Lauridsen B.W.,Copenhagen University |
Surlyk F.,Copenhagen University |
Bromley R.G.,Geological Museum
Cretaceous Research | Year: 2011
Trace fossils from an upper Maastrichtian cyclic chalk-marl succession, the Rørdal Member, exposed in the Rørdal quarry, Denmark, are analysed in order to test whether the changes in substrate lithology exerted any control over the ichnodiversity, tiering complexity, and density of the infauna. The cyclicity is interpreted as caused by orbital changes within the Milankovitch frequency band. The carbonate content varies between 71 and 82 weight% in the marl and 82-92 weight% in the chalk beds. The material is based on 19 samples collected from six chalk and marl beds. The investigated bedding-normal sample surfaces vary in area between 29 and 155cm2. Eight ichnogenera and two undetermined ichnogenera are recognised. The member is characterised by three ichnofabrics (A, B and C). The ichnofabric analysis is based on texture and internal structure of the sediments resulting from bioturbation. Ichnofabric A is found only in chalk samples and shows a poor preservation of trace fossils, whereas ichnofabric C is found in a few chalk and all marl samples and comprises a very dense, diverse and well preserved ichnofauna representing a high tiering complexity. Ichnofabric B represents an intermediate situation between ichnofabrics A and C and occurs in chalk samples immediately adjacent to marl beds. The observed changes in ichnofabrics between chalk and marl are related to the amount of clay in the samples and the differences in the occurrence of trace fossils are interpreted as due to differences in the visibility of traces between chalk and marl and not due to differences in ecological stress upon the endobenthic community of the two lithologies. The study thus provides an excellent example of how the effect of taphonomic factors may give a misleading and biased impression of apparent differences in the endobenthic community between chalk and marl. © 2011 Elsevier Ltd.
Brooks K.,Geological Museum
Geology Today | Year: 2012
Throughout Earth history there have been many important milestones: e.g. the emergence of life, the rise of oxygen in the atmosphere, snowball Earth events. One of these major events was the emergence of multicellular life, which, as we are all told in Palaeontology lectures, took place in the Cambrian, when a sudden flowering of life forms emerged, including all of the major groups we have today: the 'Cambrian explosion'. Two great questions emerge: what happened before this (a problem which worried Darwin as it seemed to threaten his thesis of steady evolution) and how, in detail did this 'explosion' take place?. © 2012 Blackwell Publishing Ltd, The Geologists' Association & The Geological Society of London.
Bertelli S.,Ornithologie |
Lindow B.E.K.,Geological Museum |
Lindow B.E.K.,University College Dublin |
Dyke G.J.,University College Dublin |
Chiappe L.M.,The Dinosaur Institute
Palaeontology | Year: 2010
We describe a new, exceptionally well-preserved fossil bird recovered from marine deposits of the Early Eocene Fur Formation of Denmark. Morsoravis sedilis gen. et sp. nov. is known by a single specimen that consists of a three-dimensional skull, vertebral column, ribs, pelvis, and left hindlimb and associated parts of the right hindlimb. Comparisons based on overall morphology and particularly characters of the skull, vertebrae and pelvis indicate that the new specimen is morphologically similar to charadriiform birds (the shorebirds and relatives). This similarity is also expressed by a phylogenetic analysis of higher neornithine (modern birds) taxa, which supports a close relationship between the new fossil and modern charadriiforms. The morphology of the hindlimbs, in particular, shows that the new fossil corresponds to a new taxon that is distinguishable from modern charadriiform clades. One interesting aspect of its morphology is the presence of hindlimb specializations that are most commonly found among perching birds - these suggest that ecologically the new Danish fossil bird may have differed from the wading habits typical of most charadriiforms. © The Palaeontological Association.
Jakobsen J.K.,University of Aarhus |
Jakobsen J.K.,University of Iceland |
Tegner C.,University of Aarhus |
Brooks C.K.,Geological Museum |
And 4 more authors.
Contributions to Mineralogy and Petrology | Year: 2010
Troctolite blocks with compositions akin to the Hidden Zone are exposed in a tholeiitic dyke cutting across the Skaergaard intrusion, East Greenland. Plagioclase in these blocks contains finely crystallised melt inclusions that we have homogenised to constrain the parental magma to 47.4-49.0 wt.% SiO 2, 13.4-14.9 wt.% Al2O3 and 10.7-14.1 wt.% FeOT. These compositions are lower in FeOT and higher in SiO2 than previous estimates and have distinct La/SmN and Dy/YbN ratios that link them to the lowermost volcanic succession (Milne Land Formation) of the regional East Greenland flood basalt province. New major- and trace element compositions for the FG-1 dyke swarm, previously taken to represent Skaergaard magmas, overlap with the entire range of the regional flood basalt succession and do not form a coherent suite of Skaergaard like melts. These dykes are therefore re-interpreted as feeder dykes throughout the main phase of flood basalt volcanism.
El-Saadawi W.,Ain Shams University |
M. Kamal-El-Din M.,Ain Shams University |
Attia Y.,Geological Museum |
El-Faramawi M.W.,Ain Shams University
Review of Palaeobotany and Palynology | Year: 2011
Scattered palaeobotanical information pertaining to the Cairo Petrified Forest in the Eastern Desert is summarized here, for the first time since over 150. years. Examined wood specimens recently collected from the Cairo Petrified Forest belonged to seven legume species of which five are new records for Egypt, bringing the total known from this Forest to twenty-one species and from Egypt to sixty species. Descriptions and affinities of the seven species, the distribution of the twenty-one species and palaeoclimatic inferences are given with relevant comments. © 2011 Elsevier B.V.