How Did Green Mill Run Become A Fossil Heaven?

[NCdustin]

What is it about the location that makes fossils so easily obtainable. It looks to me like any stream or creek east of it that cuts that deep in the earth would produce fossils. But thats not the case, although I'm sure there are some that do. Can anyone explain?

[THobern]

Not necessarily so; it must also cut through the right type of rock (sedimentary), deposits of the right age, and through areas in which fossils were deposited.

[MikeD]

Perhaps this example will help. Stratigraphy of an area is not necessarily flat (as some diagrams might lead you to believe). On the southeast side of Texas, the geological layers are tilted down toward the Gulf coast. At the coast, the older layers are deep underground. As you move inland (northwest), progressively older layers become exposed on the surface (which you can see on the map below). So what you find in creeks, road cuts, etc., depends on exactly where you are geographically and geologically and as THobern said, "it must also cut through the right type of rock (sedimentary), deposits of the right age, and through areas in which fossils were deposited." In reality, it is not quite as simple as this because of the way layers were deposited, eroded, redeposited, shifted by faults, blah, blah, blah, but it is the basic idea.

map borrowed from TBEG

[THobern]

Yeah, as Mike said, it can get fairly complicated. If I were you, I'd consult a geological map.

[tracer]

fossils are not at all universally distributed throughout a given rock layer. the specific conditions required for them to be preserved can be very localized at times. that is why it's important for you to check all over when you're searching for good locations. if you're off by a short distance, you might miss one of the best places ever to find fossils. some formations are much better than others, so we target those formations, but still, the quality, quantity, and variety of fossils varies very widely. that's why we stop at every roadcut and creek and piece of bare ground we can.

do some googling of how fossils form, and you'll begin to see how the conditions had to be just right in a given place.

[Monkeyfuss]

What is it about the location that makes fossils so easily obtainable. It looks to me like any stream or creek east of it that cuts that deep in the earth would produce fossils. But thats not the case, although I'm sure there are some that do. Can anyone explain?

Who cares! Let's got look whats washed up after the recent showers!!! ;-)

[NCdustin]

Who cares! Let's got look whats washed up after the recent showers!!! ;-)

Ha! I actually plan on going Sunday morning! Not sure if I'm going to enter at Green Springs or Elm St.

[non-remanié]

Along with just the right geologic formations being exposed, stream maturity is quite important. GMR is in an active early stage of stream incision (where long term erosion exceeds sedimentation). The stream is currently experiencing channelization, bed lowering, and widening. Urban runoff is surely the main factor in this, greatly increasing peak flow conditions during storms. The result is continual erosion into the bedrock fossiliferous sediments and the concentration of the denser clasts from them(rocks and fossils) into stream gravels and point bars, while fine sediments are removed downstream into the Tar river drainage. If the stream were in a stage of equilibrium, deposition of sand, silt and organic matter would eventually restabilize the stream bed and banks. As net erosion ceases the stream might meander back and forth across areas where the fossiliferous formations may have already been removed if they were previously exposed to begin with. Sure, many of the streams in eastern NC have probably cut down deep enough to expose fossiliferous sediments at one time or another, but if the bedrock erosion is not very active and maybe you have to dig through 3 feet of sand and mud to get to the gravels where the fossils MAY have accumulated, it will be much more difficult!

What is it about the location that makes fossils so easily obtainable. It looks to me like any stream or creek east of it that cuts that deep in the earth would produce fossils. But thats not the case, although I'm sure there are some that do. Can anyone explain?

[Rsmull]

I have been hunting the GMR for about 15 yrs now. When I first started walking the creek there was 2-3 ft of sand and sediment before you struck the dark clay bottom. When I first started walking the creek I would find nice megs right on top. Now, I have noticed alot of change in the creek. There are areas that are completely devoid of the sandy bottom. I believe the GMR has become so popular and has so many people digging in it that we have really changed geography of the creek. It used to be I could go to an area and dig in the sand about a 6ft diameter and find dozens of shark teeth and fossils. Now the fossils are harder to find and you have to spend more time searching different areas. However, it is still a good creek and every now and then I find some interesting fossils.

[firemanjosh_c]

I'm new to the forum, just learned about it while at Green Mill Run this weekend. (I think that was you RSMull, but not sure). Regardless, I wanted to introduce myself and say that yes, the recent rain has shaken a bunch of stuff loose at GMR, and I had a blast today. No camera, but probably a dozen teeth in the 1-1 1/2 range, plus many smaller ones. Hope to see some of you down there, or somewhere else around ENC.

[NCdustin]

I stopped there Sunday and you could have held a white water rafting event there. I knew there would be some good stuff found the next few days but I can't make it back at the moment.