upstate New York in 1913. He was both musically and scientifically gifted, winning a scholarship to Cornell University where he trained in entomology, eventually earning an M.A. degree there. An interest in fossil dragonflies drew him into paleontology, and a chance to take an extended geological field trip sealed his new interest in fossils. He had an eventful few years in the New York State Museum and the University of Indiana, finally earning his PhD at the University of Cincinnati in 1939. After bouts of unemployment during the war years, he went back to the New York State Museum to fill various temporary positions. In 1951 he took a job as Stratigraphic Geologist at the State Bureau of Mines & Mineral Resources in New Mexico, where he stayed for the rest of his life.
Flower took on his new Western identity with gusto, wearing cowboy garb and sometimes brandishing a bullwhip. He traveled the world studying corals and cephalopods and amassing an enormous collection that people are still sorting through. He published some 1800 pages of paleontological work, naming dozens of new taxa and making major contributions to our understanding of cephalopod evolution and paleobiology, coral systematics, and western North American stratigraphy. He was acerbic and, shall we say, confident in his analyses, so he made as many enemies as friends. Over half of his work was published in the memoir series of the New Mexico Bureau — so much that some suspected it was his private journal. On top of all this, he was also a prominent music and arts critic in New Mexico. Rousseau Flower earned his fearsome reputation!
Flower, R.H. and Kummel, B. 1950. A classification of the Nautiloidea. Journal of Paleontology 24: 604-616.
Mutvei, H. 2013. Characterization of nautiloid orders Ellesmerocerida, Oncocerida, Tarphycerida, Discosorida and Ascocerida: new superorder Multiceratoidea. GFF 135: 171-183.
Wolberg, D.L. 1988. Rousseau Hayner Flower, p. viii-x, in: Contributions to Paleozoic Paleontology and Stratigraphy in Honor of Rousseau H. Flower. New Mexico Bureau of Geology & Mineral Resources, Memoir 44, 415 pp.
Mark Wilson October 12th, 2015
Gloria and I and our daughter Amy took advantage of the first days of Fall Break at Wooster to visit the Gettysburg Battlefield in Pennsylvania, about a 5.5 hour drive from home. The weather was spectacularly beautiful, as you can see in these images. The blue skies and bright sun made the place all the more heart-wrenching, though, considering the events of July 1-3, 1863, commemorated so vigorously here. This is one of the best maintained battlefield in the world, and one of the most visited. Over four million tourists (or, arguably, pilgrims) travel to this site in eastern Pennsylvania every year. They are greeted by more than 1200 monuments (“stone sentinels“) to this American Civil War battle. There were over 45,000 casualties on both sides, making it the bloodiest battle in North American history.
The geology of the Gettysburg battlefield is very well known, and much has been written about how the bedrock provided the dramatic setting and constrained the tactics of both sides. In a simple summary, during the Triassic break-up of the supercontinent Pangaea, rift basins occurred along what would become the northeastern margin of North America. A variety of sediments filled these widening valleys as the terrain around them eroded. The thinning crust below produced considerable igneous activity and these sediments were intruded by dikes and sills made of the igneous rock diabase. Diabase is very hard and resistant, so when this area was later eroded, the igneous bodies stood in relief from the softer materials around them, forming rocky hills and ridges. In the top image we see this diabase exposed at a place on the battlefield known as Devil’s Den. During the battle the Union forces occupied most of the high ground underlain by these diabase rocks, including iconic names like Little Round Top, Cemetery Ridge and Culp’s Hill.
I have no intent of telling the story of the Gettysburg battle here. What follows are just a few images of the places most meaningful to me.
It is at Devil’s Den that we see the best exposures of the diabase. This place was occupied by Confederates during most of the battle, and is probably most famous for the photographs of Confederate dead. The top surfaces of these rocks are worn slick by the shoes of visitors over the past 150 years.
The hard diabase was immediately useful to Union troops, who constructed these low stone breastworks across the western slopes of Little Round Top, Cemetery Ridge and Culp’s Hill. The bedrock is very close to the surface, so it was impossible to dig useful trenches or foxholes.
The focus of my pilgrimage every time I visit Gettysburg is Little Round Top, seen here from Devil’s Den looking eastward. In one of the most dramatic actions of the battle, college professor Colonel Joshua Lawrence Chamberlain led his men of the 20th Maine in a desperate bayonet charge downhill into advancing Confederates. This surprising action on the second day, for which Colonel Chamberlain won the Congressional Medal of Honor, stopped the Confederate assault on the far left of the Union line, saving it from collapse. That decision to charge, and the Maine men’s willingness to do it, likely saved the battle for the Union, and maybe even the war.
Above is a view from the Union line on Cemetery Ridge westward across the fields to Seminary Ridge, which was occupied by the Confederates. On the third and last day of the battle, General Robert E. Lee ordered General James Longstreet to organize a general attack across these fields against the center of the Union line here. This is known to history as Pickett’s Charge. It was a foolish move, and everyone but Lee seemed to know that it was a hopeless, murderous gesture. The failure of this charge marked the end of the battle. General Lee retreated the next day.
I was taken by this unusual monument to the 20th Massachusetts Infantry, which was one of the Union units that repulsed Pickett’s Charge on the third day of battle. Rather than statuary, the veterans of the 20th Massachusetts chose to transport a large rock from a neighborhood of Boston to be placed on their spot of the battlefield. The message was, of course, that here stood men of Massachusetts rock who could not be moved.
The rock is known as Roxbury Puddingstone, more formally called the Roxbury Conglomerate. It is the official state rock of Massachusetts. (Do you know your state rock?)
This rock contains a jumble of clasts of different sizes and maybe a dozen compositions. It is Ediacaran in age and likely accumulated in deep-sea fans as turbidites that formed when gravity-driven slurries of sediment flowed down submarine slopes. Or you can believe another story told in an 1830 poem by the future Supreme Court Justice Oliver Wendell Holmes, Jr., called “The Dorchester Giant“, who fed his rowdy family “a pudding stuffed with plums” that they flung about, leaving us the fossil evidence. Holmes served as an officer in the 20th Massachusetts.
Brown, A. 2006. Geology and the Gettysburg Campaign. Pennsylvania Geological Survey Educational Series 5, published by the Commonwealth of Pennsylvania/Department of Conservation and Natural Resources/ Bureau of Topographic and Geological Survey: 14 pp.
Murray, J.M. 2014. On a Great Battlefield: The Making, Management, and Memory of Gettysburg National Military Park, 1933–2012. Univ. of Tennessee Press.
Newman, R.J. 2015. When the secular is sacred: The Memorial Hall to the Victims of the Nanjing Massacre and the Gettysburg National Military Park as pilgrimage sites. Global Secularisms in a Post-Secular Age 2: 261-270.
Weeks, J. 1998. Gettysburg: Display window for popular memory. The Journal of American Culture 21: 41-56.
Weeks, J. 2003. Gettysburg: Memory, market, and an American shrine. Princeton University Press.
Mark Wilson October 10th, 2015
Oscar Mmari (’14) is a Wooster Geology alumnus who did field work in Israel as part of his Independent Study. After his graduation he has had excellent geological experience in Africa and Europe, most involving mining and other resource-related industries. He has kindly given us this account of a field trip he took on August 4, 2015, near Dar es Salaam, Tanzania.
Appreciating the Rocks
By Guest Poster Oscar Joseph Mmari (’14)
A Dar es Salaam traffic jam, like those in most African cities, is a memorable experience for anyone who has braved the streets of the commercial capital. The narrow roads are constantly chocked with sluggishly moving cars and fumes suffocating the air. This can be inconvenient and people have missed flights let alone been tardy to momentous meetings. It is a far cry from the orderly multiple-lane highways spanning through Ohio. Equipped with this knowledge, our trip to four different outcrops spanning two regions all in one day had to be immaculately planned.
Geology field trips are vital to the growth of every geoscientist. The trips, apart from allowing geologists visit exotic places on earth, reinforce fundamental field skills important to the discipline. In addition, it underscores the scale difference between outcrops in the field and seismic wiggles in Petrel. This is why when my supervisor was in town, I organized a field trip. The overarching theme of the trip was to observe different sedimentary successions in the Coastal area around Dar es Salaam. Additionally, one of the outcrops provided an analogue to Songo Songo gas field. Geological outcrop analogues serve a great purpose in understanding new fields because of their capability of providing information at a scale and lateral that cannot be determined from seismic and well data in the subsurface. Songo Songo gas field is a Lower Cretaceous reservoir aged Neocomian to Albian sandstone reservoir producing 80 MMscf/day for gas plants in the United Republic of Tanzania.
The trip started early at 7:30 am and the first stop was just a few yards from the office in Dar es Salaam. Oyster Bay plays home to host of different marine organisms that congregate in and around an extensive coral environment.
Corals provide shelter and food for many organisms and can support enormous ecosystems. As the sea level changed, the effects of waves and tides on these rocks can be seen especially in the neatly exposed corals on the beach. Being geologists, we spent some time looking at fossils and the sedimentary fabrics pondering about the effects of deposition and erosion in the area.
The second stop was a little further from the office. The Pugu Hills are located about 15 miles south-west of the BG Tanzania office but the outcrops we were trying to find were elusive. After asking several locals, making a few phone calls to colleagues and gingerly passing along overgrown ancient roads, where the GPS was not very helpful, we reached the former kaolinite quarries in Pugu. The Pugu Hills form one of the highest points in the region due to uplifts within the last 5 million years. The sediments in the quarry are amalgamated fluvial sandstones with gravel lags, which are cut by a number of NNE trending faults and joints. The intensely weathered sandstone-clay sequence is now dominated by the clay mineral kaolinite which provided raw material for the now dilapidated factory and was extracted for pottery manufacture. It also contains refractory minerals such as quartz and zircon which are resistant to alteration.
The next stop, after an excellent lunch, was at Msolwa area were we looked at Lower Cretaceous fluvial and estuarine sand deposits, which are of similar age as the gas-bearing sands of Songo Songo. We spent some time discussing the direction of flow and the possible depositional environment. The last stop was in the Wami River valley where we observed metamorphic rocks uplifted to the surface and an impeccable sedimentary-metamorphic contact.
On our way back we saw several signs of the on-going hydrocarbon exploration in on shore Tanzania, which was an optimistic sign in the current oil price climate. When we got back to the city, it was dark, we were tired, but it had been a day well spent. The traffic was jammed solid and there was no clever planning that would get us out of this one. Well, at least we had to some rock stories to discuss.
Wooster’s Fossils of the Week: A rugose coral and its encrusters from the Middle Devonian of New York
Mark Wilson October 9th, 2015
This week’s fossils were found on a most excellent field trip to the Niagara region of New York in August. One of our outcrops was a small patch of gravel in Bethany Center where the Centerfield Limestone Member of the Ludlowville Formation (Givetian, Middle Devonian) was exposed. My colleagues and I found many interesting fossils here. The largest specimen I collected was the above rugose coral.
It is Heliophyllum halli Milne-Edwards and Haime, 1850. This species is very common throughout the Devonian Hamilton Group of New York, Ontario and surrounding areas. The 90-degree bend in the specimen is a result of the living coral being knocked over onto its side and then twisting to grow upwards again.
These corals are called “rugose” because of their “wrinkled” exteriors, easily seen in this view. The solitary forms, like this one, are a single corallite that held one polyp in life. Their conical growth form gives them another nickname: “horn corals”. Rugose corals also come in colonial varieties, which we’ve covered before in this blog. Their skeletons are made of thick calcite, so they are almost always well preserved. These corals are distinguished from others by their strong internal vertical walls (septa) and relatively few horizontal or angled partitions (tabulae and dissepiments). They lived like most other corals as sessile benthic (stationary on the bottom) predators catching food with their tentacles. It is still uncertain whether they had photosynthetic symbionts (zooxanthellae) like modern corals. Emily Damstra has a nice reconstruction of living Heliophyllum halli.
This particular coral has a collection of encrusting organisms on its exterior. Above is a remnant of a bryozoan.
The encrusting coiled shell in the lower left is a nice microconchid (a mysterious lophophorate) and at the top is another type of bryozoan. Many of these encrusters are found on eroded parts of the coral skeleton, so they likely encrusted it after death.
Heliophyllum halli was named by Milne-Edwards and Haime in 1850. We’ve introduced Henri Milne-Edwards (1800-1885) before, and even James Hall (1811–1898) for whom the species is named. Jules Haime (1824-1856) is less known. He died too young at age 32, which may explain why we have no images of him. HIs father was a prominent physician, Auguste Haime (1790-1877). Jules, like many 19th Century paleontologists, started in medicine (studying in Tours) but gravitated toward the excitement in natural history, becoming a zoologist and paleontologist. He specialized in corals, joining up early in his career with Milne-Edwards. Haime rose fast in his new profession. One year before his death he became a professor of natural history at the Lycée Napoléon in Paris. In 1856 he was appointed vice-president of the Société géologique de France, but died a few months later.
Baird, G.C. and Brett, C.E. 1983. Regional variation and paleontology of two coral beds in the Middle Devonian Hamilton Group of Western New York. Journal of Paleontology 57: 417-446.
Brett, C.E. and Baird, G.C. 1994. Depositional sequences, cycles, and foreland basin dynamics in the late Middle Devonian (Givetian) of the Genesee Valley and western Finger Lakes region. In: Brett, C.E., and Scatterday, J., eds., Field trip guidebook: New York State Geological Association Guidebook, no. 66, 66th Annual Meeting, Rochester, NY, p. 505-585.
Milne-Edwards, H. and Haime, J. 1850-1854. A monograph of the British fossil corals. London, Palaeontographical Society. 736 pages.
gwiles October 6th, 2015
Geomorphology (Geology 300) has been taking advantage of the good weather this Fall traveling in the area. Above the full class stands on a point bar of the Apple Creek. Waves go out to Brian Merritt who experienced an injury earlier in the semester, we wish his a speedy recovery and sure could use his expertise in hydrology, carrying heavy equipment and doing much of the work (see below).
Brian augers a hole in the Kame at Browns Lake, in the background is a 350 year old white oak and we hypothesize that this area may contain old soils that have never seen the plow.
Surveying in the discharge transects and well locations.
The gaging team sets up another transect.
Taking notes – greatly appreciated when we return to the lab and try to make sense of what we measured.
The shallow wells were measured for relative water levels and water temperature.
A surprise the team discovered – Roy takes a sample from the upper unit as Julia takes careful notes. The hypothesis is that this layer, which lies uncomformably on top of fluvial gravels, is in the class of legacy sediments, eroded soils and windblown dust empounded at the site when a mill was operating in the valley.
Possible Mill or dam site?
Much of the class at Zollingers Pit in Rittman – Krysden and Andrew are not present as they were excavating sediment for their project.
The group at Browns Lake.
Discussing why we install a shallow and deep well side by side.
Returning to the vans after work in Wooster Memorial Park (aka Spangler).
A bald eagle circled overhead at the Apple Creek site.
Wooster’s Fossil of the Week: A spherical bryozoan from the Upper Ordovician of northeastern Estonia
Mark Wilson October 2nd, 2015
Way back in July 2007 we had our first Team Estonia doing geological field research. Andrew Milligan (’08) and I, with our friend Dr. Olev Vinn of the University of Tartu, explored the Upper Ordovician of the northeastern part of the country, perilously close to the Russian border. Most of our work was stratigraphic and related to echinoderms, but I picked up several of these beautiful spherical bryozoans. This specimen comes from the Kiviõli Member, Viivikonna Formation, Kukruse Stage, Upper Ordovician, of Kohtla-Nõmme Quarry (N 59.35665º E 27.22343º). You won’t find the quarry on a map, though, because it was soon afterwards erased by continual mining. Now it is a grassy field. Since we are studying bryozoans this week in my Invertebrate Paleontology course, I’m bringing these specimens to the blog.
In this closer view you can see the polygonal outlines of the zooecia, now filled with calcite. In the lower right is a boring that cut through the skeleton soon after the bryozoan’s death on the Ordovician seafloor. It has a bit of sediment that filled the boring except for the very center, which apparently held the body of the borer.
This bryozoan is the trepostome Esthoniopora subsphaerica (Bassler, 1911). Bassler originally called it Hemiphragma subsphaericum, which is a nod to its abundant hemiphragms (curving partitions in the zooecial tubes). As bryozoans go, this one has a fairly simple structure with no exozone, endozone, monticules or spines. How it lived on the seafloor with such a spherical shape is a bit of a mystery. A slightly flattened patch is probably where the sphere contacted the sediment. The borings in these bryozoans were studied by Wyse Jackson and Key (2007).
The species author, Raymond S. Bassler (1878-1961), was an American paleontologist prominent in the study of bryozoans and other encrusting organisms. He was born in Philadelphia and became very interested in fossils from childhood. He received his bachelor’s degree from that paleontological bastion the University of Cincinnati in 1902, followed quickly by his master’s (1903) and PhD (1905) degrees from George Washington University, where he served as a professor for over forty years. He also began work at the United States National Museum in Washington in 1910, rising through the ranks to become Head Curator in 1929. His main interests were bryozoans from the Cenozoic of the Gulf and Atlantic coasts, on which he had long collaborations with the French bryozoologist Ferdinand Canu. He also worked closely with Charles Schuchert, Carl Ludwig Rominger, and Edward Oscar Ulrich. Ray Bassler died in 1961.
Bassler, R.S. 1911. The Early Paleozoic Bryozoa of the Baltic Provinces. Bulletin of the US National Museum 77: 1-382.
Koromyslova, A.V., Fedorov, P.V. and Ershova, V.B. 2009. New records of bryozoans from the Lower Ordovician of the Leningrad Region and intercolonial variability in Esthoniopora lessnikowae (Modzalevskaya). Paleontological Journal 43:39–45.
Wyse Jackson, P.N. and Key, M.M. 2007. Borings in trepostome bryozoans from the Ordovician of Estonia: two ichnogenera produced by a single maker, a case of host morphology control. Lethaia 40: 237-252.