Geological evolution of the tethys belt from the atlantic to the pamirs since the LIAS

Dolomite: occurrence, evolution and economically important associations

Products and distinguishing criteria of bacterial and thermochemical sulfate reduction

A detailed carbon- and oxygen-isotope stratigraphy has been generated from Upper Cretaceous coastal Chalk sections in southern England (East Kent; Culver Cliff, Isle of Wight; Eastbourne and Seaford Head, Sussex; Norfolk Coast) and the British Geological Survey (BGS) Trunch borehole, Norfolk. Data are also presented from a section through the Scaglia facies exposed near Gubbio, Italian Apennines. Wherever possible the sampling interval has been one metre or less. Both the Chalk and Scaglia carbon-isotopic curves show minor positive excursions in the mid-Cenomanian, mid- and high Turonian, basal Coniacian and highest Santonian-lowest Campanian; there is a negative excursion high in the Campanian in Chalk sections that span that interval. The well-documented Cenomanian-Turonian boundary 'spike' is also well displayed, as is a broad positive excursion centred on the upper Coniacian. A number of these positive excursions correlate with records of organic-carbon-rich deposition in the Atlantic Ocean and elsewhere. The remarkable similarity in the carbon-isotope curves from England and Italy enables cross-referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the Turonian, Coniacian and Santonian stages. The oxygen-isotope values of the various Chalk sections, although showing different absolute values that are presumably diagenesis-dependent, show nonetheless a consistent trend. The East Kent section, which is very poorly lithified, indicates a warming up to the Cenomanian-Turonian boundary interval, then cooling thereafter. Regional organic-carbon burial, documented for this period, is credited with causing drawdown of CO2 and initiating climatic deterioration (inverse greenhouse effect). Data from other parts of the world are consistent with the hypothesis that the Cenomanian-Turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth.

/pdf/carbon-and-oxygen-isotope-stratigraphy-of-the-english-chalk-2soto6wbc9.pdf

Carbon- and oxygen-isotope stratigraphy of the English Chalk and Italian Scaglia and its palaeoclimatic significance

http://www.vliz.be/imisdocs/publications/ocrd/261786.pdf

Contourites and associated sediments controlled by deep-water circulation processes: State-of-the-art and future considerations

Organic-rich Upper Cretaceous sequences in Israel were deposited in an extensive, highly productive upwelling-linked system which prevailed along the southern Tethys margin, and lasted for ∼19 m.y. (Santonian to late Maastrichtian). An understanding of the spatial and temporal characteristics of this system was gained through detailed paleontological and geochemical analyses of subsurface sequences in two basins in Israel, representing an outer (Shefela) and an inner (Zin) facies belt. The nature of the upwelling system, and its effect on the sedimentary record, is related to two basic environmental parameters, namely paleoproductivity intensity and oxygen levels at the bottom. The assessment of these parameters and their interrelationship has been performed through the development of paleontological (foraminiferal) criteria, which are independent of the organic matter content. Following the establishment of these criteria, it is concluded that the productivity reached its maximum intensity during the late Campanian, which was also the time of most notable differentiation between the center of the upwelling system in the inner belt and the less intense conditions in the outer basin. This distribution is expressed in varied lithology (organic-rich carbonates, phosphorites, and siliceous rocks) at the core of upwelling and a uniform lithology (organic-rich carbonates) at the margin of this system. The uniform lithology of the Maastrichtian in both basins, composed of organic-rich carbonates, is ascribed to a gradual weakening of productivity. The bottom conditions in the inner belt during the late Campanian (the time of maximum surface productivity) were near anoxic, changing to more aerated (dysaerobic) conditions during the early Maastrichtian. In the outer belt a more aerated bottom (dysaerobic) prevailed throughout the late Campanian to late Maastrichtian. The elevated organic matter content in both basins reflects the overall environment of high productivity; its actual variations, however, seem to be unrelated to changes in surface productivity and bottom oxygen levels.

Late Cretaceous upwelling system along the Southern Tethys Margin (Israel): Interrelationship between productivity, bottom water environments, and organic matter preservation

Upper Cretaceous organic-rich carbonates in Israel contain benthonic foraminifera and varying amounts of early diagenetic infilling of sparry calcite. The sparry calcite has oxygen-isotope values (down to -9.5‰ PDB) that are significantly lower than those of the coexisting skeletal calcite (averaging -2‰ PDB). Low δ18O values are very common in carbonates that are associated with organic matter. These occurrences are conventionally explained as being due to carbonate formation under conditions of low salinity and/or elevated temperature. On the basis of petrographic data and local geologic evidence, however, none of the conventional explanations can be applied in this case. We advance an alternative model that relates the light oxygen compositions of the diagenetic calcite to depletion of 18O in pore water of normal salinity. The proposed operating mechanism is a direct consequence of organic matter decomposition in the sulfate-reducing zone. Being inherent to reducing marine environments, this model can be applied to many organic-rich rock associations.

Oxygen-isotope composition of diagenetic calcite in organic-rich rocks: Evidence for 18O depletion in marine anaerobic pore water

Dinoflagellate cysts, paleoproductivity and upwelling systems: A Late Cretaceous example from Israel

The Cretaceous (Albian-Turonian) Talme Yafe Formation is a huge prismshaped accumulation (more than 3000 m thick, about 20 km wide, and at least 150 km long) of calcareous detritus at the northwest continental margin of the Arabian Craton (Israel). Its sources of clastic material are biochemical carbonates and skeletal fragments derived from rudistid reefs deposited on the wide epicontinental platform located east of the accumulation site. Transport of the material from the shelf platform over the edge onto the slope was probably done by storms and by tidal and seasonal currents. Downslope movement was by nepheloid layers and by gravity-induced currents (turbidity currents?) whereas contour currents are considered the main dispersing and shaping agent active on the slope proper. No clear-cut evidence indicating turbidites was perceived; however, they would be expected to be found west of the study area, on the abyssal plain where they are usually ponded.

The Cretaceous Talme Yafe Formation: a contour current shaped sedimentary prism of calcareous detritus at the continental margin of the Arabian Craton

Sulfur sinks and organic carbon relationships in Cretaceous organic-rich carbonates; implications for evaluation of oxygen-poor depositional environments

Amos Bein

Papers

Late Cretaceous upwelling system along the Southern Tethys Margin (Israel): Interrelationship between productivity, bottom water environments, and organic matter preservation

Oxygen-isotope composition of diagenetic calcite in organic-rich rocks: Evidence for 18O depletion in marine anaerobic pore water

Dinoflagellate cysts, paleoproductivity and upwelling systems: A Late Cretaceous example from Israel

The Cretaceous Talme Yafe Formation: a contour current shaped sedimentary prism of calcareous detritus at the continental margin of the Arabian Craton

Sulfur sinks and organic carbon relationships in Cretaceous organic-rich carbonates; implications for evaluation of oxygen-poor depositional environments