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, Frédéric; Courtillot, Vincent

doi:10.1007/s00445-017-1189-6

Cited by 17 publications

(16 citation statements)

References 52 publications

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“…Next, we compile lobe thickness measurements from other CFB provinces (for a total of ∼ 3,800 individual measurements) from multiple studies. In concert with other studies (e.g., Bondre et al, 2004;Duraiswami et al, 2017;Jay et al, 2018) our results help illustrate the variety in a specific morphological lava feature (lobe thickness), both within a single CFB formation and for entire CFB provinces. Additionally, we can possibly use lobe thickness distributions to quantitatively compare and group together various CFBs with similar flow emplacement dynamics.…”

Section: Introductionsupporting

confidence: 86%

“…This observation was interpreted as being indicative of a lava morphology change due to changing distance from source. Although the idea has been disputed by others (Bondre et al, 2004;Self et al, 2006;Jay et al, 2018), our new dataset can help further quantitatively test this hypothesis. Next, we compile lobe thickness measurements from other CFB provinces (for a total of ∼ 3,800 individual measurements) from multiple studies.…”

Section: Introductionmentioning

confidence: 90%

“…Thus, given the current geochemical stratigraphic framework (Figure 3B; Beane et al, 1986;Jay and Widdowson, 2008), we can clearly assign each flow lobe to a geochemical formation. We have similar logs for the CRB and Karoo flood basalt provinces (Jay et al, 2018;Moulin et al, 2017), collected by the authors. For the Deccan and Karoo, the logs are exemplified by those in Figure 3A (Supplementary Figure S1, see also Figure 4 in Jay et al, 2009 andJay et al, 2018).…”

Section: Datasets Logs From Field Work and Occasionally Drill Coresmentioning

confidence: 99%

“…We address these challenges by comparing lava flow morphology (with a clearly defined terminology) across multiple CFB provinces and modern analogs with a specific focus on the Deccan Traps (henceforth Deccan). A simple expression of flow morphology is lava-lobe thickness, as this represents the essential morphological difference reported from CFB p ahoehoe (phh) lavassheet-lobe-dominated (simple) vs. hummocky-lobe-dominated (compound) lavas (e.g., Walker, 1971;Bondre et al, 2004;Sheth, 2006;Jay et al, 2018). The thickness of lobes or flows is also perhaps the only physical property of basalt lavas consistently reported across many studies.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Introductionsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 90%

Section: Datasets Logs From Field Work and Occasionally Drill Coresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2021

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“…The upper Karoo Supergroup of southern Africa, encompassing the upper Stormberg and lower Drakensberg Groups, is one of the few stratigraphic units globally that contains diverse continental rocks as well as body and trace fossil assemblages to allow a meaningful assessment of the events leading up to the Toarcian turnover, a global multi-phased extinction event. This area is also unique because it is most proximal to the trigger of the event: the Karoo-Ferrar flood basalt outpourings (e.g., [11,12,33,34]), and preserves the rock record of this globally significant event in spectacular outcrops suitable for multidisciplinary investigations.…”

Section: Introductionmentioning

confidence: 99%

Tracking the Pliensbachian–Toarcian Karoo firewalkers: Trackways of quadruped and biped dinosaurs and mammaliaforms

et al. 2020

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The Karoo igneous rocks represent one of the largest continental flood basalt events (by volume) on Earth, and are not normally associated with fossils remains. However, these Pliensbachian-Toarcian lava flows contain sandstone interbeds that are particularly common in the lower part of the volcanic succession and are occasionally fossiliferous. On a sandstone interbed in the northern main Karoo Basin, we discovered twenty-five tridactyl and tetradactyl vertebrate tracks comprising five trackways. The tracks are preserved among desiccation cracks and low-amplitude, asymmetrical ripple marks, implying deposition in low energy, shallow, ephemeral water currents. Based on footprint lengths of 2-14 cm and trackway patterns, the trackmakers were both bipedal and quadrupedal animals of assorted sizes with walking and running gaits. We describe the larger tridactyl tracks as "grallatorid" and attribute them to bipedal theropod dinosaurs, like Coelophysis, a genus common in the Early Jurassic of southern Africa. The smallest tracks are tentatively interpreted as Brasilichniumlike tracks, which are linked to synapsid trackmakers, a common attribution of similar tracks from the Lower to Middle Jurassic record of southern and southwestern Gondwana. The trackway of an intermediate-sized quadruped reveals strong similarities in morphometric parameters to a post-Karoo Zimbabwean trackway from Chewore. These trackways are classified here as a new ichnogenus attributable to small ornithischian dinosaurs as yet without a body fossil record in southern Africa. These tracks not only suggest that dinosaurs and therapsids survived the onset of the Drakensberg volcanism, but also that theropods, ornithischians and synapsids were among the last vertebrates that inhabited the main Karoo Basin some 183 Ma ago. Although these vertebrates survived the first Karoo volcanic eruptions, their rapidly dwindling habitat was turned into a land of fire as it was covered by the outpouring lavas during one of the most dramatic geological episodes in southern Africa.

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Complex layering of the Orange Mountain Basalt: New Jersey, USA

et al. 2018

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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

Cited by 17 publications

References 52 publications

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

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

Tracking the Pliensbachian–Toarcian Karoo firewalkers: Trackways of quadruped and biped dinosaurs and mammaliaforms

Complex layering of the Orange Mountain Basalt: New Jersey, USA

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