Pub Date : 2023-05-10DOI: 10.1080/08120099.2023.2200476
E. Lounejeva, J. Steadman, R. Large, K. Grice, P. Olin, I. Belousov
Abstract Sedimentary pyrite trace-element composition is an established proxy for determining paleo-ocean geochemistry and atmospheric oxygen concentrations through deep time. However, its applicability over shorter time-scales (i.e. <20 Ma) is not well known. To test this, we targeted fine-grained pyrite in the Hovea Member of the Kockatea Shale (Perth Basin, Western Australia), which encompasses the late Permian inertinitic interval and the end-Permian to Early Triassic sapropel, and spans approximately 10 million years. The end-Permian mass extinction (EPME) was the largest extinction event in Earth history, and its greatest effect is documented in the marine environment. Samples were collected from two oil exploration wells—Redback-2 and Hovea-3—spaced ∼20 km apart. In the two boreholes, a change in depositional facies (i.e. between the inertinite and sapropel) occurs below the Permian–Triassic boundary and records the transition from a marginal marine to a shelf environment. This transition is highlighted by several lithogeochemical indicators (e.g. negative shift δ13C values and Corg reduction; increases in Ca, Fe and P), which are themselves tied to fundamental changes in modal mineralogy between the two zones. Importantly, the sapropel also records a major increase in iron sulfide burial over that in the inertinite. LA-ICPMS analyses of pyrite demonstrate that trace-element abundance is highest in samples below the facies transition, and in places reaches a few percent, particularly of Ni (4 wt%), Co (1.5 wt%) and As (2.8 wt%). Moreover, these and other trace elements decrease by an order of magnitude in concert with the negative shift in δ13C values in the sapropel zone. Various whole-rock based paleosalinity indicator ratios (e.g. B/Ga) indicate that the areas of the Perth Basin intersected by Redback-2 and Hovea-3 were not fully connected to the open ocean at the time of the EPME, which leads us to conclude that the very high trace-element values in the sedimentary sulfides are reflective of regional environmental shifts rather than a global signal. Nonetheless, a geochemical contribution from a distant igneous province, such as the Siberian Traps Large Igneous Province, cannot be ruled out. Our work underscores the strength of sedimentary pyrite as a robust paleoenvironmental proxy in the marine environment and highlights the need for further investigation of pyrite trace-element profiles across the mass extinction interval in other sedimentary sequences around the globe. KEY POINTS LA-ICPMS-based geochemistry of sedimentary pyrite from the Hovea Member of the Kockatea Shale is considered within a lithochemostratigraphic context. The overall interpretation of the results involves a change in depositional setting from the marginal in the late Permian brackish waters to shelfal marine and loss of oxygen in the Early Triassic Perth Basin.
{"title":"Lithogeochemical and sulfide trace-element systematics across the Permian–Triassic boundary, Perth Basin, Western Australia: constraints on the shallow marine environment during the end-Permian mass extinction","authors":"E. Lounejeva, J. Steadman, R. Large, K. Grice, P. Olin, I. Belousov","doi":"10.1080/08120099.2023.2200476","DOIUrl":"https://doi.org/10.1080/08120099.2023.2200476","url":null,"abstract":"Abstract Sedimentary pyrite trace-element composition is an established proxy for determining paleo-ocean geochemistry and atmospheric oxygen concentrations through deep time. However, its applicability over shorter time-scales (i.e. <20 Ma) is not well known. To test this, we targeted fine-grained pyrite in the Hovea Member of the Kockatea Shale (Perth Basin, Western Australia), which encompasses the late Permian inertinitic interval and the end-Permian to Early Triassic sapropel, and spans approximately 10 million years. The end-Permian mass extinction (EPME) was the largest extinction event in Earth history, and its greatest effect is documented in the marine environment. Samples were collected from two oil exploration wells—Redback-2 and Hovea-3—spaced ∼20 km apart. In the two boreholes, a change in depositional facies (i.e. between the inertinite and sapropel) occurs below the Permian–Triassic boundary and records the transition from a marginal marine to a shelf environment. This transition is highlighted by several lithogeochemical indicators (e.g. negative shift δ13C values and Corg reduction; increases in Ca, Fe and P), which are themselves tied to fundamental changes in modal mineralogy between the two zones. Importantly, the sapropel also records a major increase in iron sulfide burial over that in the inertinite. LA-ICPMS analyses of pyrite demonstrate that trace-element abundance is highest in samples below the facies transition, and in places reaches a few percent, particularly of Ni (4 wt%), Co (1.5 wt%) and As (2.8 wt%). Moreover, these and other trace elements decrease by an order of magnitude in concert with the negative shift in δ13C values in the sapropel zone. Various whole-rock based paleosalinity indicator ratios (e.g. B/Ga) indicate that the areas of the Perth Basin intersected by Redback-2 and Hovea-3 were not fully connected to the open ocean at the time of the EPME, which leads us to conclude that the very high trace-element values in the sedimentary sulfides are reflective of regional environmental shifts rather than a global signal. Nonetheless, a geochemical contribution from a distant igneous province, such as the Siberian Traps Large Igneous Province, cannot be ruled out. Our work underscores the strength of sedimentary pyrite as a robust paleoenvironmental proxy in the marine environment and highlights the need for further investigation of pyrite trace-element profiles across the mass extinction interval in other sedimentary sequences around the globe. KEY POINTS LA-ICPMS-based geochemistry of sedimentary pyrite from the Hovea Member of the Kockatea Shale is considered within a lithochemostratigraphic context. The overall interpretation of the results involves a change in depositional setting from the marginal in the late Permian brackish waters to shelfal marine and loss of oxygen in the Early Triassic Perth Basin.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"716 - 730"},"PeriodicalIF":1.2,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48059182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-08DOI: 10.1080/08120099.2023.2207198
P. Plummer
Abstract Throughout the Flinders Ranges of South Australia, the red bed Brachina sequence comprises the lower of two regressive, coarsening-upward successions that together constitute the Ediacaran-aged Wilpena Group. Detailed examination of the Brachina sequence has identified evidence of ice-rafting, supporting the contention that frigid climatic conditions continued well after cessation of the Marinoan Glaciation, as well as features postulated to be harbingers of the macroscopic metazoans that occur in abundance higher in the local stratigraphy. Although tuffaceous and lying stratigraphically between deposits of the Marinoan Glaciation and the Acraman Impact/Gaskiers Glaciation, no absolute age dates exist for the sequence. However, through correlation to the global carbon isotope profile, the timespan of Brachina sequence deposition can be constrained to between 635 and 586 Ma, when the regression climaxed with terrestrial deposition upon a local disconformity. The tuffaceous input is timed to have begun at 620 Ma, essentially coincident with initial formation of the passive volcanic continental margin of southeastern Australia and initiation of both the Volyn Large Igneous Province and activity within the Central Iapetus Magmatic Province, all components marking the demise of Rodinia and initial amalgamation of Gondwana. KEY POINTS Correlation to the global carbon isotope profile dates the early Ediacaran Brachina sequence of the Flinders Ranges to between 635 and 586 Ma. The ABC Range Quartzite in the central Flinders Ranges is derived from, and hence younger than, the deltaic ABC Range Quartzite in the southwestern Flinders Ranges. Several volcanic outpourings across the Ediacaran globe during the final breakup of Rodinia and initial assembly of Gondwana, including that associated with the development of the eastern Australian passive margin, produced an abundance of atmospheric ash that settled during and beyond deposition of the Brachina sequence.
{"title":"The early Ediacaran Brachina sequence, Flinders Ranges, South Australia: its age, formation and plate tectonic setting","authors":"P. Plummer","doi":"10.1080/08120099.2023.2207198","DOIUrl":"https://doi.org/10.1080/08120099.2023.2207198","url":null,"abstract":"Abstract Throughout the Flinders Ranges of South Australia, the red bed Brachina sequence comprises the lower of two regressive, coarsening-upward successions that together constitute the Ediacaran-aged Wilpena Group. Detailed examination of the Brachina sequence has identified evidence of ice-rafting, supporting the contention that frigid climatic conditions continued well after cessation of the Marinoan Glaciation, as well as features postulated to be harbingers of the macroscopic metazoans that occur in abundance higher in the local stratigraphy. Although tuffaceous and lying stratigraphically between deposits of the Marinoan Glaciation and the Acraman Impact/Gaskiers Glaciation, no absolute age dates exist for the sequence. However, through correlation to the global carbon isotope profile, the timespan of Brachina sequence deposition can be constrained to between 635 and 586 Ma, when the regression climaxed with terrestrial deposition upon a local disconformity. The tuffaceous input is timed to have begun at 620 Ma, essentially coincident with initial formation of the passive volcanic continental margin of southeastern Australia and initiation of both the Volyn Large Igneous Province and activity within the Central Iapetus Magmatic Province, all components marking the demise of Rodinia and initial amalgamation of Gondwana. KEY POINTS Correlation to the global carbon isotope profile dates the early Ediacaran Brachina sequence of the Flinders Ranges to between 635 and 586 Ma. The ABC Range Quartzite in the central Flinders Ranges is derived from, and hence younger than, the deltaic ABC Range Quartzite in the southwestern Flinders Ranges. Several volcanic outpourings across the Ediacaran globe during the final breakup of Rodinia and initial assembly of Gondwana, including that associated with the development of the eastern Australian passive margin, produced an abundance of atmospheric ash that settled during and beyond deposition of the Brachina sequence.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"681 - 690"},"PeriodicalIF":1.2,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47355844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-08DOI: 10.1080/08120099.2023.2202719
H. Kurnio, Y. Dahlan, J. Kanily
Abstract Placer gold deposits in marine sediments in Indonesian waters, especially in Bayah southwest of Java Island, Banten Province, have many characteristics. In Bayah coastal waters, gold mostly accumulates in very fine sands and is associated with magnetic minerals. Elsewhere, coarser sand and gravel sediments tend to have higher Au contents. Gold exploitation in marine sediments has begun with a trial carried out in the coastal water of Bayah using local fishing boats. The successful trial has required pumping of large volumes of bottom sediments onto the deck of a cargo ship with 13.103 tonne capacity that are then stockpiled and processed. Laboratory studies reveal that secondary gold is mostly silt-sized flakes (0.002–0.05 mm).
{"title":"Gold placer characteristics in marine sediments of Bayah, West Java, Indonesia","authors":"H. Kurnio, Y. Dahlan, J. Kanily","doi":"10.1080/08120099.2023.2202719","DOIUrl":"https://doi.org/10.1080/08120099.2023.2202719","url":null,"abstract":"Abstract Placer gold deposits in marine sediments in Indonesian waters, especially in Bayah southwest of Java Island, Banten Province, have many characteristics. In Bayah coastal waters, gold mostly accumulates in very fine sands and is associated with magnetic minerals. Elsewhere, coarser sand and gravel sediments tend to have higher Au contents. Gold exploitation in marine sediments has begun with a trial carried out in the coastal water of Bayah using local fishing boats. The successful trial has required pumping of large volumes of bottom sediments onto the deck of a cargo ship with 13.103 tonne capacity that are then stockpiled and processed. Laboratory studies reveal that secondary gold is mostly silt-sized flakes (0.002–0.05 mm).","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"741 - 750"},"PeriodicalIF":1.2,"publicationDate":"2023-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43236284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-27DOI: 10.1080/08120099.2023.2201628
N. James, J. Clarke, Anita Andrew
Abstract The Israelite Plain, a narrow terrace at the western edge of the Great Australian Bight, is characterised by a series of schizohaline, ephemeral lakes leeward of a marginal marine eolianite dune complex that has many similarities to the Coorong Coastal Plain (CCP). The late Pleistocene and Holocene sediments are a mixture of dominantly quartzose sand and lesser carbonate components. Paleolagoon to shallow marine MIS 5e, mollusc-rich quartzose deposits are capped by calcrete or karst and contain a biota similar to the well-documented, coeval Glanville Formation on the CCP. Holocene sands with minor carbonate are also lagoonal and resemble many modern Coorong Lagoon deposits. Both deposits are interpreted to reflect marine accumulation during sea-level highstands. Lakes today range from dry to water-filled with most floored by calcareous quartzose sand. Microbial influenced sedimentary structures in the form of pustular to laminated mats veneer lake margin bedrock and sediment. Carbonate minerals are mostly calcite with abundant accessory magnesium-calcite, aragonite and traces of magnesite, monohydrocalcite and halite. Gypsum is minor but ubiquitous and floors one of the smaller, marginal-marine lakes. Although having a similar evaporative climate and evidence of groundwater resurgence like Coorong lakes, there is no significant synsedimentary dolomite. This aspect is interpreted to reflect the narrow width of the plain, and the Mg-poor source of groundwater from the nearby karst Nullarbor Plain to the north. The Israelite Plain, together with other coeval, young successions marginal to the Southern Ocean under a semiarid climate now illustrate the depositional variations and early diagenetic differences that can occur in similar environments adjacent to a cool ocean. KEY POINTS The Israelite Plain is a narrow, marginal marine terrace covered by Quaternary, lagoonal, eolian to lacustrine, calcareous siliciclastic sands, similar to several other calcareous terraces along the southern Australia coast. The interpreted sediment ages are late Pleistocene stage MIS 5e with the deposit sporadically overlain by similar Holocene deposits. Most 14C age dates are suspicious because of interpreted diagenesis or MIS 5e age, whereas U/Th age dates appear correct or altered by diagenesis. Pleistocene biota is dominated by the bivalve Anadara trapezia, whereas Holocene deposits contain a varied array of cooler water molluscs. The carbonates are similar to those on the Coorong Coastal Plain but do not contain any dolomite likely because of climate and lack of Mg-groundwater flow.
{"title":"Israelite Plain, southwestern Australia, a siliciclastic, late Quaternary Coorong analogue, without dolomite","authors":"N. James, J. Clarke, Anita Andrew","doi":"10.1080/08120099.2023.2201628","DOIUrl":"https://doi.org/10.1080/08120099.2023.2201628","url":null,"abstract":"Abstract The Israelite Plain, a narrow terrace at the western edge of the Great Australian Bight, is characterised by a series of schizohaline, ephemeral lakes leeward of a marginal marine eolianite dune complex that has many similarities to the Coorong Coastal Plain (CCP). The late Pleistocene and Holocene sediments are a mixture of dominantly quartzose sand and lesser carbonate components. Paleolagoon to shallow marine MIS 5e, mollusc-rich quartzose deposits are capped by calcrete or karst and contain a biota similar to the well-documented, coeval Glanville Formation on the CCP. Holocene sands with minor carbonate are also lagoonal and resemble many modern Coorong Lagoon deposits. Both deposits are interpreted to reflect marine accumulation during sea-level highstands. Lakes today range from dry to water-filled with most floored by calcareous quartzose sand. Microbial influenced sedimentary structures in the form of pustular to laminated mats veneer lake margin bedrock and sediment. Carbonate minerals are mostly calcite with abundant accessory magnesium-calcite, aragonite and traces of magnesite, monohydrocalcite and halite. Gypsum is minor but ubiquitous and floors one of the smaller, marginal-marine lakes. Although having a similar evaporative climate and evidence of groundwater resurgence like Coorong lakes, there is no significant synsedimentary dolomite. This aspect is interpreted to reflect the narrow width of the plain, and the Mg-poor source of groundwater from the nearby karst Nullarbor Plain to the north. The Israelite Plain, together with other coeval, young successions marginal to the Southern Ocean under a semiarid climate now illustrate the depositional variations and early diagenetic differences that can occur in similar environments adjacent to a cool ocean. KEY POINTS The Israelite Plain is a narrow, marginal marine terrace covered by Quaternary, lagoonal, eolian to lacustrine, calcareous siliciclastic sands, similar to several other calcareous terraces along the southern Australia coast. The interpreted sediment ages are late Pleistocene stage MIS 5e with the deposit sporadically overlain by similar Holocene deposits. Most 14C age dates are suspicious because of interpreted diagenesis or MIS 5e age, whereas U/Th age dates appear correct or altered by diagenesis. Pleistocene biota is dominated by the bivalve Anadara trapezia, whereas Holocene deposits contain a varied array of cooler water molluscs. The carbonates are similar to those on the Coorong Coastal Plain but do not contain any dolomite likely because of climate and lack of Mg-groundwater flow.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"659 - 680"},"PeriodicalIF":1.2,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48151105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-13DOI: 10.1080/08120099.2023.2193620
C. Pain
Abstract Eighteen Middle–Upper Pleistocene (ca 200 ka) tephra units in the highlands of Papua New Guinea (PNG) are mapped and described. The study area is about 24 000 km2, extending from Tari in the west to Kainantu and the Kassam Pass in the east. It is estimated that at least 75 000 km2 of highland PNG received ≥50 cm tephra from various highland sources, and the total volume would have been well over 300 km3. Total tephra thicknesses near sources are >20 m, with thicknesses of individual units near source ranging from 1–2 to >4 m. Several units were deposited with coarse ash and lapilli basal layers that have been weathered to fine ash and clay sizes. Hagen, Giluwe and Yelia volcanoes are the main sources, with smaller centres near Giluwe and north of Hagen also producing mappable tephra units. One unit (Birip) was erupted about 40 ka, but most of the tephra units are 200 ka and older. Volumes of tephra suggest that many of the eruptions had volcanic explosivity indices of 4–6. On stable bedrock, tephras are present on slopes up to 35°, demonstrating the high stability of the tephra materials. Gaps in the tephra cover coincide with bedrock that weathers to unstable regolith where tephras did not accumulate; the tephra cover thus provides an indicator of bedrock stability. Mapped tephra units provide the potential for correlation of other Quaternary materials and can be used as widespread marker beds. The tephras are also important as the parent material for the dominant agricultural soils in the highlands. KEY POINTS In the highlands of Papua New Guinea at least 75 000 km2 received >50 cm of tephra mainly from Hagen, Giluwe and Yelia volcanoes. This work extends knowledge of highland volcanic history, which will allow correlation of surfaces and events across the highlands. The tephras are important parent materials of soils that support highly productive agriculture in the highland valleys. The long-term stability of tephra-covered slopes maintains a soil cover for thousands, if not tens of thousands, of years.
{"title":"Middle–Upper Pleistocene tephras in the Papua New Guinea highlands","authors":"C. Pain","doi":"10.1080/08120099.2023.2193620","DOIUrl":"https://doi.org/10.1080/08120099.2023.2193620","url":null,"abstract":"Abstract Eighteen Middle–Upper Pleistocene (ca 200 ka) tephra units in the highlands of Papua New Guinea (PNG) are mapped and described. The study area is about 24 000 km2, extending from Tari in the west to Kainantu and the Kassam Pass in the east. It is estimated that at least 75 000 km2 of highland PNG received ≥50 cm tephra from various highland sources, and the total volume would have been well over 300 km3. Total tephra thicknesses near sources are >20 m, with thicknesses of individual units near source ranging from 1–2 to >4 m. Several units were deposited with coarse ash and lapilli basal layers that have been weathered to fine ash and clay sizes. Hagen, Giluwe and Yelia volcanoes are the main sources, with smaller centres near Giluwe and north of Hagen also producing mappable tephra units. One unit (Birip) was erupted about 40 ka, but most of the tephra units are 200 ka and older. Volumes of tephra suggest that many of the eruptions had volcanic explosivity indices of 4–6. On stable bedrock, tephras are present on slopes up to 35°, demonstrating the high stability of the tephra materials. Gaps in the tephra cover coincide with bedrock that weathers to unstable regolith where tephras did not accumulate; the tephra cover thus provides an indicator of bedrock stability. Mapped tephra units provide the potential for correlation of other Quaternary materials and can be used as widespread marker beds. The tephras are also important as the parent material for the dominant agricultural soils in the highlands. KEY POINTS In the highlands of Papua New Guinea at least 75 000 km2 received >50 cm of tephra mainly from Hagen, Giluwe and Yelia volcanoes. This work extends knowledge of highland volcanic history, which will allow correlation of surfaces and events across the highlands. The tephras are important parent materials of soils that support highly productive agriculture in the highland valleys. The long-term stability of tephra-covered slopes maintains a soil cover for thousands, if not tens of thousands, of years.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"627 - 658"},"PeriodicalIF":1.2,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44566618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-13DOI: 10.1080/08120099.2023.2194945
C. Yule, J. Daniell, D. Edwards, N. Rollet, E. Roberts
Abstract The Canning Basin is a prospective hydrocarbon frontier basin and is unusual for having limited offshore seismic and well data in comparison with its onshore extent. In this study, seismic mapping was conducted to better resolve the continuity of 13 key stratigraphic units from onshore to offshore to delineate prospective offshore hydrocarbon-bearing units, and better understand the distribution of mafic igneous units that can compartmentalise migration pathways and influence heat flow. The offshore Canning Basin strata are poorly constrained in six wells with limited seismic coverage; hence data availability was bolstered by integrating data from the onshore portion of the basin and adjacent basins into a single 3D seismic stratigraphic model. This model integrates over 10 000 km of historical 2D seismic data and 23 exploration wells to allow mapping of key stratal surfaces. Mapped seismic horizons were used to construct isochores and regional cross-sections. Seven of the 13 units were mapped offshore for the first time, revealing that the onshore and offshore stratigraphy are similar, albeit with some minor differences, and mafic igneous units are more interconnected than previously documented whereby they may constitute a mafic magmatic province. These basin-scale maps provide a framework for future research and resource exploration in the Canning Basin. To better understand the basin’s geological evolution, tectonic history and petroleum prospectivity, additional well data are needed in the offshore Canning Basin where Ordovician strata have yet to be sampled. Key Points Coastlines act as barriers that can prevent parity of stratigraphic interpretations and geoscience data acquisition for adjacent onshore, offshore areas. This study features seismic stratigraphic mapping of 13 key units in the Canning Basin coastal area, including seven units mapped continuously from onshore to offshore for the first time. This research delivers a framework for future exploration and a better understanding of the Canning Basin’s geological history.
{"title":"Reconciling the onshore/offshore stratigraphy of the Canning Basin and implications for petroleum prospectivity","authors":"C. Yule, J. Daniell, D. Edwards, N. Rollet, E. Roberts","doi":"10.1080/08120099.2023.2194945","DOIUrl":"https://doi.org/10.1080/08120099.2023.2194945","url":null,"abstract":"Abstract The Canning Basin is a prospective hydrocarbon frontier basin and is unusual for having limited offshore seismic and well data in comparison with its onshore extent. In this study, seismic mapping was conducted to better resolve the continuity of 13 key stratigraphic units from onshore to offshore to delineate prospective offshore hydrocarbon-bearing units, and better understand the distribution of mafic igneous units that can compartmentalise migration pathways and influence heat flow. The offshore Canning Basin strata are poorly constrained in six wells with limited seismic coverage; hence data availability was bolstered by integrating data from the onshore portion of the basin and adjacent basins into a single 3D seismic stratigraphic model. This model integrates over 10 000 km of historical 2D seismic data and 23 exploration wells to allow mapping of key stratal surfaces. Mapped seismic horizons were used to construct isochores and regional cross-sections. Seven of the 13 units were mapped offshore for the first time, revealing that the onshore and offshore stratigraphy are similar, albeit with some minor differences, and mafic igneous units are more interconnected than previously documented whereby they may constitute a mafic magmatic province. These basin-scale maps provide a framework for future research and resource exploration in the Canning Basin. To better understand the basin’s geological evolution, tectonic history and petroleum prospectivity, additional well data are needed in the offshore Canning Basin where Ordovician strata have yet to be sampled. Key Points Coastlines act as barriers that can prevent parity of stratigraphic interpretations and geoscience data acquisition for adjacent onshore, offshore areas. This study features seismic stratigraphic mapping of 13 key units in the Canning Basin coastal area, including seven units mapped continuously from onshore to offshore for the first time. This research delivers a framework for future exploration and a better understanding of the Canning Basin’s geological history.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"691 - 715"},"PeriodicalIF":1.2,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43287192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-12DOI: 10.1080/08120099.2023.2194960
F. Zhao, C. L. Hu, C. Han, Y. Q. Dong, Q. X. Yuan
Abstract Paleocurrent reconstruction is an important aspect of basin research, playing a key role in the reconstruction of sediment development and understanding the evolution of sedimentary environments. The reconstruction of paleowind direction is an important part of the study of paleoatmospheric circulation, playing a vital role in revealing the characteristics and evolution of paleoclimate. Water flow and wind movement present similar interactions with ground objects and leave direction information. This paper summarises the current common reconstruction theories of paleocurrent and paleowind direction, analyses the advantages and disadvantages of the reconstruction theories, and analyses the characteristics of reconstruction results. Based on the technical structure of paleocurrent and paleowind direction reconstruction, the development of reconstruction theories, processes and results are highlighted. The analysis shows that paleocurrent and paleowind directions can be used for paleoatmospheric circulation research, resource exploration, paleogeographic environment reconstruction and planetary geological research. KEY POINTS The current common theories of paleocurrent and paleowind direction reconstruction are outlined. The advantages, disadvantages and scope of application of the reconstruction theory are summarised. Applications and developments in the reconstruction of paleocurrent and paleowind directions are identified.
{"title":"Paleocurrent and paleowind direction reconstruction research progress and perspectives: a review","authors":"F. Zhao, C. L. Hu, C. Han, Y. Q. Dong, Q. X. Yuan","doi":"10.1080/08120099.2023.2194960","DOIUrl":"https://doi.org/10.1080/08120099.2023.2194960","url":null,"abstract":"Abstract Paleocurrent reconstruction is an important aspect of basin research, playing a key role in the reconstruction of sediment development and understanding the evolution of sedimentary environments. The reconstruction of paleowind direction is an important part of the study of paleoatmospheric circulation, playing a vital role in revealing the characteristics and evolution of paleoclimate. Water flow and wind movement present similar interactions with ground objects and leave direction information. This paper summarises the current common reconstruction theories of paleocurrent and paleowind direction, analyses the advantages and disadvantages of the reconstruction theories, and analyses the characteristics of reconstruction results. Based on the technical structure of paleocurrent and paleowind direction reconstruction, the development of reconstruction theories, processes and results are highlighted. The analysis shows that paleocurrent and paleowind directions can be used for paleoatmospheric circulation research, resource exploration, paleogeographic environment reconstruction and planetary geological research. KEY POINTS The current common theories of paleocurrent and paleowind direction reconstruction are outlined. The advantages, disadvantages and scope of application of the reconstruction theory are summarised. Applications and developments in the reconstruction of paleocurrent and paleowind directions are identified.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"603 - 626"},"PeriodicalIF":1.2,"publicationDate":"2023-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45391309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-05DOI: 10.1080/08120099.2023.2194358
J. Clemens
Abstract The magmas that formed each Devonian, S-type, volcanic complex in central Victoria were generated through partial melting of a distinct assemblage of rock types in the crustal source region. The more silicic rhyolites were formed independently of the rhyodacitic to dacitic magmas, rather than as differentiates. Within every complex, each ignimbritic unit is also heterogeneous in its chemical and isotopic characteristics. Thus, in this part of Paleozoic Australia, magma heterogeneity occurred on at least three scales—the individual rock unit, the complex and across the region. This means that the Selwyn Block, the logical source of the ignimbrite magmas, is highly heterogeneous, probably in three dimensions. The statistically significant differences in the ages of the various complexes suggest that the heat sources for partial melting of the deep crust were themselves rather local in extent, and probably reflected numerous asynchronous intrusions of mantle-derived mafic magmas, most likely in relatively small batches. Thus, there should be no thick underplated or intraplated layer of gabbroic rock in the deep crust here. Thinner bodies of hot mafic magmas were probably emplaced in different places and at different levels, inducing local high-grade metamorphic conditions. Published radiometric dates for various volcanic units suggest that the magmatic heating of the crust occurred over a period of at least 17 Myr, although maximum intensity occurred between ca 375 and ca 371 Ma. Thus, a model of the deep crust here should involve numerous, perhaps thin metasedimentary units with highly variable ages and original clay contents, as well as sills of Late Devonian mafic rocks scattered both vertically and horizontally and intruded episodically. The dominantly meta-igneous sources of crustally derived I-type magmas generally lie at higher structural levels, where they did not experience metamorphic temperatures sufficient to cause the higher-temperature melting reactions needed to form I-type volcanic magmas. KEY POINTS Each Late Devonian, S-type, volcanic magma in central Victoria formed through melting of a distinct assemblage of crustal source rocks, most likely within the Selwyn Block. The rhyolites formed independently of the rhyodacitic to dacitic magmas, not as differentiates. The mafic magma heat sources for partial melting of the deep crust were emplaced as numerous, relatively small batches, in sheets distributed horizontally and vertically. The dominantly meta-igneous and shallower crustal sources of I-type magmas did not experience the higher temperatures required to form I-type volcanic magmas.
{"title":"Devonian ignimbrites of central Victoria: explosive magmas from multiple sources, and deep crustal structure in the Selwyn Block","authors":"J. Clemens","doi":"10.1080/08120099.2023.2194358","DOIUrl":"https://doi.org/10.1080/08120099.2023.2194358","url":null,"abstract":"Abstract The magmas that formed each Devonian, S-type, volcanic complex in central Victoria were generated through partial melting of a distinct assemblage of rock types in the crustal source region. The more silicic rhyolites were formed independently of the rhyodacitic to dacitic magmas, rather than as differentiates. Within every complex, each ignimbritic unit is also heterogeneous in its chemical and isotopic characteristics. Thus, in this part of Paleozoic Australia, magma heterogeneity occurred on at least three scales—the individual rock unit, the complex and across the region. This means that the Selwyn Block, the logical source of the ignimbrite magmas, is highly heterogeneous, probably in three dimensions. The statistically significant differences in the ages of the various complexes suggest that the heat sources for partial melting of the deep crust were themselves rather local in extent, and probably reflected numerous asynchronous intrusions of mantle-derived mafic magmas, most likely in relatively small batches. Thus, there should be no thick underplated or intraplated layer of gabbroic rock in the deep crust here. Thinner bodies of hot mafic magmas were probably emplaced in different places and at different levels, inducing local high-grade metamorphic conditions. Published radiometric dates for various volcanic units suggest that the magmatic heating of the crust occurred over a period of at least 17 Myr, although maximum intensity occurred between ca 375 and ca 371 Ma. Thus, a model of the deep crust here should involve numerous, perhaps thin metasedimentary units with highly variable ages and original clay contents, as well as sills of Late Devonian mafic rocks scattered both vertically and horizontally and intruded episodically. The dominantly meta-igneous sources of crustally derived I-type magmas generally lie at higher structural levels, where they did not experience metamorphic temperatures sufficient to cause the higher-temperature melting reactions needed to form I-type volcanic magmas. KEY POINTS Each Late Devonian, S-type, volcanic magma in central Victoria formed through melting of a distinct assemblage of crustal source rocks, most likely within the Selwyn Block. The rhyolites formed independently of the rhyodacitic to dacitic magmas, not as differentiates. The mafic magma heat sources for partial melting of the deep crust were emplaced as numerous, relatively small batches, in sheets distributed horizontally and vertically. The dominantly meta-igneous and shallower crustal sources of I-type magmas did not experience the higher temperatures required to form I-type volcanic magmas.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"535 - 547"},"PeriodicalIF":1.2,"publicationDate":"2023-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49369979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-04-02DOI: 10.1080/08120099.2023.2188489
N. Langsford, J. Jago
Abstract Widespread tuffs are known from the lower Cambrian succession of the Arrowie Basin, Flinders Ranges, mainly from the lower parts of both the Mernmerna Formation and the Billy Creek Formation. Up to 2.5 m of potassium-rich (K2O 6.32–9.60 wt%) rhyolite tuffs are known from the Mernmerna Formation, with the ‘Big Green Tuff’ from Bunyeroo Gorge yielding a TIMS age of 515.4 ± 0.2 Ma (i.e. unnamed Cambrian stage 3). The petrography of the Big Green Tuff, with numerous glass shards, suggests an explosive subaqueous pyroclastic deposit or ash-flow tuff. The presence of several layers of identical green tuff indicates that these were produced by a multi-phase volcanic event. There are up to thirty tuff horizons (5–50 cm thick) within the Warragee Member of the Billy Creek Formation. The tuffs within the Billy Creek Formation occur over a wide area, with an east–west extent of 250 km and a north–south extent of up to 80 km. It is suggested that they are in part ash-flow tuffs. A previous TIMS age for the Billy Creek Formation was 511.87 ± 0.14 Ma (i.e. unnamed Cambrian stage 4). The source of the tuffs, both from the Mernmerna Formation and the Billy Creek Formation is unknown. Detailed study of the whole-rock and trace-element geochemistry is required to fully document them. KEY POINTS Widespread tuffs have been known for about sixty years from the lower Cambrian Mernmerna and Billy Creek formations in the Flinders Ranges, but only a limited amount of work has been done on them. The potassium-rich rhyolitic tuffs of the Mernmerna Formation occur in several horizons up to 2.5 m thick, thus indicating a substantial volcanic event. Sources of the tuffs from both the Mernmerna and Billy Creek formations are unknown. The widespread distribution of both the Billy Creek Formation tuffs and the rhyolitic tuffs in the Mernmerna Formation and the uppermost Wilkawillina Formation indicates that the volcanic activity within the Arrowie Basin was widespread and at times intense.
{"title":"Lower Cambrian volcanism in the Hawker Group and the Billy Creek Formation, Arrowie Basin, Flinders Ranges, South Australia","authors":"N. Langsford, J. Jago","doi":"10.1080/08120099.2023.2188489","DOIUrl":"https://doi.org/10.1080/08120099.2023.2188489","url":null,"abstract":"Abstract Widespread tuffs are known from the lower Cambrian succession of the Arrowie Basin, Flinders Ranges, mainly from the lower parts of both the Mernmerna Formation and the Billy Creek Formation. Up to 2.5 m of potassium-rich (K2O 6.32–9.60 wt%) rhyolite tuffs are known from the Mernmerna Formation, with the ‘Big Green Tuff’ from Bunyeroo Gorge yielding a TIMS age of 515.4 ± 0.2 Ma (i.e. unnamed Cambrian stage 3). The petrography of the Big Green Tuff, with numerous glass shards, suggests an explosive subaqueous pyroclastic deposit or ash-flow tuff. The presence of several layers of identical green tuff indicates that these were produced by a multi-phase volcanic event. There are up to thirty tuff horizons (5–50 cm thick) within the Warragee Member of the Billy Creek Formation. The tuffs within the Billy Creek Formation occur over a wide area, with an east–west extent of 250 km and a north–south extent of up to 80 km. It is suggested that they are in part ash-flow tuffs. A previous TIMS age for the Billy Creek Formation was 511.87 ± 0.14 Ma (i.e. unnamed Cambrian stage 4). The source of the tuffs, both from the Mernmerna Formation and the Billy Creek Formation is unknown. Detailed study of the whole-rock and trace-element geochemistry is required to fully document them. KEY POINTS Widespread tuffs have been known for about sixty years from the lower Cambrian Mernmerna and Billy Creek formations in the Flinders Ranges, but only a limited amount of work has been done on them. The potassium-rich rhyolitic tuffs of the Mernmerna Formation occur in several horizons up to 2.5 m thick, thus indicating a substantial volcanic event. Sources of the tuffs from both the Mernmerna and Billy Creek formations are unknown. The widespread distribution of both the Billy Creek Formation tuffs and the rhyolitic tuffs in the Mernmerna Formation and the uppermost Wilkawillina Formation indicates that the volcanic activity within the Arrowie Basin was widespread and at times intense.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"70 1","pages":"476 - 493"},"PeriodicalIF":1.2,"publicationDate":"2023-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46139668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-22DOI: 10.1080/08120099.2023.2186951
M. Zhao, Y. Liu, X. Jiao, D. Zhou, Z. Meng, Y. Yang
Abstract The Permian Lucaogou oil shales in the eastern Junggar Basin have long been regarded as important source rocks and reservoirs for tight oil exploration. The oil shales can also be used to assess the provenance and tectonic setting of the East Junggar region using major, trace and rare earth element geochemistry. The low chemical index of alteration ratios (37.36–64.18, 45.54 on average), low plagioclase index of alteration ratios (26.99–62.95, 42.99 on average), and high index of compositional variability ratios (0.64–1.66, 1.10 on average) suggest that the Permian Lucaogou oil shales mostly consist of immature sediments that have experienced a weak weathering intensity. The samples have low TiO2/Al2O3 and TiO2/Zr ratios that indicate a felsic origin with minor intermediate igneous rocks. The high Th/Sc and Zr/Sc ratios suggest a felsic origin without sediment recycling. The samples show fractionated light rare earth elements and relatively flat heavy rare earth elements patterns with weak negative Eu anomalies, which implies that the main provenance is lower Carboniferous intermediate–acid volcanic rocks. In addition, multiple major- and trace-element‐based discrimination diagrams show that the parent rock of clastic sediments formed mainly in a continental island arc and active continental margin environment, consistent with previous studies on the tectonic background of the East Junggar region during the late early Carboniferous. Key Points Immature sediments are present in the Permian Lucaogou oil shales and have a weak weathering intensity. The provenance of the clastic sediments of the Permian Lucaogou oil shales was predominantly early Carboniferous intermediate–acid volcanic rocks. The clastic sediments of the Permian Lucaogou oil shales were developed in a continental island arc and active continental margin environments. The Permian Lucaogou oil shales provide crucial information for tectonic setting and evolution of the northern Xinjiang during the Carboniferous–Permian.
{"title":"Major, trace and rare earth element geochemistry of the Permian Lucaogou oil shales, eastern Junggar Basin, NW China: implications for weathering, provenance and tectonic setting","authors":"M. Zhao, Y. Liu, X. Jiao, D. Zhou, Z. Meng, Y. Yang","doi":"10.1080/08120099.2023.2186951","DOIUrl":"https://doi.org/10.1080/08120099.2023.2186951","url":null,"abstract":"Abstract The Permian Lucaogou oil shales in the eastern Junggar Basin have long been regarded as important source rocks and reservoirs for tight oil exploration. The oil shales can also be used to assess the provenance and tectonic setting of the East Junggar region using major, trace and rare earth element geochemistry. The low chemical index of alteration ratios (37.36–64.18, 45.54 on average), low plagioclase index of alteration ratios (26.99–62.95, 42.99 on average), and high index of compositional variability ratios (0.64–1.66, 1.10 on average) suggest that the Permian Lucaogou oil shales mostly consist of immature sediments that have experienced a weak weathering intensity. The samples have low TiO2/Al2O3 and TiO2/Zr ratios that indicate a felsic origin with minor intermediate igneous rocks. The high Th/Sc and Zr/Sc ratios suggest a felsic origin without sediment recycling. The samples show fractionated light rare earth elements and relatively flat heavy rare earth elements patterns with weak negative Eu anomalies, which implies that the main provenance is lower Carboniferous intermediate–acid volcanic rocks. In addition, multiple major- and trace-element‐based discrimination diagrams show that the parent rock of clastic sediments formed mainly in a continental island arc and active continental margin environment, consistent with previous studies on the tectonic background of the East Junggar region during the late early Carboniferous. Key Points Immature sediments are present in the Permian Lucaogou oil shales and have a weak weathering intensity. The provenance of the clastic sediments of the Permian Lucaogou oil shales was predominantly early Carboniferous intermediate–acid volcanic rocks. The clastic sediments of the Permian Lucaogou oil shales were developed in a continental island arc and active continental margin environments. The Permian Lucaogou oil shales provide crucial information for tectonic setting and evolution of the northern Xinjiang during the Carboniferous–Permian.","PeriodicalId":8601,"journal":{"name":"Australian Journal of Earth Sciences","volume":"47 4","pages":"585 - 602"},"PeriodicalIF":1.2,"publicationDate":"2023-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41310192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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