63 research outputs found
The Carboniferous carbon isotope record from sedimentary organic matter: can we disentangle the carbon cycle?
A comprehensive analysis of the 13C composition of sedimentary organic matter from Euramerican
Carboniferous successions indicates there are significant shifts in 13C through this key time interval.
Our studies have revealed that, at an individual location, the source and delivery mechanism of the
sediment contribute to the type of organic matter preserved and, in turn this influences the
measured 13C values from bulk sedimentary organic matter of organic matter
Rebuilding terrestrial ecosystems after the end-Devonian mass extinction: insights from the TW:eed Project
The TW:eed (Tetrapod World: early evolution and diversification) project is a
major research initiative that will generate a coherent picture of the biotic,
environmental and geological conditions of the 15-20 million years recovery period
following the major extinction event at the end-Devonian that was a major turning point
in terrestrial evolution. A paucity of terrestrial invertebrates and few fossils of early
tetrapods have been found in post-Devonian successions from the immediate aftermath
(Romerâs Gap) and yet, during a relatively brief time period in the Early Carboniferous,
fully terrestrial vertebrates evolved, terrestrial arthropods radiated, ray-finned fishes took
over from lobe-finned forms and plant groups diversified. Several new localities in
Carboniferous successions in southern Scotland and northern England are providing
completely new insights into this pivotal period for the evolution of life on land.
Significant new tetrapod material is helping to populate Romerâs Gap. Localities are also
yielding a diverse fauna of fish (gyracanthids, lungfish, rhizodonts and
actinopterygians), invertebrates (malacostracans, eurypterids, ostracods, scorpions and
myriapods) and plants. The fossil localities are within the Ballagan Formation, a
distinctive unit comprising mudstones with interbedded sandstones, palaeosols and thin
beds of dolomitic âcementstoneâ. The sediments were deposited on an extensive low
relief, muddy, vegetated floodplain that was traversed by numerous river systems.
Periodically the river-derived floods submerged the floodplains generating extensive
shallow freshwater lakes. The presence of gypsum and anhydrite indicates that there
were occasional marine transgressions across a marginal coastal plain. So far, most of
the fossils have been found towards the top of the Ballagan Formation, but a coastal
exposure of the entire formation provides a unique opportunity to search for fossils
across a time interval of about 15 million years at the base of the Carboniferous.
In addition to the detailed analysis of key outcrops, a drilling program in the
Tweed Basin is in the process of acquiring 500 m of continuous core through these
earliest Carboniferous successions. A tight stratigraphic framework for tetrapod
localities across the region will be generated by integrating the sedimentological
(lithostratigraphy), micropalaeontological (biostratigraphy), chemostratigraphical (carbon
and oxygen stable isotopes) and petrophysical data from the core and outcrops. The
borehole will provide the high-resolution datasets required to investigate the local, and
potentially, global palaeoclimate and its evolution through this time interval. This
multifaceted project is a unique opportunity to examine the progression, causes and
context of the rebuilding of an ecosystem following a major extinction
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