Since Alvarez et al. (1980) found new evidence for the impact of catastrophic events on earth’s biota, hypothesis and theories explaining the fossil record (re)gained a lot of attention. The extraterrestrial origin of the anomalous iridium concentrations seemed highly controversial at first, but nowadays the Chicxulub ‘accident’ has become the marker for the start/base of the Paleogene. Its pivotal role in the Mesozoic-Cenozoic faunal turnover cannot be refuted (Schulte et al 2010). However, alternative theories remain being published. Of these, the Deccan volcanism with its widespread flood basalts stepped prominently forward as one of the main triggers, especially when trying to explain the gradual diversity decline within the fossil record. The inconsistencies between the proposed theories generally root in too narrowly geographically and geologically spread datasets. This applies to most fossil groups, and especially to the ammonoids (Class Cephalopoda, °Early Devonian – †Late Cretaceous). A compilation of ammonoid occurrences of Late Maastrichtian age published by Kiessling & Claeys (2002) evidenced the lack of a globally well distributed dataset. In this compilation, North Africa was left as a blind spot, while Tunisia had been the centre of the K/Pg mass extinction debate for almost three decades, e.g. with the definition of the GSSP for the base of the Paleogene at El Kef. Both at the GSSP and several other sections in the Tunisian Trough Basin, ammonoids were found within the topmost meters of the Maastrichtian, until very close to the K/Pg boundary level. About 900 uppermost Maastrichtian ammonoids were collected, all from within the last 420.000 years of the Cretaceous. With 22 species on record, belonging to 18 genera and 10 families, and with representatives of each of the four large ammonoid suborders (Phylloceratina, Lytoceratina, Ammonitina and Ancyloceratina), the Tunisian fauna demonstrates that ammonoids were both taxonomically and morphologically diverse until their very end. An updated version of the compilation of latest Maastrichtian ammonoid occurrences documents at least 53 species, 29 genera and 13 families in the ultimate half million year of the Cretaceous, in many more localities and occurring in a wide variety of settings. When the Tunisian ammonoid species richness data are plotted next to all time constraints of the possible causes, the possibility of Deccan flood basalt volcanism negatively influencing ammonoid diversity must be refuted. A major extinction caused by the Chicxulub impact seems the most plausible theory at present. Through inducing a mass kill of the marine plankton, the juvenile ammonoids lost their primary food source leading to their final extinction. Alvarez, L.W., Alvarez, W., Asaro, F., Michel, H.V., 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science, 208, 1095-1108. Kiessling, W., Claeys, P., 2002. A geographic database approach to the KT Boundary. In Buffetaut, E., Koeberl, C. (Eds), Geological and Biological Effects of Impact Events, Springer-Verlag Berlin, 83-140. Schulte, P. & 40 authors, 2010. The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science 327, 1214-1218.
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The river Senne has disappeared from the urban landscape since it was vaulted over in the 19th century, but it played a crucial role in the origin and economic development of the medieval city. In 2019 the remains of the medieval port on the river Senne were brought to light during a large excavation (nearly 6000m2) in the city centre of Brussels. Besides the discovery of a 12th-13th century bank reinforcement and an impressive stone quay wall (mainly 14th-15th century), meters thick excellently preserved waterlogged fluvial deposits from different phases of the river were excavated. These layers, dating between the 10th and 15th century, were extensively sampled for archaeobotanical(macrobotanical remains, pollen and phytoliths), archaeozoological and geoarchaeological studies. In this presentation we will discuss the results of the interdisciplinary study of these numerous samples, with a main focus on the plant remains. The assemblages consist of a mixture of naturally deposited material from the vegetation in the Senne valley and waste dumped in the river. Indeed, as urbanisation intensified, the river became used as an open sewer in which all kinds of refuse were disposed of. Thanks to the interdisciplinary approach and comparison with assemblages from several other sites in Brussels diverse types of waste could be distinguished, including artisanal(e.g. textile working and dyeing), domestic and consumption waste as well as remains of fuel and human and animal excrements. The exceptional diversity of the plant material (>300 taxa) recovered from this fluvial urban context and its perfect preservation offer a unique insight into various aspects of daily life in the city.
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RBINS Staff Publications 2023
