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fandomhigh2006-01-30 12:53 pm
dr-tommy.livejournal.com) wrote in fandomhigh2006-01-30 12:53 pm
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Paleontology, Jan 30th, Period 7
"Okay, so this week we start learning things in preparation for our excavation field trip." Tommy says, once it's time for class to start.
"The first step when excavating a site is to remove the topsoil. After that, we draw a site plan- which used to be done with the aid of tape measures, but these days it's more common to use something called a 'total station'.
A strategy for sampling the features can then be formulated which may involve total excavation of each feature or only portions. It is normal to excavate the latest features first and the earliest features last. A grid is usually set up, dividing the site into 5m squares to better aid the positioning of the features on the overall site plan.
Small fossils are easily excavated with small hand tools. Large fossils require more effort and bigger tools in order to expose the specimen; these tools include shovels, picks, jack-hammers, or even explosives.
Small and large fossils are excavated differently, but both have to be treated with care to avoid breakage. Before removing a crumbling or fragile fossil, a quick-setting glue can be brushed on to it. Then the fossil can be removed from the surrounding rock.
After being found, a fossil must be carefully freed from the rock where it's been for millions of years without damaging it. First the fossils should be labelled and photographed while still encased in the rock. Its position should be carefully noted on the site plan.
Most of the overlying rock is removed using large tools like picks and shovels, but the 2-3 inches of rock closest to the fossil are removed with smaller hand tools like trowels, hammers, whisks, and dental tools. The exposed fossil is photographed and labeled again. Frequently, only some of the overlying rock is removed at the dig site. The rest of the overburden can be removed later, in the lab.
The fossil must be packed very carefully to be moved to the lab. Small fossils can be packed in boxes or bags. Large fossils can be first wrapped in paper or burlap, with a layer of plaster applied, much like setting a broken bone.
Any questions?" Tommy looked around the class.
"Second order of business today is presentations, as per usual. Any volunteers?" Tommy asks.
"The first step when excavating a site is to remove the topsoil. After that, we draw a site plan- which used to be done with the aid of tape measures, but these days it's more common to use something called a 'total station'.
A strategy for sampling the features can then be formulated which may involve total excavation of each feature or only portions. It is normal to excavate the latest features first and the earliest features last. A grid is usually set up, dividing the site into 5m squares to better aid the positioning of the features on the overall site plan.
Small fossils are easily excavated with small hand tools. Large fossils require more effort and bigger tools in order to expose the specimen; these tools include shovels, picks, jack-hammers, or even explosives.
Small and large fossils are excavated differently, but both have to be treated with care to avoid breakage. Before removing a crumbling or fragile fossil, a quick-setting glue can be brushed on to it. Then the fossil can be removed from the surrounding rock.
After being found, a fossil must be carefully freed from the rock where it's been for millions of years without damaging it. First the fossils should be labelled and photographed while still encased in the rock. Its position should be carefully noted on the site plan.
Most of the overlying rock is removed using large tools like picks and shovels, but the 2-3 inches of rock closest to the fossil are removed with smaller hand tools like trowels, hammers, whisks, and dental tools. The exposed fossil is photographed and labeled again. Frequently, only some of the overlying rock is removed at the dig site. The rest of the overburden can be removed later, in the lab.
The fossil must be packed very carefully to be moved to the lab. Small fossils can be packed in boxes or bags. Large fossils can be first wrapped in paper or burlap, with a layer of plaster applied, much like setting a broken bone.
Any questions?" Tommy looked around the class.
"Second order of business today is presentations, as per usual. Any volunteers?" Tommy asks.