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Re: Did dinosaurs become oil

>I don't know if this has been mentioned yet, but just because oil is found in,
>say, Miocene sediments it doesn't necessarily mean that the oil itself is of
>Miocene age. Oil will migrate upwards, courtesy of its low density, to become
>trapped below impervious rocks. For example, several large oil fields that are
>tapped from the Jurassic rocks of the North Sea migrated through the rocks
>below. The source is thought to be underlying Carboniferous strata. No 
>dinosaursinvolved in this case.

The story I learned (for the oil in the Monterey), was that the source is
the diatomites that form much of the Monterey.  Trapping layers keep the
oil in or near the source rock.  The diatomites get altered to opal-C/T
and then to chert.  The chert gets highly fractured by tectonic activity
and the oil migrates toward the top of anticlines where the trapping
layers cause reservoirs to form.  Theres not much underlying the Monterey
that's likely to provide the organics for oil.