ProfessorMarkSephton

Perry RS, Kolb VM, Lynne BY, Sephton MA, Mcloughlin N, Engel MH, Olendzenski L, Brasier M, Staley JTet al., 2005, How desert varnish forms? (art. no. 59060V), Conference on Astrobiology and Planetary Missions, Publisher: The International Society for Optical Engineering, Pages: 1-12

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Sephton MA, Meredith W, Sun CG, Snape CEet al., 2005, Hydropyrolysis of steroids: a preparative step for compound-specific carbon isotope ratio analysis, RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Vol: 19, Pages: 3339-3342, ISSN: 0951-4198

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• Citations: 9

Sephton MA, Looy CV, Visscher H, Brinkhuis H, de Leeuw JWet al., 2005, The combined petrographic and chemical analysis of end-Permian kerogens, 8th International Meeting on Response of the Earth System to Impact Processes (IMPACT), Pages: 467-478

The end of the Permian was marked by one of the greatest mass extinctions of all time. A valuable record of life and death during this event is contained within sedimentary organic matter. The stable isotopic, molecular and morphological information contained within remains of end-Permian organisms represent an important resource for scientists attempting to produce paleoenvironment reconstructions. Most meaningful data derive from multidisciplinary analyses of the same samples. In these circumstances it is desirable that sample preparation for one approach does not hinder subsequent analysis by another. To ensure compatibility of sample processing procedures the petrographic and chemical consequences of two common kerogen preparation steps, demineralization and screening (sieving), were simultaneously monitored using transmitted light microscopy and flash pyrolysis. Two end-Permian sediments, whose organic content was predominated by land-plant debris, were chosen for this purpose. A limestone was used to assess the problem of fluoride production when dematerializing carbonates and a marl was used to investigate the possibility of introducing a sampling bias following kerogen screening. Flash pyrolysis results of demineralization residues indicate that neoformed fluorides can be effectively removed by repeated treatments with excess concentrated HCl. Flash pyrolysis of screened size fractions (< 10 mu m, 10-18 mu m, 18-30 mu m, 30-125 mu m, 125-250 mu m, > 250 mu m) suggest that, for the end-Permian kerogen used, the various fractions are qualitatively representative of the unscreened kerogen. In a paleoenvironmental context, the homogeneity of the land plant derived kerogen reflects a period of organic accumulation on land followed by rapid deposition and burial in a marine setting. These findings constitute a step forward in the quest for parity between petrographic and chemical analyses of the same kerogen samples.

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Watson JS, Sephton MA, Looy CV, Gilmour Let al., 2005, Oxygen-containing aromatic compounds in a Late Permian sediment, ORGANIC GEOCHEMISTRY, Vol: 36, Pages: 371-384, ISSN: 0146-6380

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• Citations: 26

Koeberl C, Farley KA, Peucker-Ehrenbrink B, Sephton MAet al., 2004, Geochemistry of the end-Permian extinction event in Austria and Italy: No evidence for an extraterrestrial component, GEOLOGY, Vol: 32, Pages: 1053-1056, ISSN: 0091-7613

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• Citations: 64

Sephton MA, James RH, Bland PA, 2004, Lithium isotope analyses of inorganic constituents from the Murchison meteorite, ASTROPHYSICAL JOURNAL, Vol: 612, Pages: 588-591, ISSN: 0004-637X

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• Citations: 14

Visscher H, Looy CV, Collinson ME, Brinkhuis H, Cittert JHAVKV, Kürschner WM, Sephton MAet al., 2004, Environmental mutagenesis during the end-Permian ecological crisis, PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 101, Pages: 12952-12956, ISSN: 0027-8424

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• Citations: 194

Martins Z, Botta O, Sephton MA, Ehrenfreund Pet al., 2004, Purines and pyrimidines in carbonaceous chondrites: A re-analysis, ISSN: 1086-9379

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Sephton MA, Bland PA, Pillinger CT, Gilmour Iet al., 2004, The preservation state of organic matter in meteorites from Antarctica, METEORITICS & PLANETARY SCIENCE, Vol: 39, Pages: 747-754, ISSN: 1086-9379

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• Citations: 30

Sephton MA, 2004, Organic matter in ancient meteorites, ASTRONOMY & GEOPHYSICS, Vol: 45, Pages: 8-14, ISSN: 1366-8781

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• Citations: 21

Sephton MA, Love GD, Watson JS, Verchovsky AB, Wright IP, Snape CE, Gilmour Iet al., 2004, Hydropyrolysis of insoluble carbonaceous matter in the Murchison meteorite: New insights into its macromolecular structure, GEOCHIMICA ET COSMOCHIMICA ACTA, Vol: 68, Pages: 1385-1393, ISSN: 0016-7037

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• Citations: 103

Butterworth AL, Aballain O, Chappellaz J, Sephton MAet al., 2004, Combined element (H and C) stable isotope ratios of methane in carbonaceous chondrites, MON NOT R ASTRON SOC, Vol: 347, Pages: 807-812, ISSN: 0035-8711

We have performed the first ever combined-element stable isotopic measurements of extraterrestrial molecules. Methane from two carbonaceous chondrites, Murchison and Cold Bokkeveld, was measured for its hydrogen and carbon isotopic compositions. The combined isotopic composition of meteoritic methane reveals information about the indigenous nature of volatile aliphatic organic matter in meteorites and its probable extraterrestrial source environment. Deuterium enrichments relative to the solar nebula 4.6 Gyr ago reflect a contribution from low-temperature chemical reactions in interstellar space. Similar carbon but different hydrogen isotopic compositions for methane in the two meteorite samples probably represent comparable primary origins but varying levels of secondary processing and exchange with isotopically light hydrogen. Our high precision laboratory-obtained measurements provide valuable reference points for observational spectroscopists undertaking astronomical investigations of the stable isotopic composition of extraterrestrial methane.

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Sephton MA, Verchovksy AB, Wright IP, 2004, Carbon and nitrogen isotope ratios in meteoritic organic matter; indicators of alteration processes on the parent asteroid, INT J ASTROBIOL, Vol: 3, Pages: 221-228, ISSN: 1473-5504

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Gilmour I, Sephton MA, 2004, An introduction to astrobiology, Cambridge, Publisher: Cambridge University Press, ISBN: 9780521837361

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Sephton MA, 2004, Origin of Life, An introduction to astrobiology, Editors: Gilmour, Sephton, Cambridge, Publisher: Cambridge University Press, Pages: 1-41, ISBN: 9780521837361

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Butterworth AL, Aballain A, Chappellaz J, Sephton MAet al., 2004, Combined element (H and C) stable isotope ratios of methane in carbonaceous chondrites, MON NOT R ASTRON SOC, Vol: 347, Pages: 807-812, ISSN: 0035-8711

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Pearson VK, Kearsley AT, Sephton MA, 2004, The in-situ detection of organic material in extraterrestrial samples, MICROS ANAL, Pages: 5-10, ISSN: 0958-1952

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Watson JS, Pearson VK, Sephton MA, Gilmour Iet al., 2004, Molecular, isotopic and in-situ analytical approaches to the study of meteoritic organic material, International Journal of Astrobiology, Vol: 3, Pages: 107-116, ISSN: 1473-5504

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Sephton MA, 2004, Compound specific isotope analysis of the organic constituents in meteorites, Handbook of stable isotope analytical techniques, Editors: de Groot, London, Publisher: Elsevier, Pages: 229-236, ISBN: 9780444511140

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Sephton MA, Verchovsky AB, Bland PA, Gilmour I, Grady MM, Wright IPet al., 2003, Investigating the variations in carbon and nitrogen isotopes in carbonaceous chondrites, GEOCHIMICA ET COSMOCHIMICA ACTA, Vol: 67, Pages: 2093-2108, ISSN: 0016-7037

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• Citations: 118

Wignall PB, Zonneveld JP, Sephton MA, 2003, Carbon and nitrogen isotope disturbances and an end-Norian (Late Triassic) extinction event : comment and reply, GEOLOGY, Vol: 7, Pages: e25-e25, ISSN: 0091-7613

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Watson JS, Pearson VK, Gilmour I, Sephton MAet al., 2003, Contamination by sesquiterpenoid derivatives in the Orgueil carbonaceous chondrite, ORGANIC GEOCHEMISTRY, Vol: 34, Pages: 37-47, ISSN: 0146-6380

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• Citations: 16

Sephton MA, Amor K, Franchi IA, Wignall PB, Newton R, Zonneveld JPet al., 2002, Carbon and nitrogen isotope disturbances and an end-Norian (Late Triassic) extinction event, GEOLOGY, Vol: 30, Pages: 1119-1122, ISSN: 0091-7613

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• Citations: 69

Pearson VK, Sephton MA, Kearsley AT, Bland PA, Franchi IA, Gilmour Iet al., 2002, Clay mineral-organic matter relationships in the early solar system, METEORITICS & PLANETARY SCIENCE, Vol: 37, Pages: 1829-1833, ISSN: 1086-9379

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• Citations: 108

Verchovsky AB, Sephton MA, Wright IP, Pillinger CTet al., 2002, Separation of planetary noble gas carrier from bulk carbon in enstatite chondrites during stepped combustion, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 199, Pages: 243-255, ISSN: 0012-821X

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• Citations: 51

Sephton MA, Wright IP, Gilmour I, de Leeuw JW, Grady MM, Pillinger CTet al., 2002, High molecular weight organic matter in martian meteorites, PLANETARY AND SPACE SCIENCE, Vol: 50, Pages: 711-716, ISSN: 0032-0633

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• Citations: 61

Sephton MA, 2002, Organic compounds in carbonaceous meteorites, NATURAL PRODUCT REPORTS, Vol: 19, Pages: 292-311, ISSN: 0265-0568

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• Citations: 520

Sephton MA, Looy CV, Veefkind RJ, Brinkhuis H, De Leeuw JW, Visscher Het al., 2002, Synchronous record of delta C-13 shifts in the oceans and atmosphere at the end of the Permian, International Interdisciplinary Conference on Catastrophic Events and Mass Extinctions - Impacts and Beyond, Pages: 455-462

In conjunction with the profound ecologic crisis at the end of the Permian, the most conspicuous geochemical event is the worldwide negative shift in the carbon isotopic composition (delta(13)C) of both carbonates and sedimentary organic matter. Comparative carbon isotopic analyses of carbonates and the molecular fossils of land plant leaf cuticles from a marine Permian-Triassic transition section in the southern Alps, northeastern Italy, substantiates the concept of synchronous disturbances in oceanic and atmospheric chemistry and, therefore, verifies the primary nature of the end-Permian delta(13)C disturbance. The delta(13)C excursion appears to be a consequence of the ecological crisis, and the global reservoir of soil organic matter may be the only plausible source of C-13-depleted carbon.

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Sephton MA, Veefkind RJ, Looy CV, Visscher H, Brinkhuis H, de Leeuw JWet al., 2002, Lateral variations in end-Permian organic matter in northern Italy, 3rd Workshop of the European-Science-Foundation IMPACT Programme, Publisher: SPRINGER-VERLAG BERLIN, Pages: 11-24

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• Citations: 9

Sephton MA, Smith S, 2002, Landforms and cycles, London, Publisher: Open University Press, ISBN: 9780749252076

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