Chert/Flint Artifacts Found in Limestone-How is this possible??
Ok-I need additional help as I am utterly confused. I have been walking through a local forest and in a few areas, the trail is coated with CA-6 limestone. In many areas, the trail appears to be asphalt and in other dirt. I am attaching a picture I found on the web that closely resembles my area-however the picture has a lot more stone than mine.
Over the last 3 weeks-I have found 22 artifacts ranging from scrapers, a knife, reduction flake and a ton of utilized flakes. These are made of chert and flint. I am attaching some pictures of these finds. I had these looked at in person-they are hand worked.
I need to mention that where these were found-indians lived for hundreds of years-left in in about 1836.
What I don't understand is that the artifacts are embedded only with the limestone-nowhere else. The limestone was quarried from several areas-however it is unknown where. The pieces I found are chert and a real nice piece if flint-turns out to be a reduced flake. Real pretty blue/gray piece (picture attached as well).
I am stumped-can limestone from a quarry contain artifacts like these? Many are in nice condition and really look out of place. Or could these be from the area that are by chance surfaced with the limestone? Of the entire 3 mile trail, only 2 areas contained artifacts-the rest were simply limestone and nothing else.
Lastly-I am really trying to figure out how old these could be and I am coming to a road block here as well.
Any ideas/comments will be GREATLY appreciated!
11-20-2012 04:05 PM
Let’s start with how quickly does limestone form (ie how young could it be)? Surprisingly, the answer is anything from a few hours upwards! That would only happen in mineral-rich hot springs (as flowstone) or on small scale where water is percolating through a lime-rich cave (as speleothems). In an open environment, grains that are packed together by pressure after being buried could consolidate to limestone in a few decades but they wouldn’t form something hard enough to be called rock unless there was something to cement the grains together. That would only happen quickly if they were deposited in lime-rich water. Otherwise, it normally takes many thousands of years.
The youngest true bedrock limestones are typically coralline and associated with the last inter-glacial period – so a tertiary age of around 1.6 million years (and not normally younger than a million years) would be typical for many locations. At these kinds of ages you couldn’t find artifacts actually “in” the limestone on the American continents although it could theoretically be possible in Africa and some parts of Asia or Europe.
Bedrock limestone which contains chert (as nodules or seams) would normally be much older - many millions of years – and so would certainly not contain artifacts at any location. It would not be unusual for a limestone quarry floor to be littered with chert spalls, waste flakes or even artifacts if the site was mined for chert by Native Americans.
I would be extremely wary of identifying such items in CA-6 “roadmix” limestone aggregate quarried in modern times, since it has been through a crusher and a fair amount of chert may have gone through as well. I would envisage a lot of jagged, flaked and apparently edge-worked “pseudo-artifacts” coming out the other end.
So in your estimation, these could be much older than a few thousand years? There is a limestone quarry near where these were found but wasn't inhabited until 10000 years ago or so. I am not familiar with limestone road mix so based on what you see, these are not modern?
Tribal Council Member
Originally Posted by painshill
I have seen this locally in oil and gas roads and well platforms. Crushed limestone is used from central TX or eastern OK that contains chips flakes and chunks of high grade rootbeer flint that resulted from nodules being crushed with the limestone.
Roger, can you explain the geologic process that forms these chert and flint nodules in limestone and chalk, and why they can be found in certain horizons within the limestone bed?
Does the insitu picture show the limestone you are writing about? If so, I don't see quarried & crushed limestone, I see gravel. (3rd picture from the bottom.)
Gravel can be quarried in a gravel pit, but often municipalities would just scoop it out of local rivers and gravel bars. It can also be the sift left over from sand pits. It would be expected to see relics (of all ages) in river/creek gravel and sand pits.
If it's truly crushed limestone, then I'd say the chances of them being relics is ZERO %. Crushed nodules of flint will break and fracture along sharp edges, and people walking or driving over them can "flake" those edges into worked looking edges.
The in situ picture was found next to a limestone part of the path-on top of what you see in the picture. What is odd is that the limestone appears to have been put down years ago. Lots of it is gone, leaving behing dirt and pebbles/gravel.
I found a really nice scraper next to the limestone, but not in it. Some pieces we're on top of the limestone-but most were near the bottom of it- near the bottom layer. Many parts of the path is just dirt. Any area outside of the path is also just dirt/sand. Not a single rock to be found so it looks like the trail rocks were brought in. Would it be possible that the artifacts I find are just from the area and surfacing? However they are all limited to a 100 foot stretch of path stone/dirt. There is nothing anywhere else in the 2-3 mile trail. Many of the newer trails has limestone that is crushed very well -just a bit larger than sand. Perhaps this was quarried years ago but they are true artifacts-many have real nice edge work and glossy surfaces due to scraping work.
Joshuarem is spot-on with his assessment; the limestone in the picture is gravel. It appears that this trail is near a stream; if that is the case the gravel might be on a high terrace and not hauled in. Since the limestone is gravel and not crushed stone the flakes of flint you have are almost certainly made by NA's as waste from reduction or casual/expedient flake tools. You should find some better artifacts either in this area or wherever the material originated from.
I’m not sure the questions make complete sense in the context of my response. To put it more simply:
Originally Posted by arrowhead1776
- Limestone can be recent, but if it contains chert deposits, it will be ancient (millions of years). There will be no artefacts in it… just potentially useable chunks of raw material.
- Native Americans - at any time - could have quarried the limestone to extract the chert as a material for artefact production – whether they were inhabiting the area or just visiting from a place where such material was not available.
- If such activity took place, chert lithic scatter on the floor of the quarry would be expected, and there might also be artefacts.
- Anyone quarrying that material, scooping it up from the quarry floor and putting it through a crusher to create CA-6 in modern times for roads and paths would not only likely destroy any artefacts, but also create “pseudo-artefacts” in large numbers that would be difficult to distinguish from true debitage and flake-tools.
- The use of this kind of material for roads dates from around 1820 and Eli Whitney Blake unveiled the first commercial crusher in 1857 when he was tasked with improving the city streets in Connecticut.
- If that is the kind of material on your path then I would doubt that you’re gonna be seeing any artefacts in it. If you are finding artefacts (doubtful) then they didn’t originate from that source. As Joshua says, you might well find them in alluvial gravels.
Originally Posted by Palmwood
Both chert and flint are microcrystalline silica. On this side of the pond we usually reserve the term “flint” for material from chalk deposits and chert for material from limestone deposits, but they are essentially formed in the same way. Chalk may become limestone with a bit of something approaching metamorphosis, but both are still very much sedimentary rocks. You could think of some cherts as partly metamorphosed flints.
Most chalk was formed principally from tiny planktonic sea-critters called Coccolithophores (a form of green algae) which had tiny “plates” of calcium carbonate and this accumulated in sea-bed layers over millions of years. Limestone more usually formed from the degraded calcium carbonate skeletons of corals and the tiny “shells” of Foraminifera (amoeboid protists). In both cases, that was also supplemented by partly decomposed mollucs and other organisms with a calcium carbonate structure. Within those layers there were also the skeletal remnants of vast numbers of simple sponges, composed of tiny needle-like spicules of silica.
When the sediments accumulated sufficient depth and became buried by enough subsequent material to create high pressures (and also high temperatures) the calcium carbonate compacted to chalk (or eventually limestone) and the silica dissolved. The dissolved gelatinous silica solution accumulated by replacement, filling any cavities in the chalk – such as burrows made by crustacea or burrowing marine organisms and voids left behind by decaying organic debris. Later, it also seeped into the zones representing the major bedding planes of the chalk arising from climatic change and geologic history.
A subsequent change in chemical conditions was the trigger for the silica to recrystallize in solid form and that’s what ultimately became flint (or chert). Those chemical changes may have arisen from the decomposition of organic material and/or diagenesis in the rock itself. Frequently some organic debris acted as a nucleus and the silica accumulated gradually by accretion. Flints sometimes contain a white or cream coloured soft powdery chalk deposit known as "flint meal" and this frequently contains remnant Echinoids and other marine fossils.
The redeposition is seen mostly in the bedding plane layers of chalk or limestone. When it’s a continuous layer we normally call it “tabular” and when it’s in the form of scattered nodules or lenses we call it “nodular” but those nodules still normally represent a bedding plane and are not as randomly distributed as may appear to be the case.
The preservation of uncompressed fossils such as Echinoids and Ammonites in flint indicates that the replacement commenced early in the lithification of the chalk. The presence of flint sheets along joints and faults shows that the quartz remained mobile and recrystallised during subsequent burial, folding and faulting. Flint or chert beds (whether tabular or nodular) closely parallel the bedding planes in the chalk or limestone respectively.
Last edited by painshill; 11-21-2012 at 09:27 AM.
Roger (in the UK)
The area where I took the in situ pictures were up on a very high part of the trail-right next to the river-probably the closest part. There were a lot of other rocks off the trail-cobblestone and such-In this same area. This is really the only area that artifacts were found. Are these gravel stones natural or would they be brought in as well?