The Experts below are selected from a list of 14298 Experts worldwide ranked by ideXlab platform
Julien Moreau - One of the best experts on this subject based on the ideXlab platform.
-
lower palaeozoic unconformities in an intracratonic platform setting Glacial Erosion versus tectonics in the eastern murzuq basin southern libya
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidie and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidie (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
-
Lower Palaeozoic unconformities in an intracratonic platform setting: Glacial Erosion versus tectonics in the eastern Murzuq Basin (southern Libya)
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
-
Lower Palaeozoic unconformities in an intracratonic platform setting: Glacial Erosion versus tectonics in the eastern Murzuq Basin (southern Libya)
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
Jean-loup Rubino - One of the best experts on this subject based on the ideXlab platform.
-
lower palaeozoic unconformities in an intracratonic platform setting Glacial Erosion versus tectonics in the eastern murzuq basin southern libya
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidie and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidie (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
-
Lower Palaeozoic unconformities in an intracratonic platform setting: Glacial Erosion versus tectonics in the eastern Murzuq Basin (southern Libya)
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
-
Lower Palaeozoic unconformities in an intracratonic platform setting: Glacial Erosion versus tectonics in the eastern Murzuq Basin (southern Libya)
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
Johan M. Bonow - One of the best experts on this subject based on the ideXlab platform.
-
re exposed basement landforms in the disko region west greenland disregarded data for estimation of Glacial Erosion and uplift modelling
Geomorphology, 2005Co-Authors: Johan M. BonowAbstract:Classifications of large-scale landscapes in Greenland have traditionally been based on type and intensity of Glacial Erosion, with the general idea that present landforms are mainly the result of ...
-
Re-exposed basement landforms in the Disko region, West Greenland ¿ disregarded data for estimation of Glacial Erosion and uplift modelling
Geomorphology, 2005Co-Authors: Johan M. BonowAbstract:Classifications of large-scale landscapes in Greenland have traditionally been based on type and intensity of Glacial Erosion, with the general idea that present landforms are mainly the result of ...
Jean-françois Ghienne - One of the best experts on this subject based on the ideXlab platform.
-
lower palaeozoic unconformities in an intracratonic platform setting Glacial Erosion versus tectonics in the eastern murzuq basin southern libya
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidie and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidie (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
-
Lower Palaeozoic unconformities in an intracratonic platform setting: Glacial Erosion versus tectonics in the eastern Murzuq Basin (southern Libya)
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
-
Lower Palaeozoic unconformities in an intracratonic platform setting: Glacial Erosion versus tectonics in the eastern Murzuq Basin (southern Libya)
International Journal of Earth Sciences, 2013Co-Authors: Jean-françois Ghienne, Lionel Degermann, Julien Moreau, Jean-loup RubinoAbstract:The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply Erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic Glacial Erosion surface showing corrugated Glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician Glacial Erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician Glacial Erosion surface amalgamate together. Here, an estimate of the Glacial Erosion depth cannot be derived from the stratigraphic hiatus beneath the Glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related Glacial Erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities.
Frédéric Herman - One of the best experts on this subject based on the ideXlab platform.
-
Quantifying post-Glacial Erosion at the Gorner glacier, Switzerland, using OSL and 10Be surface exposure dating.
2020Co-Authors: Joanne Elkadi, Benjamin Lehmann, Georgina E. King, Olivia Steinemann, Susan Ivy-ochs, Marcus Christl, Frédéric HermanAbstract:<p>Quaternary Erosion through Glacial and post-Glacial processes has left an imprint on Alpine topography. There are few methods capable of resolving these processes on Late Glacial to Holocene timescales. The aim of this study is to contribute towards a more detailed understanding of post-Glacial Erosion across the Central and Western Alps by better constraining the post-Glacial Erosion history of the Gorner glacier in Zermatt, Switzerland. This is done using a new approach that combines Optically Stimulated Luminescence (OSL) and <sup>10</sup>Be cosmogenic nuclide surface exposure dating to invert for post-Glacial Erosion rates (Lehmann et al., 2019). Both dating methods are influenced by surface Erosion but operate on different spatial scales- OSL signals form within the first 1-5 mm of a rock surface (Sohbati et al., 2011) whereas the <sup>10</sup>Be signal accumulates within approximately the first 3 m (Lal, 1991). Six bedrock samples, exposed progressively since the Last Glacial Maximum, were collected along a vertical transect spanning an elevation of 641 m. Preliminary results show inheritance in the bottom three samples suggesting multiple advances and retreat. Further results for the post-Glacial Erosion rates down the transect, and comparison to other glaciers in the Western Alps, will be presented.</p><p>References:</p><p>Lal, D., 1991. Cosmic ray labelling of Erosion surfaces: in situ nuclide production rates and Erosion models. Earth and Planetary Science Letters, 104, 424-439.</p><p>Lehmann, B et al., 2019. Evaluating post-Glacial bedrock Erosion and surface exposure duration by coupling in situ optically stimulated luminescence and <sup>10</sup>Be dating. Earth Surface Dynamics, 7.</p><p>Sohbati, R. et al., 2011. Investigating the resetting of OSL signals in rock surfaces. Geochronometria, 38(3), 249-258.</p>
-
Mid-latitude Glacial Erosion hotspot related to equatorial shifts in southern Westerlies
Geology, 2015Co-Authors: Frédéric Herman, Mark T. BrandonAbstract:Glaciation has affected the shape of mountain ranges and has induced a global increase in Erosion rates during the past 2 m.y. The observed increase in Erosion rates appears to vary with latitude, reaching a maximum at mid-latitudes that is particularly well defined in the Southern Hemisphere. Although it is likely that climate played an important role, the processes responsible for such latitudinal distribution of Erosion are unclear. Here we exploit the meridional extent of the Patagonian Andes and identify an Erosion hotspot at ∼44°S. Using a Glacial Erosion model and formally inverting the available thermochronometric and geobarometric data, we show that this hotspot coincides with the location of maximum precipitation that follows the Southern Hemisphere Westerlies during Glacial periods. We propose that the increased precipitation rates at ∼44°S led to greater ice sliding velocities and faster Glacial Erosion. Our results imply that the migration of the westerly wind belt toward the equator since 2–3 Ma may have played an important role in determining the distribution of mountain Erosion in the Southern Hemisphere.
-
rapid exhumation in the western alps driven by slab detachment and Glacial Erosion
Geology, 2015Co-Authors: Frédéric Herman, Edi Kissling, Sean D WillettAbstract:Identifying topographic and Erosion rate response to tectonic and climatic forcing remains challenging. This is in part because of the difficulty in isolating the respective roles of climate and tectonics. Here we exploit 2500 thermochronometric data points collected over several decades of research, using a new inverse technique, to image the space-time evolution of Erosion rate across the European Alps over the past 35 m.y. The most striking feature of our results is a two- to three-fold increase in Erosion rate over the past 2 m.y. exclusively within the Western and Central Alps. This increase appears to be controlled by the inferred high rock uplift rate due to the progressive detachment of the European slab under the Western Alps. The similarity in mean elevation between the Western and Eastern Alps indicates a surprisingly low topographic response to this differential tectonic forcing, and points to the role of enhanced Glacial Erosion in response to surface uplift.
-
Controls of initial topography on temporal and spatial patterns of Glacial Erosion
Geomorphology, 2014Co-Authors: Vivi Kathrine Pedersen, Frédéric Herman, Ritske S. Huismans, David L. EgholmAbstract:Abstract Here we investigate the influence of initial pre-Glacial topography on spatial and temporal patterns of Glacial Erosion using numerical surface process modelling, including a higher order ice sheet model. First, we consider glacier dynamics when simulating glaciation in two real landscapes, representing plateau-type topography (southeast Australia) and characteristic steady-state fluvial topography (southern Taiwan). We find that the different initial landscape configurations result in distinctly different ice configurations and patterns of basal sliding. The sliding patterns are controlled by ice configuration and the resulting basal shear stresses and by the thermal properties at the base of the ice. We then investigate how these characteristic patterns of basal sliding control Glacial Erosion and long-term landscape evolution using synthetic representations of the two landscapes. The two landscape configurations result in markedly different spatial and temporal patterns of Glacial Erosion. However, the resulting landscapes may have similar morphology, irrespective of initial landscapes and Glacial Erosion patterns being significantly different. The numerical experiments also suggest that, in addition to basal temperature, basal shear stress is important in restricting long-term Glacial Erosion, which is relevant for the preservation of landforms during glaciations. Specifically, pre-Glacial landforms may be eroded although they are initially protected by cold-based ice, when the ice configuration promotes significant basal shear stress (Glacial Erosion) at the edge of a plateau-like landscape. In contrast, pre-Glacial landforms may be preserved irrespective of the ice being warm-based, when low gradients in the ice surface act to limit basal shear stress.
-
Bimodal Plio-Quaternary Glacial Erosion of fjords and low-relief surfaces in Scandinavia
2013Co-Authors: Philippe Steer, Pierre G. Valla, Ritske Huismans, Sébastien Gac, Frédéric HermanAbstract:Glacial landscapes are characterized by dramatic local relief, but they also commonly exhibit high-elevation, lowrelief surfaces. These surfaces have been attributed to Glacial headward Erosion and periGlacial processes in Alpine settings. However, the timing and processes responsible for their formation in northern high-latitude regions remain elusive. Here, we infer the topographic evolution of western Scandinavia during the Plio-Quaternary glaciations (0-2.8 Ma) by linking onshore Erosion to offshore sedimentation. We estimate the rate of fjord Erosion from geophysical relief and compare that with the Erosion reflected by offshore sedimentation. We find that the sediments generated by fjord Erosion (65-100 103 km3) over the entire western Scandinavia during the Plio-Quaternary glaciations accounts for only 35–55% of the equivalent bedrock Erosion deduced from total sediment volume deposited off the coast of Norway. This large mismatch implies that during this period, significant Erosion (300-400 m) must have also taken place away from the fjords at high elevation and thus indicates a bimodal distribution of Glacial Erosion. Furthermore, comparing the distribution of the high-elevation, low-relief surfaces with estimates of the long-term glacier equilibrium line altitude supports the idea that effective Erosion in extensively glaciated areas limits topographic height, a process known as the Glacial buzzsaw. We therefore conclude that Glacial and periGlacial processes have a substantial impact on the formation of low-relief surfaces observed in glaciated mountain belts and high-latitude continental margins.