Wooster’s Fossil of the Week: A Tully Monster! (Late Carboniferous of Illinois)

Mark Wilson January 1, 2012 1:33 am

We have several examples of one of the strangest fossils known: Tullimonstrum gregarium Richardson 1966 — otherwise affectionately known as the Tully Monster. The above specimen is from the Francis Creek Shale Member (Carbondale Formation) at Mazon Creek near Chicago, Illinois. Even if it wasn’t labeled this is an easy call: all Tully Monsters are from the same place!

The above diagram is from Johnson and Richardson (1969, Fig. 63). It shows just about all we know about the morphology of Tullimonstrum gregarium. It was a soft-bodied animal preserved as an outline in ironstone concretions split in half, so we usually get this long view. They have three body regions: head, trunk and tail. The head has a stalk-like proboscis with a sharp-toothed claw on the end. The anterior of the trunk has two bar organs of unknown function (you can just barely see them on our specimen). The tail has two fins.

Above is another of our Tullimonstrum specimens, this one folded inside its concretion. The transverse bar and one of the bar organs is visible.

Tullimonstrum cannot be placed in any known phylum. It may be some kind of worm (that’s always easy to say!), a mollusk, or somehow related to the arthropods, but it has no features sufficient to classify it. It looks a bit like Opabinia, a strange beast from the Cambrian with a similar clawed proboscis. We can at least say both were swimming carnivores!

The first specimen of what would become Tullimonstrum gregarium was found by an amateur collector, Francis Tully (pictured above courtesy the Field Museum). He was collecting in waste piles from strip mines near Chicago, splitting open ironstone concretions. The concretions formed around dead and decaying organisms in a shallow embayment during the Late Carboniferous. They preserved impressions and outlines of soft tissues, making the Mazon Creek Fauna a famous lagerstätte.

A charismatic fossil like the Tully Monster gets plenty of attention. One of the best visual reconstructions is on the sides of U-Haul trucks! It is also the state fossil of Illinois.

This entry is posted, by the way, on the one-year anniversary of Wooster’s Fossil of the Week. It is the 53rd in the series. Here is the very first post, which was on a gorgeous little Devonian auloporid.

References:

Johnson, R.G. and Richardson, E.S. 1969. Pennsylvanian invertebrates of the Mazon Creek Area, Illinois: the morphology and affinities of Tullimonstrum. Fieldiana: Geology 12: 119-149.

Richardson, E.S., Jr. 1966. Wormlike fossil from the Pennsylvanian of Illinois. Science 151 (3706): 75–76.

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Wooster’s Fossil of the Week: a siliquariid gastropod (Eocene of Alabama)

Mark Wilson December 25, 2011 1:51 am

It is hard to believe that this twisty tube is a snail, but it is. Tenagodus vitis (Conrad, 1835) is the scientific name for this worm-like gastropod from the Claiborne Sand (Eocene) of Alabama. It was originally named by Conrad as Siliquaria vitis, a name still commonly used even though it was made a junior synonym by CoBabe and Allmon (1994).

This kind of gastropod with its awkward shell clearly didn’t crawl around. It was a sessile benthic epifaunal filter-feeder, meaning that it lived stationary on the seafloor filtering organic material from the water. Some of these sessile snails twisted their tubes around each other and formed a kind of gastropod reef.
The twisty part of Tenagodus vitis shows its true snaily nature.
The related Siliquaria anguina. (From Cooke et al., 1895, Cambridge Natural History, volume 3, Fig. 153.)
The discoverer of Tenagodus vitis was Timothy Abbott Conrad (1803-1877). He was a conchologist (one who studies shells) and paleontologist in New York and New Jersey, and he was a paleontological consultant during the early days of the Smithsonian Institution.

References:

CoBabe E.A. and Allmon, W.D. 1994. Effects of sampling on paleoecologic and taphonomic analyses in high-diversity fossil accumulations: an example from the Eocene Gosport Sand, Alabama. Lethaia 27: 167-178.

Conrad, T.A. 1835. Fossil shells of the Tertiary formations of North America, illustrated by figures drawn on stone by T.A.Conrad. vol. 1, no. 3, p. 29-56, pl. 15-18 (pp. 77-110, pl. 15-18 in 1893 reprint by G.D. Harris [with pl. 19-20 not included in original by Conrad], reprinted 1963 by the Paleontological Research Institution, Ithaca, NY).

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Wooster’s Fossil of the Week: A cornulitid (Late Ordovician of Indiana)

Mark Wilson December 18, 2011 1:18 am

This may look like just another wormtube on a shell — a recurring theme on this blog — but it is special, of course. This is the common Paleozoic genus Cornulites Schlotheim 1820, specifically Cornulites flexuosus (Hall 1847). It was found in the Whitewater Formation (Upper Ordovician) during a College of Wooster field trip to southeastern Indiana.

Above is a larger view of the substrate for this wormtube: the ventral valve exterior of a strophomenid brachiopod. If you look closely at the costae (fine radiating lines) of the brachiopod you can see that it was alive when the cornulitid landed on its shell. As both animals continued to grow, the wormtube bent toward the commissure (opening) of the brachiopod, no doubt to snatch some suspended food from its feeding current. The cornulitid was thus a parasite on the host brachiopod. (See Morris and Rollins, 1971; Vinn and Mutvei, 2005; and Vinn and Wilson, 2010, for much more detail on cornulitid paleoecology.)

Suggested cornulitid internal anatomy (from Olev Vinn).

Cornulitids (Ordovician – Carboniferous) belong to a large group of tube-dwelling organisms that, surprisingly, may be closely related to brachiopods and bryozoans. Cornulitids, along with fellow tube-dwellers the microconchids, tentaculitids and hederelloids, have a foliated shell ultrastructure with various other features indicating they may be part of a larger group called the lophophorates (see Taylor et al., 2010). Much work still needs to be done on their systematics and paleoecology to sort out the evolutionary relationships here, but we have a good start.
The genus Cornulites was described and named by Ernst Friedrich, Baron von Schlotheim (1764-1832), a German palaeontologist and politician born in Almenhausen, Thuringia, Germany. As a noble, he was home-schooled (as we’d say now) and then sent to the Gymnasium (like a high school) in Gotha, Germany. After graduation, he attended Göttingen where he studied political administration and the natural sciences with Johann Friedrich Blumenbach. He enjoyed geology very much and so went off to Freiburg to learn from the famous Abraham Gottlob Werner of Neptunist fame. One of his friends was the scientist-explorer Alexander von Humboldt. After this extraordinary education, Schlotheim entered the civil service in Gotha in 1792, eventually rising all the way up to Lord High Marshal a few years before his death. During his administrative work, though, he continued serious paleontological studies, being one of the first paleontologists to use Linnean binomial nomenclature, making fossils much more useful for stratigraphy and later evolutionary studies. Schlotheim had some very progressive ideas about what we would later call uniformitarianism, and he recognized that geology could tell a history of the Earth quite different from that outlined by theological scholars.

Here’s to the intellectual innovations and courage of Baron von Schlotheim and the little fossil wormtube that reminds us of him!

References:

Morris, W. R., and H. B. Rollins. 1971. The distribution and paleoecological interpretation of Cornulites in the Waynesville Formation (Upper Ordovician) of southern Ohio. The Ohio Journal of Science 71: 159-170.

Schlotheim, E.F. von. 1820. Die Petrefakten-Kunde auf ihrem jetzigen Standpunkte durch die Beshreibung seiner Sammlung versteinerter und fossiler Ueberreste des their-und Planzenreichs der Vorwelt erlaeutert. Gotha, 437 p.

Taylor, P.D., Vinn, O. and Wilson, M.A. 2010. Evolution of biomineralization in ‘lophophorates’. Special Papers in Palaeontology 84: 317-333.

Vinn, O. and Mutvei, H. 2005. Observations on the morphology and affinities of cornulitids from the Ordovician of Anticosti Island and the Silurian of Gotland. Journal of Paleontology 79: 726-737.

Vinn, O. and Wilson, M.A. 2010. Abundant endosymbiotic Cornulites in the Sheinwoodian (Early Silurian) stromatoporoids of Saaremaa, Estonia. Neues Jahrbuch für Geologie und Paläontologie 257: 13-22.

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Wooster’s Fossils of the Week: Eurypterids (Late Silurian of New York)

Mark Wilson December 11, 2011 1:35 am

Few fossils are more dramatic than the long-extinct eurypterids. Above is one of Wooster’s best fossils: Eurypterus remipes De Kay 1825 from the Bertie Waterlime (Upper Silurian) of New York. (Thanks to Roy Plotnick for help with the identification.) As far as eurypterid fossils go, it is average (see Samuel J. Ciurca’s wonderful eurypterid pages for superb specimens), but for our little teaching collection it is a gem. Note that some of the fine details on the appendages are preserved.

Here’s looking at you: a eurypterid head showing the pair of compound eyes. The anterior margin “lip” indicates that this is a “carcass” specimen and not a molt fragment.

Eurypterids are commonly called the “sea scorpions” because of their long segmented body (opisthosoma), fused head segments (prosoma), sharp tail piece (telson) and claws (chelicerae). The scorpions and eurypterids, in fact, likely share a similar common ancestor. It should be no surprise to learn that eurypterids were swimming predators. The name comes from the Greek eury- for “broad” and -pteron for “wing”, referring to the large swimming appendages. Most eurypterids were relatively small like our specimen above, but some were almost two meters in length. They lived from the Ordovician to the end of the Permian Period.

Eurypterid reconstruction in Clarke and Ruedemann (1912). The artist is the famous paleontological illustrator Charles R. Knight.

Eurypterus remipes was the first eurypterid fossil formally described. The American zoologist James Ellsworth De Kay (1792-1851) did the honors while working in upstate New York. De Kay was orphaned at a young age but still managed to attend Yale (but no degree) and then complete an MD at the University of Edinburgh. He was not excited by medicine (one time he said it was “repugnant” to him), so he found himself doing many other things, such as traveling through Turkey (about which he wrote a book) and negotiating ship building contracts with emerging South American countries. Eventually he landed a job with the new Geological Survey of New York, publishing a multi-volume set called Zoology of New York State. Back then the boundaries between the natural sciences were less strict.

James Ellsworth De Kay (1792-1851)

Eurypterus fischeri (Eichwald) from the 47th plate of Ernst Haeckel’s Kunstformen der Natur (1904).

De Kay’s Eurypterus remipes was so charismatic that it became the state fossil of New York (although it took them until 1984 to declare it), and it was a global sensation in the mid-nineteenth century. Our little specimen is certainly one of Wooster’s paleontological treasures.

References:

Clarke, J.M. and Ruedemann, R. 1912. The Eurypterida of New York. Volume 1. New York State Museum Memoir 14.

De Kay, J.E. 1825. Observations on a Fossil Crustaceous Animal of the Order Branchiopoda. Annals of the Lyceum of Natural History of New York, i, 1825, p. 375, pl. 29.

Kjellesvig-Waering, E.N. 1963. Note on Carcinosomatidae (Eurypterida) in the Silurian Bertie Formation of New York. Journal of Paleontology 37: 495-496.

Tetlie, O.E. 2006. Two new Silurian species of Eurypterus (Chelicerata: Eurypterida) from Norway and Canada and the phylogeny of the genus. Journal of Systematic Palaeontology 4: 397-412.

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A Tale of Two Museums: Part 2 — The Creation Museum

Mark Wilson December 7, 2011 7:18 am

The Creation Museum

This past Saturday Elizabeth Schiltz of the Philosophy Department and I took our First-Year Seminar students on a long drive to the infamous Creation Museum in Petersburg, Kentucky. It was a beautiful day and we had a good time, if you set aside the intellectual travesties and pseudoscientific contradictions of the place. Our Wooster students were very polite and inquisitive, and they had many observations after we left the premises. The museum is uber-slick and the staff extremely helpful and friendly. We were on their property and grateful that they are willing to share their story and facilities with anyone who pays admission and follows the rules. Still, we felt both astonished and oppressed by the place.

The scene above is just inside the entrance of the museum. The juxtaposition of an animatronic dinosaur and a happy child tell us much about the philosophy and science of the organization: this is not a museum in the traditional sense. Dinosaurs with people is one thing — the dinosaur not eating the child is another!

Elizabeth’s First-Year Seminar section is titled “On the Meaning of Life“. Her students have been working through worldviews and why people hold them, so this trip was most appropriate. My First-Year Seminar is on “Nonsense and Why it is so Popular“. It is obvious why we were here!

The Creation Museum has been reviewed many times by scientists and other skeptics. (Here is a detailed account of a visit.) I am just presenting our impressions here with a few photographs.

One of the first displays in the Creation Museum is this life-sized diorama of two paleontologists excavating a dinosaur skeleton. (Geologists should note how important they are to the creationist worldview.) The scientist on the right is a traditional evolutionist; the older man on the left is a heroic scientific creationist we meet several times later in displays and videos. Both are looking “at the same facts”, but they have different “perspectives” and reach wildly different conclusions. From the start we saw a surprisingly post-modern view of science — it is all in the presuppositions of the observer with the “facts” as just a text for subjective analysis.

Especially to a geologist, the time scale of creationists is bizarre. At the Creation Museum the old Archbishop Ussher chronology is used, giving the first year of the Universe as 4004 BC. Here you see the timeline combined with the “7 C’s of History“. A literal reading of Genesis (and the rest of the Bible) is essential to the Young Earth Creationist view of Christian salvation.

An irony much noted by our students is that throughout the Creation Museum the displays denigrate “human reason” and elevate “God’s Word”, yet they appeal to human reasoning in every display of “evidence” and argument. Here we see the peculiar creationist view of “evolution within kinds” which allows for “microevolution” but not the appearance of new kinds of life. (Yes, there is a very fuzzy definition for “kind”.)

We all agreed that the models for Adam and Eve were … well … hot. They were so well done that, in this case especially, we felt like we were intruding on intimate moments. Just above this happy pair, out of view, the snake awaits with his temptation.

After their disobedience to God and their Fall, Eve and Adam look far less babelicious. Here they are making a bloody sacrifice for their Original Sin. Lots more blood and angst follows.

The Flood of Noah gets a lot of attention, of course, at the Creation Museum. Among many other things, it is used to explain the fossil record and the current distribution of life. I suspect the museum designers also derive a bit of pleasure from the idea of sinners dying in misery and despair as a small remnant of the righteous survives.

A critical part of the message in this museum is that the “evolutionary worldview” has brought much pain and destruction to our civilization. This elaborate and rather odd display shows the concept of “millions of years” destroying a church building. (Just think what billions of years would do!) Again, note the threat of modern geology to the fabric of God-fearing society.

Dinosaurs are a huge part of the Creation Museum’s program. Because kids love them so much, the Answers in Genesis people call them “missionary lizards“. (I don’t know which is most offensive: calling them missionaries … or calling them lizards!) The dinosaur models are, like their human equivalents, spectacular. Their star T. rex looks a bit overweight, but otherwise the reconstructions would pass in a real museum. The information on the signs, of course, is another story. Note the approximate date for the Upper Jurassic and that they ate meat only after the Fall. (Before that there was no death on Earth and thus no predation.)

Most disturbing is the effect of an institution like the Creation Museum on the education of children. This display makes sure you get the point that kids are at last hearing the real story outside of their corrupting public schools. The museum caters to home-schooled children for their “science” components, as well as to many private Christian schools. We often overheard parents and teachers telling their students “what we believe”. I caught a couple conversations describing a fallacious view of evolution (using the classic “I don’t know why there are still monkeys if we evolved from them” argument) that will likely go unchallenged in that child’s life. Very sad.

At the end of our experience we visited the outdoor portion of the museum with beautiful gardens and, to our delight, a petting zoo! This was the best way to discharge the tension built up during our visit: playing with innocent goats, feeding llamas, and watching albino peacocks display. All products of a long evolutionary history despite whatever stories we tell.

 

 

 

 

 

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A Tale of Two Museums: Part 1 — The Cleveland Museum of Natural History

Mark Wilson December 6, 2011 3:33 pm

Last week I had the marvelous opportunity to visit two very different museums with Wooster Geologists. This is the first of two posts with short vignettes of the memorable sights and sounds.

The first museum was the Cleveland Museum of Natural History. Greg Wiles and his Climate Change class invited me to accompany them to see the visiting climate change exhibit. It was an excellent display of the latest ideas about changing climates, including accurate accounts of the evidence, controversies and possible solutions to the problem of anthropogenic global warming and its associated troubles. It was a pleasure to see this presentation with Greg because of his deep and very current knowledge of the science and politics.

Since the above links give plenty of information about the museum and climate change exhibit, I’ll just highlight two features in front of the museum I found very interesting:

The large sundial above represents the history of life by geological periods. Note the beautiful ammonite fossil model as part of the gnomon (the portion that casts the shadow).

Each segment of the horizontal portion of the sundial is a geological period. Can you tell which periods are shown here?

Finally, I think this sculpture in the front garden entitled “Venus From The Ice Field” by Charles Herndon is ingenious. It is carved from a granite boulder found in the local glacial till.

My next post will be about the second museum — a very different place!

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“Whisky Stones” of Vermont: A Wooster Geologist Connection

Mark Wilson December 5, 2011 6:35 am

Vermont Soapstone, a small business in Perkinsville, Vermont, located at the base of Hawks Mountain with a mill and showroom.

The following is a guest blog post from Wooster Geology Senior Lindsey Bowman, a native of Londonderry, Vermont:

A metamorphic rock composed mainly of talc, soapstone is found all over the world and has unique qualities such as high heat retention and a long history as a carving material for various cultures. On a more personal note, I also know that carrying a 6-foot slab of soapstone up a staircase is extremely difficult, that soapstone looks best with an even coating of mineral oil, and that soapstone can be cut and sanded with wood-working tools. My Dad owns Vermont Soapstone, a small business that creates custom soapstone sinks and countertops, as well as the occasional fireplace, pizza oven or lately, small cubes of soapstone that are called “Whisky stones”.

Due to the high amounts of metamorphism that Vermont has experienced throughout its geologic history, it makes sense that soapstone (as well as marble and granite) would be found throughout the state. Perkinsville, Vermont, where Vermont Soapstone is based, is the original site of Hawks Mountain quarry, a soapstone quarry that opened in the 1850s.

Hawks Mountain Quarry, circa 1875, (Unknown source).

Quarrying technology was limited, and transport of the stone required a lot of ox-power.

Oxen pull a cart full of soapstone through downtown Chester, Vermont (Clements and Robinson, 1996, p. 232).

Back then soapstone was often used in wood stoves, as it still radiated heat long after the fire burnt out. Soapstone slabs were also used as griddles and often as feet warmers for long winter sleigh rides.

Today, my Dad imports most of his stone from Brazil, and has visited the quarries to assess new sources of soapstone, as well as familiarize himself with the quality and character of the stone that’s coming out of each quarry. My first rock in my rock collection was a chunk of quartz tinged red from the Brazilian soil that my Dad brought me back from a trip.

One of the quarries that my Dad visited on a trip to Brazil (Photo credit: Glenn Bowman).

People always ask me why I’m a geology major, and I always respond “I took a great geology course in high school”, but I’m starting to think that with rock being the family business it was kind of unavoidable. When I go home on breaks, I often help my Dad with installations in people’s homes of sinks and countertops. Lately, though, my Dad has been busy working on a different project.

Recently, a company called Teroforma has been working with Vermont Soapstone to create Whisky Stones, small soapstone “ice cubes”. The idea is that you can cool your beverage without diluting it- a simple idea but a great one. I recently talked to my Dad on the phone and he told me in preparation for the holiday season, they’re making Whisky Stones 24/7, and this is not a factory chugging them out- this is one guy, one table saw, and one cement mixer. I foresee myself doing a couple shifts while I’m home.

See the video on this link (scroll down) for a great representation of my Santa-resembling, soapstone-cutting, hard-working Vermonter Dad. The Whisky Stones remind me of the small soapstone cubes he always carries in his pocket, worn almost to spheres with the constant jostling against change and keys. He always left them under my pillow (do other little kids know about the rock fairy?) when he would go away for long install trips; when I went off to Wooster he gave me a whole pile of them. They’re right in the middle of my rock collection, reminding me of home.

Reference:

Clements, R., and Robinson, D., 1996, The Carlton Quarry: Chester, Windsor County, Vermont: Rocks and Minerals, v. 71, p. 231-235. (Courtesy of Duncan “Monk” Ogden.)

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Wooster’s Fossil of the Week: A new microconchid genus and species (Permian of Texas)

Mark Wilson December 4, 2011 1:50 am

Two years ago I was invited to Texas by Tom Yancey (Texas A&M) to look at some curious wiggly tubular fossils in the Lower Permian (about 280 million years old). They form small reefs a meter or so across and have traditionally been referred to as serpulid worm tubes. We suspected otherwise. After field and lab work, and collaboration with our Estonian colleague Olev Vinn, we determined that they are a new genus and species of microconchid. Our paper describing this taxon has just appeared: Wilson, Vinn and Yancey (2011).

A tangled collection of Helicoconchus elongatus Wilson, Vinn and Yancey 2011.

Helicoconchus elongatus is, as you may suspect from the name, an elongate coiled tube. The walls are impunctate (meaning they have no pores) and have diaphragms (horizontal partitions) with little dimples in their centers. They have two kinds of budding: fission (shown in the top image) and lateral budding (shown below). They grew into thick intertwined disks in shallow marine waters where they lived with snails, clams, echinoids and foraminiferans.

A small lateral bud on the side of a microconchid tube.

An acetate peel showing a longitudinal cross-section of a microconchid tube. The thin diaphragm running vertically in this image shows an inflection for the "dimple".

Microconchids (Ordovician – Jurassic) are an evolutionarily interesting group because they appear to be related to bryozoans and brachiopods (much to everyone’s surprise). This is based on their shell structure and their manner of budding (Zatoń and Vinn, 2011). Helicoconchus elongatus will tell us much about the relationships of microconchids to other groups because of the detail we can see in its budding styles and its marvelous preservation.

Helicoconchus elongatus in the field.

References:

Wilson, M.A., Vinn, O. & Yancey, T.E. 2011. A new microconchid tubeworm from the Artinskian (Lower Permian) of central Texas, USA. Acta Palaeontologica Polonica 56: 785-791.

Zatoń, M. & Vinn, O. 2011. Microconchids and the rise of modern encrusting communities. Lethaia 44:5-7.

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Wooster’s Fossil of the Week: an orthid brachiopod (Upper Ordovician of Indiana)

Mark Wilson November 27, 2011 12:56 am

This beautiful brachiopod is Vinlandostrophia ponderosa (Foerste, 1909), an orthid brachiopod from the Maysvillian (Upper Ordovician) of southern Indiana. Until recently it had been traditionally known as Platystrophia ponderosa until a critical paper by Zuykov and Harper (2007) investigated the “Platystrophia plexus” of species and convincingly made P. ponderosa the type species of Vinlandostrophia.

Brachiopods are filter-feeding, bivalved marine invertebrates who have been with us since the Cambrian Period. They were among the most common animals of the Ordovician. The fossils of the Cincinnatian Series in southern Indiana, southwestern Ohio and northern Kentucky have extraordinary numbers and varieties of fossil brachiopods — so many they roll under your feet in some places.

August F. Foerste (1862-1936) described what he called Platystrophia ponderosa in 1909. He was a pioneering paleontologist who grew up and worked in the Dayton area. Foerste went to Denison University where he was a very successful undergraduate, publishing several geological papers. He returned to Dayton after graduation with a PhD from Harvard, teaching high school for 38 years. When he retired he was offered a teaching position at the University of Chicago, but instead went to work at the Smithsonian Institution until the end of his life.

This is, by the way, the 500th post of the Wooster Geologists blog. It is great fun.

References:

Foerste, A.F. 1909. Preliminary notes on Cincinnatian fossils. Denison University, Scientific Laboratories, Bulletin 14: 208-231.

Zuykov, M.A. and Harper, D.A.T. 2007. Platystrophia (Orthida) and new related Ordovician and Early Silurian brachiopod genera. Estonian Journal of Earth Science 56: 11-34.

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Wooster Geologist on the Crampton’s Gap Battlefield in northern Maryland

Mark Wilson November 26, 2011 8:13 pm

In September 1862, Union forces under General George B. McClellan pursued General Robert E. Lee‘s Army of Northern Virginia through northwestern Maryland. Lee had invaded Maryland to demoralize the North ahead of the November elections, and to convince Europe that the Confederacy had legs and deserved recognition. A copy of Lee’s orders were lost (famously found by Union soldiers wrapping three cigars), alerting McClellan to his plans. The key to defeating Lee lay in capturing three passageways through South Mountain, one of which is known as Crampton’s Gap (shown above in this Google Earth image).
Crampton’s Gap as viewed from the southern side looking north. There were no structures here during the battle.

South Mountain is a north-south extension of the famous Blue Ridge into Maryland. It is a sharp ridge made of resistant metamorphic rocks, including gneisses, schists and quartzites. The slopes on either side are unusually steep and so passing from east to west over the mountain is best done through “gaps” made by eroding antecedent river systems. Water gaps are deepest and have streams currently flowing through them. (One is made by the Potomac River.) A wind gap was also made by river erosion, but the water was long ago snatched away by stream piracy. Crampton’s Gap (39° 24′ 36″ N, 77° 38′ 24″ W) is a wind gap less than 300 meters wide.

Quartzite exposed in Crampton’s Gap, probably from the Late Precambrian (?) Swift Run Formation Cambrian Antietam Formation (thanks, Callan).

On September 14, 1862, McClellan finally moved on Lee and attacked the three gaps through South Mountain to turn back Lee’s invasion. Crampton’s Gap was the southernmost part of what later became known as the Battle of South Mountain.
Union forces under Major General William B. Franklin, after a long preparation, attacked from the east a much smaller Confederate force at Crampton’s Gap. The Confederates resisted all day, taking advantage of the steep slopes and narrow pass with a battery of cannon. By the end of the day, though, the Union force broke through the Confederate lines, sending the remaining rebels down the western slopes. Strangely, Franklin failed to follow up on his victory, allowing the rebel troops to join Stonewall Jackson to capture the Union garrison and arsenal at Harpers Ferry. The overall battle was a Union victory as it blunted Lee’s invasion, forcing him to stand at Antietam and eventually retreat from Maryland. The resistant rocks of South Mountain protected his army long enough for him to frighten the Northern public, but those ancient wind gaps were his undoing.

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