Abstract Detail

Paleobotanical Section

Taylor, David W. [1], Zinniker, David  [2], McCorkle, Erin [3], Hu, Shusheng [4], Barbanti, Silvana M.  [5], Moldowan, J. Michael  [2].

Tracking angiosperm molecular fossils: New results from analysis of basal living angiosperm clades.

A growing number of molecular fossils are common and abundant in many Cretaceous and Tertiary sediments, but rare in older sediments. The observed spatial and temporal distribution of the biomarker oleanane (and the widespread occurrence of functionalized oleanoids in living monocots and eudicots) has led to oleanane’s use as a qualitative indicator of angiosperm input in sediments. Other potential molecules include des-A-oleanane (a putative byproduct of oleanane), and bicadinanes (known from dimerization and diagenesis of sesquiterpenoids in resinites from Dipterocarpaceae). However, interpretations of oleanane occurrence are limited by incomplete taxonomic surveys for natural products in living angiosperms and other seed plants. To examine biomarker distribution at the base of the angiosperm tree, we sample species from the three most basal orders, Amborellales, Nymphaeales and Austrobaileyales, as well as Chloranthales, Magnoliales, Laurales, Piperales, Acorales, Alismatales, Ceratophyllales and Ranunculales. The samples were subjected to hydrous pyrolysis, extracted, hydrogenated using an ionic reduction procedure, and separated into saturate and aromatic fractions. The presence of appropriate functionalized natural products was tested using GCMS and GC-MRM-MS techniques. The procedure was designed to mimic conditions of diagenesis and burial which transforms diverse functionalized natural products into a limited number of identifiable molecular fossils. Oleanoids were found in the most basal orders and a parsimony reconstruction supports the hypothesis that they are ancestral to
angiosperms. The two diagenetic transformation products, oleanane and des-A-oleanane, have similar distributions but des-A-oleanane is more easily measured in plant pyrolysates. This distribution is not surprising as oleanane and des-A-oleanane occurrence have been correlated (correlation coefficient 1.0) in a 100+ oil-sample set derived from source rocks of a wide variety of geologic ages and depositional environments. Lastly, basal angiosperms do not seem to be a direct source for bicadinanes, supporting previous work showing low correlation to oleanane source rock occurrence, and suggesting they are usually the result of diagenesis and restructuring of existing sesquiterpenoid.

Broader Impacts:
This research integrates professor, post-doc and undergraduate researchers.

1 - Indiana University Southeast, Department of Biology, 4201 Grant Line Road, New Albany, IN, 47150
2 - Stanford University, Dept. Geol. Environ. Sci, Stanford, CA, USA
3 - Indiana University Southeast, Biology, 4201 Grant Line Rd., New Albany, IN, 47150, USA
4 - Yale University, Peabody Museum of Natural History, 170 Whitney Ave., New Haven, CT, 06511
5 - IPEX Co., Rio de Janeiro, RJ, Brazil

Keywords:
biogeochemistry
biomarkers
Fossil
angiosperm
evolution.

Presentation Type: Oral Paper:Papers for Sections
Session: 32
Location: 555A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 11:45 AM
Number: 32007
Abstract ID:396