Marine biodiversity through the Late Cenomanian–Early Turonian: palaeoceanographic controls and sequence stratigraphic biases

Changes in the marine macro- and microfauna, sedimentary geochemistry and surface-water palaeoproductivity through the last 500 000 years of the Cenomanian and first 300 000 years of the Turonian are documented. These are based on the succession at Eastbourne, the thickest and most complete section through the Late Cenomanian and Early Turonian in the Anglo-Paris Basin. Two levels of rapid faunal and geochemical change are identified, one coincident with a significant increase in siliciclastic input at the base of the Plenus Marls Member, and the other with a marked drop in surface water productivity near the top of the same unit. Faunal change is demonstrated to be largely a pattern of immigration-emigration rather than true extinction, and our sequence stratigraphical analysis shows that it was coincident with major sea-lever changes. No evidence is found to support the hypothesis that reduced bottom water oxygenation developed and was responsible for extinctions amongst the benthos in mid-shelf environments. The onset of pure chalk facies is interpreted to mark the breakdown of shelf-break fronts and the spread of oligotrophic oceanic waters over much of the continental shelf, initialed by rising sea-lever. The Cenomanian-Turonian event, far from recording a mass extinction of shelf fauna, is most probably an artifact caused by a significant switch in the nature of the surviving sedimentary record as a result of a major, but perfectly ordinary, oceanographic change

Corporate Governance and Asset Sales: The Effect of Internal and External Control Mechanisms

We investigate firms that sell assets to determine whether corporate governance mechanisms are effective at controlling agency problems. Our evidence shows that these firms have lower managerial ownership and are more likely to make unrelated acquisitions, suggesting weak internal controls. Analysis of insider trading activity shows that, on average, net buying increases before the asset sale and shareholders benefit more when this occurs. Results suggest that how managers reach a given level of ownership provides more information about incentive alignment than just the level of ownership. Our results also highlight the dynamic nature of corporate restructuring as firms acquire and then sell assets. Copyright 2006, The Eastern Finance Association.

The geostationary tropospheric pollution explorer (GeoTROPE) mission: objectives, requirements and mission concept

International audienceOne of the major challenges facing atmospheric sciences is to assess, understand and quantify the impact of natural and an-thropogenic pollution on the quality of life on Earth on a local, regional and continental scale. It has become apparent that pollution originating from local/regional events can have serious effects on the composition of the lower atmosphere on a continental scale. However, to understand the effects of regional pollution on a continental scale there is a requirement to transcend traditional atmospheric spatial and temporal scales and attempt to monitor the entire atmosphere at the same time. In the troposphere the variability of chemical processes, of source strength and the dynamics induce important short term, i.e., sub-hourly, variations and significant horizontal and vertical variability of constituents and geophysical parameters relevant to a range of contemporary issues such as air quality. To study tropospheric composition, it is therefore required to link diurnal with seasonal and annual timescales, as well as local and regional with continental spatial scales, by performing sub-hourly measurements at appropriate horizontal and vertical resolution. Tropospheric observations from low-Earth orbit (LEO) platforms have already demonstrated the potential of detecting constituents relevant for air quality but they are limited, for example by the daily revisit time and local cloud cover statistics. The net result of this is that the troposphere is currently significantly under sampled. Measurements from Geostationary Orbit (GEO) offer the only practical approach to the observation of diurnal variation from space with the pertinent horizontal resolution. The Geostationary Tropospheric Pollution Explorer (GeoTROPE) is an attempt to determine tropospheric constituents with high temporal and spatial resolution. The paper will summarise the needs for geostationary observations of tropospheric composition and will give the mission objectives and the requirements