Palaeoenvironments of the Middle–Late Mississippian Moscow Basin were a Everglades Analog

Palaeoenvironments of the Middle–Late Mississippian Moscow Basin (Russia) from multiproxy study of palaeosols and palaeokarsts

Authors:

Alekseeva et al

Abstract:

Numerous pedogenically altered subaerial exposure surfaces within Middle–Late Mississippian (Viséan–Serpukhovian) shallow carbonates in the Moscow Basin attest to sea-level fluctuations and climate change. In total, fifteen palaeosols at seven stratigraphical levels from five open pits were described and studied in detail. They show both stratigraphic and lateral soil type variability. The factors of major influence are substrate type, time of exposure (tectonics and relief), and climate. All palaeosols are polycyclic and consist of at least two parts. The lower unit (substrate), consisting mainly of limestone, with siliciclastic deltaic and palustrine beds, was altered to different degrees by weathering/pedogenesis. Depending on climate, the limestone was transformed into calcrete or caliche. The substrate is capped by a terrigeneous topclay which represents an individual palaeosol developed prior to subsequent marine flooding. Indications of gley conditions, as well as the presence of coal, sphaerosiderite and framboidal pyrite, indicate a wet peat–swamp environment that was, however, periodically dry. The calculated mean annual precipitation (MAP) based on a CIA-K proxy of siliciclastic units shows that the climate was characterized by alternating periods of aridity and humidity, with the most humid conditions (~ 1250 mm) during the middle Visean. The same proxy applied to Late Mississippian sediments of the Appalachian Basin shows a similar MAP range. High-amplitude sea-level fluctuations at the Mikhailovian–Venevian boundary followed by prolonged exposure resulted in the development of a laterally extensive deep karst capped by a pedocomplex and then by a palustrine bed. The structure and scale of this unconformity are comparable to those of the Florida Everglades environment, which represents a modern marsh landscape. The majority of topclays are smectitic, except for the most humid and most arid environments, which are dominated by kaolinite and palygorskite, respectively. Besides mineralogy, we also provide data regarding geochemistry, carbon isotopic composition of carbonate, organic matter characteristics including solid state 13C NMR and δ13C data, and evidence of vegetation types based on field observations and SEM images.

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.

Evidence of a Greenhouse Climate During the Visean-Serpukhovian in the Midst of the Carboniferous Ice Ages

A greenhouse interval between icehouse times: Climate change, long-distance plant dispersal, and plate motion in the Mississippian (late Visean-earliest Serpukhovian) of Gondwana

Authors:

Hermann W. Pfefferkorn, Vera Alleman and Roberto Iannuzzi

Abstract:

The late Paleozoic ice age (LPIA) is the closest example that can be compared with current climate conditions. Near the beginning of the LPIA fossil plants of Mississippian (late Visean to earliest Serpukhovian) age indicate a widespread frost-free climate in a wide belt on Gondwana indicating an interval of greenhouse conditions between the earlier Visean and later Serpukhovian icehouse times. This warm-temperate floral belt has been named the Paraca floral belt after the locality on the Peruvian coast where it was first recognized. The origin of this particular zono-biome was due to the interplay of (1) climate oscillations, (2) several kinds of long-distance plant dispersal within, between or through zono-biomes, and (3) plate motion. The Carboniferous age strata on the Paracas Peninsula in Peru serve as an example for an analysis of these large scale patterns through the analysis of local geology, paleobotany, and paleoecology. The processes observed during this time interval can serve as a model for long-distance plant dispersal at other times.