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Sofyan Primulyana - One of the best experts on this subject based on the ideXlab platform.
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The Orange Tuff: a Late Pleistocene tephra-fall deposit emplaced by a VEI 5 silicic Plinian eruption in West Java, Indonesia
Bulletin of Volcanology, 2019Co-Authors: Christopher J. Harpel, James Stimac, Cecilia F. Avendaño Rodríguez De Harpel, Sofyan PrimulyanaAbstract:A VEI 5 dacite eruption emplaced the Orange Tuff about between 34.3 cal kBP and 17.2 cal kBP. Gunung Salak is the unit’s source and the Orange Tuff represents the most recent such eruption from any of the volcanoes southwest of Bogor, Indonesia. The Orange Tuff is the region’s first such documented tephra-fall deposit whose characteristics and phenocryst geochemistry make it readily identifiable over at least 1250 km^2. Magnetite compositions and temperature and f O_2 estimates inferred from Fe-Ti oxide compositions are particularly useful for identifying the unit. Deposit characteristics suggest that the eruption lasted 1–11 h with mass eruption rates of 1.0–8.3 × 10^8 kg/s and a column height of 31–40 km. The eruption’s column height and the deposit’s 2.5–11 km^3 volume suggest that the unit was dispersed over a much wider area than mapped. The unit is a Marker Bed throughout its mapped distribution and has potential to be applied over a much broader area as a regional Marker Bed. The large population and infrastructure proximal to Salak suggest that the unit should be considered in hazards assessments despite its age and the lack of subsequent similar eruptions.
Davide Olivero - One of the best experts on this subject based on the ideXlab platform.
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The late Barremian Halimedides horizon of the Dolomites (Southern Alps, Italy)
Cretaceous Research, 2012Co-Authors: Alexander Lukeneder, Alfred Uchman, Christian Gaillard, Davide OliveroAbstract:A new trace fossil Marker level, the Halimedides horizon, is proposed for the Lower Cretaceous pelagic to hemipelagic succession of the Puez area (Southern Alps, Italy). The horizon occurs in the middle part of the late Barremian Gerhardtia sartousiana Zone (Gerhardtia sartousiana Subzone). It is approximately 20 cm thick and restricted to the uppermost part of the Puez Limestone Member (marly limestones; Hauterivian Barremian; Puez Formation). It is fixed to the top 20 cm of Bed P1/204. The grey whitish limestone Bed of the G. sartousiana Zone is penetrated by Aptian red marls-siltstones of the RedBed Member. The horizon is documented for the first time from the Southern Alps, including the Dolomites, and can be correlated with other Mediterranean localities. The trace fossil assemblage of this Marker Bed with the co-occurrence of Halimedides, Spongehomotpha and Zoophycos sheds light on the Lower Cretaceous sedimentological history and current system of the Puez area within the Dolomites. It also highlights the palaeoenvironmental evolution of basins and plateaus and provides insights into the late Barremian interval. (C) 2012 Elsevier Ltd. All rights reserve
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The late Barremian Halimedides horizon of the Dolomites (Southern Alps, Italy).
Cretaceous research, 2012Co-Authors: Alexander Lukeneder, Alfred Uchman, Christian Gaillard, Davide OliveroAbstract:A new trace fossil Marker level, the Halimedides horizon, is proposed for the Lower Cretaceous pelagic to hemipelagic succession of the Puez area (Southern Alps, Italy). The horizon occurs in the middle part of the late Barremian Gerhardtia sartousiana Zone (Gerhardtia sartousiana Subzone). It is approximately 20 cm thick and restricted to the uppermost part of the Puez Limestone Member (marly limestones; Hauterivian–Barremian; Puez Formation). It is fixed to the top 20 cm of Bed P1/204. The grey–whitish limestone Bed of the G. sartousiana Zone is penetrated by Aptian red marls–siltstones of the RedBed Member. The horizon is documented for the first time from the Southern Alps, including the Dolomites, and can be correlated with other Mediterranean localities. The trace fossil assemblage of this Marker Bed with the co-occurrence of Halimedides, Spongeliomorpha and Zoophycos sheds light on the Lower Cretaceous sedimentological history and current system of the Puez area within the Dolomites. It also highlights the palaeoenvironmental evolution of basins and plateaus and provides insights into the late Barremian interval.
Bruce M. Simonson - One of the best experts on this subject based on the ideXlab platform.
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Isotopic dating of an Archean bolide impact horizon, Hamersley basin, Western Australia
Geology, 1998Co-Authors: Jon D. Woodhead, Janet M. Hergt, Bruce M. SimonsonAbstract:Detailed geologic field work in the Hamersley basin of Western Australia has identified a single horizon that contains predominantly sand-sized spherules similar to those found in impact ejecta such as at the Cretaceous-Tertiary boundary. Evidence suggests that these spherules represent a reworked distal strewn field formed by a large bolide impact in late Archean time. This so-called “spherule Marker Bed” occurs throughout the main body of the Hamersley basin and in stratigraphically equivalent, but shallower-water lithologies in the northeastern corner. Carbonate constitutes both a matrix component of the spherule Marker Bed and minor interBeds in the local stratigraphic section. We have utilized carbonate Pb-Pb dating methods to provide, for the first time, an age estimate (2541 +18/−15 Ma) for this important Marker Bed and therefore of the bolide impact event. Samples from both facies define, within error, an identical isochron age that is also consistent with the few zircon-based age estimates for the Hamersley succession. These findings highlight the great potential of carbonate Pb-Pb geochronology in the dating of Archean and Proterozoic sedimentary rocks.
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carbonate sedimentology of the early precambrian hamersley group of western australia
Precambrian Research, 1993Co-Authors: Bruce M. Simonson, Kathryn A Schubel, Scott W HasslerAbstract:Abstract The early Precambrian Hamersley Group of Western Australia contains both major and minor occurrences of well-preserved carbonate sedimentary rock. The Carawine Dolomite and the middle or Paraburdoo Member of the Wittenoom Formation are the two most extensive occurrences. The Carawine Dolomite is restricted to the eastern part of the Hamersley Basin and contains abundant stromatolites, oncolites, and wave ripples, as well as local occurrences of evaporite crystal pseudomorphs and oolitic to pisolitic textures. These carbonate strata were deposited in a shallow-water paleoenvironment herein referred to as the Carawine Platform. In contrast, the Wittenoom Formation is restricted to the centraland western parts of the Hamersley Basin, and such shallow-water features are entirely absent from its carbonate strata. These strata consist largely of thinly laminated lutite, but also include some thin carbonate turbidites. The carbonate sedimentary rocks of the Wittenoom Formation, as well as some in the Carawine Dolomite which display similar characteristics, are therefore interpreted as sediments that were deposited off-platform in deeper-water paleoenvironments. Paleocurrent, thickness, and grain size trends of the carbonate turbidites indicate they were deposited by paleoflows moving south and west. Even though the Carawine Dolomite lies to the northeast of the Wittenoom Formation, stratigraphic correlations using a newly recognized Marker Bed of probable impact origin suggest that the carbonate strata of the Carawine Dolomite are younger than the Paraburdoo Member of the Wittenoom Formation. If true, the Carawine Platform could not have been a source of sediment for most of the carbonate sedimentary rocks in the Wittenoom Formation, but it may havebeen the sediment source for similar carbonate turbidites in younger formations such as the Mt. McRae Shale and the Dales Gorge Member of the Brockman Iron Formation. This, in turn, suggests that carbonate sediments were accumulating in the shallower parts of the Hamersley Basin while some of the BIFs were being deposited simultaneously in the deeper parts.
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Geological evidence for a 2.6-Ga strewn field of impact spherules in the Hamersley Basin of Western Australia
1992Co-Authors: Bruce M. SimonsonAbstract:Sand-sized spherules up to 1.7 mm across with spherulitic, vesicular, and other crystalline textures that consist mainly of K-feldspar help define a unique horizon in the well-preserved 2.6-Ga Wittenoom Formation in the Hamersley Basin of Western Australia. This layer is informally known as the spherule Marker Bed. In the northeastern part of the Hamersley Basin, similar spherules again occur at only one horizon, but here they are a minor constituent of a dolomitic debris-flow deposit known as the dolomixtite layer. The dolomixtite layer occurs in the Carawine Dolomite, which is stratigraphically equivalent to the Wittenoom Formation. Moreover, paleocurrent data from closely associated carbonate and volcaniclastic turbidites indicate the spherule Marker Bed was deposited in deeper-water paleoenvironments than the dolomixtite layer. Therefore, the dolomixtite layer is believed to be a proximal equivalent of the spherule Marker Bed. The layers that host the spherules are interpreted to be the deposits of a major sediment gravity flow that exhumed and redeposited most of the spherules after shallow burial, although the flow is not believed to have been a direct result of the proposed impact. The most likely site for the proposed impact would have been in the early Precambrian ocean close to the northeastern edge of the Pilbara Craton. Another thin horizon in the overlying Brockman Iron Formation contains spherules that again consist largely of K-feldspar and have internal textures strikingly similar to those of the Wittenoom Formation and Carawine Dolomite. The close resemblance of these spherules to those of the Wittenoom Formation and Carawine Dolomite suggests they also originated as impact melt droplets, even though they are admixed with volcaniclastic detritus. The stratigraphic separation between the two suggests that a second major impact occurred near the Hamersley Basin after a time interval of about 75 m.y. elapsed. This suggests the record of impacts in early Precambrian strata is richer than is generally appreciated.
Christopher J. Harpel - One of the best experts on this subject based on the ideXlab platform.
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The Orange Tuff: a Late Pleistocene tephra-fall deposit emplaced by a VEI 5 silicic Plinian eruption in West Java, Indonesia
Bulletin of Volcanology, 2019Co-Authors: Christopher J. Harpel, James Stimac, Cecilia F. Avendaño Rodríguez De Harpel, Sofyan PrimulyanaAbstract:A VEI 5 dacite eruption emplaced the Orange Tuff about between 34.3 cal kBP and 17.2 cal kBP. Gunung Salak is the unit’s source and the Orange Tuff represents the most recent such eruption from any of the volcanoes southwest of Bogor, Indonesia. The Orange Tuff is the region’s first such documented tephra-fall deposit whose characteristics and phenocryst geochemistry make it readily identifiable over at least 1250 km^2. Magnetite compositions and temperature and f O_2 estimates inferred from Fe-Ti oxide compositions are particularly useful for identifying the unit. Deposit characteristics suggest that the eruption lasted 1–11 h with mass eruption rates of 1.0–8.3 × 10^8 kg/s and a column height of 31–40 km. The eruption’s column height and the deposit’s 2.5–11 km^3 volume suggest that the unit was dispersed over a much wider area than mapped. The unit is a Marker Bed throughout its mapped distribution and has potential to be applied over a much broader area as a regional Marker Bed. The large population and infrastructure proximal to Salak suggest that the unit should be considered in hazards assessments despite its age and the lack of subsequent similar eruptions.
Alexander Lukeneder - One of the best experts on this subject based on the ideXlab platform.
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The late Barremian Halimedides horizon of the Dolomites (Southern Alps, Italy)
Cretaceous Research, 2012Co-Authors: Alexander Lukeneder, Alfred Uchman, Christian Gaillard, Davide OliveroAbstract:A new trace fossil Marker level, the Halimedides horizon, is proposed for the Lower Cretaceous pelagic to hemipelagic succession of the Puez area (Southern Alps, Italy). The horizon occurs in the middle part of the late Barremian Gerhardtia sartousiana Zone (Gerhardtia sartousiana Subzone). It is approximately 20 cm thick and restricted to the uppermost part of the Puez Limestone Member (marly limestones; Hauterivian Barremian; Puez Formation). It is fixed to the top 20 cm of Bed P1/204. The grey whitish limestone Bed of the G. sartousiana Zone is penetrated by Aptian red marls-siltstones of the RedBed Member. The horizon is documented for the first time from the Southern Alps, including the Dolomites, and can be correlated with other Mediterranean localities. The trace fossil assemblage of this Marker Bed with the co-occurrence of Halimedides, Spongehomotpha and Zoophycos sheds light on the Lower Cretaceous sedimentological history and current system of the Puez area within the Dolomites. It also highlights the palaeoenvironmental evolution of basins and plateaus and provides insights into the late Barremian interval. (C) 2012 Elsevier Ltd. All rights reserve
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The late Barremian Halimedides horizon of the Dolomites (Southern Alps, Italy).
Cretaceous research, 2012Co-Authors: Alexander Lukeneder, Alfred Uchman, Christian Gaillard, Davide OliveroAbstract:A new trace fossil Marker level, the Halimedides horizon, is proposed for the Lower Cretaceous pelagic to hemipelagic succession of the Puez area (Southern Alps, Italy). The horizon occurs in the middle part of the late Barremian Gerhardtia sartousiana Zone (Gerhardtia sartousiana Subzone). It is approximately 20 cm thick and restricted to the uppermost part of the Puez Limestone Member (marly limestones; Hauterivian–Barremian; Puez Formation). It is fixed to the top 20 cm of Bed P1/204. The grey–whitish limestone Bed of the G. sartousiana Zone is penetrated by Aptian red marls–siltstones of the RedBed Member. The horizon is documented for the first time from the Southern Alps, including the Dolomites, and can be correlated with other Mediterranean localities. The trace fossil assemblage of this Marker Bed with the co-occurrence of Halimedides, Spongeliomorpha and Zoophycos sheds light on the Lower Cretaceous sedimentological history and current system of the Puez area within the Dolomites. It also highlights the palaeoenvironmental evolution of basins and plateaus and provides insights into the late Barremian interval.