The upper part of Shirgesht (UPS) and lower part of Niur (LPN) formations (Ordovician-Silurian) consist of sandstone, shale and limestone, respectively. The petrography and geochemical analysis conducted to evaluate provenance of siliciclastic deposits in order to understand the paleogeography of Central Iran during the Early Paleozoic time. This study shows that quartz and K-feldspar are the m...

A Silurian shift in fluvial stratigraphic architecture, coincident with the appearance of terrestrial vegetation fossil record, is traditionally cited as evidence for exclusively shallow, braided planforms pre-vegetation rivers. While recent recognition deep, single-thread channels pre-Silurian strata challenge this paradigm, it unclear how these rivers maintained stable banks. Here, we reconst...

TWO hypotheses have been suggested by previous workers to explain the relatively elevated radon activities of ground water in certain areas of southwestern Ohio and southeastern Indiana. First, radon may be produced close to or at the Ordovician-Silurian unconformity by the concentration of uranium and radium on iron and manganese oxides and hydroxides and on clay minerals at this zone of weath...

Abstract The Ordovician–Silurian (~485–419 Ma) was a time of considerable evolutionary upheaval, encompassing both great diversification and one the first major mass extinctions. Ordovician coincided with global climatic cooling paleocontinental collision, ecological impacts which were mediated by region-specific processes including substrate changes, biotic invasions, tectonic movements. From ...

Data from a new comprehensive macrofossil-based compilation of early plant genera are analyzed via Q-mode factor analysis. This ranges the Silurian to earliest Carboniferous and illustrates key vegetation changes that took place during configuration terrestrial ecosystems. Results reveal four factors can be used explain more than 90% variance in data. These interpreted as major phases land evol...

Understanding ancient climate changes is hampered by the inability to disentangle trends in ocean temperature from trends in continental ice volume. We used carbonate "clumped" isotope paleothermometry to constrain ocean temperatures, and thereby estimate ice volumes, through the Late Ordovician-Early Silurian glaciation. We find tropical ocean temperatures of 32° to 37°C except for short-lived...