CHAPTER 2 - Death and Fossilization Flashcards
what is Taphonomy
the study of all natural processes that involve an organism after it dies – this includes how it decays, is scavenged by other organisms, becomes fossilized, and erodes.
Shortly after death, decay may cause a body to swell with putrid gasses, and this may cause the carcasses of even large animals to float easily and to be transported by shallow and weakly flowing water. This is Called
bloat-and-float
Plastic deformation occurs when
pressure causes the shape of a buried fossil to be changed such that, even when the pressure is later removed, the fossil does not return to its original shape.
River and stream deposits are called
fluvial deposits
when Animals die and are preserved in lakes it is called
lacustrine deposits
With only a few rare exceptions, all fossils are found in what type of rock
sedimentary rocks
Sedimentary rocks are rocks that form when
mineral and organic particles accumulate and become either cemented or compacted together
igneous rocks form when
magma or lava cools
metamorphic rocks form when
form deep underground when sedimentary or igneous rocks are changed by extreme heat and pressure.
Sedimentology is the science of how
sedimentary rocks form.
Understanding the environmental conditions that led to the formation of the particular sedimentary rocks that contain a fossil can
give important clues about the habitat of the fossil organism.
Sedimentary rocks that form from mud and silt are called __ and __
mudstone AND shale
Sedimentary rocks that form from sand are called
sandstone
Coal is a special kind of sedimentary rock that forms from
the compressed remains of plants, and coal indicates a former swampy environment.
Limestone is formed from
from the accumulation of shells and exoskeletons of small marine invertebrates, and limestone always indicates a former shallow marine environment.
The different ways that fossils form are called
preservation styles
Most dinosaur bone fossils form through either
Permineralization or Replacement
Permineralization occurs when
the empty internal spaces of a bone are filled with minerals. These minerals are first dissolved in water and are then deposited in the empty bone spaces as water soaks through the bone.
Replacement occurs when
the original bone gradually decays and minerals fill the space that the bone once occupied.
Why are the badlands an optimal place for fossil search?
Because to prevent a fossil from eroding away, it must remain buried. However, the burial process must be at least partially reversed in order for the fossil to be near enough to the surface to be found. Dinosaur fossils are, therefore, most commonly found in modern environments where there is considerable recent erosion.
Overburden is the
rock and earth that covers a fossil specimen and that must be removed before the full extent of the specimen can be judged. Overburden removal usually involves large indelicate tools like shovels, pickaxes, and occasionally even jackhammers and bulldozers.
Disarticulation of a skeleton may occur as
carnivores eat the carcass, or because the specimen was transported by water.
long bones (like the femur or humerus) that are aligned in the same direction indicate that
the bones were transported by water, and tell us the direction the water was flowing.
The amount of abrasion on the bones can give a relative sense for
how far the bones may have been transported by flowing water.
Stages in the final excavation of a large dinosaur bone step 1
First, the top surface and sides of the fossil are fully unearthed.
Stages in the final excavation of a large dinosaur bone step 2
a protective and cushioning layer of soft and tight-fitting material is added – in this case, moist paper towels.
Stages in the final excavation of a large dinosaur bone step 3
the fossil is covered by strips of burlap saturated with plaster. Once hardened, the protective jacket is complete and the fossil may be safely lifted and carried away.
