>Some of the most amazing items are contained in the periodicities and
>thickness ratios of tidal rhythmites. One can determine the length of the
>year, the period of the moon's orbit (and thus its distance) the rate of
>the earth's rotation etc. This can all be accomplished from tidal
>rhythmites today.
I have on my desk a chunk of a Pennsylvanian 'rythmite' from a classical
locality in Michigan. Only problem is there is a vertical Neuropteran
frond that crosses two complete sets of so-called tidal cycles. Either
there is some other explanation for the accumulation of tidal rhythmites or
the delicate lace-like frond remained intact and extended vertically from
the sedimentary surface (perpendicular to bedding) while the tidal cycle
sediments accumulated around it and eventually buried it after two months.
Art
http://biology.swau.edu