Paleosols and Other Lithic Indicators of Latest Silurian–Early Devonian Climate Change (Arid to Dry Sub-Humid), Southeastern Laurussia: Clam Bank Formation, Western Newfoundland, Canada

Paleoclimate change from arid to dry sub-humid conditions is recorded in the upper Silurian (Přídolí) through lowermost Devonian (Lochkovian) Clam Bank Formation, western Newfoundland, based on the stratigraphy of reworked paleosol material, in situ pedogenic and groundwater calcretes, and other lithic paleoclimatic indicators. Reworked paleosol material appears in anomalous debris and streamflow deposits within an arid low-gradient Přídolí lowland. Fragments of surface to near-surface dolocrete, barite-bearing nodules, and loessial paleosol interred within an upland ferruginous and soil-bearing dolomitic regolith document a protracted paleosol history following Salinic orogenesis. Protosol development in a lower Lochkovian tidal/supratidal succession is associated with increased coastal humidity reflected in coastal-zone polsterland and brakeland floral assemblages. A dense interstratification of near-synsedimentary pedogenic and groundwater calcretes in alluvial stratigraphy, with local preservation of phreatophyte rhizoliths, comprises the uppermost (middle? Lochkovian) formation. Stable isotope geochemistry resolves the effects of evaporation and dilution on calcrete formation; microfractures identify shrinkage, likely defining some seasonality of water supply; and Sr-isotope ratios differentiate pedogenic and groundwater flow. The increased availability of surface- and groundwater through the Silurian–Devonian transition marks the local, but earliest, expression of an eventual hemispheric shift along southeast Laurussia from late Silurian aridity to wetter conditions during the Emsian (Early Devonian).