Saturday, August 13, 2011

Quest for Great White Shark Teeth

Check the gravel bars visually for fossils, then try sifting the
deeper water for those that are not on the surface.
Don't ask me how I did it, but at the end of our family vacation, I convinced my wife to spend a day in North Carolina while my daughter and I hit a popular small stream, Greens Mill Run, commonly known as GMR, in search of nice great white shark teeth to add to our collection.  The Atlantic Coastal Plain formations found along this particular creek include the Cretaceous formations known as the Black Creek and Pee Dee, the Yorktown formation and possibly the Eocene Castle Hayne formation, or at least some reworked material from it.  The term "reworked" means that fossil material that normally occurs in other formations became mixed in with the known formation of an area.  Weather and erosion usually contribute to this, but it could also occur as a result of the existance of life during the time of the formation of younger deposits.  An example would be something like some sort of animal excavating a burrow, perhaps a shrimp, where the burrow was deep enough that it extended from the substrate surface into an older underlying formation.  As the animal makes it's burrow, the material dredged from the burrow may contain older fossils and is pushed out of the burrow, being "reworked" out of the older formation and into the younger sedimentary deposits (or a future fossil formation).

It's no secret that it gets pretty hot in the Carolinas in the summer, but fortunately for us, the temperatures were normal for this time of year while back at home in Maryland we were experiencing higher than normal termperatures in the low hundreds with heat indices around 110 degrees F or higher.  Nevertheless, it was hot and humid in North Carolina yet we could take some comfort knowing that we'd be wading a small stream with a shady tree canopy overhead.

We brought two sifters, one with a half inch mesh and one with a quarter inch mesh, both home made ala Ditchweezil design.  Here's the link so that you can make your own sifter if you like this design:  http://www.blackriverfossils.org/Sifter/tabid/79/Default.aspx.  Obviously, the smaller mesh sized sifter will yield more fossils and shark teeth than the larger mesh sifter simply because the smaller fossils that would fall through the half inch mesh are trapped in the quarter inch mesh.  The advantage of the larger sifter is that you can cover a lot more larger material and not spend time picking out the smaller fossils.  Which one you use depends on what you are after, more fossils including smaller sized ones, or larger fossils only.

My finds for the day were mostly as a result of sifting, but I
did find one great white shark tooth with a broken root and
several smaller teeth on the gravel bank.
My daughter, meanwhile, spent the entire day surface collecting.  That is, simply walking around or sitting on the stream bed picking up fossils from the surface of the stream bottom or exposed gravel bars.  I did a little of that, but mostly put the work in by primarily sifting.  How effective were the techniques?  I'll let the next three pictures tell you, both techniques proved effective though.  During times when the water levels are higher or murkier, surface collecting may not be all that effective in some streams.  In this case, the stream was very low and clear, so that technique worked out just fine on this day.

I used the larger half inch mesh sifter for most of the time in search of the larger shark teeth.  You still sometimes get some smaller teeth that adhere to the gravel in your sifter, but most of the smaller ones fall through. 

Here are my daugher's finds, including a two inch worn
megalodon tooth and a larger mako tooth, and many very
worn fragments of megalodon and other large sharks.
In this particular stream, you really have to be careful, watching out for broken glass and other sharp man made objects as you sort through your sifted material.  Basically, it's a very simple plan, find gravel in the stream, shovel it into your sifter, and then sift and sort through that material pulling out any fossils that you find.  In the picture above, you'll see that sharks teeth were common in the stream that we were collecting in.  In addition to shark teeth, you'll find belemnites from the Cretaceous period, which are fossilized internal skeletons of an extinct squid like creature.  You also have a chance to find other fossils from the Cretaceous, including mosasaur and plesiosaur teeth, crocodile teeth, and various types of fish teeth like the extinct saber toothed salmon, Enchodus, and an extinct pycnodont drum fish, probably Anomaeodus.

Meanwhile, while I'm worked my butt off shoveling, sifting, and sweating profusely, my daughter is walked around surface collecting along the gravel bars.  The water was low and clear from lack of rain apparently.  The two pictures to the right are her finds, much more than I found.  I probably walked around over much of that material not seeing them as fossils.  Duh.  So that's one reason she has twice as many fossils collected as I do, my poor eyesight and her perfect 20-20 vision or better.  The other reason is that the smaller teeth were probably dropping through my half inch screen.  Excuses, excuses, right?  She has an eye for this, a gift I'd say.  I always thought that I did, but I'm no where near the eagle eye that she is.  Anyway, you can see that she found a lot of material, including a two inch worn megalodon tooth, and lots of fragments of teeth from "megs" and other large sharks.  She also found a bunch of belemnites, the amber colored bullet shaped fossils shown on the lower right portion of the paper in both pictures.

In the top row in this picture are teeth from the great white
shark, Carcharodon carcharias. The second row are extinct
mako shark teeth.  Notice the similarity of the top left row
great white tooth and the mako below it.  The mako below
is Cosmopolitodus hastalis, the extinct giant mako that many
scientists believe was the direct ancestor to our great white.
I have to say that I did find several nice teeth while surface collecting including a rootless great white blade stuck in the side of the creek bank.  But, again, most of my stuff came via the back breaking hard work of shoveling and sifting.  You never know from one sift to the next what you'll find, so every sift could be an adventure and yield a tooth of a lifetime.

I found several nice mako teeth and some worn meg and mako fragments while using the half inch mesh sifter.  I was hot, cranky, and soaked in sweat, and not finding the number of teeth that I had hoped for.  I picked likely spots, tried a few sifts, and if I didn't find anything worthwhile, moved on working my way along the stream.  My daughter trailed behind me picking up tooth after tooth.  So, being frustrated, I decided after a couple hours to switch to the quarter inch screen and start padding my fossil numbers with smaller teeth. 

My first sift with the quarter inch screen gave me a nice one.
The very first sift presented me with my best great white shark tooth to date, a 1 3/4" perfect beauty of a tooth.  There are bigger nice teeth to be found here, but I haven't had that much luck doing it, so this tooth may not be much to some that collect here, but for me it made my trip.
The good thing about using the smaller sifter is that you'll find a lot more teeth, and the bigger ones will still be there.  The drawback is that there is so much material to pick through and so many teeth to pull out, that you spend a lot of time picking through each sift.  I actually felt that the added time spent looking through these sifts became a welcome break for my back and allowed me to slow the rate of sweating.  It was so humid that sweat was dripping off my eyebrows and onto my glasses, and my shirt was so soaked that I had nothing dry to wipe them with, hindering my poor old eyesight all the more.  It didn't help that there was absolutely no wind at all to help dry us out.
 
Carcharodon carcharias, great white shark
I really can't complain though, we had plenty of water with us and I was out collecting fossils with my daughter.  You can't beat that for quality time with your family.  My wife, however, isn't into it.  She was hanging out at the Hotel pool worshipping the sun.

Here's a worn "meg" tooth that my daughter found, which
brought a smile to her face! 
Basically, the fossils that you'll find here from the Pliocene can be in really good shape, or very worn.  The great white shark teeth are the prize and probably the most sought after fossils here, but you have a chance to find some big megalodon teeth.  Many are very worn, but I know some folks that have found some very nice ones too.  In addition to the great whites and megs, you will find mako teeth, bull shark teeth, and once in a while you'll find the modern tiger shark, Galeocerdo curvier.  There are plenty of fossiled bone fragments from whales, porpoises, and other marine mammals from that time, and every now and then you'll find a fossilized land mammal tooth.

In addition to fossils, it's quite possible to find Native American artifacts.  On the two fossil forums that I frequent (check out my links), there are folks that have found some very nice artifacts too, including pottery, arrowheads or points, and spear points.  You may also find various other evidence of human activity as I mentioned before including old coins and bottles, but more than likely you'll encounter metal trash and broken glass, so care should be taken when sorting through your sifted material.  Gloves are a good idea, but I'll admit that I didn't have them with me the last time.

This is a whale inner ear bone, or tympanic bulla from GMR
from the Pliocene Yorktown formation.
You may also find fossils from two Cretaceous formations mixed in with the Pliocene material.  Those formations are the Black Creek group, and the Pee Dee formation.  You may encounter fossilized mosasaur teeth, plesiosaur teeth, crocodile teeth, and possibly other marine reptiles from that time, the age of the dinosaurs.  Shark teeth from the Cretaceous mostly include three species of extinct crow sharks, extinct sand tiger sharks, and an extinct goblin shark.  The crow shark species include Squalicorax kaupi, the most common crow shark, the larger Squalicorax pristodontus, and the less common weird looking Squalicorax bassani.  In addition to the teeth, you may find vertebra, bones, scutes, and broken turtle shells from the various marine vertebrates.  Invertebrate fossils include various oyster shells, clams, gastropods, and belemnites.  Personally, I like finding fossils from the Cretaceous because they are not common from my neck of the woods, so it's a treat for me to visit this creek and bring some material from that fascinating time home with me.  Perhaps that's a good reason to use the quarter inch sifter, because most of the teeth from that time are smaller and fall through the half inch mesh.
 
The three crow shark teeth in this picture are from one of
the less common ones, Squalicorax bassani.  I've found one
of these cool teeth in my life, and my daughter finds three
of them on this trip alone!
You may also find other fossils from other formations, perhaps from the Eocene or Miocene, that were most likely reworked, as mentioned earlier.  Some of the shark teeth that you may find include Carcharocles chubutensis, megalodon's direct ancestor, and Eocene ancestors, Carcharocles auriculatus and possibly Otodus obliquus.  Since many of these teeth are extremely worn, it's difficult to identify them because the identifiable characteristics, like cusplets and serrations, are mostly broken or worn away on these teeth.

Within the material that you're sifting, the fossils are found in what is known as "float" deposits.  Basically, these deposits consist of material eroded from the formation itself, and deposited along the stream bottom through time.  In other words, the material is no longer physically connected within the formation. So, it's really technically difficult to determine exactly what formation a particular fossil was from.  Another example of float deposits are beaches that contain fossils, like Myrtle Beach.  We know probably what formation the fossils are from simply because you can compare them to specimens of known fossil species that were discovered directly in the formations.  In many cases, the fossils that you're collecting are unique to a certain formation.

This was my third trip to GMR.  I've seen people post some amazing trip results from this place.  Although I have yet to have a day like that on GMR, each time I go I find something different that I've never found to add to my collection.  It's hard work but well worth it in my opinion.  You'll feel it at the end of the day, but at the same time you'll be satisfied with what you find.

What tools do you need for this type of fossil collecting?  For GMR, obviously this time my daughter didn't need much except her keen eyesight and the ability to bend over, pick up and check out potential fossils all day long.  But, for sifting, you can build a sifter like the one linked above, or fashion one out of a wood frame, and a shovel to fill your sifter with.  During hot weather, wet wading is OK, so wear clothing and shoes that are comfortable but you aren't worried about getting soiled.  I prefer wading boots with felt soles to give me foot protection, ankle support, and traction on potential slippery stream surfaces.  Other things you'd need during hot weather would be plenty of fluids, a back pack to carry your stuff in, a container for your fossils (and perhaps something to protect your better finds from being broken during transport), a change of clothes and a towel for when you're done, and probably most importantly, plenty of bug spray.  For cooler months of the year, it would be advisable to wear waders or hip boots.  Waders tend to give you more flexiblity when navigating through deeper water.

I'm going to finish this post with a statement about some common sense and some pictures from my past trips to show you some of the other fossils that I've discussed earlier in this post.  When working streams like these for fossils, make sure that you're only digging into the float material on the stream bed or gravel bars.  Do not dig into the sides of the streams unless you have specific permission from the land owner to do so.  This causes unnecessary erosion and could result in our privileges being revoked and areas like these posted or such activities prohibited.  Don't think it can happen?  It sure can, as witnessed in Summerville, SC, where it's now illegal to walk streams in the city limit with any kind of tools for digging.  So please, use some common sense to protect our resources and ensure that future generations may enjoy collecting fossils and other artifacts from our local streams.

And for the anglers out there, how's this one?
I had one sift several years ago that resulted in
the catch of a bluegill sunfish!!!!!

Mosasaur tooth from GMR that I found a few years ago.
Crow sharks, Squalicorax pristodontus (left) and Squalicorax bassani.
Cosmopolitodus hastalis, extinct giant mako shark that was
most likely the ancestor to the modern great white shark.

For more info on fossils, and to interact with other fossil collectors, please visit the following links:
http://www.thefossilforum.com/
http://www.blackriverfossils.org/
Make sure that you register, it's worth it!

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