Re: Widespread depositional systems (was re: inference)

Arthur V. Chadwick (
Mon, 17 Nov 1997 23:09:25 -0800

>Each age had a dominant to predominant type of deposition. There is the
>widespread quartzites of the lowest Cambrian, the mottled, algal dolomites
>of the lower Ordovician (Beekmantown, Red River etc), the red-beds and salt
>of the Silurian, the black shales of the Devonian, the Crinoidal limestones
>of the Mississipian, the coals and cyclicity of the Pennsylvanian, the
>redbeds and salt of the Permian and Triassic, the oolites of the Jurassic,
>the chalk and greensands of the Cretaceous, and the diatomites of the lower
>Tertiary. Today we have widespread clastic deposition. This is merely a
>continuation of what we have seen in previous geologic periods, only a
>different lithology

You raise an interesting question... Why is the geologic record a singularity?
Why are different periods successively different lithologies (and different
paleocurrent patterns?)