Last day of fieldwork in England: A working quarry and another great unconformity

June 26th, 2015

1 Doulting quarry sawBRISTOL, ENGLAND (June 26, 2015) — Tim Palmer has a professional interest in building stones, and a passion for sorting out their characteristics and historical uses. He thus has many contacts in the stone industry, from architects to quarry managers. This morning we visited the Doulting Stone Quarry on the outskirts of Doulting near Shepton Mallet in Somerset. Here a distinctive facies of the Jurassic Inferior Oolite is excavated for a variety of purposes. The rock has a lovely color, is relatively easy to work, and is durable. Above is a quarry saw that cuts out huge blocks from the natural exposure.

2 Thalassinoides layer DoultingSuch sawing produces great cross-sections for geologists to examine. We were particularly interested in that light-colored unit above with the irregular top and dark sediment-filled holes. The holes are part of a network of Thalassinoides burrows (tunnels made by Jurassic crustaceans) and reduce the value of the rock as a building stone. There is thus lots of it laying around the quarry yard for study.

3 Pinnid likely Trichites cross section DoultingOne impressive fossil exposed by the sawing is this pinnid bivalve, probably Trichites.

4 Burrow fill sediments DoultingThe Thalassinoides burrows are filled with a poorly-cemented sediment. It is full of little fossils, so we collected a bag of it for microscopic examination. It may give us clues as to what communities lived on the surface of this burrowed unit when it was part of the Jurassic seafloor.

5 shaping saw DoultingWe had a tour of the quarry shops, which included seeing these giant rock saws in action. Many of the saws are controlled by computers, so elaborate cuts can be made.

6 Medieval stone breaking marksThis rock has been quarried since Roman times, so there is over 2000 years of stone working here. The quarry owner set aside this rock face which shows chisel marks made in Medieval times. Wooden wedges were jammed into chiseled channels and then pulled over days to eventually crack the stone free.

7 Tedbury Camp wavecut surface along strikeAfter the quarry visit, Tim Palmer and I tromped through the woods and eventually found (with the help of several locals) an exposure known as Tedbury Camp. It is another Jurassic-on-Carboniferous unconformity like we saw at Ogmore-By-Sea earlier in the week. A century ago quarry workers cleared off this surface of Carboniferous limestone. It is a wave-cut platform on which Jurassic sediments (the Inferior Oolite) were deposited. The surface has many geological delights, including faults, drag folds, differentially-weathered cherts and carbonates, and Jurassic borings and encrusters. Beautiful.

8 wavecut surface foldingIn this view of the surface you may be able to see the odd folding of the dark chert layers in the right middle of the image. These seem to be drag folds along a fault. They clearly predate the Jurassic erosion of the limestone surface. The overlying Jurassic can be seen in the small outcrop on the left near Tim.

9 section view of wavecut surfaceIn this cross-section of the erosional surface you can clearly see we’re working with an angular unconformity.

10 filled borings wavecutTrypanites borings are abundant across this surface, most filled with lighter Jurassic sediment. There are other borings here too that deviate from the straight, cylindrical nature of Trypanites.

11 curved borings wavecutI don’t know yet how to classify these curved borings. They resemble Palaeosabella.

12 Encrusting bivalve wavecutHere is a Jurassic bivalve attached to the Carboniferous limestone at the unconformity. Most of the encrusters have been eroded away.

13 Tim on wavecut platformThere are many possibilities for further study of the Tedbury Camp unconformity. This was a productive site for our last field visit in England this year. Thank you very much to Tim Palmer, seated above, for his expertise, great companionship, and generosity with his time. It was a reminder of how much fun we had together in the field twenty years ago.

My month of geology in the United Kingdom has now come to an end. My next two days will be devoted to packing up and making the long train and then plane flights home. What a wonderful time I had, as did my students on the earlier part of the trip, Mae Kemsley and Meredith Mann. Thank you again to Paul Taylor for his work with us in Scarborough. I am very fortunate with my fine British friends.

For the record, the important locality coordinates from this trip —

GPS 089: Millepore Bed blocks N54.33877°, W00.42339°

GPS 090: Spindle Thorn Member, Hundale Point N54.16167°, W00.23326°

GPS 091: Robin Hood’s Bay N54.41782°, W00.52501°

GPS 092: Northern limit of Speeton Clay N54.16654°, W00.24567°

GPS 093: Northern limit of Red Chalk N54.15887°, W00.22261°

GPS 094: South section Filey Brigg N54.21674°, W00.26922°

GPS 095: North section Filey Brigg N54.21823°, W00.26904°

GPS 096: Filey Brigg N54.21560°, W00.25842°

GPS 097: D6 of Speeton Clay N54.16635°, W00.24520°

GPS 098: C Beds of Speeton Clay N54.16518°, W00.24226°

GPS 099: Lower B Beds of Speeton Clay N54.16167°, W0023326°

GPS 100: Possible A Beds of Speeton Clay N54.16129°, W00.23207°

GPS 101: A/B Beds of Speeton Clay N54.16035°, W00.22910°

GPS 102: C7E layer of Speeton Clay N54.16447°, W00.24043°

GPS 103: Lavernock Point N51.40589°, W03.16947°

GPS 104: Triassic deposits, Ogmore-By-Sea N51.46543°, W03.64094°

GPS 105: Sutton Stone Unconformity N51.45480°, W03.62609°

GPS 106: Sample of lowermost Sutton Stone N51.45455°, W03.62545°

GPS 107: Nash Point N51.40311°, W03.56212°

GPS 108; Devil’s Chimney N51.86402°, W02.07905°

GPS 109: Fiddler’s Elbow N51.82584°, W02.16541°

GPS 110: Doulting Stone Quarry N51.18993°, W02.50245°

GPS 111: Tedbury Camp unconformity N51.23912°, W02.36515°

 

Wooster Geologist in England (again)

June 25th, 2015

1 old quarry face cotswoldsBRISTOL, ENGLAND (June 25, 2015) — Our little geological exploration of southern Britain now passes into England. Tim Palmer and I crossed the River Severn and drove to the Cotswolds to examine old quarry exposures and Medieval stonework. We are parked above in Salterley Quarry near Leckhampton Hill.

2 devils chimney leckhamptonOur theme again is Jurassic. At Leckhampton Hill we examined exposures of the Middle Jurassic Inferior Oolite. It is not, of course, inferior to anything in the modern sense. The name, originally from William Smith himself, refers to its position below the Great Oolite. This is Devil’s Chimney, a remnant of stone left from quarrying in the 19th Century.

3 fiddlers elbow hdgd and Pea GritWe stopped along a bend in a Cotswold road called Fiddler’s Elbow and found an old carbonate hardground friend in the Inferior Oolite. Borings are evident in this flat, eroded surface. Next to the hammer are pieces of the Pea Grit, a coarser facies. I want to examine the grains for microborings and encrusters.

4 Dogrose leckhamptonThis is the gorgeous dog-rose (Rosa canina, not surprisingly), which is common in the Cotswolds. It is the model for the Tudor Rose in heraldry.

5 Fiddlers elbow orchidsThese tall orchids were also abundant near our outcrops.

6 fiddlers elbow orchids closeA closer view of the orchids. When I learn the name for this plant, I’ll amend this post. [And we have one! Caroline Palmer identified the flowers as Dactylorhiza sp. Thanks, Caroline!]

7 Painswick church and yewsAt the end of the day we stopped by St. Mary’s Church in Painswick, with its distinctive churchyard and variety of building stones. The sculptured trees are English yews.

8 Tim and Painswick gravestonesThe gravestones date back to the early 18th Century, with older ledger stones inside the church.

9 Painswick church pyramid markerThe unique pyramidal tomb of the stonemason John Bryan (1716-1787). He was apparently responsible for most of the 18th Century ornate monuments in this churchyard.

10 copper markers killing lichen PainswickMany of the gravestones have copper plates affixed to their upper faces. The rain washes copper ions out of the metal and over the limestone, killing the lichens and other encrusting organisms. This leaves the lighter patch of bare limestone. Somewhere in this is a study of microbiome ecological gradients!

11 St Marys church Painswick shot divot 1643The Painswick church was the site of a 1643 battle during the English Civil War. There are numerous bullet and shot marks on the exterior stones. Tim commented on the remarkable resilience of this stone to stay coherent after almost 400 years of weathering of these pits.

A great unconformity in South Wales

June 24th, 2015

1 Dinantian Sutton unconformity wide viewBRIDGEND, WALES (June 24, 2015) — Today Tim Palmer and I visited a famous unconformable rock plane in South Wales. I last saw it thirty years ago, when I knew a lot less about eroded, bored and encrusted surfaces. It is an unconformity between a Carboniferous limestone (High Tor Limestone, Dinantian in age) and an overlying Jurassic limestone (Sutton Stone, Hettangian, Lower Jurassic) exposed on the coast near Ogmore-By-Sea. It was most thoroughly described in 2004 by Johnson and McKerrow (Palaeontology 38: 529-541). You can see it as the surface above, with the Jurassic rocks on top of it to the right. (I know, gray rocks on gray rocks. It takes close examination to tell them apart after they both have been subjected to coastal weathering.)

2 Dinantian Sutton close viewHere is a closer view with part of the Lower Jurassic Sutton Stone broken away to show fresh material. (We didn’t do this, despite the guilty-looking hammer. The hammer is Paul Taylor’s, by the way. Thanks, Paul!) Note the pebbles in the Sutton Stone. They are made of the Carboniferous limestone beneath. Classic unconformity.

3 Dinantian Sutton borings wide viewThe Carboniferous limestone is punctured by numerous small borings (Trypanites) drilled by filter-feeding worms of some kind when the Early Jurassic sea covered this surface. They are the clusters of small black dots shown above.

4 Dinantian Sutton borings closeIn this closer view of the borings you can see that they are filled with a lighter Jurassic sediment. The openings have been somewhat enlarged by weathering.

5 Dinantian Sutton reliefThis erosion surface shows some relief, probably formed by cobbles and pebbles washing over it during the Early Jurassic. This matches what we see on modern wave-cut rocky platforms.

6 Triassic Dinantian unconformityOn the same stretch of shoreline there is a small section where Triassic wadi deposits cut down into the Carboniferous limestone — another even more dramatic unconformity, but without marine fossils.

7 Triassic wadi deposits Ogmore by seaComing from a desert myself, I have an affinity for wadi sediments. They are coarse, angular and poorly sorted. These grains are entirely from the underlying Carboniferous limestone. They were likely generated from steep rocky canyons through which intermittent streams flowed.

8 Nash Point viewAt the end of the day Tim and I visited Nash Point, again on the coast of South Wales. Here the Lias is brilliantly (and dangerously!) exposed as a series of alternating limestones and shales.

9 Nash Point CliffWe didn’t get too close to these unstable cliffs. The limestone blocks fall often as the interbedded soft shales holding them in place weather away.

10 Nash PointA view of Nash Point at low tide. Tim always wears that red jacket, so he’s easy to spot. (Classic Redcoat!)

11 Nash Point cobblesWe didn’t find much to paleontologically interest us at this last outcrop, but it was beautiful on another stunning coastal day. These cobbles, all made of Lias limestones, are pretty to look at, but tiresome to walk through. We were ready for a slow dinner after this excellent day.

 

A Wooster Geologist goes to Washington for a different kind of fieldwork

September 18th, 2013

1photo1_091813WASHINGTON, DC–Today I was in Washington, DC, with 70 other colleagues for the annual Geosciences Congressional Visits Day organized by the American Geosciences Institute (AGI). I was ostensibly representing the Paleontological Society as its secretary, but I was really a member of the Ohio delegation there to speak to staffers in the offices of Ohio senators and representatives. The weather was strikingly beautiful, and all the more lovely considering how much time I spent looking at it through windows in one office or another.

The AGI organized this set of visits with great precision. We were split into state teams (my partner was Pete MacKenzie of the Ohio Oil and Gas Association), each guided by a coordinator (we had Julie McClure, a science policy fellow). Our Ohio team went to the offices of Senators Rob Portman and Sherrod Brown, Congressmen James Renacci and Pat Tiberi, and then we met with a counsel for the Senate Energy and Natural Resources Committee. We had a few minutes in each office to make the case for “steady federal investments” in Earth and space sciences. It was a difficult “ask” because of the diversity of agencies and constituents, so I hope our enthusiasm at least left an impression. I am SO grateful to Pete and Julie for their experience and leadership in our little squad.

2photo9_091813This is a rotunda in the Russell Senate Office Building, with Pete Mackenzie serving as scale. This is a spot commonly used for television interviews of senators. The statue is of Senator Richard Russell himself.

3photo8_091813Literally one of the halls of Congress. This is again in the Russell Senate Office Building.

4photo6_091813We saw these clocks throughout the Russell Senate Office Building. The lights indicate the number of buzzers sounded to call senators to various votes and quorum calls. The red light means the Senate is in session.

5photo7_091813Yes, here is Country Mouse outside the office of his representative: James Renacci of the Ohio 16th District (“the fighting 16th!”). I felt casually dressed, and one staffer said I must be the professor with “that hair”. While I learned a lot, I can’t say I was comfortable with the process. I’m grateful for all the bright people who enjoy these things!

6photo2_091813OK, out of the offices in time for a little sight-seeing on the way back to the airport. Here is one of my favorite statues in the capitol: Nathan Hale. This tragic hero looks so much like a college student to me.

7photo5_091813You just have to love democracy in action at the heart of our government! This is just one example of the many temporary and permanent demonstrations going on in the capitol. I’ve resisted showing you the displays of the anti-circumcisionists!

8photo3_091813Finally, there must be a little geology here. This was the first time I’ve visited the extraordinary National Museum of the American Indian. Highly recommended, and the food court is to die for. The architecture is intended to resemble southwestern cliffs of sandstone with inset dwellings. I think it is a spectacular success.

9photo4_091813Some of the stone is set with the bedding planes facing outwards. Several trace fossils are visible. These were formed by worm-like animals burrowing through muds sandwiched between layers of sand. I wish I knew the age and location of this deposit.

My visit to Washington was an excellent experience and the basis for future such work with science policy issues. It was surprisingly easy to visit congressional offices, so one primary value of our trip was to show other scientists that their elected representatives are anxious to hear our opinions and use our knowledge and skills for crafting legislation. Of course, everyone we talked to was preoccupied by the latest political maneuvers associated with trying to pass a budget for the next fiscal year (good luck with that), but we were always listened to carefully and treated with respect.

You may also notice in the top photo that the flags are at half-staff on the capitol building. This is because on Monday, the first day of our training workshop, there was a mass shooting at the Navy Yard in DC. This tragedy was a shadow over us all, and it was a reminder of how important good governance is in an unpredictable world.

 

Field reconnaissance in the northern Negev of Israel

July 1st, 2013

1FoldedPhosphates070113MITZPE RAMON, ISRAEL–This morning Team Israel 2013 met our friend Yoav Avni, a geologist with the Geological Survey of Israel (GSI), and we traveled north to our field localities. We did a survey of the sites so that we could put together an efficient schedule for our work over the next two weeks. We had a four-wheel drive vehicle from the GSI so we could get to places our little Budget rental car could only have nightmares about.

The first locations were for Oscar Mmari’s Cretaceous phosphorite work. The outcrop pictured at the top of this entry is on the east side of Makhtesh Gadol (N 30.93657°, E 035.03312°). We are looking toward the west at an incredibly asymmetric limb of a syncline. In the upper part of the exposure you can see the rocks dipping almost vertically, yet in the foreground they are nearly horizontal. They make an almost 90° bend. The Mishash Formation phosphatic zone is partly exposed as the white rocks along the side of the wadi. The phosphorites here are very thick and chalky.

2MishhashPhosphates070113A second phosphorite exposure for Oscar is in Wadi Havarim (N 30.84269°, E 34.75509°) not too far north of Mitzpe Ramon. The top of the cherty portion of the Mishash Formation is on the left in the middle; the light-colored units above are phosphorites. In the background is Nahal Zin, a deep valley formed by water draining north into the Dead Sea. The base level of the Dead Sea is so low that the wadis leading to it are rapidly downcut.

3OscarPhosphorite070113Here is Oscar getting is first look at the phosphorites at Wadi Havarim. Later this week we will measure at least one section at each locality and take plenty of samples for thin-sectioning and scanning electron microscopy.

4TraceFossil070113Steph Bosch’s hand gives us a scale for a nice set of trace fossils found in the phosphorite at Wadi Havarim. These look like callianassid shrimp burrows to me. We found some preserved as burrow-fills with apparent fecal pellets forming the outer walls. If true then the trace fossil ichnogenus is Ophiomorpha. This is a good indicator of shallow water.

5PhosphateSign070113We also briefly visited two phosphate mining sites east of Makhtesh Gadol. One has this helpful sign outside describing the geology of these deposits. The phosphorites are shown in yellow. Note that they formed in two synclines, both highly asymmetrical (as shown in our top photo).

6PhosphateMinedValleyWe viewed one phosphate mine where virtually the whole valley has been quarried, producing enormous piles of waste materials. Reclaiming mined terrain like this is especially difficult in this arid climate. Oscar will not only be looking at the geology of these phosphate deposits, but also the economics of mining, which now includes remediation and controls on emissions and water pollution.

7MatmorCollectingFirstDay070113After lunch we drove down into the center of Makhtesh Gadol and plotted out future localities for Steph and Lizzie to do their work in the Matmor Formation. (The above site is at N 30.93837°, E 34.97907°.) I’ve been to these sites many times with students, so it was relatively easy to make our plan for collecting crinoids and encrusting bryozoans tomorrow and next week.

8NabateanCistern070113Finally, no fieldwork in Israel is complete without a touch of archaeology. Yoav took us into a Nabatean cistern and showed us the clever engineering (and strategic plastering) necessary to make this hand-cut cavern into a water trapping and storage facility. This cistern is cut into the Menuha Formation, a chalk unit very familiar to Andrew Retzler (’11). This cistern was originally made sometime between 100 BCE and 100 CE. After the nabateans it was used by the Romans, Byzantines and Arabs. It was last used by Israeli pioneers over 60 years ago.

Tomorrow we return to Makhtesh Gadol and work in the hot sunlight filling collecting bags with tiny bits of crinoids and assorted encrusters. We’ve had a very good start.

Spectacular shrimp burrows from the Miocene of Sicily

June 5th, 2013

Siciliancountryside060513NOTO, SICILY, ITALY–The first stop on our International Bryozoology Association field trip today was a newly-opened quarry near Cugni di Rio in the dry southeastern countryside of Sicily, a view of which is above. New quarries are always interesting to geologists — a new view of the Earth’s bones.

OphiomorphaAshcontact060513This is a portion of the quarry wall with the inevitable volcaniclastic unit of ash and marine sediments shown as the greenish layered unit above and below limestones dated as Tortonian (Upper Miocene). On top of the ash you can see what look like tubes sticking out of the brownish layer of sediment.

OphiomorphaSlab1_060513When that brownish layer is exposed as the underside of the bedding plane, it looks like this. These branching features are infilled tunnels made by marine shrimp. The walls of the tubes are ornamented by pellets placed there by the shrimp in their frenetic activity. Combining these pellets with the branching style we can place this trace fossil in the venerable ichnogenus Ophiomorpha.

OphiomorphaSlab2_060513This is a closer view showing the branched galleries and maybe a bit of the pitted surface showing where the pellets were attached. These tunnels are completely filled, so we refer to this preservation as full relief.

I know, I know, I should be recording the bryozoans from this stop, but they were far from photogenic!

Wooster’s Fossil of the Week: A twisty trace fossil (Lower Carboniferous of northern Kentucky)

January 27th, 2013

My Invertebrate Paleontology students know this as Specimen #8 in the trace fossil exercises section: “the big swirly thing”. It is a representative of the ichnogenus Zoophycos Massalongo, 1855. This trace is well known to paleontologists and sedimentologists alike — it is found throughout the rock record from the Lower Cambrian to modern marine deposits. It has a variable form but is generally a set of closely-overlapping burrow systems that produce a horizontal to oblique set of spiraling lobes. It was produced by some worm-shaped organism plunging into the sediments in a repetitive way, gradually making larger and larger downward-directed swirls.

Zoophycos is a useful indicator of ancient depositional conditions. It give its name, in fact, to an ichnofacies — a set of fossils and sediments characterize of a particular environment. In the Paleozoic it is found in shallow water and slope environments; from the Mesozoic on it is known almost entirely from deep-sea sediments. Our specimen is from the Borden Formation and was found amidst turbidite deposits, so it is probably from an ancient slope system.

There has been much debate about the behavior and objectives of the organisms who made Zoophycos. The traditional view is that it was formed by an animal mining the sediment for food particles, a life mode called deposit-feeding. Some workers, though, have suggested it could have been a food cache, a sewage system, and even an agricultural garden of sorts to raise fungi for food. I think in the end the simplest explanatory model is deposit-feeding, although with such a long time range, a variety of behaviors likely produced this trace.

Zoophycos was named in 1855 by the Italian paleobotanist Abramo Bartolommeo Massalongo (1824-1860). Massalongo was a member of the faculty of medicine at the University of Padua, chairing their botany department. (Medicine had broad scope in those days!) Why was he studying this trace fossil? Like most of the early scientists who noticed trace fossils, he thought it was some kind of fossil plant.
Zoophycos villae (Massalongo, 1855, plate 2)

References:

Bromley, R.G. 1991. Zoophycos: strip mine, refuse dump, cache or sewage farm? Lethaia 24: 460-462.

Ekdale, A.A. and Lewis, D.W. 1991. The New Zealand Zoophycos revisited: morphology, ethology and paleoecology. Ichnos 1: 183-194.

Löwemark, L. 2011. Ethological analysis of the trace fossil Zoophycos: Hints from the Arctic Ocean. Lethaia 45: 290–298.

Massalongo, A. 1855. Zoophycos, novum genus Plantarum fossilum, Typis Antonellianis, Veronae, p. 45-52.

Olivero, D. 2003. Early Jurassic to Late Cretaceous evolution of Zoophycos in the French Subalpine Basin (southeastern France). Palaeogeography, Palaeoclimatology, Palaeoecology 192: 59-78.

Osgood, R.G. and Szmuc, E.J. 1972. The trace fossil Zoophycos as an indicator of water depth. Bulletin of American Paleontology 62 (271): 5-22.

Sappenfield, A., Droser, M., Kennedy, M. and Mckenzie, R. 2012. The oldest Zoophycos and implications for Early Cambrian deposit feeding. Geological Magazine 149: 1118-1123.

Wooster’s Fossil of the Week: A bivalve boring from the Upper Ordovician of southern Ohio

December 16th, 2012

This week’s fossil is from close to home. In fact, it sit in my office. The above is a trace fossil named Petroxestes pera. It was produced on a carbonate hardground by a mytilacean bivalve known as Modiolopsis (shown below). Apparently the clam rocked back and forth on this substrate to make a small trench to hold it in place for its filter-feeding. This particular specimen of Petroxestes was found in the Liberty Formation (Upper Ordovician) of Caesar Creek State Park in southern Ohio. This is a place many Wooster paleontology students know well from field trips.
The original Petroxestes was at first known only from the Cincinnatian Group, but now it is known from many other places and time intervals, even including the Cretaceous and Miocene. It is a good lesson about trace fossils. They are defined by their morphology, not what organisms made them. It turns out that this slot-shaped trace can be made by other animals besides Modiolopsis, which went extinct in the Permian.

References:

Jagt, J.W.M., Neumann, C. and Donovan, S.K. 2009. Petroxestes altera, a new bioerosional trace fossil from the upper Maastrichtian (Cretaceous) of northeast Belgium. Bulletin de l’Institut royal des Sciences naturelles de Belgique, Sciences de la Terre 79: 137-145.

Pickerill, R.K., Donovan, S.K. and Portell, R.W. 2001. The bioerosional ichnofossil Petroxestes pera Wilson and Palmer from the Middle Miocene of Carriacou, Lesser Antilles. Caribbean Journal of Science 37: 130-131.

Pojeta Jr., J. and Palmer, T.J. 1976. The origin of rock boring in mytilacean pelecypods. Alcheringa 1: 167-179.

Tapanila, L. and Copper, P. 2002. Endolithic trace fossils in Ordovician-Silurian corals and stromatoporoids, Anticosti Island, eastern Canada. Acta Geologica Hispanica 37: 15–20.

Wilson, M.A. and Palmer, T.J. 1988. Nomenclature of a bivalve boring from the Upper Ordovician of the midwestern United States. Journal of Paleontology 62: 306-308.

Wilson, M.A. and Palmer, T.J. 2006. Patterns and processes in the Ordovician Bioerosion Revolution. Ichnos 13: 109–112.

Wooster’s Fossil of the Week: Birch wood with beetle borings (Oligocene of Oregon)

November 4th, 2012

We may be at the Geological Society of America annual meeting today, but that doesn’t stop Fossil of the Week! This week’s fossil is a beautifully-detailed piece of petrified birch wood (Betula) with tree rings and insect borings throughout. It was found in the Little Butte Formation (Oligocene) of Linn County, Oregon. This rock unit consists of thick tuffs and volcanic breccias representing volcanic mudflows and nuée ardente deposits that buried diverse hardwood forests. This formation is known for its spectacular silicified fossil wood.
The beetle borings, shown in closer view above, are very similar to those bored in birch trees today. There is little work done on the ichnotaxonomy of these trace fossils, so I can’t yet give them a name, but at least we can see typical beetle activity in the twists and turns. The holes are apparently filled with a cemented mix of insect feces and wood fragments called frass, just like we find in modern birch wod today.

References:

Beaulieu, J.D., Hughes, P.W., and Mathiot, R.K. 1974. Environmental geology of western Linn County, Oregon. Oregon Department of Geology and Mineral Industries Bulletin, no. 84, 117 p.

Rozefelds, A.C. and De Baar, M. 1991. Silicified Kalotermitidae (Isoptera) frass in conifer wood from a mid-Tertiary rainforest in central Queensland, Australia. Lethaia 24: 439-442.

Wooster’s Fossils of the Week: Bivalve Borings (Upper Miocene of Spain)

October 28th, 2012

This beautiful object has a complex history. In the center is a gray limestone cobble that eroded from an underwater ridge and rolled free on a shallow coral reef in an area now near Abanilla, southeastern Spain. It was encrusted by a scleractinian coral, which grew thickly all around the cobble because it was turned continually by wave and current action. Larvae of the bivalve Lithophaga landed on the surface of the coral and quickly began to bore downwards, creating the trace fossil Gastrochaenolites torpedo Kelly and Bromley, 1984. They bored in some cases all the way into the cobble nucleus. The whole set was then buried in transgressive sediments of the Los Banós Formation during the Late Miocene. In the summer of 1989, my student Genga Thavi (“Devi”) Nadaraju (’90) found it as part of her Keck Geology Consortium fieldwork for her Independent Study project. It now resides proudly in the trace fossil collection at Wooster.

Closer view of the gray limestone cobble in the center. Note the remnants of Lithophaga shells still in the borings.

The bivalve boring Gastrochaenolites was named in 1842 by a French geologist with a magnificent name: Alexandre Félix Gustave Achille Leymerie (1801-1878). He was a prolific author with a long career spent primarily studying Cretaceous rocks and fossils in France and northern Spain.

References:

Kelly, S.R.A. and Bromley, R.G. 1984. Ichnological nomenclature of clavate borings. Palaeontology 27: 793-807.

Leymerie, M.A. 1842. Suite de mémoire sur le terrain Crétacé du département de l’Aube. Mémoire des Société Géologique de France 5: 1-34.

Mankiewicz, C. 1995. Response of reef growth to sea-level changes (late Miocene, Fortuna Basin, southeastern Spain). Palaios 10: 322-336.

Mankiewicz, C. 1996. The middle to upper Miocene carbonate complex of Níjar, Almería Province, southeastern Spain, in Franseen, E.K., Esteban, M., Ward, W.C., and Rouchy, J.-M., eds., Models for carbonate stratigraphy from Miocene reef complexes of the Mediterranean regions: Tulsa, SEPM (Society for Sedimentary Geology), p. 141-157.

Nadaraju, G.T. 1990. Borings associated with a Miocene coral reef complex, Fortuna basin, southeastern Spain. Third Keck Research Symposium in Geology (Smith College), p. 165-168.

Taylor, P.D. and Wilson, M.A. 2003. Palaeoecology and evolution of marine hard substrate communities. Earth-Science Reviews 62: 1-103.

Next »