Abstract The Late Palaeozoic glaciation was the longest of the Phanerozoic era. It is recorded in numerous Gondwanan basins, with some, such as the Chaco Basin, having a high petroleum potential. In this basin, the quality of the available seismic, well and outcrop data permits us to characterize the Late Palaeozoic glacial record. Palaeovalleys that are c . 500 m deep and c . 7 km wide have been analysed here. Focusing on the glaciogenic Carboniferous deposits, seismic data with well ties and outcrop analogues provide new sedimentological insights. The palaeovalley infill is imaged as a chaotic seismic facies overlain by an aggrading–prograding prism, interpreted as tillites covered by a fluvio-deltaic system. Tillites form both under the ice and during rapid ice recession, whereas fluvio-deltaic systems can only originate from a stable ice margin and last until the ice sheets withdraw inland. These two depositional modes are repeated several times, generating a progressive burial of the Carboniferous palaeovalleys. This succession of erosions and fills records major glacial stages, including a series of glacial and interglacial phases from the Late Devonian to the Early Permian. Depicting the Late Palaeozoic glacial history of the Chaco Basin seems crucial for the localization of potential good reservoirs.

Abstract The architecture, distribution and development of channelized sandstone bodies are described from Late Ordovician paraglacial successions of the Tassili N'Ajjer (SE Algeria and SW Libya) based on satellite images and field data (sedimentary logs, photomosaics). Sandstone bodies have a ribbon-like form at outcrop (often referred to as ‘cordons’ in the literature). They typify a fluvioglacial outwash plain deposited between a continental ice front and a marine delta-front zone. Channelized sandstone bodies are straight to sinuous, with widths ( W ) in the 60–600 m range, thicknesses ( T ) in the 5–30 m range and they have a mean W / T ratio of 16.5. They develop within an aggradational–progradational sand-dominated deltaic topset succession including at its distal end a terminal distributary channel and mouth-bar environments. The architecture of channel bodies and the related depositional facies, which includes climbing-dune cross-stratification, indicates that channelized sandstone bodies represent plugs of isolated channels related to high-magnitude flood events (glacier outbursts). These plugs form fossilized networks of both braided channels and interlaced anastomosed channels, offering snapshots of an outburst-related unconfined proglacial outwash braidplain constituted by the amalgamation of adjacent, elongated outwash fans.