The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups

Óskarsson, Birgir V.; Riishuus, Morten S.

doi:10.1016/j.jvolgeores.2014.11.009

Cited by 19 publications

(18 citation statements)

References 78 publications

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“…Likewise, on Iceland, individual Miocene lava sequences in both the northwestern and eastern parts of the island can be traced for 10–20 km (Bodvarsson & Walker, ; McDougall et al, ). Óskarsson and Riishuus () also mapped individual Pleistocene lava flows for 15–20 km, which they link to high effusion rates and enhanced mantle temperatures during eruption. Topography has an important control on the morphology of lava flows.…”

Section: Geological Setting and Previous Workmentioning

confidence: 99%

Characterization of Seaward‐Dipping Reflectors Along the South American Atlantic Margin and Implications for Continental Breakup

et al. 2018

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Thick packages of lavas forming seaward‐dipping reflectors (SDRs) are diagnostic features of volcanic passive margins. Despite their significance to continental breakup studies, their formation mechanism is still debated. We use ~22,000 km of high‐quality, depth‐migrated, seismic data to document the three‐dimensional geometry of SDRs offshore South America. We find two types: Type I are planar and occur as fault‐bounded wedges. Type II are characterized by reflections that become more convex‐upward in the downdip direction and terminate against a subhorizontal base. We interpret the transition from Type I to Type II SDRs to represent a continuum from continental rifting to full plate separation with formation of new, subaerially generated, magmatic crust. Type I SDRs formed in half grabens during the stretching of continental crust, while Type II lavas infill the space produced by flexing of the crust due to the solidification of the underlying feeder dikes as the magmatic crust moved away from the spreading center. Type II SDRs vary in length and thickness along the margin. In the north, close to the Paraná flood basalts, they are long (tens of kilometers), reach thicknesses of up to 15 km, and have an across margin width of up to 600 km. To the south the Type II SDRs are thinner with lava lengths of <10 km. We propose that Type II lavas in the north erupted from a subaerial, plate spreading center above the Tristan mantle plume and that the shorter lava flows to the south indicates eruption into water, consistent with a cooler, off‐plume mantle.

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Section: Geological Setting and Previous Workmentioning

confidence: 99%

Characterization of Seaward‐Dipping Reflectors Along the South American Atlantic Margin and Implications for Continental Breakup

et al. 2018

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“…Those from Morocco show modes of PDFs of 8-10 m (Figure 9C), presumably thin SLs, with thicker lobes in places up to 50 m (Argana, El Hachimi et al, 2011;Marzoli et al, 2019). This suggests that the sequences in Morocco are dominated by thin sheet lobes, but in NE North America much thicker CAMP lobes have been recorded, with thicknesses of lobes from 60 m up to 180 m in the Newark and Fundy basins (e.g., Phillpotts, 1998;Whiteside et al, 2007: Olsen, 1980, Olsen et al, 1989Schaller et al, 2011;Puffer et al, 1992;Puffer et al, 2018), and these are convincingly inflated SLs.…”

Section: Other Cfb Provinces and Hawai'imentioning

confidence: 96%

Thickness Characteristics of Pāhoehoe Lavas in the Deccan Province, Western Ghats, India, and in Continental Flood Basalt Provinces Elsewhere

2021

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Constraining the eruption rates of flood basalt lava flows remains a significant challenge despite decades of work. One potential observable proxy for eruption rates is flood basalt lava-flow lobe thicknesses, a topic that we tackle here quantitatively. In this study, we provide the first global compilation of pāhoehoe lava-lobe thicknesses from various continental flood basalt provinces (∼ 3,800 measurements) to compare characteristic thicknesses within and between provinces. We refer to thin lobes (∼ ≤5 m), characteristic of “compound” lavas, as hummocky pāhoehoe lava flows or flow-fields. Conversely, we term thicker lobes, characteristic of “simple” flows, as coming from sheet-lobe-dominated flows. Data from the Deccan Traps and Columbia River flood-basalt provinces are archetypal since they have the most consistent datasets as well as established chemo- and litho-stratigraphies. Examining Deccan lobe thicknesses, we find that previously suggested (and disputed) distinct temporal and regional distributions of hummocky pāhoehoe and sheet-lobe-dominated flow fields are not strongly supported by the data and that each geochemically defined formation displays both lobe types in varying amounts. Thin flow-lobes do not appear to indicate proximity to source. The modal lobe thickness of Deccan formations with abundant “thin” lava-lobes is 8 m, while the mode for sheet-lobe-dominated formations is only 17 m. Sheet-lobes up to 75–80 m are rare in the Deccan and Columbia River Provinces, and ones >100 m are exceptional globally. For other flood basalt provinces, modal thickness plots show a prevalence toward similar lobe thicknesses to Deccan, with many provinces having some or most lobes in the 5–8 m modal range. However, median values are generally thicker, in the 8–12 m range, suggesting that sheet-lobes dominate. By contrast, lobes from non-flood basalt flow-fields (e.g., Hawai’i, Snake River Plain) show distinctly thinner modes, sub-5 m. Our results provide a quantitative basis to ascertain variations in gross lava morphology and, perhaps, this will in future be related to emplacement dynamics of different flood basalt provinces, or parts thereof. We can also systematically distinguish outlier lobes (or regions) from typical lobes in a province, e.g., North American Central Atlantic Magmatic Province lava-lobes are anomalously thick and are closely related to feeder-intrusions, thus enabling a better understanding of conditions required to produce large-volume, thick, flood basalt lava-lobes and flows.

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“…The lava pile is primarily composed of flood basalt lavas, some of which are widespread and can be traced over long distances and used as marker horizons (e.g. (Óskarsson & Riishuus, 2013(Óskarsson & Riishuus, , 2014Walker, 1958).…”

Section: Geological Settingmentioning

confidence: 99%

“…Several collapse calderas, sub-volcanic intrusions, and large amounts of effusive silicic rocks are preceded by, and intercalated with, voluminous flood basalts. These basalts have been suggested to reflect a more pronounced and wider-spread activity of the Iceland plume (Óskarsson & Riishuus, 2013(Óskarsson & Riishuus, , 2014.…”

Section: Introductionmentioning

confidence: 98%

Geology of a Neogene caldera cluster in Northeast Iceland – clues into rift zone architecture on a young Iceland

Burchardt¹,

Óskarsson²,

Gústafsson³

et al. 2021

Preprint

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The Borgarfjörður-Loðmundarfjörður area in Northeast Iceland hosts an unusual volume of silicic rocks, as well as volcanic and sub-volcanic structures emplaced in the Miocene between 13.5 and 12.2 Ma. Here, we summarise the geology of the area and present a new geological map to summarise the current state of knowledge. We describe the prominent features of the volcanic centres, as well as regional marker horizons. Notably, the volume of silicic rocks, the distribution of eruptive centres, calderas, and intrusion swarms, as well as the interplay between regional flood basalts and silicic magmatism indicate a rift zone architecture different to that of the present day.

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The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups

Cited by 19 publications

References 78 publications

Characterization of Seaward‐Dipping Reflectors Along the South American Atlantic Margin and Implications for Continental Breakup

Characterization of Seaward‐Dipping Reflectors Along the South American Atlantic Margin and Implications for Continental Breakup

Thickness Characteristics of Pāhoehoe Lavas in the Deccan Province, Western Ghats, India, and in Continental Flood Basalt Provinces Elsewhere

Geology of a Neogene caldera cluster in Northeast Iceland – clues into rift zone architecture on a young Iceland

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