A. Leier | University of South Carolina (original) (raw)

Papers by A. Leier

Research paper thumbnail of Global climate forcing on late Miocene establishment of the Pampean aeolian system in South America

Wind-blown dust from southern South America links the terrestrial, marine, atmospheric, and biolo... more Wind-blown dust from southern South America links the terrestrial, marine, atmospheric, and biological components of Earth's climate system. The Pampas of central Argentina (~33°-39°S) contain a Miocene to Holocene aeolian record that spans an important interval of global cooling. Upper Miocene sediment provenance based on n = 3299 detrital-zircon U-Pb ages is consistent with the provenance of Pleistocene-Holocene deposits, indicating the Pampas are the site of a long-lived fluvial-aeolian system that has been operating since the late Miocene. Here, we show the establishment of aeolian sedimentation in the Pampas coincided with late Miocene cooling. These findings, combined with those from the Chinese Loess Plateau (~33°-39°N) underscore: (1) the role of fluvial transport in the development and maintenance of temporally persistent mid-latitude loess provinces; and (2) a global-climate forcing mechanism behind the establishment of large mid-latitude loess provinces during the late Miocene.

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Research paper thumbnail of A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America

Nature Communications

The Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of lat... more The Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7° (1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper- and lower-level) wind system over the southern Puna Plateau (to at least ~27° S) during periods of high dust accumulation in Tafí del Valle.

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Research paper thumbnail of Detrital zircon provenance and transport pathways of Pleistocene-Holocene eolian sediment in the Pampean Plains, Argentina

Geological Society of America Bulletin, 2022

The Pampas of Argentina contain a broad distribution of Pleistocene to Holocene loessic sediments... more The Pampas of Argentina contain a broad distribution of Pleistocene to Holocene loessic sediments and eolian dune deposits. Models describing the sediment provenance of this eolian system have, at times, conflicted. We address the provenance of these deposits through U-Pb detrital-zircon geochronology. Our results indicate broad similarity in age distributions between samples, with a dominant Permian-Triassic mode, and widespread but lesser Cenozoic, Devonian-Mississippian, Ediacaran-Cambrian, and Mesoproterozoic modes. These data are inconsistent with a large contribution of detritus from Patagonia as previously suggested. These data are consistent with very limited contribution of first cycle volcanogenic zircon to the Pampean eolian system, but abundances of older Neogene zircon indicate proto-sources in the Andes. The ríos Desaguadero, Colorado, and Negro contain populations that were likely within the dust production pathways of most of the loess, paleosol, and eolian dune deposits, but the derivation of the zircon ages in these sediments cannot be explained solely by these river systems. One statistical outlier, a loess sample from the Atlantic coast of the Pampa region, indicates quantitative similarity to the age spectra from the ríos Colorado and Negro, consistent with derivation from these subparallel rivers systems during subaerial exposure of the continental shelf under high global ice-volume. Another statistical outlier, a paleosol sample from the Río Paraná delta region, has zircon ages more closely associated with sediments in the Paraná region than in rivers south of the Pampa region. Collectively, these data point to the complexity of the Pampean eolian system and substantial spatial-temporal variation in this Pleistocene-Holocene eolian system.

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Research paper thumbnail of A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America

Nature Communications, 2022

The Tafí del Valle depression (~27°S) in the eastern Andes of Argentina provides a record of late... more The Tafí del Valle depression (~27°S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7°(1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper-and lowerlevel) wind system over the southern Puna Plateau (to at least~27°S) during periods of high dust accumulation in Tafí del Valle.

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Research paper thumbnail of Lhasa detrital zircon data

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Research paper thumbnail of The Gangdese retroarc thrust belt revealed

GSA Today, 2007

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Research paper thumbnail of Lower Cretaceous Strata in the Lhasa Terrane, Tibet, with Implications for Understanding the Early Tectonic History of the Tibetan Plateau

Journal of Sedimentary Research, 2007

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Research paper thumbnail of Mountains, monsoons, and megafans

Geology, 2005

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Research paper thumbnail of Sediment dispersal in an evolving foreland: Detrital zircon geochronology from Upper Jurassic and lowermost Cretaceous strata, Alberta Basin, Canada

Geological Society of America Bulletin, 2013

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Research paper thumbnail of The Takena Formation of the Lhasa terrane, southern Tibet: The record of a Late Cretaceous retroarc foreland basin

Geological Society of America Bulletin, 2007

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Research paper thumbnail of Stable isotopic results from paleosol carbonate in South Asia: Paleoenvironmental reconstructions and selective alteration

Earth and Planetary Science Letters, 2009

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Research paper thumbnail of A stratigraphic framework for Late Jurassic-Early Cretaceous gas-bearing strata (Monteith Formation) in the subsurface of northwest Alberta

Bulletin of Canadian Petroleum Geology, 2012

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Research paper thumbnail of Detrital zircon geochronology of Carboniferous?Cretaceous strata in the Lhasa terrane, Southern Tibet

Basin Research, 2007

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Research paper thumbnail of Evidence of Cretaceous Foreland Basin Systems in the Lhasa Terrane and the Implications for the Tectonic Evolution of Southern Tibet

Any model attempting to explain the relationship between the Indo-Asian collision and the uplift ... more Any model attempting to explain the relationship between the Indo-Asian collision and the uplift of the Tibetan plateau must first consider the tectonic circumstances in southern Asia immediately preceding the collision. Current hypotheses regarding Cretaceous tectonism in the Lhasa terrane of southern Tibet range between end-member models involving regional extension and regional contraction. We examined the Cretaceous sedimentary strata of

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Research paper thumbnail of Sedimentology and stratigraphy of the Lower Cretaceous Isachsen Formation: Ellef Ringnes Island, Sverdrup Basin, Canadian Arctic Archipelago

Marine and Petroleum Geology, 2014

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Research paper thumbnail of Garzón Massif basement tectonics: Structural control on evolution of petroleum systems in upper Magdalena and Putumayo basins, Colombia

Marine and Petroleum Geology

The Garz on Massif, is an active Laramide style basement uplift flanked by the Upper Magdalena Va... more The Garz on Massif, is an active Laramide style basement uplift flanked by the Upper Magdalena Valley (UMV) and the Putumayo Basin. In this paper we use new gravity, magnetic, well and seismic data for the first geophysical interpretation of the Garz on Massif. The Garz on/Algeciras fault has been previously interpreted as a right-lateral strike-slip fault. The new seismic, well, and gravity data demonstrates that the Garz on fault is also a low-angle (12e17) Andean age fault thrusting PreCambrian basement 10 e17 km northwestward over Miocene sediments of the UMV in a prospective footwall anticline. The new geophysical data as well as previous field mapping were used to produce the first gravity and magnetic maps and retrodeformable structural cross section of the northern Garz on Massif. The new model distinguishes for the first time distinct episodes of " thinskinned " and " thickskinned " deformation in the Garz on Massif. The model indicates approximately 43 km of Early to Middle Miocene shortening by " thinskinned " imbricate thrusting contemporaneous with the uplift of the nearby southern Central Cordillera (~9e16 Ma) and the main hydrocarbon expulsion event for the UMV and Putumayo Basin. This was followed by at least 22 km of Late Miocene (3e6 Ma) " thickskinned " Andean shortening and 7 km of uplift on the symmetrical Garz on thrust and a SE-verging basement thrust fault zone. The Andean uplift interrupted and exposed the hydrocarbon migration pathways to the Putumayo Basin. 3-D volume fracture analysis was used for the first time in this paper together with the first seismic and well data published for the Topoyaco and Miraflor structures to test closure models for the Topoyaco foothills. Intense fracturing is observed in the Topoyaco basement monocline from the near-surface to depths of over 3.5 km. The high level of fracturing permitted freshwater flushing and oil biodegradation and hydrocarbon escape. In contrast, the Miraflor-1 well, located just southwest of the Topoyaco block, tested light gravity oil and is sealed from groundwater flushing and biodegradation by a backthrust.

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Research paper thumbnail of The Cretaceous evolution of the Lhasa terrane, southern Tibet

ABSTRACT

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Research paper thumbnail of Provenance of the Cretaceous Athabasca Oil Sands, Canada: Implications for Continental-Scale Sediment Transport

Journal of Sedimentary Research, 2014

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Research paper thumbnail of Mountains, Monsoons, and Fluvial Megafans

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Research paper thumbnail of Lower Jurassic Foreland Basin in Western Canada

2010 GSA Denver Annual Meeting, 2010

The earliest stages of the Cordilleran foreland basin in western Canada, namely the question of h... more The earliest stages of the Cordilleran foreland basin in western Canada, namely the question of how and when the region evolved from a stable margin to a retro-arc foreland basin, remain enigmatic. Here we integrate subsidence analysis with existing datasets to shed light on ...

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Research paper thumbnail of Global climate forcing on late Miocene establishment of the Pampean aeolian system in South America

Wind-blown dust from southern South America links the terrestrial, marine, atmospheric, and biolo... more Wind-blown dust from southern South America links the terrestrial, marine, atmospheric, and biological components of Earth's climate system. The Pampas of central Argentina (~33°-39°S) contain a Miocene to Holocene aeolian record that spans an important interval of global cooling. Upper Miocene sediment provenance based on n = 3299 detrital-zircon U-Pb ages is consistent with the provenance of Pleistocene-Holocene deposits, indicating the Pampas are the site of a long-lived fluvial-aeolian system that has been operating since the late Miocene. Here, we show the establishment of aeolian sedimentation in the Pampas coincided with late Miocene cooling. These findings, combined with those from the Chinese Loess Plateau (~33°-39°N) underscore: (1) the role of fluvial transport in the development and maintenance of temporally persistent mid-latitude loess provinces; and (2) a global-climate forcing mechanism behind the establishment of large mid-latitude loess provinces during the late Miocene.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America

Nature Communications

The Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of lat... more The Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7° (1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper- and lower-level) wind system over the southern Puna Plateau (to at least ~27° S) during periods of high dust accumulation in Tafí del Valle.

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Research paper thumbnail of Detrital zircon provenance and transport pathways of Pleistocene-Holocene eolian sediment in the Pampean Plains, Argentina

Geological Society of America Bulletin, 2022

The Pampas of Argentina contain a broad distribution of Pleistocene to Holocene loessic sediments... more The Pampas of Argentina contain a broad distribution of Pleistocene to Holocene loessic sediments and eolian dune deposits. Models describing the sediment provenance of this eolian system have, at times, conflicted. We address the provenance of these deposits through U-Pb detrital-zircon geochronology. Our results indicate broad similarity in age distributions between samples, with a dominant Permian-Triassic mode, and widespread but lesser Cenozoic, Devonian-Mississippian, Ediacaran-Cambrian, and Mesoproterozoic modes. These data are inconsistent with a large contribution of detritus from Patagonia as previously suggested. These data are consistent with very limited contribution of first cycle volcanogenic zircon to the Pampean eolian system, but abundances of older Neogene zircon indicate proto-sources in the Andes. The ríos Desaguadero, Colorado, and Negro contain populations that were likely within the dust production pathways of most of the loess, paleosol, and eolian dune deposits, but the derivation of the zircon ages in these sediments cannot be explained solely by these river systems. One statistical outlier, a loess sample from the Atlantic coast of the Pampa region, indicates quantitative similarity to the age spectra from the ríos Colorado and Negro, consistent with derivation from these subparallel rivers systems during subaerial exposure of the continental shelf under high global ice-volume. Another statistical outlier, a paleosol sample from the Río Paraná delta region, has zircon ages more closely associated with sediments in the Paraná region than in rivers south of the Pampa region. Collectively, these data point to the complexity of the Pampean eolian system and substantial spatial-temporal variation in this Pleistocene-Holocene eolian system.

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Research paper thumbnail of A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America

Nature Communications, 2022

The Tafí del Valle depression (~27°S) in the eastern Andes of Argentina provides a record of late... more The Tafí del Valle depression (~27°S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7°(1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper-and lowerlevel) wind system over the southern Puna Plateau (to at least~27°S) during periods of high dust accumulation in Tafí del Valle.

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Research paper thumbnail of Lhasa detrital zircon data

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Gangdese retroarc thrust belt revealed

GSA Today, 2007

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Research paper thumbnail of Lower Cretaceous Strata in the Lhasa Terrane, Tibet, with Implications for Understanding the Early Tectonic History of the Tibetan Plateau

Journal of Sedimentary Research, 2007

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Research paper thumbnail of Mountains, monsoons, and megafans

Geology, 2005

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Sediment dispersal in an evolving foreland: Detrital zircon geochronology from Upper Jurassic and lowermost Cretaceous strata, Alberta Basin, Canada

Geological Society of America Bulletin, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The Takena Formation of the Lhasa terrane, southern Tibet: The record of a Late Cretaceous retroarc foreland basin

Geological Society of America Bulletin, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Stable isotopic results from paleosol carbonate in South Asia: Paleoenvironmental reconstructions and selective alteration

Earth and Planetary Science Letters, 2009

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Research paper thumbnail of A stratigraphic framework for Late Jurassic-Early Cretaceous gas-bearing strata (Monteith Formation) in the subsurface of northwest Alberta

Bulletin of Canadian Petroleum Geology, 2012

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Detrital zircon geochronology of Carboniferous?Cretaceous strata in the Lhasa terrane, Southern Tibet

Basin Research, 2007

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Evidence of Cretaceous Foreland Basin Systems in the Lhasa Terrane and the Implications for the Tectonic Evolution of Southern Tibet

Any model attempting to explain the relationship between the Indo-Asian collision and the uplift ... more Any model attempting to explain the relationship between the Indo-Asian collision and the uplift of the Tibetan plateau must first consider the tectonic circumstances in southern Asia immediately preceding the collision. Current hypotheses regarding Cretaceous tectonism in the Lhasa terrane of southern Tibet range between end-member models involving regional extension and regional contraction. We examined the Cretaceous sedimentary strata of

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Sedimentology and stratigraphy of the Lower Cretaceous Isachsen Formation: Ellef Ringnes Island, Sverdrup Basin, Canadian Arctic Archipelago

Marine and Petroleum Geology, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Garzón Massif basement tectonics: Structural control on evolution of petroleum systems in upper Magdalena and Putumayo basins, Colombia

Marine and Petroleum Geology

The Garz on Massif, is an active Laramide style basement uplift flanked by the Upper Magdalena Va... more The Garz on Massif, is an active Laramide style basement uplift flanked by the Upper Magdalena Valley (UMV) and the Putumayo Basin. In this paper we use new gravity, magnetic, well and seismic data for the first geophysical interpretation of the Garz on Massif. The Garz on/Algeciras fault has been previously interpreted as a right-lateral strike-slip fault. The new seismic, well, and gravity data demonstrates that the Garz on fault is also a low-angle (12e17) Andean age fault thrusting PreCambrian basement 10 e17 km northwestward over Miocene sediments of the UMV in a prospective footwall anticline. The new geophysical data as well as previous field mapping were used to produce the first gravity and magnetic maps and retrodeformable structural cross section of the northern Garz on Massif. The new model distinguishes for the first time distinct episodes of " thinskinned " and " thickskinned " deformation in the Garz on Massif. The model indicates approximately 43 km of Early to Middle Miocene shortening by " thinskinned " imbricate thrusting contemporaneous with the uplift of the nearby southern Central Cordillera (~9e16 Ma) and the main hydrocarbon expulsion event for the UMV and Putumayo Basin. This was followed by at least 22 km of Late Miocene (3e6 Ma) " thickskinned " Andean shortening and 7 km of uplift on the symmetrical Garz on thrust and a SE-verging basement thrust fault zone. The Andean uplift interrupted and exposed the hydrocarbon migration pathways to the Putumayo Basin. 3-D volume fracture analysis was used for the first time in this paper together with the first seismic and well data published for the Topoyaco and Miraflor structures to test closure models for the Topoyaco foothills. Intense fracturing is observed in the Topoyaco basement monocline from the near-surface to depths of over 3.5 km. The high level of fracturing permitted freshwater flushing and oil biodegradation and hydrocarbon escape. In contrast, the Miraflor-1 well, located just southwest of the Topoyaco block, tested light gravity oil and is sealed from groundwater flushing and biodegradation by a backthrust.

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Research paper thumbnail of The Cretaceous evolution of the Lhasa terrane, southern Tibet

ABSTRACT

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Research paper thumbnail of Provenance of the Cretaceous Athabasca Oil Sands, Canada: Implications for Continental-Scale Sediment Transport

Journal of Sedimentary Research, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mountains, Monsoons, and Fluvial Megafans

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Lower Jurassic Foreland Basin in Western Canada

2010 GSA Denver Annual Meeting, 2010

The earliest stages of the Cordilleran foreland basin in western Canada, namely the question of h... more The earliest stages of the Cordilleran foreland basin in western Canada, namely the question of how and when the region evolved from a stable margin to a retro-arc foreland basin, remain enigmatic. Here we integrate subsidence analysis with existing datasets to shed light on ...

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