The OM source parameters of analysed samples were calculated based on distributions and abundances of n-alkanes, isoprenoids, steranes
and terpanes (Fig.
The coal and shale extracts in the Mamu Formation contain significant amounts of diasteranes, which appear to form through the interaction of steranes
with clay mineral surfaces in source rocks (Rubinstein et al, 1975; Sieskind et al, 1979).
The effect of biodegradation on steranes
and terpanes in crude oils".
Above that temperature the steranes
included in the calcitc would decay.
An abundance of C27 steranes
relative to C29 counterparts, indicates the likelihood of an algal based origin with the analysis of the aromatic fraction indicating a very high level of thermal maturity (>1% RO).
Yet the samples also held small quantities of hopanes, a class of organic chemicals produced by cyanobacteria and some other bacteria, as well as steranes
, which are produced only by eukaryotes.
16] bicyclic alkanes extensive removed 6 smaller steranes
removed, larger steranes
heavy altered, 25-norhopanes formed 7 all steranes
removed, 25-norhopanes more heavy abundant 8 hopanes altered very heavy 9 hopanes removed, disteranes altered, severe
JAHNKE: Regarding the timing of the origin of eukaryotes, there is some very excellent evidence in the organic molecular record for steranes
in the 1500 to 1600 million year range.
Furthermore, the degree of isomerization of biological markers, such as steranes
and hopanes, is now widely applied to indicate the maturity of source rocks and petroleum.
A low resolution was obtained from analysis by GC-MS of saturate (terpanes and steranes
, m/z 191,217 and 218); and aromatic fractions (mono and triaromatic steroids, m/z 231 and 253), due to the advanced state in thermal maturity.
Biomarkers for Geologists: A Pratical Guide to the Application of Steranes
and Triterpanes in Petroleum Geology.
Airborne PM was predominantly (> 99% by particle number) in the fine and ultrafine fractions (Figure 2) and contained a large amount of organic carbon and high concentrations of polycyclic aromatic hydrocarbons, nitrates, hopanes, and steranes
, suggesting that much of the PM was combustion derived and related to traffic sources [see Supplemental Material, Table Si (http://dx.