Shark Tooth Trip to Sherman Creeks
Saturday, July 14
The largest Cretaceous shark teeth in Texas come from the creeks around the Sherman/Denison, Texas area. Since the area’s so heavily collected, we’ve found success in digging/screening for the teeth. You can simply surface collect – rake through the gravel or actually screen – dry or wet.
We’re collecting in the equivalent geology of the Midlothian quarries – the Austin/Eagle Ford contact or basically the Turonian/Coniacian boundary of the Upper Cretaceous – so the teeth are the same as there. The only difference is that there is no visible boundary here like in the quarries. The Austin Chalk down through the basal Atco formation has been eroded away into these creeks. So, we’ll be collecting ‘float’ material as opposed to in situ fossils. Sometimes you can find secondary deposition (Pleistocene deposits in the walls) containing this ‘contact’ material.
Some screens will be available for use, but if you would like to build your own, here are a few tips.
Hardware stores usually have the materials you will need to build yourself a screen.
A simple approach is to use ½” PVC pipe with flotation in the form of foam swimming tubes or 2 liter pop bottles. All this can be attached with twist ties. See photo below.
If you want to make a series of screens to stratify various sizes of material, this works pretty well.
Screen material: ½” hardware cloth (wire) mesh
then 1/4" hardware cloth
metal (brass preferable) window screen
½ mm stainless steel (for the serious collectors)
Framing material: 1x2" wood strips fastened together with wood screws and/or L-brackets
½” PVC pipe and joints
1 1/2' - 2' screen (box) sizes are usually easiest to handle. Various methods of attaching the screen to the frame can be used including a wood lathe strip sandwiching the screen so no rough screen edges are exposed. If you're working by yourself you can build a leg onto one side of your screen so you can do your sorting without having to hold up the entire weight of the screen and contents. Rope loops thru the bottom screen frame will allow you to dunk your layer of screens efficiently. Screens can be nested, one inside the other, or simply stacked (see photos below – made by Gerald Bogan).
Of course, you'll need a shovel to load your screens.
Know that there are multiple hazards on these urban creeks including snakes, fire ants, stinging insects, broken glass and metal construction materials to name a few.
We'll LEAVE the Jack-in-the-Box at Hwy 75 and FM 1417 (just south of Sherman) at 8:30.
After lunch at nearby Dickies BBQ, we’ve been invited to tour the most extensive local shark tooth collection/display in this part of Texas. It was mainly collected before the creeks became so popular and you could collect a handful of nice teeth on an outing. After that we can see about some more collecting (or a nap).
Email me with your questions: rffarish@verizon,.net or call Roger’s cell 972-898-2700 on game day.