Difference between reworked fossil and insitu fossilgeology
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There isn't any difference in morphology, although there could be differences in preservation. In situ fossils would be those that are found in the stratum in which they were originally deposited. Sometimes, by some means or other, fossils can get relocated. For example, a river channel may dig its way into older fossil yielding rock, and that can cause fossils from the banks to fall into a rock stratum that's younger than they are. Or the sea can eat into a cliff and the tide can carry some fossils into new positions. Such natural means of transport are known as reworking, and the fossils thus relocated have been reworked.
This sort of thing has happened at some localities in the Hell Creek Formation of Montana. It so happens thatt some younger, Paleocene fossil localities formed just on top of slightly older ones from the Upper Cretaceous. River channels dating from the Paleocene have, in such cases, ended up with a somewhat mixed fauna of both Paleocene and Upper Cretaceous mammals, among other vertebrates. At one time, that was taken as an indication that those sites might have been transitional in terms of time between the Upper Cretaceous and Paleocene faunas. However, as such localities there only occur in former river channels, reworking is much the stronger explanation. The morphology of the reworked Cretaceous fossils is the same as those at other localities found in situ.
Differences in perservation could arrive as a side-effect of the transportation. Should a playful stream have carried fossils along for a bumpy ride, then they can get rolled, chipped and otherwise bashed about. However, should they just fall down from a river bank and not get transported very far, then that kind of damage needn't arise.
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This sort of thing has happened at some localities in the Hell Creek Formation of Montana. It so happens thatt some younger, Paleocene fossil localities formed just on top of slightly older ones from the Upper Cretaceous. River channels dating from the Paleocene have, in such cases, ended up with a somewhat mixed fauna of both Paleocene and Upper Cretaceous mammals, among other vertebrates. At one time, that was taken as an indication that those sites might have been transitional in terms of time between the Upper Cretaceous and Paleocene faunas. However, as such localities there only occur in former river channels, reworking is much the stronger explanation. The morphology of the reworked Cretaceous fossils is the same as those at other localities found in situ.
Differences in perservation could arrive as a side-effect of the transportation. Should a playful stream have carried fossils along for a bumpy ride, then they can get rolled, chipped and otherwise bashed about. However, should they just fall down from a river bank and not get transported very far, then that kind of damage needn't arise.
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