Paleosols in Late Moscovian (Carboniferous) Marine Carbonates of the East European Craton Revealing "Great Calcimagnesian Plain" Paleolandscapes

Abstract

Late Paleozoic strata commonly include lithologic cycles (''cyclothems''), driven by sea-level fluctuations that repeatedly flooded and exposed broad expanses of epeiric shelves. Such successions, commonly with multiple unconformities, are well documented in Permo-Pennsylvanian sedimentary successions, but remain less understood in the East European Craton (EEC), part of the Euramerican continental shelf rim. This study documents unconformities and paleosols from the Podolskian to Myachkovian (middle Pennsylvanian) epeiric-carbonate succession of the EEC and explores the non-actualistic soil types, landscapes, and the character and density of vegetation in this Pennsylvanian calcimagnesian dryland environment.Thin (mostly , 1 m) paleosols developed at seven successive unconformities consist of an upper terrestrial clay layer or ''topclay,'' a crust of beta calcrete beneath the topclay, and a weakly karsted substrate limestone with rare rhizocretions. Solution pits and small (, 3 m deep) karst sinkholes are rare. Nontruncated topclays commonly consist of two layers: in situ clayey epipedons and resedimented terrestrial clays. The latter are interpreted as playa sediments. The Myachkovian unconformities of the northernmost localities studied, near Arkhangelsk, lack beta calcrete and root traces, and the limestone beneath these unconformities is sepiolitized. In Podolskian paleosols of the southern Moscow Basin, the topclays are predominantly palygorskitic. The Myachkovian paleosol clays are smectitic-illitic with occasional chlorite admixture. The majority of late Moscovian paleosols surveyed formally conform to lithic (rendollic) haplocalcids within the aridisol class or rendzic calcic leptosols. A detailed study of a representative Podolskian paleo-pedon reveals development of shallow soil carbonate, low alumina/bases and Ba/Sr ratios, enhanced Mn and Sr, presence of soil gypsum and opal, and a characteristic peak in magnetic susceptibility, all suggesting a semiarid to arid pedogenic environment. The palygorskite clay of this paleopedon retains 1.1-1.5% of connate organic matter in the form of covalently bound organomineral complexes, and is fulvatedominated resembling organic matter from extant dryland soils.The palygorskitic composition of Podolskian topclays and shallow (, 30 cm) pedogenic carbonates is interpreted to reflect hot, well-drained semidesert conditions with precipitation less than 300 mm/yr. The transition from palygorskitic to smectitic soil clays across the Podolskian-Myachkovian boundary, apparently deeper soil carbonate, and an increase in the degree of karstification record a general increase in humidity such that annual precipitation may have exceeded 300-400 mm.The available data reconstruct the ''great calcimagnesian plain'' landscapes formed during low sea level, supposedly glacial phases, across tens of thousands of square kilometers of the EEC. This non-actualistic system apparently lacked a fluvial network and was covered by uniform soils and playas. The primary productivity of this e...

Sequence stratigraphy and onlap history of the Donets Basin, Ukraine: Insight into Carboniferous icehouse dynamics

“…A shift from humid to semi-arid climates across the paleotropics during the mid-to-late Pennsylvanian has long been noted in sedimentologic and paleobotanical records (Phillips and Peppers, 1984;West et al, 1997;Hilton and Cleal, 2007;Kabanov et al, 2010), and more recently has been documented in high-latitude Gondwanan basins (Gulbranson et al, 2010). This period of widespread aridification coincided with a progressive restructuring of paleotropical floral ecosystems involving a shift from lycopsid-to tree fern-dominance in wetland habitats throughout Euramerica (Gastaldo et al, 1996;DiMichele et al, 2001;Cleal and Thomas, 2005) including the Donets Basin (Schegolev, 1975;Sachsenhofer et al, 2003).…”

Climate- and eustasy-driven cyclicity in Pennsylvanian fusulinid assemblages, Donets Basin (Ukraine)

“…Fusulina evolved into early Kasimovian Quasifusulinoides and late Kasimovian-Gzhelian Quasifusulina. We interpret the extinction of cooler water fusulinids, which were adapted to normal salinity and possibly hyposalinity, and the proliferation of warmer water, high salinity tolerant fusulinids to a major shift from perhumid conditions of the Moscovian to semi-arid climates in the Late Pennsylvanian that has long been noted in sedimentologic and paleobotanical records (Phillips et al, 1985;West et al, 1997;Hilton and Cleal, 2007;Kabanov et al, 2010). Notably, the fusulinid extinction occurs towards the beginning of a long-term (~7 m.y.)…”

“…In other words, the fusulinid assemblages we have defined for different sea-level stands are not only associated with depth, but obviously with some other specific environmental conditions. Moreover, all three proposed assemblages are recognized in different lithofacies packages in the Moscow Basin, situated in a arid climatic belt (Kabanov et al, 2010), hundreds of kilometers from the Donets Basin. The simultaneous replacement of one assemblage by another every ~300-400 kyr and the widespread distribution of each assemblage indicates environmental changes happened synchronously over 100s of kms -a phenomenon that requires global drivers.…”

Stratigraphic Unconformities: Review of the Concept and Examples from the Middle-Upper Paleozoic

“…The depth of transgressive erosion greatly varies depending on induration of the exposed sediment, on the wave and tide energy of a transgressing sea, and on the slope angle of the eroded sediments. While oceanic abrasion may cut down to tens of meters into seashore cliffs, plain lands characteristic of epicontinental sedimentary environments may show negligible transgressive stripping and delicate topsoil parts of weathering profiles largely preserved (e.g., [27]). …”

“…All paleosol profiles contain evidence of rooting activity with numerous Stigmaria (rooting systems of arborescent lycopsids). The uppermost studied paleosol below [27]; (B) Kholm disconformity in top of Mikhailovian (KHU) and Akulshino palustrine marl (APB) at Novogurovsky Quarry, slightly modified from Kabanov et al [99]; yellow clayey paleosol in solution pockets is arrowed.…”