[meteorite-list] Marginally Off-Topic; Impact Fractured Fossils

From: Mike Fiedler <mlfiedler_at_meteoritecentral.com>
Date: Sat, 5 Apr 2014 21:56:58 -0700
Message-ID: <CANPcf8fwWP1OW2uKeAb39+Vju1GyKkQr2BYbRHGFi8o8UEqn1A_at_mail.gmail.com>

I'm intrigued by the physical tell-tales of impact events. Things
like tektites, spherical glass or iron-nickel droplets all have a
certain level of 'intuitive-simplicity'. Shatter-cones seem to
reflect a general direction of energy propagation, with diffraction
and redirection of wave as the advancing pressure encounters
substances of different compressibility and susceptibility to micro
fracture as the compressive and rarefaction regions proceed. (My
presumed understanding may be way off base, but these items at least
seem to make sense.)

Fractured Belemnites really puzzle me. It seems countless numbers of
these skeletal elements from ancient ancestors of today's squids were
lying about when the Ries crater was created.

Is there any discernible relationship between the direction of energy
propagation and the planes of fracture? I have seen numerous examples
of rocky matrix with multiple fractured belemnites embedded, each with
its own set of generally parallel fractures, and no two items sharing
a major horizon for cleavages. This arrangement can be seen in the
current Ebay item # 321365886158.

I have searched the web in vain for any description of the ways in
which Belemnites may have captured and directed the energy, or how the
structure of the belemnite itself would have predisposed it to these
fracture patterns. I have tried stressing in different ways whole
belemnite fossils (admittedly, a few million years of aging different
from the conditions that may have prevailed 'back then'.) Nothing I
can learn of says there is a diagonal structural weakness, yet many
fractured specimens exhibit parallel, but oblique, or diagonal
cleavages.

Can anyone point me to an explanation, on the web, or in a book?

Thanks much!
Received on Sun 06 Apr 2014 12:56:58 AM PDT