Study on a fossil nautiloid – surprising insights

Conference contribution
(Abstract of lecture)


Publication Details

Author(s): Seuß B
Publication year: 2012
Language: English


Abstract

The Buckhorn Asphalt Quarry in Oklahoma, USA, yields a Desmoinesian
(Upper Carboniferous) faunal assemblage of outstanding preservation
caused by synsedimentary or contemporary impregnation of sediments and
fauna with hydrocarbons. These hydrocarbons prevented diagenetic
processes to a high degree. The faunal assemblage evolved in a
(sub)tropical shallow marine setting and is, with more that 160 reported
species, one of the most diverse Paleozoic faunas known to date. The
succession is strongly dominated by molluscs, i.e., gastropods,
cephalopods, and bivalves, accompanied by e.g., fusulinids, ostracods,
echinoderms, and bryozoans. The sediments are mainly mixed
siliciclastic-carbonatic and exhibit a single cycle of trans- and
regression, with cephalopod-dominated sediments ("cephalopod coquina")
representing the deepest marine deposits.
Two cephalopod shell remains from the cephalopod coquina were selected
for a detailed isotope study (O, C). One shell remain derives from a so
far unidentified specimen, the second one from an orthoconic nautiloid
which was tentatively assigned to Hebetorthoceras unicamera.
Hebetorthoceras is characterized by preservation of two chambers of the
phragmocone with nicely preserved cameral and siphuncular deposits.
Before samples were prepared the shell remains were intensively studied
by using SEM, EDX, XRD-GADDS, and by a series of thin sections. As
expected, original shell microstructure and material were still
preserved accompanied by parts influenced by diagenetic alteration.
Anyhow, both altered and unaltered shell material and both, cameral
deposits and shells were sampled with high resolution. Primary isotope
signals were used to recalculate local paleotemperatures (unidentified
remain: 28-31°C; Hebetorthoceras: 14-15°C) for the sea covering the area
of the Buckhorn Asphalt Quarry. Samples exhibiting diagenetic
alteration were used to reconstruct diagenetic pathways within the
cephalopod remains. So far so good, if there weren't two distinct oval
marks on the outside of Hebetorthoceras and the rather abnormal
formation and mineralogy of the cameral deposits of this specific
specimen. In a subsequent study both, the oval marks and the cameral
deposits were examined and it turned out, that a) Hebetorthoceras was
victim of a predator, b) this attack was sublethal, c) the specimen was
able to precipitate further cameral deposits after the assault, d) it
precipitated high magnesium-calcitic cameral deposits during lifetime,
and e) the HMC was not a reaction to the heavy injury caused by the
attack, but was even formed before.

Please download the supplementary material for details on this presented
study.


FAU Authors / FAU Editors

Seuß, Barbara Dr.
Lehrstuhl für Paläoumwelt


How to cite

APA:
Seuß, B. (2012). Study on a fossil nautiloid – surprising insights. Paper presentation at Annual Meeting of the Paläontologische Gesellschaft, Berlin.

MLA:
Seuß, Barbara. "Study on a fossil nautiloid – surprising insights." Presented at Annual Meeting of the Paläontologische Gesellschaft, Berlin 2012.

BibTeX: 

Last updated on 2018-06-12 at 09:23