[meteorite-list] Coastal Chevrons and Boulders – Room for Misinterpretation

From: Paul <etchplain_at_meteoritecentral.com>
Date: Fri, 12 Jul 2019 18:00:08 -0500
Message-ID: <6eebd45c-95fd-3f1f-2fd8-bcdb1c468eac_at_att.net>

A paper worth reading is:

Spiske, M., Garcia Garcia, A.M., Tsukamoto, S. and Schmidt, V.,
High???energy inundation events versus long???term coastal
processes???room for misinterpretation. Sedimentology.
https://onlinelibrary.wiley.com/doi/abs/10.1111/sed.12524

Spiske et al. (2019) discuss the controversy concerning the
origin of two coastal features, coastal chevrons (large
parabolic sand bodies) and coastal boulders. Because
of their large clast size, the coastal boulders are often
used as indicators of prehistoric tsunamis and storms.
Coastal chevrons are often attributed to either (mega???)
tsunami, possibly caused by oceanic impacts, or to
MIS 5 "superstorms" as in case of the Bahamas and
Bermuda.

What I have not seen anyone discuss in the controversy
about coastal chevrons and coastal boulders is what is
known in geomorphology as the principle of equifinality,
in which different starting points for a given geomorphic
system results in similar end states. In simpler English,
equifinality postulates that similar landforms might arise
 ??as a result of quite different sets of geologic and / or
geomorphic processes and histories. According to this
principle, a person might suggest that it is possible
coastal chevrons and coastal boulders can be produced
by both high???energy inundation events versus long???term
coastal processes. As a result, such features are not an
unique indicator of either a specific event or process.
Even in case of high???energy inundation events (tsunamis,
"superstorms," and storms), it might be very difficult
to distinguish the specific type of event that created
a specific set of coastal chevrons and coastal boulders.

Some equifinality papers

Beven, K., 1996. 12 Equifinality and Uncertainty in
Geomorphological Modelling. In The Scientific Nature
of Geomorphology: Proceedings of the 27th Binghamton
Symposium in Geomorphology, Held 27-29 September,
1996 (Vol. 27, p. 289). John Wiley & Sons.

Beven, K., 2006. A manifesto for the equifinality thesis.
Journal of hydrology, 320(1-2), pp.18-36.

Phillips, J., 1997. Simplexity and the reinvention of
equifinality. Geographical Analysis, 29(1), pp.1-15.

A superstorm reference.

Hearty, P.J. and Tormey, B.R., 2017. Sea-level change and
superstorms; geologic evidence from the last interglacial
(MIS 5e) in the Bahamas and Bermuda offers ominous
prospects for a warming Earth. Marine Geology, 390,
pp.347-365

In other news, my family is hunkered down with our natural
gas standby generator on what passes for "high," ground in
Louisiana and prepared for Hurricane Barry. Nothing to do
now but listen to news and read a book and wait for it.

Yours,

Paul H.
Received on Fri 12 Jul 2019 07:00:08 PM PDT