The Bashkirian Pennsylvanian Carboniferous was the Peak of the Late Paleozoic Ice Age

Ice volume and paleoclimate history of the late Paleozoic ice age from conodont apatite oxygen isotopes from naqing (Guizhou, China)

Authors:

Chen et al

Abstract:

A high-resolution and continuous conodont apatite oxygen isotope record spanning the late Viséan to Middle Permian is reported from South China, which is interpreted with respect to the ice volume and/or tropical sea water temperature history of the Late Paleozoic Ice Age (LPIA). The presented δ18O record shows significant fluctuations in δ18O from the late Viséan to Middle Permian with highest values observed in the Bashkirian (Early Pennsylvanian). The δ18O maximum coincides with a major eustatic sea level fall recorded in low-latitudinal successions, and postdates the significant increases in 87Sr/86Sr and δ13Ccarb measured on well-preserved brachiopod calcite, which can be interpreted as reflecting intensified weathering as consequence of the closure of Rheic Ocean as well as enhanced carbon burial. Both processes may have contributed to lower greenhouse gas levels and cooled down the Earth's surface, triggering the maximum glaciation. The high Bashkirian δ18O values are interpreted to represent the glacial maximum of the LPIA. A coeval change in faunal composition and a decreasing diversity in climate-sensitive marine invertebrates can be ascribed to icehouse cooling and/or loss of habitat. Despite inconsistenceies with earlier interpretations that the Early Permian represented the glacial maximum of the LPIA as inferred from Gondwanan glacial sediments records, the suggested Bashkirian glacial maximum agrees well with ice extent estimates based on the regional tectonic history in Gondwana, which suggests that the Bashkirian glaciation occurred during Gondwana interior uplift promoting maximum ice cover of the entire LPIA. However, maximum glaciation is only poorly represented in the depositional record because large parts of the glacial deposits were possibly removed by erosion as outlined by a major regional unconformity.

Evidence of a Late Carboniferous Glacial Canyon From Argentina

Stratigraphy and palynology of a late Paleozoic glacial paleovalley in the Andean Precordillera, Argentina

Authors:

Liminaro et al

Abstract:

A new locality where Carboniferous glacial diamictite appears confined to paleovalleys is described in the north of the Argentinian Precordillera. The glacial deposits of the lower part of the Carboniferous Quebrada Larga Formation are divided in three stratigraphic intervals, all of them confined to a paleovalley carved into the granitic and high-grade metamorphic basement. The lower section is composed of different types of massive and stratified diamictite interpreted to record reworking of previously deposited poorly sorted glacial sediments. The middle section comprises shale with dropstones, lenticular beds of diamictite and large-scale cross-bedded sets of sandstone and conglomerate. These rocks represent a more advanced stage of deglaciation that comprises the following succeeding steps: 1) amelioration of the climatic conditions, melting of glaciers, fluvial erosion, 2) the formation of a water body (onset of the fjord system) and 3) a later progradation of Gilbert-type deltas. Diamictite is missing in the upper section, which is chiefly formed by cross-bedded sandstone and conglomerate deposited in braided fluvial plains. A quantitative analysis of palynological assemblages through the sequence allowed a reconstruction of the dynamics of the vegetation developed during the filling of the paleovalley. The presence of monosaccate pollen grains supports an age not older than Serpukhovian and the recognition of the characteristic species of the Raistrickia densa–Convolutispora muriornata Biozone reinforces a late Serpukhovian–Bashkirian age for the assemblages.

Reassessing the Extent of Serpukhovian to Bashkirian Carboniferous Southwestern Gondwana's Glaciation

Reassessment of mid-Carboniferous glacial extent in southwestern Gondwana (Rio Blanco Basin, Argentina) inferred from paleo-mass transport of diamictites

Authors:

Gulbranson et al

Abstract:

Late Paleozoic glacial diamictites occur in many localities in western Argentina, indicating that the region was strongly affected by glaciation during the mid-Carboniferous (late Serpukhovian–early Bashkirian). In most instances these diamictites are found in steeply walled paleovalley settings in the Andean Precordillera. This study presents new data from a locality north of the Precordillera that suggests an additional, distinct, volume of ice existed in the region during the Carboniferous. The glacigenic diamictites in the Rio Blanco Basin were ultimately emplaced as gravity flows, precluding inferences of paleo-ice volume. Fold nose orientation and soft-sediment groove orientations within the diamictites indicate that the deposits were emplaced from north to south, suggesting that glacial ice was most likely not sourced from the proto-Precordillera at this locality, requiring the need for another ice center to the north of the basin. Diamictite facies indicates that the sediment was initially supplied to the study area by a warm-based glacier.

A Marine Refuge During the Serpukhovian Carboniferous Mass Extinction?

The Tindouf Basin, a marine refuge during the Serpukhovian (Carboniferous) mass extinction in the northwestern Gondwana platform

Authors:

Cózar et al

Abstract:

Several macrofaunas and microfossils of the Carboniferous Saharan basins have longer stratigraphic ranges than those of other basins in the western Palaeotethys realm, particularly in the Tindouf Basin (Morocco–Algeria). Foraminifers are particularly abundant and diverse in the Serpukhovian and basal Bashkirian compared to coeval basins, and some taxa have longer ranges than in the neighbouring Reggan and Béchar basins, although this effect is more marked compared to the western Palaeotethyan assemblages in Europe. Several rugose coral species are recorded from the early Bashkirian that previously were considered to have disappeared in the Serpukhovian. The Tindouf Basin, as one of the most western Saharan basins in North Africa, shows the greatest stratigraphic ranges of taxa which diminish eastwards. Evidence for a mass extinction event during the Serpukhovian in the Tindouf Basin has not been clearly recognized, although a possible influence of glaciation is observed in the faunal diversity. Eustatic sea-level changes were experienced in Tindouf with the cyclic pattern of sedimentation, but warm water ocean currents from the palaeoequator were able to maintain tropical conditions on the platform. Tectonics in the area, led to emerging land masses and barriers, and created a partly isolated basin in this sector of the western part of the Sahara Platform in northern Gondwana. The combination of those factors controlled the environmental conditions in the area, allowing the persistence of the fauna for longer stratigraphic ranges than its equivalent counterparts in the western Palaeotethys.