| Title | Characteristics of early earthÕs critical zone based on middle-late Devonian paleosol properties (Voronezh high, Russia) |
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| Author | Alekseeva, T; Kabanov, P ; Alekseev, A; Kalinin, P; Alekseeva, V |
| Source | Clays and Clay Minerals vol. 64, 5, 2016 p. 677-694, https://doi.org/10.1346/CCMN.2016.064044 |
| Year | 2016 |
| Alt Series | Natural Resources Canada, Contribution Series 20182441 |
| Publisher | Clay Minerals Society |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Subjects | Nature and Environment; Plants |
| Released | 2016 10 01 |
| Abstract | Land colonization with vascular plants during the late Silurian-early Devonian and then arborescence during the Pragian-Givetian caused the development of new soil types. These true-rooted soils
increased the rate of pedogenesis on a global scale. Since that time, soil has become a key component of the biosphere and has given rise to profound development of the EarthÕs Critical Zone (CZ). Case studies of Devonian CZs have helped to record
the transformation from Precambrian-Lower Paleozoic Ôproto-CZs,Õ which had insufficient proto-soil cover, to modern soils with true-rooted pedosphere. Devonian (Givetian-Frasnian) paleosols from the Voronezh region of Russia are combined into
pedocomplexes which occupied the top, slope, and bottom positions of a pronounced paleo-relief. Paleosols were developed from terrigenous argillites and volcanigenic-sedimentary deposits. Each pedocomplex consisted of four or more paleosols with
different degrees of development and profile preservation. Paleosols exhibited several common characteristics including production and translocation of clay, ferruginization and the presence of siderite nodules, enhanced MnO/Al2O3 and
(Fe2O3+MnO)/Al2O3 values, and in situ roots and root-system traces. The latter are siderite/goethite substituted. Stable isotope analysis of siderite shows ?13C values of between -6.1 and -13.7% indicating that CO2 had originated from C3 plants. The
main mineral component of clay fractions in automorphic paleosols (top and slope of the paleorelief) is kaolinite. The important feature of these paleosols is the red-stained hematite-rich layer in their bases. These horizons developed at different
depths and with different thicknesses, and marked the paleogroundwater tables of each sub-CZ. Evidence of the imprints of vegetation is seen in the abundant in situ roots, plant fragments, and spores of rhyniophytes, lycopsids, progymnosperms,
cladoxylalean ferns, and phytoleims of algae-like vascular plants. The near-equatorial location and the overall characteristics of paleosols studied suggest that the aforementioned horizons were formed in a tropically warm and humid climate. The
paleo-ecological environments which accompanied pedogenesis were probably controlled by tectonic activity and volcanism. |
| GEOSCAN ID | 311031 |
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