Mark Wilson May 25th, 2010
STARKVILLE, MISSISSIPPI — We simply could not do this work without the guidance of local geologists who know the stratigraphy and the locations which are likely to yield the best results. This is especially true in eastern Mississippi where most of the outcrops are in drainage ditches, cleared building lots, and on grass-covered roadsides. There is no way we would find them on our own.
Fortunately we now have an extraordinarily knowledgeable colleague who has an ambitious schedule of fossiliferous localities to show us. George E. Phillips met us as arranged at our first outcrop in Starkville this morning. At first when I saw him get out of his official state vehicle in his impressive uniform and begin talking to Paul I thought we were about to be arrested. Far from it, of course. George is the Paleontology Curator at the Mississippi Museum of Natural Science and the Mississippi Department of Wildlife, Fisheries & Parks in Jackson.
Paul Taylor and George Phillips on the Avalon outcrop of the Prairie Bluff Formation (Upper Cretaceous) in Starkville, Mississippi.
George is a skilled paleontologist and general naturalist who knows just what sort of fossils we need for our work, and all the right places to find them. We are very impressed that the state of Mississippi employs such scientific talent and makes it available to visitors like us.
Mark Wilson May 24th, 2010
Megan found this beautiful shark's tooth in the Prairie Bluff Formation (Upper Cretaceous) near Starkville, Mississippi, this afternoon. Andrew Retzler! We want your expert identification of it in the comments below. Thanks!
Mark Wilson May 24th, 2010
STARKVILLE, MISSISSIPPI — Early this morning we left Demopolis, Alabama, and drove to Livingston, home of the University of West Alabama. Our first localities, in fact, were very close to campus as we again explored the Upper Cretaceous Prairie Bluff Formation.
Megan, Caroline and Paul doing the paleontology thing on an outcrop in Livingston, Alabama (N 32.59827°, W 88.19301°). The scene looks pretty quiet and usually is, except for the occasional utterance like, "Cool! More cyclostomes!". It is a culture all to itself.
In the early afternoon we crossed the border into Mississippi. It may be our imagination and a limited sample size, but we swear the accents got thicker and the British among us especially had difficulty understanding it. The fossils, though, know no boundaries and were just as good as their Alabama cousins.
A bored oyster waiting patiently to be collecting on a Mississippi outcrop of the Prairie Bluff Formation (N 33.48371°, W 88.85309°). The evenly-spaced holes were produced by an endolithic clionaid sponge. Note the splendid preservation of the shell and just the right kind of weathering. This is the kind of outcrop where you wonder why more people aren't here picking up this great stuff!
Her Majesty's Own Bryozoologist, Dr. Paul D Taylor, in action on a Mississippi outcrop. (Shout-out to Emma: This is the best I can do with your father. Always crouching close to the ground, he is. Bendiest man in paleontology.)
Mark Wilson May 23rd, 2010
Lonely highway near Jefferson, Alabama, at one of our roadside outcrops (N 32.39412°, W 87.92422°).
DEMOPOLIS, ALABAMA — We practically had the state to ourselves on this steamy Sunday as we drove around western Alabama looking for outcrops of the latest Cretaceous and earliest Paleogene. As is often the case, localities described in the literature disappear because of housing developments, road expansions, new dams on rivers, and the luxuriant growth of vegetation (especially kudzu down here). Still, we found that even a meter-thick strip of the Prairie Bluff Formation in a roadside ditch can be loaded with encrusted and bored fossil shells, so we collected enough specimens to make the driving worthwhile. Now we settle down for our last night in Alabama before crossing over into Mississippi tomorrow. (This gives me time to soothe the chigger bites on my ankles!)
We promised Megan and Caroline that if they crossed the muddy creek to see what was on the other side, we would immortalize their heroics in the blog.
We all had our photographs taken under this most appropriate ranch sign. (For the non-geologists, "KT" is our code for "Cretaceous-Tertiary".)
Mark Wilson May 22nd, 2010
GREENVILLE, ALABAMA — Reconnaissance is over for this part of the state, and our work commenced this morning. We want to find good sclerobiont communities above and below the Cretaceous-Tertiary boundary, so here that means we want specimens from the Upper Cretaceous (Maastrichtian) Prairie Bluff Formation and the Paleocene (Danian) Clayton Formation. That means plenty of muddy creekbeds and sun-smacked roadcuts.
Megan Innis (below) and Caroline Sogot (above) collecting bored and encrusted fossil oysters from the Prairie Bluff Formation in Mussel Creek (N 31.97259°, W 86.70387°).
Megan (in the fashionable yellow wellies) and Caroline collecting oysters from the Prairie Bluff Formation along Alabama 263 (N 32.04082°, W 86.79367°).
This would be a good time to mention that Caroline’s father is a famous magician in England with the stage name Jack Stephens. We think this is very cool. And I quickly add, Megan’s father Jeffrey is a famous pediatric geneticist at the University of Michigan. We like that too!
This is the kind of fossil we like. It is a bivalve shell from the Clayton Formation (Tertiary, Danian) thoroughly bored by sponges. Unfortunately it is also well locked into this silicified rock matrix!
Mark Wilson May 22nd, 2010
GREENVILLE, ALABAMA — The Cretaceous-Tertiary boundary at Mussel Creek, Lowndes County, Alabama, has some unusual complexity. At the southern end of the section it is simple enough, as shown in a previous blog post. Just a few meters north, though, the boundary section looks like this:
Cretaceous-Tertiary boundary section at Mussel Creek, Lowndes County, Alabama (N 31.97176°, W 086.70414°). The "K" indicates Cretaceous rock; the "T' marks Tertiary sediments; the rounded black object is charcoalized wood.
This strange stratigraphy appears to be a stream channel filled with carbonaceous (carbon-bearing) laminated sediments which were incised into the Cretaceous Prairie Bluff Formation below. Is this channel Cretaceous or Tertiary? What sort of environmental conditions does it represent? We discussed and tested many hypotheses on the outcrop this morning, which is always great fun. We finally decided that these channel-filling sediments are Tertiary, following the conclusions of some (but not all) previous authors. Still, the beds are unlike any channel-fills I’ve seen before, especially with all the carbon. My favorite idea (which has no support in the literature, I quickly add) is that this channel represents erosion of a continent devastated by the impact blast in Yucatan just across the Gulf of Mexico. The local forests were burned off in the massive wildfires (and maybe further devastated by a tsunami), leading to rapid erosion and the cutting and filling of channels on the shallow marine shelf here. All the carbon is from the enormous amounts of burned wood.
This is what we would call a romantic view of stratigraphy. It would mean that the big piece of charcoal in the section above is from a tree burned in the end-Cretaceous cataclysm. I like that idea!
Mark Wilson May 21st, 2010
Megan Innis studying the Ripley Formation rockground near Greenville, Alabama.
GREENVILLE, ALABAMA — I have a soft spot for hard places. (Always wanted to say that!) Much of my career has been spent studying marine hard substrates and the communities that have evolved on and in them. These include rocks, hardgrounds and shells on seafloors which have been encrusted and bored by diverse organisms for hundreds of millions of years. In all the many marine environments where these substrates occur, we know the organisms faced one common problem: how to occupy and defend space in an essentially two-dimensional world. This provides a thread to follow through the long evolution of sclerobionts (hard-substrate dwellers, to use one of my favorite words.)
At the top of the Maastrichtian (Upper Cretaceous) Ripley Formation is a rockground which was bored and encrusted on the seafloor in the classic way. It was ably described in a paper by Jon Bryan, and we were pleased to see that the surface is still exposed and accessible today. There were some tasty encrusting bryozoans on some of the cobbles here!
Spondylid bivalve encrusting the Ripley Formation rockground.
Mark Wilson May 21st, 2010
An Alabama Creek where, oddly enough, we found superb Paleocene nautiloids in the McBryde Member of the Clayton Formation (N 31.91739°, W 086.68906°).
GREENVILLE, ALABAMA — This is the first time I’ve done fieldwork in the southern USA. The outcrops are of course very different from my favorite desert locations and oddly similar to those I visited in western Russia last summer. I’m learning once again not to pass by the muddy creek or grass-covered hillside assuming that no useful rocks or fossils will be present. Southern geologists Jon Bryan and Peter Harries have been excellent guides here because they know what treasures lurk under the vegetation and on the river banks.
A grassy hillside with beautiful Cretaceous oysters just underneath. We collected the lot by feeling for the fossils with our feet! (N 32.02580°, W 086.76788°)
Mark Wilson May 21st, 2010
Cretaceous-Tertiary boundary at Mussel Creek, Lowndes County, Alabama (N 31.97176°, W 086.70414°). Megan's hand marks the level with the Cretaceous below and the Tertiary above.
A closer view of the same boundary. My finger is thrilled to be in such a place.
GREENVILLE, ALABAMA — It is one of the most famous geological horizons. It marks the end of the Mesozoic Era and the beginning of the Cenozoic. The “K/T boundary” is dated at 65.5 million years ago (±0.3 my) and is found around the world. It is the primary datum for our work on this expedition, and we were led right to it by our friend Jon Bryan. We want to just pause a moment and enjoy the historical and stratigraphic significance of these sediments. (And yes, I know I should be calling this the more modern “Cretaceous-Paleogene Boundary” as Megan insists, but I grew up with “K/T” since my Berkeley graduate school days and it is hard to give up!)
More later from our hot and muggy day in southern Alabama!
mpollock May 20th, 2010
We have an early morning tomorrow, since we’re running our NE-SE GSA field trip for the Pennsylvania Geological Survey. So, this post will be short and sweet. Here are a few of the highlights from today’s diabase escapades:
One of Betty Lou's cores that we cut for geochemistry and thin sections.
More awesome slickenfibers.
Contact between diabase and a felsic layer.
Quarry workers drilling holes to set up for the next blast.