Chapter 3 Vertisols

Ahmad, N.

doi:10.1016/s0166-2481(08)70614-7

Cited by 57 publications

(5 citation statements)

References 58 publications

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“…The small carbonate nodules and few slickensides suggest weak pedogenic modification of these fine-grained strata. Modern carbonate nodules in East African soils form over relatively short (historic) timescales (Cerling, 1984), whereas the slickensides are vertic structures that begin to form over tens to hundreds of years in modern soils (Ahmad, 1983). Sparse slickensides, few and small carbonate nodules, and limited horizonation suggest a formation time on the order of 10 0 to 10 3 years for floodplain palaeosols formed in Early Pleistocene half-graben rifts with semi-arid climates (Mack & Madoff, 2005) like the Turkana Basin.…”

Section: Time Represented By the Depositsmentioning

confidence: 99%

Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Lepre

2017

The Depositional Record

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The Okote Member from the northeast Turkana Basin of Kenya represents an exceptionally good archive of Early Pleistocene archaeological and fossil sites. Field study of the lower Okote Member and underlying deposits was conducted in detail at two sets of outcrops (500 to 1000 m long) separated by some 22 km of modern landscape. The examined sections (10 to 15 m thick) preserve two facies: interbedded sandstones, tuffs and mudstones (crevasse splay) and ribbon-like bodies of sandstone/tuff (crevasse channel). Mudstones are overprinted with small carbonate nodules and sparse slickensides that are interpreted as evidence of weak soil development after the cessation of suspension deposition in a floodplain. The immaturity of the ancient soils implies that sediment accumulation was fairly rapid, yet the nodules and slickensides indicate seasonal contrasts in moisture. Episodically rapid sedimentation is suggested by the types of depositional environments and their structures, and indications of soft-sediment deformation. Crevassing may have been influenced by rivers that flooded in response to monsoonal rainfall variations and the voluminous influx of fluvially reworked volcaniclastics to the basin. A well-developed palaeosol directly underlying the lower Okote Member suggests that the deposits accumulated following a significant depositional hiatus. This basal contact, in addition to the apparent pervasiveness and penecontemporaneousness of the sedimentary facies, resembles a crevasse-splay system deposited by a sub-delta lobe or river avulsion. A paucity of lacustrine/deltaic indicators might indicate that the studied deposits correspond better with an avulsion origin. Sedimentation rates calculated from prior radiometric dating of tuffs tend to overestimate the timeframe of accumulation for individual strata of the lower Okote Member. Many appear to have formed on the order of 10 0 to 10 3 years, as suggested by facies, palaeosols and observations of modern crevasse splays. This cautions against using sedimentation rates alone to infer how much time a stratum preserving fossil/archaeological information represents.

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Section: Time Represented By the Depositsmentioning

confidence: 99%

Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Lepre

2017

The Depositional Record

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“…Instead, these pedofeatures can be considered here as relics of former brown forest soils, since laminated illuvial clay coatings form in soils under dense forest cover and moist subhumid climates, where water percolation is slowed down by the closed canopy, and allows low energy settling of translocated clay (Fedoroff and Goldberg, 1982;Bullock and Thompson, 1985;Gebhardt, 1993;French, 2005;Kühn et al, 2018). Moreover, broadleaf deciduous or evergreen tree taxa are not associated with vertic soils, because the shrinking and swelling pedoturbation damages their rooting system (Ahmad, 1983;Buol, 2011). In addition, relic properties of brown forest soil might have been preserved not only in the pedofeatures found in the buried Vertisol but also in their physical-chemical properties.…”

Section: Evidence Of Anthropogenic Soil Changes In the Middle Holocenementioning

confidence: 99%

Neolithic settlement and paleopedological changes during the Middle Holocene in northern Sardinia (Italy)

Marras

Boschian

2023

Front. Environ. Archaeol.

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Sardinia is the second biggest island in the Mediterranean region and has been intensely settled since the Middle Holocene (c.7750 BP). Despite a large number of documented Neolithic archaeological sites, very little is known about human-environmental interactions, including land use and domestic activities associated with the emergence and expansion of Neolithic settlements (c. 7750 and 5500 BP). To shed new light on these issues, we carried out new geoarchaeological analyses on buried soils and archaeological sequences exposed at the Neolithic site of Contraguda, northern Sardinia. Physical-chemical analyses combined with a micromorphological study of 24 thin sections from archaeological deposits and buried soil horizons were performed to evaluate the formation processes of archaeological deposits and paleosols. Soil micromorphology detected the presence of pedofeatures originating from land clearance and agricultural activities from the buried Vertisol. Vertisol and Entisol formation largely resulted from the anthropic impact on the landscape, which changed the trajectories of soil development and caused desertification of the environment. Furthermore, sediment fabric and pedofeatures also allowed us to reconstruct Neolithic domestic practices, showing that household maintenance waste debris, which also included animal penning refusal, was dumped into pit structures. Together, our results provide the first geoarchaeological evidence of human impact on soil development within the island during the Middle Holocene and give new insight into the Middle Neolithic (c. 6500-6000 BP) domestic behaviour and land use activities. These findings have significant implications for understanding the island's pedological history and offer a valuable insight on the settlement organization of the Neolithic farming communities and their impacts on the paleoenvironment of Sardinia.

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“…As a whole, the role that fragic horizons could play in protecting biodiversity is most probably underestimated, and the sites where old forest stands associate with soils showing the presence of a fragic horizon should be considered for nature preservation. colours even when the SOC content is low (Ahmad, 1983;Virmani et al, 1982) and at a depth deeper than that of the root system.…”

Section: Fragic Horizonmentioning

confidence: 99%

Soil health, soil genetic horizons and biodiversity^#

Costantini¹,

Mocali

2022

J. Plant Nutr. Soil Sci.

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Maintaining or recovering soil health is becoming a goal of many policies carried out at national, continental and global scales to promote global health. This viewpoint is aimed at stressing the relevance of a holistic approach to soil health assessment and monitoring, which is not only related to soil functional biodiversity but also considers the genetic horizons of the soil profile and not just the topsoil. We highlight that soil health has different connotations depending on the environmental setting and may show high spatial and temporal dynamics. Although the biological activity is often concentrated in the surficial horizon, we report increasing evidence that deep soil horizons host relevant biological communities, which are regulated by soil conditions that are usually different from those present in the topsoil. The processes responsible for the formation of surface and subsurface soil genetic horizons produce soil features that select the presence of organisms. The natural self-organization of soil features is at the basis of the soil classification systems and of their ability to differentiate soil taxa and appreciate pedodiversity. Examples are reported of surface and deep soil genetic horizons as an important interpretative tool of soil functional biodiversity and soil health. Therefore, the assessing and monitoring of soil health should not be carried out at fixed depth, but according to soil genetic horizons. We conclude that the loss of the natural self-organization of genetic horizons is a form of soil health degradation.

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Chapter 3 Vertisols

Cited by 57 publications

References 58 publications

Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Neolithic settlement and paleopedological changes during the Middle Holocene in northern Sardinia (Italy)

Soil health, soil genetic horizons and biodiversity^#

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Chapter 3 Vertisols

Cited by 57 publications

References 58 publications

Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Crevasse‐splay and associated depositional environments of the hominin‐bearing lower Okote Member, Koobi Fora Formation (Plio‐Pleistocene), Kenya

Neolithic settlement and paleopedological changes during the Middle Holocene in northern Sardinia (Italy)

Soil health, soil genetic horizons and biodiversity#

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Soil health, soil genetic horizons and biodiversity^#