Interpretation Of Paleosols Research Articles

Paleosol diversity in the Olduvai Basin, Tanzania: Effects of geomorphology, parent material, depositional environment, and groundwater on soil development

Olduvai Gorge, Tanzania is known for its fossil and cultural record of early hominins. The archaeological records are typically found within pedogenically modified sediments, thus the interpretation of paleosols provides important paleoenvironmental context information. The Gorge contains a rich and diverse record of paleosols that vary spatially and temporally, however the stratigraphy can be divided into time slices using dated tuffs and studied in a paleolandscape context. Sediments were deposited in a semi-arid closed rift basin containing paleo Lake Olduvai, with volcanoes supplying volcaniclastic material to an alluvial fan system on the eastern side and quartzofeldspathic fluvial sediments derived from weathered basement rocks on the western side. The shallow saline-alkaline lake in the basin center and groundwater levels in the surrounding uplands fluctuated with Milankovitch-driven climatic (precession) cycles of ∼20,000 years. The rift basin paleolandscape (at ∼1.8 Ma) is reconstructed using sedimentology, stratigraphy and paleopedology. Standard field descriptions of physical and biogenic paleosol structures are combined with stable isotope ratios of carbonates, and whole rock geochemistry of sediments, to reveal diversity of paleosols within the basin. There are at least three distinct types of paleosols that record a paleocatena related to both landscape and drainage differences. Red tephra-rich Andisols developed on the volcaniclastic alluvial fan to the east of the paleolake, calcium-carbonate-rich, silty Aridisols developed on the interfluves and floodplain of the fluvial plain on the west, whereas clay-rich paleosols (Vertisols) developed on the lake margin and lake in the center of basin. Variances in geomorphology, depositional environment, parent material, and depth to the water table are reflected in the development of distinctly different soil types that can provide key data needed for high-resolution reconstruction of the landscape known to be utilized by early hominins.

Correlation and interpretation of paleosols and loess across European Russia and Asia over the last interglacial–glacial cycle

Loess-paleosol sequences of the last interglacial-glacial cycle are correlated from European Russia to central Siberia and the Chinese Loess Plateau. During cold periods represented by marine oxygen isotope stages (OIS) 2 and 4, loess deposition dominated in the Russian Plain and the Loess Plateau. In central Siberia, loess deposition took place also, but five to seven thin, weakly developed paleosols are identified in both stages. OIS 3, in the Chinese Loess Plateau near Yangchang, consists of a loess bed that is flanked by two weakly developed paleosols. At Kurtak, Siberia, OIS 3 is represented by two distinct, stacked paleosols with no loess bed separating the paleosols. In the Russian Plain, OIS 3 consists of a single, possibly welded paleosol, representing upper and lower stage-3 climates. Brunisols and Chernozems dominate the profiles in China and Siberia, whereas Regosols, Luvisols, and Chernozems are evident in the northern and southern Russian Plain, respectively. OIS 5 is represented in China and the Russian Plain by pedo complexes in a series of welded soils, whereas in contrast, the Kurtak site consists of six paleosols with interbedded loess. The paleosols consist largely of Brunisols and Chernozems. Although the three areas examined have different climates, geographical settings, and loess source areas, they all had similar climate changes during the last interglacial-glacial cycle.

Zur Deutung und Bedeutung von Paläoböden im (süddeutschen) Löß

Abstract. Prerequisite for the estimation of age and paleoecological interpretation of paleosols in loess is the cognizance of relief and landscape position. Examples from Southern Germany show that already by this properties (like hydromorphy or a change of soil depth and humus contents) can be explained that, in ignoring the situation, were used as criteria for character and length of climatic influences. For the comparison of loess/pa-leosol sequences, the quantitative determination of intensity and extent of soil formation (in kg per m²) concerning suitable fossil and recent soils of the same landscape is reasonable. This requires the limitation on completely preserved soils in plateau position, but does not necessarily imply the imagination of a monotypically developed soil-landscape. These soils, too, have been alternated by periglacial features. The different importance of soil horizons for the reconstruction of the paleoclimate is put out finally.

The Underthrust Slide—An Unusual Type of Mass Movement

The name underthrust slide is given to a type of mass movement characterised by a series of under- thrust shear surfaces in coeval buried soils, subparallel transverse ridges, a marked bulging toe and overlapping erosional and depositional zones. These mass movement features have formed in red weathered greywacke and tephric deposits on relatively gentle hillslopes in several areas of the North Island of New Zealand. The mechan- ics of slope failure have not been thoroughly investi- gated but progressive (downslope) failure would appear to be important. The presence of several coeval but superposed soils suggests that interpretation of paleosols or prior groundsurfaces may prove fallacious in areas where underthrust slides have been identified.