earthworms, armadillos, and arrowheads....

[willybee]

turns out that animals and insects move artifacts around a lot more than i thought possible.

ants can bury stuff by building mound over artifacts, and then they sink into collapsed tunnels. earthworms move stuff underground at measured rates of about an inch a year in some places by building tunnels that collapse. larger animals can even move artifacts UPWARD to the surface.

its called bioturbation-

there are some cool experiments where numbered artifacts were buried in armadillo pens. armadillos were allowed to dig through these buried layers of artifacts. they even chart out where the artifacts ended up after a year.

(see link at bottom of post)


some archy's spent a lot of time coming up with the following animated diagram of bioturbation. click the >animation< tab and then click the >start animation< tab.


https://netfiles.uiuc.edu/jdomier/ww...biomantle.html

awesome animation-excellent work.


not many would actually read these-but i found the stuff below interesting enough.



the text below was written by a man with the curious name of Anile Cook (scientist but not an archy).
_________________________________________________

In 1837, only one year after his famed travels to the Galapagos Islands, Charles Darwin visited an uncle who took him out to his back fields to show him something remarkable.

It was an area where he had spread a layer of limestone that, after 15 years, was now buried under a layer of soil. Then his uncle told him something that, at the time, seemed crazy— he believed this to be the work of earthworms. This fascinating suggestion sparked a curiosity in Darwin that remained with him until his death.

Darwin immediately set about studying the phenomenon and within a few weeks delivered a speech to the Royal Geological Society in which he described the movement of soil by earthworms. When the paper was roundly dismissed, he gave up on his study of worms.

Then, during the last 10 years of his life, he decided to revisit his earlier ideas regarding worms. Aided by his family, he began a series of experiments and the results were compiled into a 326-page book, The Formation of Vegetable Mould Through The Action of Worms, With Observations of Their Habits, published in 1881.

Although the scientific community continued to reject his observations, the book had a huge influence on popular opinion of the slimy invertebrates. At the time, earthworms were thought of as mere garden pests, but now their true importance had been revealed.

This book, which Darwin himself referred to as “a curious little book of small importance” and “a subject that I have perhaps treated in foolish detail,” is now regarded as the seminal study of the process that soil scientists now refer to as bioturbation. Today these findings have great import in the fields of geology, soil science, marine biology and even archeology.

What is bioturbation?

In his book Darwin made observations that earthworms are able to transport matter from the surface to the depths and push soil and fecal castings back to the surface. Although the term wasn’t coined until the 1950’s, what he was seeing was bioturbation-- the mixing and rearranging of soils by biological organisms acting within it. Besides earthworms, many different forces work create bioturbation: plant roots, burrowing animals such as moles and gophers, foraging animals (armadillos, wild hogs), and other insects (ants, beetles, termites) burrowing through the soil. Additionally, physical forces such as fallen trees can powerfully move and mix the soil, as well as cyclical freezing and thawing (cryoturbation) and earthquakes (seismoturbation). Bioturbation refers to the activity that takes place in the biomantle, primarily the topsoil and subsoil layers.

The major ecological effect of bioturbation is the mixing of all the varied aspects of soil: clay, organic matter, metal oxides and adsorbed contaminants, microbes, viruses, cysts, protests, nematodes and eggs.

The importance of earthworm burrowing behavior in soil bioturbation is hard to overstate. Burrowing earthworms counteract compaction, create aggregation with ingestion and glues secreted for building tubes, segregate particles due to digestion, and induce spatial heterogeneity owing to particle selective feeding (Meysman, p.693). They influence porosity, permeability and stimulate microbial activity. Importantly, their deceptively mundane lives result in the creation of vital niche environments that support soil biodiversity.

Even large particles resting on the ground surface “sink” through the soil and come to rest along the rocky substrate. This sinking action of artifacts and large particles (stones) is thought to be due to the random collapsing and rebuilding of burrows through time: as small mammals are capable of moving larger stones and objects, earthworms are not.

Ecosystem engineers

In the 1990s a system classifying soil fauna according to their function and affect on the soil became popular. Earthworms were placed in the class of “ecosystem engineers,” which is defined as organisms that create, modify and maintain habitats. In the biomantle, ecosystem engineers are important in the regulation of soils properties and processes, the processing of organic matter, and nutrient cycling and soil biological activity.

Earthworms munch their way through the soil, building burrows. They come out of their holes at night, grab tasty bits of organic matter and pull it underneath into the burrow, digesting it and excreting the very nutritious castings. Burrows are created and collapse and recreated. Castings are pushed out on to the surface creating little mounds. The surface doesn’t get higher due to the collapsing of tunnels underneath.

They move the soil about, not really adding or taking away. During warm months there is a flurry of activity. As temp cools, activity slows down, worms burrow deep to avoid freeze, even burrowing around the rocks in the aggregate below.

All this feeding and burrowing of the earthworms effect soil structure and hydrological processes on the scale of meters. Soil and nutrient movement from bottom to top, and then down again increases nutrient recycling and integration of organic matter.

Bioturbation changes the soil over long periods of time. In his book, Darwin relates how he covered a patch of a nearby field with broken chalk and 30 years later he went back and found that the chalk had been buried in a layer of castings and soil. He was able to measure the depth at 8 inches, which turns out to be a rate of burial of 2 inches per year.

Darwin started worm gardens in which he placed stones on the surface in order to monitor the rate of sink. He died before the experiments were completed but his son was able to record the observations and found that stones sank at a rate of 9 inches over a period of 10 years.

Rate of soil movement depends on number and species of worms, weather and other actors. In the American Midwest, artifacts 5,000 years old have been found buried 30 centimeters deep. In England, Darwin recorded 2,000 year-old Roman ruins that were buried completely. On the other hand, some sites in the Ozarks are not buried after even 10,000 years.

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i read some interesting archaeology papers in researching bioturbation.

this first one is about the ROLE OF ARMADILLOS in movement of archaeological materials! its good information and more interesting than most archaeological papers i read.


http://infoscopio.files.wordpress.com/2008/10/tatu.pdf


this next paper by a girl archy is good also. go down to the bottom for discussion and conclusions for the meat of this paper.


http://alliance.la.asu.edu/rockart/scans/Balek.pdf


willy

[dogteam]

Very interesting!
I know that out of curiousity I've placed objects on ant hills and have seen that by the following day they're gone, buried...
Heard of some cases of the opposite, too, where digging animals have bought artifacts back up and they're found perched on their burrow mound...

[Palmwood]

Good info Willybee.
There are some other forces at work over time that allow or force rocks to move deeper into the soil. I think simple expansion and contraction that happens from moisture content and temperature changes will allow rocks to sink. Even if it is only one millimeter per year that adds up after thousands of years. Papers have been published about the effects of earthquakes also. It only takes a few events over a few thousand years to shuffle the ground and create a size sorting.

And floodplain level rocks are under the influence of river sedimentation.
There was an interesting article in National Geographic about 20 years ago describing the discovery and excavation of the steamboat Arabia that sank on the Missouri River in 1856. It was found 45 feet below the surface.

And then you have another condition in bluff shelters where the ceiling will sluff off over time and bury anything below along with all the other influences. You always hear about prybars and jacks being found in shelters where point hunters will lift slabs to get to the older points like Dalton.

[jbridered]

Good info! I found one of my best points thanks to an armadillo.

[MO816]

Thanks willy for the info! I didn't know that about the worms but yea bioturbation is everywhere.
Palmwood that boat is downtown in KC and I would visit it if u ever got the chance. Everyone from local school districts visits the museum and its cool.