Lithostratigraphy, sedimentary petrography and geochemistry of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin, Botswana

Franchi, Fulvio; Kelepile, Tebogo; Capua, Andrea Di; Wit, Mike C.J. de; Kemiso, Onalethata; Lasarwe, Reneilwe; Catuneanu, Octavian

doi:10.1016/j.jafrearsci.2020.104025

Cited by 15 publications

(7 citation statements)

References 37 publications

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“…The region was then affected by several extensional tectonic episodes between the Carboniferous and the late‐Cenozoic: the Permo‐Triassic Karoo rifting, a late Mesozoic‐Cenozoic extensional episode and the Cenozoic still active EARS opening (Castaing, 1991; Van der Beek et al., 1998). During the Karoo rifting episode, detrital sedimentary series were deposited in the MOZB within NE‐SW oriented grabens, as well as thick basaltic flows (e.g., Franchi et al., 2021; Jourdan et al., 2005). The MOZB is also cross‐cut by a WNW‐ESE dolerite dykes network aged of ∼179 Ma (Jourdan et al., 2004; Le Gall et al., 2002, 2005).…”

Section: Geological and Geomorphological Settingsmentioning

confidence: 99%

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Gaudaré,

Dauteuil,

Jolivet

2024

Tectonics

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The Southwestern Branch of the East African Rift System propagates through the Central and Southern African plateaus and ends in the Okavango Makgadikgadi Zambezi Basin. This basin hosts the Okavango Graben and the Eiseb Graben, considered as the terminus of the Southwestern Branch of the rift. To the southeast, the Makgadikgadi Basin is affected by a series of normal faults forming the Makgadikgadi Rift Zone (MRZ) which regional geodynamic significance remains unclear. Based on fieldwork and geomorphic analysis, we revisited the geomorphological features associated with paleolakes and the fault pattern within the Makgadikgadi Basin to better constrain the dynamics of the MRZ. Fault scarps and offsets along linear dunes show normal‐dip kinematics of faults, indicating a NW‐SE extension direction in the area. Furthermore, lacustrine shorelines in the basin are undeformed, proving that they post‐date the fault activity. The previously published ages of these shorelines demonstrate that the MRZ currently has a low tectonic activity. Integrated in the geodynamic framework of the region, these results suggest that present‐day deformation shifts toward the Okavango Graben north of the MRZ. We therefore propose a “zip‐opening” model to explain the propagation of the Southwestern Branch of the East African Rift System where the tip of the system progressively progresses southwestward, driven by motions of the continental plates.

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Section: Geological and Geomorphological Settingsmentioning

confidence: 99%

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Gaudaré,

Dauteuil,

Jolivet

2024

Tectonics

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“…The Makgadikgadi Pans lie within a fault-bounded basin that consists of crystalline basement and the volcano-sedimentary units of the Karoo Supergroup (Eckardt et al, 2016;Schmidt et al, 2023). The Karoo Supergroup units in the area include basal Late Carboniferous glacial deposits of the Dwyka Group (Dukwi Formation in Botswana; Dietrich et al, 2019) unconformably overlain by the Carboniferous to Early Permian Ecca Group, by the Upper Permian to Lower Triassic Beaufort Group (Tlhabala Formation in Botswana; see review in Bordy, 2020) and by the Middle Triassic to the Middle Jurassic continental sandstones and mudstones of the Lebung Group (see Franchi et al, 2021 for a review). Along the northern and southern edges of the Makgadikgadi Basin, the bedrock geology is characterized by Early Jurassic (ca.…”

Section: Bedrock Geologymentioning

confidence: 99%

Structural influences on groundwater circulation in the Makgadikgadi salt pans of Botswana? Implications for martian playa environments

Schmidt

Luzzi²,

Franchi³

et al. 2023

Front. Astron. Space Sci.

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Across the surface of Mars, evidence of past lacustrine and evaporitic environments has been found within basins and craters, where often layered sedimentary deposits and hydrated minerals are observed. However, the intensity, duration, and precise phases of aqueous processes during their deposition remain unresolved mostly for our inability to model subsurface structures. Although several geological processes and locations on Earth have been previously proposed as examples to describe these deposits on Mars, we lack a strong visualization of what water activity might have looked like during evaporitic stages within basins and craters. Here we propose to investigate the shallow subsurface of the Makgadikgadi salt pans of Botswana as a potential analog for understanding groundwater upwelling on Mars. The pans are found within the Makgadikgadi Basin, a depression located at the southwestern end of a northeast-southwest set of graben linked with the East African Rift. The Makgadikgadi Pans are evaporitic environment rich in hydrated minerals and groundwater activity. The purpose of this work is to identify buried faults and areas of relative water saturation within the lacustrine sediment of the Makgadikgadi Basin by means of electrical resistivity surveys. This work represents the first electrical resistivity survey of the basin floor which provides a precursory investigation of the relationship between groundwater, faults, basement depth, and the lacustrine sediments. We present four electrical survey lines from different locations in the pans which reveal distinct sedimentary units. Several faults are inferred from the vertical displacement of these units and accompanying low resistivity where displacement is observed. These results provide a framework for visualizing the sedimentary sequences of infilled basins and craters on Mars, which can broaden the ongoing discussion of hydrogeological processes that were active in the planet’s past. We propose Meridiani Planum, as well as Oyama and Becquerel crater of Arabia Terra as locations to establish this framework. Since such processes are still ongoing in the Makgadikgadi Basin, imaging the subsurface of the pans helps explain the formation of layered and salty deposits on the surface of Mars, how they may have interacted with flowing water, and whether they might have hosted life.

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“…The bedrock of the MB consists of Carboniferous to Early Jurassic volcano-sedimentary units belonging to the Karoo Supergroup (Figure 2; see details in Modie and Le Hérrissé, 2009;Bordy, 2020;Franchi et al, 2021). The MB is crossed by an ESE-WNW trending doleritic dyke swarm of the Karoo large igneous province (∼187 Ma old; Elburg and Goldberg, 2000; Figure 2).…”

Section: Geological Settingmentioning

confidence: 99%

Late Pleistocene–Holocene Palaeoenvironmental Evolution of the Makgadikgadi Basin, Central Kalahari, Botswana: New Evidence From Shallow Sediments and Ostracod Fauna

et al. 2022

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The Makgadikgadi Basin in Botswana hosts a system of salt lakes, which developed from the Upper Pleistocene onward due to the gradual shrinking of the giant Lake Palaeo-Makgadikgadi. Stratigraphic and palaeoclimatic studies of this area are difficult due to the influence of several factors, such as a complex history of regional tectonic activities, as well as climatic changes coupled with dryland diagenetic processes. This lake, in the central Kalahari, is the key to understanding the climatic variability in the southern part of Africa in the Quaternary and has played an important role in the evolution of numerous taxa, including our own. In this study, detailed sedimentological analyses (grain size and major elements distribution) of shallow sediments from the Makgadikgadi Pans were combined with the first comprehensive study of the encountered ostracod fauna to establish trends in the environmental changes in the area from the late Quaternary. Ostracod fossil assemblages from the cores of the Makgadikgadi Pans are dominated by the Limnocythere ssp., an opportunistic taxa commonly colonizing the littoral areas of shallow evaporative, ephemeral lakes, together with the subordinate occurrences of Sarcypridopsis ochracea, Sclerocypris cf. bicornis, Candonopsis spp., and Ilyocypris spp. The sediments from the pans show fluctuations in the Cl/K and Ca/Cl ratios, often in phase with the relative abundance of Limnocythere suggesting a cyclicity induced by changes of salinity and alkalinity in the water. This multi-proxy study of the cores collected from the pans suggests a Late Pleistocene shallow, playa lake environment with strongly alkaline water, interrupted by a prolonged drought with sustained aeolian conditions between ∼16 and 2 ka BP. Increasing diversity of ostracod fauna in the top 20–30 cm of the cores indicates that a temporary shift toward higher humidity occurred around 2–1.5 ka BP and lasted through the Medieval Warm Period. This humid period was followed by an overall desiccation trend that started with the Little Ice Age and continues until the present day.

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Lithostratigraphy, sedimentary petrography and geochemistry of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin, Botswana

Cited by 15 publications

References 37 publications

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Geomorphology of the Makgadikgadi Basin (Botswana): Insight Into the Propagation of the East African Rift System

Structural influences on groundwater circulation in the Makgadikgadi salt pans of Botswana? Implications for martian playa environments

Late Pleistocene–Holocene Palaeoenvironmental Evolution of the Makgadikgadi Basin, Central Kalahari, Botswana: New Evidence From Shallow Sediments and Ostracod Fauna

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