The Experts below are selected from a list of 5361 Experts worldwide ranked by ideXlab platform

Andrea Zerboni - One of the best experts on this subject based on the ideXlab platform.

  • Age, palaeoenvironment, and preservation of prehistoric petroglyphs on a boulder in the oasis of Salut (northern Sultanate of Oman)
    Quaternary International, 2021
    Co-Authors: Andrea Zerboni, Michele Degli Esposti, Filippo Brandolini, Guido S. Mariani, Federica Villa, Paolo Lotti, Francesca Cappitelli, Marzia Sasso, Agostino Rizzi, G. Diego Gatta
    Abstract:

    The preservation of rock art in open-air contexts is a global issue controlled by several environmental processes, which are less investigated than the cultural significance of engravings and paintings. For that reason, we discuss the age, preservation, and palaeoenvironmental context of petroglyphs discovered on the flat, almost vertical face of a large boulder fallen along the western slope of Jabal Hammah, a rocky hill that borders the oasis of Salut (northern Sultanate of Oman). Geoarchaeological investigation highlighted that, in the region, the preservation of petroglyphs is due to the interplay of two contrasting Weathering processes. On one hand, karst dissolution - even if it is a very slow process in arid and semi-arid lands - gradually levels the surface of boulders. On the other hand, a biomineralized Mn- and Fe-rich rock varnish has developed inside the grooves of the engravings, thus sheltering them from extreme dissolution and promoting the preservation of the pristine shape of the representations. Moreover, organics trapped within the rock varnish have been radiocarbon dated to 2600 +/- 60 uncal. years BP. This result allows establishing a limit ante quem for the production of these specific engravings and to root it to the Bronze or Iron Age exploitation of the area. This result is of particular relevance in a region where well-dated rock art is virtually absent. Today, the biogeochemical processes leading to the formation of the protective crust are almost inactive, and not consistent with the present dry environmental settings. Their occurrence is in accordance with other local palaeoclimatic record, and suggests Bronze and Iron Age climatic conditions wetter than today. A broader implication of our work is that it shows how a multidisciplinary approach to the study of rock art provides the opportunity of understanding the age of rock art and its paleoenvironmental significance. We demonstrate that physical, chemical, and Biological Weathering processes are in charge of the preservation and/or destruction of rock art; such processes have to be seriously taken into account in projects of rock art field assessment.

  • rock pigments and Weathering a preliminary assessment of the challenges and potential of physical and biochemical studies on rock art from southern ethiopia
    Quaternary International, 2020
    Co-Authors: Marina Gallinaro, Andrea Zerboni
    Abstract:

    Abstract Over the past decade, physical and chemical analyses have been widely applied to the study of rock art contexts, particularly to examine the composition of rock art paintings and for direct radiometric dating. Different sampling and analytical methods have been applied to rock art from different parts of the world. However, in Africa these analyses are still at an embryonic stage. The results are often problematic in terms of reliability, mainly as concerns the chronology. This is due to a wide range of fossil and active biodegradation processes affecting rock surfaces and pigments; such processes are still widely underestimated. This paper aims to discuss the state of the art of the physical and chemical analyses undertaken on African rock art contexts, and the urgent need to establish protocols and best practices for sampling and analysis. The preliminary results of a new project in southern Ethiopia are presented here as an example of an integrated study of a rock art context, combining Archaeology and Earth Sciences. Preliminary field observations and SEM-EDS analyses, run on samples from two rock shelters in the Borana area, reveal the presence of a complex set of physical, chemical, and Biological Weathering processes with manifold effects on the rock art evidence.

G. Diego Gatta - One of the best experts on this subject based on the ideXlab platform.

  • Age, palaeoenvironment, and preservation of prehistoric petroglyphs on a boulder in the oasis of Salut (northern Sultanate of Oman)
    Quaternary International, 2021
    Co-Authors: Andrea Zerboni, Michele Degli Esposti, Filippo Brandolini, Guido S. Mariani, Federica Villa, Paolo Lotti, Francesca Cappitelli, Marzia Sasso, Agostino Rizzi, G. Diego Gatta
    Abstract:

    The preservation of rock art in open-air contexts is a global issue controlled by several environmental processes, which are less investigated than the cultural significance of engravings and paintings. For that reason, we discuss the age, preservation, and palaeoenvironmental context of petroglyphs discovered on the flat, almost vertical face of a large boulder fallen along the western slope of Jabal Hammah, a rocky hill that borders the oasis of Salut (northern Sultanate of Oman). Geoarchaeological investigation highlighted that, in the region, the preservation of petroglyphs is due to the interplay of two contrasting Weathering processes. On one hand, karst dissolution - even if it is a very slow process in arid and semi-arid lands - gradually levels the surface of boulders. On the other hand, a biomineralized Mn- and Fe-rich rock varnish has developed inside the grooves of the engravings, thus sheltering them from extreme dissolution and promoting the preservation of the pristine shape of the representations. Moreover, organics trapped within the rock varnish have been radiocarbon dated to 2600 +/- 60 uncal. years BP. This result allows establishing a limit ante quem for the production of these specific engravings and to root it to the Bronze or Iron Age exploitation of the area. This result is of particular relevance in a region where well-dated rock art is virtually absent. Today, the biogeochemical processes leading to the formation of the protective crust are almost inactive, and not consistent with the present dry environmental settings. Their occurrence is in accordance with other local palaeoclimatic record, and suggests Bronze and Iron Age climatic conditions wetter than today. A broader implication of our work is that it shows how a multidisciplinary approach to the study of rock art provides the opportunity of understanding the age of rock art and its paleoenvironmental significance. We demonstrate that physical, chemical, and Biological Weathering processes are in charge of the preservation and/or destruction of rock art; such processes have to be seriously taken into account in projects of rock art field assessment.

David J Beerling - One of the best experts on this subject based on the ideXlab platform.

  • Biological Weathering and the long term carbon cycle integrating mycorrhizal evolution and function into the current paradigm
    Geobiology, 2009
    Co-Authors: Lyla L Taylor, Jonathan R Leake, K Hardy, Steven A Banwart, Joe Quirk, David J Beerling
    Abstract:

    The dramatic decline in atmospheric CO2 evidenced by proxy data during the Devonian (416.0–359.2 Ma) and the gradual decline from the Cretaceous (145.5–65.5 Ma) onwards have been linked to the spread of deeply rooted trees and the rise of angiosperms, respectively. But this paradigm overlooks the coevolution of roots with the major groups of symbiotic fungal partners that have dominated terrestrial ecosystems throughout Earth history. The colonization of land by plants was coincident with the rise of arbuscular mycorrhizal fungi (AMF), while the Cenozoic (c. 65.5–0 Ma) witnessed the rise of ectomycorrhizal fungi (EMF) that associate with both gymnosperm and angiosperm tree roots. Here, we critically review evidence for the influence of AMF and EMF on mineral Weathering processes. We show that the key Weathering processes underpinning the current paradigm and ascribed to plants are actually driven by the combined activities of roots and mycorrhizal fungi. Fuelled by substantial amounts of recent photosynthate transported from shoots to roots, these fungi form extensive mycelial networks which extend into soil actively foraging for nutrients by altering minerals through the acidification of the immediate root environment. EMF aggressively weather minerals through the additional mechanism of releasing low molecular weight organic chelators. Rates of biotic Weathering might therefore be more usefully conceptualized as being fundamentally controlled by the biomass, surface area of contact, and capacity of roots and their mycorrhizal fungal partners to interact physically and chemically with minerals. All of these activities are ultimately controlled by rates of carbon-energy supply from photosynthetic organisms. The Weathering functions in leading carbon cycle models require experiments and field studies of evolutionary grades of plants with appropriate mycorrhizal associations. Representation of the coevolution of roots and fungi in geochemical carbon cycle models is required to further our understanding of the role of the biota in Earth's CO2 and climate history.

  • Biological Weathering in soil the role of symbiotic root associated fungi biosensing minerals and directing photosynthate energy into grain scale mineral Weathering
    Mineralogical Magazine, 2008
    Co-Authors: Jonathan R Leake, Adele L Duran, K Hardy, Irene Johnson, David J Beerling, Steven A Banwart, Mark M Smits
    Abstract:

    Biological Weathering is a function of biotic energy expenditure. Growth and metabolism of organisms generates acids and chelators, selectively absorbs nutrient ions, and applies turgor pressure and other physical forces which, in concert, chemically and physically alter minerals. In unsaturated soil environments, plant roots normally form symbiotic mycorrhizal associations with fungi. The plants provide photosynthate-carbohydrate-energy to the fungi in return for nutrients absorbed from the soil and released from minerals. In ectomycorrhiza, one of the two major types of mycorrhiza of trees, roots are sheathed in fungus, and 15–30% of the net photosynthate of the plants passes through these fungi into the soil and virtually all of the water and nutrients taken up by the plants are supplied through the fungi. Here we show that ectomycorrhizal fungi actively forage for minerals and act as biosensors that discriminate between different grain sizes (53–90 μm, 500–1000 μm) and different minerals (apatite, biotite, quartz) to favour grains with a high surface-area to volume ratio and minerals with the highest P content. Growth and carbon allocation of the fungi is preferentially directed to intensively interact with these selected minerals to maximize resource foraging.

Jonathan R Leake - One of the best experts on this subject based on the ideXlab platform.

  • Biological Weathering and the long term carbon cycle integrating mycorrhizal evolution and function into the current paradigm
    Geobiology, 2009
    Co-Authors: Lyla L Taylor, Jonathan R Leake, K Hardy, Steven A Banwart, Joe Quirk, David J Beerling
    Abstract:

    The dramatic decline in atmospheric CO2 evidenced by proxy data during the Devonian (416.0–359.2 Ma) and the gradual decline from the Cretaceous (145.5–65.5 Ma) onwards have been linked to the spread of deeply rooted trees and the rise of angiosperms, respectively. But this paradigm overlooks the coevolution of roots with the major groups of symbiotic fungal partners that have dominated terrestrial ecosystems throughout Earth history. The colonization of land by plants was coincident with the rise of arbuscular mycorrhizal fungi (AMF), while the Cenozoic (c. 65.5–0 Ma) witnessed the rise of ectomycorrhizal fungi (EMF) that associate with both gymnosperm and angiosperm tree roots. Here, we critically review evidence for the influence of AMF and EMF on mineral Weathering processes. We show that the key Weathering processes underpinning the current paradigm and ascribed to plants are actually driven by the combined activities of roots and mycorrhizal fungi. Fuelled by substantial amounts of recent photosynthate transported from shoots to roots, these fungi form extensive mycelial networks which extend into soil actively foraging for nutrients by altering minerals through the acidification of the immediate root environment. EMF aggressively weather minerals through the additional mechanism of releasing low molecular weight organic chelators. Rates of biotic Weathering might therefore be more usefully conceptualized as being fundamentally controlled by the biomass, surface area of contact, and capacity of roots and their mycorrhizal fungal partners to interact physically and chemically with minerals. All of these activities are ultimately controlled by rates of carbon-energy supply from photosynthetic organisms. The Weathering functions in leading carbon cycle models require experiments and field studies of evolutionary grades of plants with appropriate mycorrhizal associations. Representation of the coevolution of roots and fungi in geochemical carbon cycle models is required to further our understanding of the role of the biota in Earth's CO2 and climate history.

  • Biological Weathering in soil the role of symbiotic root associated fungi biosensing minerals and directing photosynthate energy into grain scale mineral Weathering
    Mineralogical Magazine, 2008
    Co-Authors: Jonathan R Leake, Adele L Duran, K Hardy, Irene Johnson, David J Beerling, Steven A Banwart, Mark M Smits
    Abstract:

    Biological Weathering is a function of biotic energy expenditure. Growth and metabolism of organisms generates acids and chelators, selectively absorbs nutrient ions, and applies turgor pressure and other physical forces which, in concert, chemically and physically alter minerals. In unsaturated soil environments, plant roots normally form symbiotic mycorrhizal associations with fungi. The plants provide photosynthate-carbohydrate-energy to the fungi in return for nutrients absorbed from the soil and released from minerals. In ectomycorrhiza, one of the two major types of mycorrhiza of trees, roots are sheathed in fungus, and 15–30% of the net photosynthate of the plants passes through these fungi into the soil and virtually all of the water and nutrients taken up by the plants are supplied through the fungi. Here we show that ectomycorrhizal fungi actively forage for minerals and act as biosensors that discriminate between different grain sizes (53–90 μm, 500–1000 μm) and different minerals (apatite, biotite, quartz) to favour grains with a high surface-area to volume ratio and minerals with the highest P content. Growth and carbon allocation of the fungi is preferentially directed to intensively interact with these selected minerals to maximize resource foraging.

K Hardy - One of the best experts on this subject based on the ideXlab platform.

  • Biological Weathering and the long term carbon cycle integrating mycorrhizal evolution and function into the current paradigm
    Geobiology, 2009
    Co-Authors: Lyla L Taylor, Jonathan R Leake, K Hardy, Steven A Banwart, Joe Quirk, David J Beerling
    Abstract:

    The dramatic decline in atmospheric CO2 evidenced by proxy data during the Devonian (416.0–359.2 Ma) and the gradual decline from the Cretaceous (145.5–65.5 Ma) onwards have been linked to the spread of deeply rooted trees and the rise of angiosperms, respectively. But this paradigm overlooks the coevolution of roots with the major groups of symbiotic fungal partners that have dominated terrestrial ecosystems throughout Earth history. The colonization of land by plants was coincident with the rise of arbuscular mycorrhizal fungi (AMF), while the Cenozoic (c. 65.5–0 Ma) witnessed the rise of ectomycorrhizal fungi (EMF) that associate with both gymnosperm and angiosperm tree roots. Here, we critically review evidence for the influence of AMF and EMF on mineral Weathering processes. We show that the key Weathering processes underpinning the current paradigm and ascribed to plants are actually driven by the combined activities of roots and mycorrhizal fungi. Fuelled by substantial amounts of recent photosynthate transported from shoots to roots, these fungi form extensive mycelial networks which extend into soil actively foraging for nutrients by altering minerals through the acidification of the immediate root environment. EMF aggressively weather minerals through the additional mechanism of releasing low molecular weight organic chelators. Rates of biotic Weathering might therefore be more usefully conceptualized as being fundamentally controlled by the biomass, surface area of contact, and capacity of roots and their mycorrhizal fungal partners to interact physically and chemically with minerals. All of these activities are ultimately controlled by rates of carbon-energy supply from photosynthetic organisms. The Weathering functions in leading carbon cycle models require experiments and field studies of evolutionary grades of plants with appropriate mycorrhizal associations. Representation of the coevolution of roots and fungi in geochemical carbon cycle models is required to further our understanding of the role of the biota in Earth's CO2 and climate history.

  • Biological Weathering in soil the role of symbiotic root associated fungi biosensing minerals and directing photosynthate energy into grain scale mineral Weathering
    Mineralogical Magazine, 2008
    Co-Authors: Jonathan R Leake, Adele L Duran, K Hardy, Irene Johnson, David J Beerling, Steven A Banwart, Mark M Smits
    Abstract:

    Biological Weathering is a function of biotic energy expenditure. Growth and metabolism of organisms generates acids and chelators, selectively absorbs nutrient ions, and applies turgor pressure and other physical forces which, in concert, chemically and physically alter minerals. In unsaturated soil environments, plant roots normally form symbiotic mycorrhizal associations with fungi. The plants provide photosynthate-carbohydrate-energy to the fungi in return for nutrients absorbed from the soil and released from minerals. In ectomycorrhiza, one of the two major types of mycorrhiza of trees, roots are sheathed in fungus, and 15–30% of the net photosynthate of the plants passes through these fungi into the soil and virtually all of the water and nutrients taken up by the plants are supplied through the fungi. Here we show that ectomycorrhizal fungi actively forage for minerals and act as biosensors that discriminate between different grain sizes (53–90 μm, 500–1000 μm) and different minerals (apatite, biotite, quartz) to favour grains with a high surface-area to volume ratio and minerals with the highest P content. Growth and carbon allocation of the fungi is preferentially directed to intensively interact with these selected minerals to maximize resource foraging.