Distinct magnetic properties of marine sediments that record the Palaeocene–Eocene thermal maximum (PETM) have been suggested to be due to a bacterial magnetofossil signal that is linked to enhanced weathering conditions during the PETM. We document the dominance of bacterial magnetite in deep-sea sediments from southern Kerguelen Plateau (Ocean Drilling Program Hole 738C, southern magnetofossi...

This study reconstructs the depositional conditions of ironstones within Chulym-Yenisey basin and assesses iron source. The detrital minerals studied deposits include quartz feldspar. authigenic are goethite, siderite, aragonite, dolomite, calcite, apatite, barite, pyrite. clay components chlorite group (possible chamosite), nontronite, kaolinite, illite, beidellite. Local bacterial sulfate red...

We have studied the magnetic properties of wet and dry late Pleistocene Lake Lisan sediments and the Holocene Dead Sea sediments. Our initial prediction was that the properties of both would be quite similar, because they have similar source and lake conditions, unless diagenetic change had occurred. Rock magnetic and paleomagnetic experiments revealed three stages of magnetization acquisition....

Early diagenetic modification of magnetic properties is an important process in marine sediments, but temporal and spatial variability of diagenetic processes have rarely been reported for recent coastal sediments. The magnetic properties of sediments from the Ria de Vigo (NW Spain) define a marked three-part zonation with depth. The uppermost zone is magnetically dominated by (titano-)magnetit...

Low oxygen isotope values (;216‰, relative to Peedee belemnite standard) obtained from microbial carbonates of the Green River Formation have been interpreted as evidence for snowmelt and high elevations surrounding this early Eocene lake basin. However, low values from microbial precipitates could also represent a diagenetic overprint. We investigate these alternate hypotheses by measuring the...

A suite of 10 di€erent marine evaporitic oil samples from Sergipe-Alagoas Basin, Brazil was studied for its biomarker content, in particular its acidic constituents. The oils showed di€erent molecular distributions and relative abundances of n-alkanoic, isoprenoid and hopanoic acids. The observed di€erences were assigned to the incorporation of immature organic matter in the oils and fractionat...

The diagenetic history of Triassic sandstone from the Beacon Supergroup, Victoria Land, Antarctica, can be divided into three main phases of shallow burial diagenesis, contact diagenesis (temperatures of 200-300oC), and post-contact diagenesis, on the basis of petrographic and geochemical analyses. Shallow burial diagenesis is characterised by minor compaction, K-feldspar alteration to illite, ...

Introduction: Careful characterization of terrestrial concretions and Mars “blueberries” yields important criteria for distinguishing their diagenetic origin in comparison to other models for small, spherical forms. The Jurassic Navajo Sandstone in the Grand Staircase Escalante National Monument (GSENM), southern Utah, contains many hydrous ferric oxide mineralization geometries (HFO phases inc...

To date more than 3650 organohalogen compounds are known to be naturally produced by biogeochemical processes [1]. The current understanding of the abiotic formation of organohalogens during early diagenetic processes in soils and sediments are reviewed. Next to volatile alkyl halides and polar organohalogens such as haloacetates there is evidence that even semivolatile organohalogens (e.g. pol...

Quaternary magnetic studies have provided the conceptual framework to bridge magnetic studies into ancient systems. In cases where environmental materials have been subjected to diagenetic alteration two questions come to mind: 1) What part of the magnetic signal is preserved in the rocks; and 2) can the preserved signal be used to infer/identify magnetic patterns that are characteristic of the...