New chemical analyses of the Suurberg volcanic rocks and their significance in relation to Mesozoic volcanism in Southern Africa
- Marsh, Julian S, Lock, B E, Fuchter, W H
- Authors: Marsh, Julian S , Lock, B E , Fuchter, W H
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133231 , vital:36951
- Description: Volcanic rocks are found associated with several of the late Mesozoic basins of southern South Africa. Bentonites are known from Plettenberg Bay and, according to an unconfirmed report, they are also found in the Worcester Basin, while vitric tuffs have been recorded from east of Oudtshoorn. The most extensive occurrences, however, are those of the Suurberg Group, which crops out sporadically around the margins of the Algoa Basin.
- Full Text:
- Date Issued: 1979
- Authors: Marsh, Julian S , Lock, B E , Fuchter, W H
- Date: 1979
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133231 , vital:36951
- Description: Volcanic rocks are found associated with several of the late Mesozoic basins of southern South Africa. Bentonites are known from Plettenberg Bay and, according to an unconfirmed report, they are also found in the Worcester Basin, while vitric tuffs have been recorded from east of Oudtshoorn. The most extensive occurrences, however, are those of the Suurberg Group, which crops out sporadically around the margins of the Algoa Basin.
- Full Text:
- Date Issued: 1979
Excursion to Granitberg and the Klinghardt Mountains, southern Namibia
- Authors: Marsh, Julian S
- Date: 1998
- Language: English
- Type: text , field guide
- Identifier: http://hdl.handle.net/10962/132118 , vital:36801
- Description: Three small subvolcanic intrusions (Granitberg, Pomona and Drachenberg) and associated dykes of Cretaceous age, occur between Bogenfels and Prinzen Bucht, S of Luderitz, Namibia. This field trip will chiefly be concerned with rocks that have crystallized from magmas of nepheline syenite composition.
- Full Text:
- Date Issued: 1998
- Authors: Marsh, Julian S
- Date: 1998
- Language: English
- Type: text , field guide
- Identifier: http://hdl.handle.net/10962/132118 , vital:36801
- Description: Three small subvolcanic intrusions (Granitberg, Pomona and Drachenberg) and associated dykes of Cretaceous age, occur between Bogenfels and Prinzen Bucht, S of Luderitz, Namibia. This field trip will chiefly be concerned with rocks that have crystallized from magmas of nepheline syenite composition.
- Full Text:
- Date Issued: 1998
Karoo and Etendeks flood basalt provinces, southern Africa and the tectonic development of their adjacent margins:
- Marsh, Julian S, Watkeys, M K
- Authors: Marsh, Julian S , Watkeys, M K
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144868 , vital:38386
- Description: Southern Africa hosts remnants of two continental flood basalt provinces emplaced in association with fragmentation of Gondwana. The earliest is the 183 Ma Karoo Province whose relationship to continental breakup and sea floor spreading is complex. Geochemical stratigraphy, Ar-Ar Dating and palaeomagnetism indicate that Karoo mafic igneous rocks throughout Southern Africa were emplaced over a very short interval at 183 Ma.
- Full Text:
- Date Issued: 1996
- Authors: Marsh, Julian S , Watkeys, M K
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144868 , vital:38386
- Description: Southern Africa hosts remnants of two continental flood basalt provinces emplaced in association with fragmentation of Gondwana. The earliest is the 183 Ma Karoo Province whose relationship to continental breakup and sea floor spreading is complex. Geochemical stratigraphy, Ar-Ar Dating and palaeomagnetism indicate that Karoo mafic igneous rocks throughout Southern Africa were emplaced over a very short interval at 183 Ma.
- Full Text:
- Date Issued: 1996
Karoo volcanic and intrusive rocks: Lesotho and Eastern Cape
- Authors: Marsh, Julian S
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144890 , vital:38388
- Description: The Karoo Igneous Province is one of the classic Mesozoic continental flood basalt provinces. At present erosion levels it comprises numerous eroded remnants of an extensive, thick volcanic sequence (largely lava flows) and a well-exposed subvolcanic intrusive complex of dykes and sheets which are particularly abundant in the underlying Karoo sedimentary strata.
- Full Text:
- Date Issued: 2013
- Authors: Marsh, Julian S
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144890 , vital:38388
- Description: The Karoo Igneous Province is one of the classic Mesozoic continental flood basalt provinces. At present erosion levels it comprises numerous eroded remnants of an extensive, thick volcanic sequence (largely lava flows) and a well-exposed subvolcanic intrusive complex of dykes and sheets which are particularly abundant in the underlying Karoo sedimentary strata.
- Full Text:
- Date Issued: 2013
Distribution and petrogenesis of the basic rocks of the Etendeka Formation of northwestern Namibia
- Marsh, Julian S, Duncan, Andrew R, Milner, Simon C, Erlank, Anthony J
- Authors: Marsh, Julian S , Duncan, Andrew R , Milner, Simon C , Erlank, Anthony J
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131667 , vital:36709
- Description: The igneous rocks which comprise the Etendeka Formation in northwestern Namibia cover an area of 78 000 km² and consist dominantly of interbedded basalts and quartz latites, with minor latites. They are spatially associated with, and intruded by, two suites of dolerites. The rocks of the Etendeka Formation are included in the Karoo Igneous Province but differ from most other Karoo volcanics with respect to their younger age (Cretaceous) and aspects of their mineralogy and geochemistry.
- Full Text:
- Date Issued: 1988
- Authors: Marsh, Julian S , Duncan, Andrew R , Milner, Simon C , Erlank, Anthony J
- Date: 1988
- Language: English
- Type: text , abstracts
- Identifier: http://hdl.handle.net/10962/131667 , vital:36709
- Description: The igneous rocks which comprise the Etendeka Formation in northwestern Namibia cover an area of 78 000 km² and consist dominantly of interbedded basalts and quartz latites, with minor latites. They are spatially associated with, and intruded by, two suites of dolerites. The rocks of the Etendeka Formation are included in the Karoo Igneous Province but differ from most other Karoo volcanics with respect to their younger age (Cretaceous) and aspects of their mineralogy and geochemistry.
- Full Text:
- Date Issued: 1988
Geochemical stratigraphy of the Mohale Dame-Katse Dam areas, Lesotho. Report on contract LHDA, Mohale Tunnel: Sampling and Testing of Cores. Lesotho Highlands Tunnel Partnership (Mohale)
- Authors: Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144857 , vital:38385
- Description: In monotonous basalt sequences, such as the Karoo basalt sequence in Lesotho, geochemistry can be a useful adjunct to stratigraphic studies. The acceptance of geochemical criteria in defining stratigraphic units arises from work in the Columbia River Group in NW SA (Swanson et al., 1979) and is now widely employed. It has recently been successfully applied in the Karoo basalts (Marsh et al., in press). In the current investigation a stratigraphic framework for construction work related to the Katse-Mohale tunnel has been developed using the compositions of basalt samples collected from a number of borehole cores in relation to the geochemical stratigraphy of Marshet al. (in press).
- Full Text:
- Date Issued: 1996
- Authors: Marsh, Julian S
- Date: 1996
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144857 , vital:38385
- Description: In monotonous basalt sequences, such as the Karoo basalt sequence in Lesotho, geochemistry can be a useful adjunct to stratigraphic studies. The acceptance of geochemical criteria in defining stratigraphic units arises from work in the Columbia River Group in NW SA (Swanson et al., 1979) and is now widely employed. It has recently been successfully applied in the Karoo basalts (Marsh et al., in press). In the current investigation a stratigraphic framework for construction work related to the Katse-Mohale tunnel has been developed using the compositions of basalt samples collected from a number of borehole cores in relation to the geochemical stratigraphy of Marshet al. (in press).
- Full Text:
- Date Issued: 1996
The Etendeka Igneous Province: magma types and their stratigraphic distribution with implications for the evolution of the Paraná-Etendeka flood basalt province
- Marsh, Julian S, Ewart, A, Milner, Simon C, Duncan, Andrew R, Miller, R McG
- Authors: Marsh, Julian S , Ewart, A , Milner, Simon C , Duncan, Andrew R , Miller, R McG
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149762 , vital:38882 , https://doi.org/10.1007/s004450000115
- Description: Detailed geochemical and field data for the volcanic sequence and intrusions of the Etendeka Igneous Province are used to construct a stratigraphic framework for petrogenetic interpretation of the evolution of the Etendeka-Paraná continental flood volcanic event. Geochemical and petrographic characterization of over 1,000 analyzed samples allows 8 mafic and 17 silicic magma types to be recognized.
- Full Text: false
- Date Issued: 2017
- Authors: Marsh, Julian S , Ewart, A , Milner, Simon C , Duncan, Andrew R , Miller, R McG
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149762 , vital:38882 , https://doi.org/10.1007/s004450000115
- Description: Detailed geochemical and field data for the volcanic sequence and intrusions of the Etendeka Igneous Province are used to construct a stratigraphic framework for petrogenetic interpretation of the evolution of the Etendeka-Paraná continental flood volcanic event. Geochemical and petrographic characterization of over 1,000 analyzed samples allows 8 mafic and 17 silicic magma types to be recognized.
- Full Text: false
- Date Issued: 2017
Tying up the continents
- Authors: Marsh, Julian S
- Date: 1989
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143282 , vital:38220
- Full Text:
- Date Issued: 1989
- Authors: Marsh, Julian S
- Date: 1989
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143282 , vital:38220
- Full Text:
- Date Issued: 1989
Karoo basalts, South Africa: Petrogenesis and the nature of their mantle rocks
- Marsh, Julian S, Eales, Hugh V
- Authors: Marsh, Julian S , Eales, Hugh V
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70141 , vital:29625
- Description: Outcrops of the Jurassic Karoo basalts and dolerites in central South Africa are remnants of a intracratonic continental igneous suite whose volume probably once exceeded 10 6km3.
- Full Text:
- Date Issued: 1982
- Authors: Marsh, Julian S , Eales, Hugh V
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70141 , vital:29625
- Description: Outcrops of the Jurassic Karoo basalts and dolerites in central South Africa are remnants of a intracratonic continental igneous suite whose volume probably once exceeded 10 6km3.
- Full Text:
- Date Issued: 1982
Implications of a new 40Ar/ 39Ar age for a basalt flow interbedded with the Etjo Formation, Northeast Namibia
- Marsh, Julian S, Swart, Roger S, Phillips, D
- Authors: Marsh, Julian S , Swart, Roger S , Phillips, D
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150364 , vital:38970 , https://doi.org/10.2113/106.4.281
- Description: A reliable 40Ar/39Ar plateau age of 180 ± 1.2 Ma (1σ) has been obtained for fresh basalt lava interbedded with aeolian Etjo Formation sandstones south-southwest of Grootfontein in northeast Namibia. This indicates that the Early Jurassic Karoo flood basalt sequence extended from Botswana into northeast Namibia at least as far as 18 east and that this may mark the eastern extent of the Early Cretaceous Etendeka Igneous Province.
- Full Text: false
- Date Issued: 2003
- Authors: Marsh, Julian S , Swart, Roger S , Phillips, D
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150364 , vital:38970 , https://doi.org/10.2113/106.4.281
- Description: A reliable 40Ar/39Ar plateau age of 180 ± 1.2 Ma (1σ) has been obtained for fresh basalt lava interbedded with aeolian Etjo Formation sandstones south-southwest of Grootfontein in northeast Namibia. This indicates that the Early Jurassic Karoo flood basalt sequence extended from Botswana into northeast Namibia at least as far as 18 east and that this may mark the eastern extent of the Early Cretaceous Etendeka Igneous Province.
- Full Text: false
- Date Issued: 2003
Evolution of a strongly differentiated suite of phonolites from the Klinghardt Mountains, Namibia
- Authors: Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140400 , vital:37885 , https://doi.org/10.1016/0024-4937(87)90023-5
- Description: Phonolites of Tertiary age occur as eroded tholoids, lava flows, ignimbrites, and coulees in the Klinghardt Mountains of southern Namibia. Sixty samples have been analyzed for major and trace elements and fourteen of these for 87SR 86SR. The phonolites lie close to the low-pressure cotectics in Q-Ne-Ks, in keeping with their petrography which indicates that most samples have phenocrysts of both nepheline and sanidine. Na has been variably lost from the rocks during crystallization and devitrification/alteration of hypocrystalline specimens.
- Full Text: false
- Date Issued: 2003
- Authors: Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140400 , vital:37885 , https://doi.org/10.1016/0024-4937(87)90023-5
- Description: Phonolites of Tertiary age occur as eroded tholoids, lava flows, ignimbrites, and coulees in the Klinghardt Mountains of southern Namibia. Sixty samples have been analyzed for major and trace elements and fourteen of these for 87SR 86SR. The phonolites lie close to the low-pressure cotectics in Q-Ne-Ks, in keeping with their petrography which indicates that most samples have phenocrysts of both nepheline and sanidine. Na has been variably lost from the rocks during crystallization and devitrification/alteration of hypocrystalline specimens.
- Full Text: false
- Date Issued: 2003
Tertiary phonolite volcanism in the Klinghardt Mountains of South West Africa/Namibia
- Authors: Marsh, Julian S , Lock, B E
- Date: 1981
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133242 , vital:36953 , https://hdl.handle.net/10520/AJA10120750_2789
- Description: The Klinghardt Mountains in South West Africa (Namibia) were the site of an important volcanic outburst late in the Eocene or early in the Oligocene. Over a hundred endogenous domes and several lava flows of the coulee type were emplaced: all analysed samples (more than 60) comprise varieties of phonolite. A sequence of ash-flow tuffs of limited areal extent is present on Glasrucken.
- Full Text:
- Date Issued: 1981
- Authors: Marsh, Julian S , Lock, B E
- Date: 1981
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133242 , vital:36953 , https://hdl.handle.net/10520/AJA10120750_2789
- Description: The Klinghardt Mountains in South West Africa (Namibia) were the site of an important volcanic outburst late in the Eocene or early in the Oligocene. Over a hundred endogenous domes and several lava flows of the coulee type were emplaced: all analysed samples (more than 60) comprise varieties of phonolite. A sequence of ash-flow tuffs of limited areal extent is present on Glasrucken.
- Full Text:
- Date Issued: 1981
The concentrations of the noble metals in Southern African flood-type basalts and MORB: implications for petrogenesis and magmatic sulphide exploration
- Maier, Wolfgand D, Barnes, Sarah-Jane, Marsh, Julian S
- Authors: Maier, Wolfgand D , Barnes, Sarah-Jane , Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150573 , vital:38985 , https://doi.org/10.1007/s00410-003-0480-z
- Description: Concentrations of the platinum-group elements have been determined in several suites of southern African flood-type basalts and mid-ocean ridge basalt (MORB), covering some 3 Ga of geologic evolution and including the Etendeka, Karoo, Soutpansberg, Machadodorp, Hekpoort, Ventersdorp and Dominion magmas.
- Full Text: false
- Date Issued: 2003
- Authors: Maier, Wolfgand D , Barnes, Sarah-Jane , Marsh, Julian S
- Date: 2003
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150573 , vital:38985 , https://doi.org/10.1007/s00410-003-0480-z
- Description: Concentrations of the platinum-group elements have been determined in several suites of southern African flood-type basalts and mid-ocean ridge basalt (MORB), covering some 3 Ga of geologic evolution and including the Etendeka, Karoo, Soutpansberg, Machadodorp, Hekpoort, Ventersdorp and Dominion magmas.
- Full Text: false
- Date Issued: 2003
The distribution of platinum group elements in the Insizwa lobe, Mount Ayliff Complex, South Africa: implications for Ni-Cu-PGE sulfide exploration in the Karoo igneous province
- Maier, W D, Marsh, Julian S, Barnes, Sarah-Jane, Dodd, D C
- Authors: Maier, W D , Marsh, Julian S , Barnes, Sarah-Jane , Dodd, D C
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150353 , vital:38969 , https://0-doi.org.wam.seals.ac.za/10.2113/gsecongeo.97.6.1293
- Description: The Mount Ayliff Complex of the Eastern Cape province of South Africa is a layered intrusion of some 800 km2 surface area and up to 1,200 m thickness. On the basis of compositional similarities and spatial association, it is generally interpreted to form part of the Karoo igneous province. Similarities between the Mount Ayliff Complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the Mount Ayliff Complex may have an enhanced potential for Noril’sk-Talnakh–type massive Ni-Cu sulfide ores, an idea that is supported by the well-known sulfide occurrence at Waterfall Gorge.
- Full Text: false
- Date Issued: 2002
- Authors: Maier, W D , Marsh, Julian S , Barnes, Sarah-Jane , Dodd, D C
- Date: 2002
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150353 , vital:38969 , https://0-doi.org.wam.seals.ac.za/10.2113/gsecongeo.97.6.1293
- Description: The Mount Ayliff Complex of the Eastern Cape province of South Africa is a layered intrusion of some 800 km2 surface area and up to 1,200 m thickness. On the basis of compositional similarities and spatial association, it is generally interpreted to form part of the Karoo igneous province. Similarities between the Mount Ayliff Complex and the staging chambers and feeder conduits to flood basalts that host magmatic sulfide ores elsewhere in the world suggest that the Mount Ayliff Complex may have an enhanced potential for Noril’sk-Talnakh–type massive Ni-Cu sulfide ores, an idea that is supported by the well-known sulfide occurrence at Waterfall Gorge.
- Full Text: false
- Date Issued: 2002
Rock magnetic stratigraphy of a mafic layered sill: a key to the Karoo volcanics plumbing system
- Maes, S M, Ferré, E E, Tikoff, B, Brown, P E, Marsh, Julian S
- Authors: Maes, S M , Ferré, E E , Tikoff, B , Brown, P E , Marsh, Julian S
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144901 , vital:38389 , https://doi.org/10.1016/j.jvolgeores.2005.07.038
- Description: The Insizwa sill is an 1 km-thick subhorizontal layered mafic intrusion and part of the Karoo Large Igneous Province in South Africa. This well-exposed intrusion consists of several superimposed petrologically and geochemically distinct units. Magnetic methods were used to study the intrusion in order to constrain the physical processes active in these types of bodies during crystallization. Rock magnetism studies indicate that within different petrologic units bulk susceptibility is controlled by primary magnetite (with minor pyrrhotite) and/or paramagnetic minerals (olivine, pyroxene). New magnetic data based on 659 specimens obtained from 3 vertical borehole cores, each spaced 5 km apart, confirm the prominent vertical zonation in low field magnetic susceptibility (Klf), degree of anisotropy (Pj) and orientation of the anisotropy of magnetic susceptibility (AMS) axes.
- Full Text:
- Date Issued: 2008
- Authors: Maes, S M , Ferré, E E , Tikoff, B , Brown, P E , Marsh, Julian S
- Date: 2008
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144901 , vital:38389 , https://doi.org/10.1016/j.jvolgeores.2005.07.038
- Description: The Insizwa sill is an 1 km-thick subhorizontal layered mafic intrusion and part of the Karoo Large Igneous Province in South Africa. This well-exposed intrusion consists of several superimposed petrologically and geochemically distinct units. Magnetic methods were used to study the intrusion in order to constrain the physical processes active in these types of bodies during crystallization. Rock magnetism studies indicate that within different petrologic units bulk susceptibility is controlled by primary magnetite (with minor pyrrhotite) and/or paramagnetic minerals (olivine, pyroxene). New magnetic data based on 659 specimens obtained from 3 vertical borehole cores, each spaced 5 km apart, confirm the prominent vertical zonation in low field magnetic susceptibility (Klf), degree of anisotropy (Pj) and orientation of the anisotropy of magnetic susceptibility (AMS) axes.
- Full Text:
- Date Issued: 2008
Significance of 87Sr/86Sr ratios in the Merensky cyclic unit of the Bushveld Complex
- Kruger, Floris J, Marsh, Julian S
- Authors: Kruger, Floris J , Marsh, Julian S
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133524 , vital:36986 , https://doi.org/10.1038/298053a0
- Description: In a number of mafic layered intrusions, layers with platinum group element (PGE) mineralization coincide with breaks in cumulus mineral composition and isotopic variation trends through the layered sequence1,2. For example, in the Bushveld Complex in South Africa, abrupt increases in initial 87Sr/86Sr ratios occur at the UG-2 and Merensky pegmatoid (or ‘reef’) horizons, both of which are exploited for PGEs. We report here the results of a detailed Sr-isotope study across the Merensky unit and its immediate foot- and hangingwall-rocks which, when considered together with new ideas on processes operating in magma chambers3–5, suggest that magma mixing and post-cumulus infiltration of liquids displaced from below were important during crystallization of the Merensky pegmatoid.
- Full Text: false
- Date Issued: 1982
- Authors: Kruger, Floris J , Marsh, Julian S
- Date: 1982
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/133524 , vital:36986 , https://doi.org/10.1038/298053a0
- Description: In a number of mafic layered intrusions, layers with platinum group element (PGE) mineralization coincide with breaks in cumulus mineral composition and isotopic variation trends through the layered sequence1,2. For example, in the Bushveld Complex in South Africa, abrupt increases in initial 87Sr/86Sr ratios occur at the UG-2 and Merensky pegmatoid (or ‘reef’) horizons, both of which are exploited for PGEs. We report here the results of a detailed Sr-isotope study across the Merensky unit and its immediate foot- and hangingwall-rocks which, when considered together with new ideas on processes operating in magma chambers3–5, suggest that magma mixing and post-cumulus infiltration of liquids displaced from below were important during crystallization of the Merensky pegmatoid.
- Full Text: false
- Date Issued: 1982
The mineralogy, petrology, and origin of the Merensky cyclic unit in the western Bushveld Complex
- Kruger, Floris J, Marsh, Julian S
- Authors: Kruger, Floris J , Marsh, Julian S
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136024 , vital:37329 , https://doi.org/10.2113/gsecongeo.80.4.958
- Description: The Merensky cyclic unit of the Bushveld Complex represents the first products to crystallize after the influx and mixing of a large new batch of magma in the chamber. Excluding the Merensky pegmatoid, the Merensky cyclic unit grades upward from an orthopyroxenite at the base, through norite to anorthosite at the top of the sequence. It is followed by the very similar Bastard cyclic unit.
- Full Text: false
- Date Issued: 1985
- Authors: Kruger, Floris J , Marsh, Julian S
- Date: 1985
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/136024 , vital:37329 , https://doi.org/10.2113/gsecongeo.80.4.958
- Description: The Merensky cyclic unit of the Bushveld Complex represents the first products to crystallize after the influx and mixing of a large new batch of magma in the chamber. Excluding the Merensky pegmatoid, the Merensky cyclic unit grades upward from an orthopyroxenite at the base, through norite to anorthosite at the top of the sequence. It is followed by the very similar Bastard cyclic unit.
- Full Text: false
- Date Issued: 1985
Dyke swarms and associated lava formations in the northern Lebombo monocline, Karoo Large Igneous Province, South Africa
- Klausen, Martin B, Marsh, Julian S, Watkeys, M K
- Authors: Klausen, Martin B , Marsh, Julian S , Watkeys, M K
- Date: 2006
- Language: English
- Type: text , Abstracts
- Identifier: http://hdl.handle.net/10962/132751 , vital:36880
- Description: As one of the early classical examples of plume-generated Large Igneous Provinces (LIPs), the Karoo is characterized by a bulls-eye distribution of High-Ti basalts, picrites, and earliest nephelinites onto a conspicuous triple rift junction (i.e., Okavango dyke swarm and the two Mwenezi and Lebombo monoclines), surrounded by Low-Ti basalts. It is noted that this regional distribution between high-and low-Ti basalts within the Jurassic Karoo LIP differs from that of the Permian Emeishan LIP; thereby undermining the use of this particular feature as evidence for mantle plume involvement.
- Full Text:
- Date Issued: 2006
- Authors: Klausen, Martin B , Marsh, Julian S , Watkeys, M K
- Date: 2006
- Language: English
- Type: text , Abstracts
- Identifier: http://hdl.handle.net/10962/132751 , vital:36880
- Description: As one of the early classical examples of plume-generated Large Igneous Provinces (LIPs), the Karoo is characterized by a bulls-eye distribution of High-Ti basalts, picrites, and earliest nephelinites onto a conspicuous triple rift junction (i.e., Okavango dyke swarm and the two Mwenezi and Lebombo monoclines), surrounded by Low-Ti basalts. It is noted that this regional distribution between high-and low-Ti basalts within the Jurassic Karoo LIP differs from that of the Permian Emeishan LIP; thereby undermining the use of this particular feature as evidence for mantle plume involvement.
- Full Text:
- Date Issued: 2006
Emplacement of inflated Pāhoehoe flows in the Naude’s Nek Pass, Lesotho remnant, Karoo continental flood basalt province: use of flow-lobe tumuli in understanding flood basalt emplacement
- Jay, A E, Marsh, Julian S, Fluteau, F, Courtillot, V
- Authors: Jay, A E , Marsh, Julian S , Fluteau, F , Courtillot, V
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/60752 , vital:27826 , https://link.springer.com/article/10.1007/s00445-017-1189-6
- Description: Physical volcanological features are presented for a 710-m-thick section, of the Naude’s Nek Pass, within the lower part of the Lesotho remnant of the Karoo Large Igneous Province. The section consists of inflated pāhoehoe lava with thin, impersistent sedimentary interbeds towards the base. There are seven discreet packages of compound and hummocky pāhoehoe lobes containing flow-lobe tumuli, making up approximately 50% of the section. Approximately 45% of the sequence consists of 14 sheet lobes, between 10 and 52-m-thick. The majority of the sheet lobes are in two packages indicating prolonged periods of lava supply capable of producing thick sheet lobes. The other sheet lobes are as individual lobes or pairs, within compound flows, suggesting brief increases in lava supply rate. We suggest, contrary to current belief, that there is no evidence that compound flows are proximal to source and sheet lobes (simple flows) are distal to source and we propose that the presence of flow-lobe tumuli in compound flows could be an indicator that a flow is distal to source. We use detailed, previously published, studies of the Thakurvadi Formation (Deccan Traps) as an example. We show that the length of a lobe and therefore the sections that are ‘medial or distal to source’ are specific to each individual lobe and are dependent on the lava supply of each eruptive event, and as such flow lobe tumuli can be used as an indicator of relative distance from source.
- Full Text:
- Date Issued: 2018
- Authors: Jay, A E , Marsh, Julian S , Fluteau, F , Courtillot, V
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/60752 , vital:27826 , https://link.springer.com/article/10.1007/s00445-017-1189-6
- Description: Physical volcanological features are presented for a 710-m-thick section, of the Naude’s Nek Pass, within the lower part of the Lesotho remnant of the Karoo Large Igneous Province. The section consists of inflated pāhoehoe lava with thin, impersistent sedimentary interbeds towards the base. There are seven discreet packages of compound and hummocky pāhoehoe lobes containing flow-lobe tumuli, making up approximately 50% of the section. Approximately 45% of the sequence consists of 14 sheet lobes, between 10 and 52-m-thick. The majority of the sheet lobes are in two packages indicating prolonged periods of lava supply capable of producing thick sheet lobes. The other sheet lobes are as individual lobes or pairs, within compound flows, suggesting brief increases in lava supply rate. We suggest, contrary to current belief, that there is no evidence that compound flows are proximal to source and sheet lobes (simple flows) are distal to source and we propose that the presence of flow-lobe tumuli in compound flows could be an indicator that a flow is distal to source. We use detailed, previously published, studies of the Thakurvadi Formation (Deccan Traps) as an example. We show that the length of a lobe and therefore the sections that are ‘medial or distal to source’ are specific to each individual lobe and are dependent on the lava supply of each eruptive event, and as such flow lobe tumuli can be used as an indicator of relative distance from source.
- Full Text:
- Date Issued: 2018
New views on the Jurassic Clarens Formation: volcano-sedimentary interaction
- Holzforster, Frank, Holzforster, Heike W, Marsh, Julian S
- Authors: Holzforster, Frank , Holzforster, Heike W , Marsh, Julian S
- Date: 2002
- Language: English
- Type: text , abstract
- Identifier: http://hdl.handle.net/10962/132716 , vital:36874
- Description: The Lower Jurassic Clarens Formation of the Great Karoo Basin is usually viewed in the literature as a aeolian and, in places, fluvio-aeolian deposit of tremendous thickness variation form 0-250 m thickness. Interaction with the overlying Karoo Flood Basalts, particularly in the Eastern Cape area and in Lesotho, has been noted but was never a major topic. Relatively widespread pyroclastic deposits sandwiched between the Clarens Formation and the Karoo Flood Basalts have been interpreted as flood-lahars.
- Full Text:
- Date Issued: 2002
- Authors: Holzforster, Frank , Holzforster, Heike W , Marsh, Julian S
- Date: 2002
- Language: English
- Type: text , abstract
- Identifier: http://hdl.handle.net/10962/132716 , vital:36874
- Description: The Lower Jurassic Clarens Formation of the Great Karoo Basin is usually viewed in the literature as a aeolian and, in places, fluvio-aeolian deposit of tremendous thickness variation form 0-250 m thickness. Interaction with the overlying Karoo Flood Basalts, particularly in the Eastern Cape area and in Lesotho, has been noted but was never a major topic. Relatively widespread pyroclastic deposits sandwiched between the Clarens Formation and the Karoo Flood Basalts have been interpreted as flood-lahars.
- Full Text:
- Date Issued: 2002