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Showing results for tags 'eagle ford'.
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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From the album: Grayson County creek - June 7th
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I haven't seen much discussion on the geology of the well-known Post Oak Creek here in North Texas. I'd usually seen it referred to the Eagle Ford Group/Formation, but without much substantiation. I really hadn't given it much care, but as is a healthy practice in science, one should often reevaluate one's beliefs especially in light of new information. I believe there is some evidence to support the Eagle Ford assignment, granted I'm not a professional nor very knowledgable about geology and I welcome discussion and contrarian input. The Eagle Ford (Kef) is exposed near Sherman, so it's a possibility. The Austin Group/Austin Chalk is also here (Kau): ^https://ngmdb.usgs.gov/Prodesc/proddesc_19387.htm Here is the evidence that I believe favors that most of the Cretaceous fossils from POC are from the Eagle Ford: 1. Lithology USGS describes the lithology of the Eagle Ford formation: "In Sherman Sheet (1967) (NE Texas) shale, selenitic, bituminous, [calcareous] concretions and septaria, thin platy beds of [sandstone] and sandy [limestone]. in middle and upper part, [medium] to [dark] gray; marine megafossils; thickness 300-400 ft." (https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=TXKef%3B0) (http://northtexasfossils.com/pdfs/shermansheet.pdf) I've found several matrix pieces with shark teeth in it that match the preservation of the vast majority of sharks in POC, which are sandstones. There are also septarian nodules like this one: 2. Presence of Cameleolopha bellaplicata Anyone who has been to POC has seen these oysters everywhere. They are often embedded in the same sandstone. Note that this illustrated one from Hook & Cobban (2011) was collected near Sherman (probably POC since they refer to it). Here is a specimen I collected: Hook & Cobban (2011) say that "Cameleolopha bellaplicata (Shumard 1860) is an easily recognized fossil oyster that occurs abundantly in sandy strata in Arizona, Colorado, New Mexico, Utah, and Texas, where it is restricted to the middle Turonian ammonite zones of Prionocyclus hyatti and P. macombi." These together are consistent with the description and age of the Eagle Ford formation. One possible strata for POC is also the lowest part of the Austin Group, the Atco. However, I've yet to find a description of the lithology which matches better than that above for EF. In addition, there is disparity in the fauna between the Atco and POC. There are many genera found in the Atco which I've yet to find after a few years of hunting Post Oak (e.g. Heterodontus, Protolamna, Dallasiella, Pariasurus, Pseudocorax, Microcorax, etc.; see Hamm & Cicimurri (2011)). This may be because I haven't looked long enough or there could be some other bias. If you have any of the sharks mentioned above from POC, I'd love to see them. That's all I've got from a one-sitting internet exploration last night, so please do double check my rambling.
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From the album: Sharks
One of my favorites - the "ginsu" shark. This one was found at the DFW airport in the 80's. -
I hadn't been out fossil hunting lately. We've been getting enough rain to make me wonder how high the water level in creeks would be, plus spring fishing is so good on Cedar Creek Lake, where I live, that on days where I don't spend a couple of hours on the bicycle, I've just been going fishing. But now we've had a couple of weeks without much rain, so I'd been wanting to make a trip back to Grayson County. I had a doctor appointment in Dallas Friday morning, so I decided I would leave from there and make the drive to Grayson County. It was 10:30 am before I reached this day's creek, rapidly approaching the heat of the day, so I knew this would be a short visit to the creek. It was hot and sunny Friday, and I got reminded just how much heat you feel from those gravel bars when you're on knees and elbows. By shortly after 1:00 pm, I was cooked and ready to make the drive home. But this part of the creek is so much more grown up than when I was last there, I had a tough time getting out of the creek without getting torn up by briars and tree limbs. I ended up looking like I had been on the short end of a fight with a wildcat. I was already carrying leg chaps, but just never stopped to put them on. I've found some old kevlar arm chaps too. I'm going to start making myself wear both when traversing the thick stuff from now on. 71 year old skin just seems to suffer a lot more damage in these situations than young skin does. But as always in Grayson County, I did find some fossils. Here are photos of some, just as they lay when I found them. Each of those last two photos have two teeth in them. It's not often that I find two teeth that close together.
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
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From the album: Grayson County creek - May 20th
