ALBERT

Description: The spatial and temporal distribution of black shales is related to the development of environments in which they accumulate and to a propitious combination of environmental variables. In recent years, much has been done to improve our understanding of the mechanisms behind the temporal distribution of black shales in the Phanerozoic and of the environmental variables that result in their deposition. However, the interpretation of ancient black shale depositional environments is dominated by an oversimplistic set of three depositional models that do not capture their complexity and dynamics. These three models, the restricted circulation, the (open) ocean oxygen minimum and the continental shelf models, are an oversimplification of the variety of black shale depositional environments that arise and coexist throughout the course of a basin's Wilson Cycle, i.e. the dynamic sequence of events and stages that characterise the evolution of an ocean basin, from the opening continental rift to the closing orogeny. We examine the spatial distribution of black shales in the context of the Wilson Cycle using examples from the Phanerozoic. It is shown that the geographical distribution of environments of black shale deposition and the position of black shales in the basin infill sequence strongly depend on basin evolution, which controls the development of sedimentary environments where black shales may be deposited. The nature of the black shales that are deposited, i.e. lithology and type of organic matter, also depends on basin evolution and palaeogeography. We propose that in studies of black shales more attention should be given to the sedimentary processes that have led to their formation and to the interpretation of their sedimentary environments.

Description: The spatial and temporal distribution of black shales is related to the development of the environments in which they accumulate and to a propitious combination of environmental variables. Whereas much has been done in recent years to improve our understanding of the mechanisms behind the temporal distribution of black shales in the Phanerozoic, the interpretation of the palaeogeographical distribution of black shales is still dominated by an oversimplistic set of three uniformitarian depositional models that do not capture the complexity and dynamics of environments of black shale accumulation. These three models, the restricted circulation, the (open) ocean oxygen minimum and the continental shelf models, are in fact a uniformitarian simplification of the variety of depositional environments that arise and coexist throughout the course of a basin's Wilson Cycle, i.e. the dynamic sequence of events and stages that characterise the evolution of an ocean basin, from the opening continental rift to the closing orogeny. We examine the spatial distribution of black shales in the context of the Wilson Cycle using examples from the Phanerozoic. It is shown that the geographical distribution of black shales, their position in the basin infill sequence and their nature (e.g. type of organic matter, lithology) depend on basin evolution because the latter controls the development of sedimentary environments where black shales may be deposited.

Description: Human CO2 emissions may drive the Earth into a next greenhouse state. They can be mitigated by accelerating weathering of natural rock under the uptake of CO2. We disprove the paradigm that olivine weathering in nature would be a slow process, and show that it is not needed to mill olivine to very fine, 10 μm-size grains in order to arrive at a complete dissolution within 1–2 year. In high-energy shallow marine environments olivine grains and reaction products on the grain surfaces, that otherwise would greatly retard the reaction, are abraded so that the chemical reaction is much accelerated. When kept in motion even large olivine grains rubbing and bumping against each other quickly produce fine clay- and silt-sized olivine particles that show a fast chemical reaction. Spreading of olivine in the world's 2% most energetic shelf seas can compensate a year's global CO2 emissions and counteract ocean acidification against a price well below that of carbon credits.