Investigating the record of Permian climate change from argillaceous sedimentary rocks, Oman

Abstract

A standard method for the analysis of carbon isotope composition of bulk organic matter (ä 13 C bulk ) in palaeoenvironmental and stratigraphic studies of sedimentary basins associated with hydrocarbons is suggested. This method includes the removal of interstitial hydrocarbon within the sediments, which is shown to have a negative effect on ä 13 C. Using the method, a ä 13 C bulk trend (c. À21 to À24‰) was found within the Lower Permian Al Khlata and lower Gharif formations of Thuleilat-16 and -42 well sections, south Oman. Palaeontological and sedimentological evidence indicates considerable palaeoenvironmental change, from a cold climate lowland fern flora and upland primitive conifer flora low in the sequence, to a lowland cycad-like and upland glossopterid or other gymnospermous flora higher in the sequence. The lithologies range from glacial diamictite at the base to calcrete horizons and redbeds at the top. It is therefore likely that the ä 13 C bulk trend is related to palaeoenvironmental change.

Significance of sedimentary organic matter input for shale gas generation potential of Mississippian Mudstones, Widmerpool Gulf, UK

“…Two samples may contain traces of siderite (samples 23 and 25), and another two contain dolomite (samples 33 and 34), neither of which could be removed. Contamination by potential migrated hydrocarbons, which would deplete bulk δ 13 C values (Stephenson et al, 2005), was excluded (see Könitzer et al, 2012) so bitumen was not extracted. For analysis, a measured amount of 5 to 100 mg of each sample was filled into tin capsules, which were subsequently squashed.…”

Stable carbon isotopes as potential sea-level indicators in salt marshes, North Carolina, USA

“…For example, some components may consist of the fraction that is soluble in common organic solvents (lipids, pigments, flavonoids) or the insoluble fraction such as lignin, tannins and structural polysaccharides (Stephenson et al, 2005(Stephenson et al, , 2008. Molecular level studies of lipids and major cell wall polymers (e.g.…”

“…lignin, tannins and structural polysaccharides) may be potential indicators of plant source and vegetation zones (Benner et al, 1991;Herenes, 2001). In particular, lignin is well preserved in salt-marsh sediments (Vane et al, 2003(Vane et al, , 2005(Vane et al, , 2006Lamb et al, 2007). Analytical pyrolysis, tetra alkyl chemolysis, and alkaline CuO oxidation are frequently applied to cleave bonds within the lignin structure and yield monomers that can be separated and identified by gas-chromatography massspectrometry (GC/MS).…”

Lower Permian brachiopods from Oman: their potential as climatic proxies

“…Eutrophic condition at the base of the Saiwan Formation evolved upward into more oligotrophic conditions. Stephenson & Osterloff (2002) and Stephenson et al (2005) studied equivalent beds in the subsurface of South Oman. In this region, the equivalent-aged rocks comprise clastic sandstones of terrestrial origin, suggesting that the Haushi sea did not transgress as far south as South Oman.…”

“…Within the bodies of brackish or salt water, an ephemeral microflora and fauna (indicated by rare acritarchs and microforaminiferal linings) developed. Evidence from the carbon isotope composition of bulk organic material from the Al Khlata and lower Gharif formations show a trend which is thought to reflect postglacial warming, since there is sedimentological and palaeontological evidence of deglaciation in the sequence (Stephenson et al 2005).…”