Inverted Channels in the Eastern Sahara—Distribution, Formation, and Interpretation to Enable Reconstruction of Paleodrainage Networks

Zaki, Abdallah S.; Giegengack, Robert; Castelltort, Sébastien

doi:10.1007/978-3-030-23315-0_6

Cited by 10 publications

(6 citation statements)

References 45 publications

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“…If coarse-grained materials had been present in significant volumes, wind would have produced widespread deflation surfaces with coarse-grained lags capping the fines, thereby hindering their long-term removal from the highlands' fine-grained stratigraphy. Deflation lags of just a few pebbles thick -somewhat thicker in rougher relief -is sufficient to shield underlying fines 47 .…”

Section: Discussionmentioning

confidence: 99%

The Oldest Highlands of Mars May Be Massive Dust Fallout Deposits

Rodriguez

Dobrea

Kargel

et al. 2020

Sci Rep

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the oldest terrains of Mars are cratered landscapes, in which extensive valleys and basins are covered by ubiquitous fluvial plains. One current paradigm maintains that an impact-generated megaregolith underlies these sediments. this megaregolith was likely largely generated during the early noachian (~4.1 to ~3.94 Ga) when most Martian impact basins formed. We examined the geologic records of NW Hellas and NW Isidis, which include this epoch's most extensive circum-basin outcrops. Here, we show that these regions include widespread, wind-eroded landscapes, crater rims eroded down by several hundred meters, pitted plains, and inverted fluvial and crater landforms. These surfaces exhibit few fresh craters, indicating geologically recent wind erosion. the deep erosion, topographic inversions, and an absence of dunes on or near talus across these regions suggest that sediments finer than sand compose most of these highland materials. We propose that basin-impact-generated hurricane-force winds created sediment-laden atmospheric conditions, and that muddy rains rapidly settled suspended sediments to construct extensive Early Noachian highlands. The implied high abundance of fine-grained sediments before these impacts suggests large-scale glacial silt production and supports the previously proposed noachian "icy highlands" hypothesis. We suggest that subglacial meltwater interactions with the sedimentary highlands could have promoted habitability, particularly in clay strata.

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Section: Discussionmentioning

confidence: 99%

The Oldest Highlands of Mars May Be Massive Dust Fallout Deposits

Rodriguez

Dobrea

Kargel

et al. 2020

Sci Rep

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“…Inverted channels capped by basalt are documented in the Wadi Awatib and Kordofan in northern Sudan (Schwarz, 1994;Bussert et al, 2018). The inverted channels in southern Egypt and northern Sudan were deposited during late Quaternary (late Pleistocene and Holocene) extreme wet climatic events, the so-called "Late Quaternary climate oscillation" (Giegengack, 1968;Butzer and Hansen, 1968;Zaki et al, 2020). During the late Quaternary climate oscillation, there were abrupt changes in climate over the Sahara that were more common at warmer than at cooler (e.g., Foucault and Stanley, 1989;Hoffmann et al, 2016); that led to several episodes of wet and dry periods causing the incision, cementation, and inversion of these paleorivers.…”

Section: Africamentioning

confidence: 99%

“…Figure 1 shows spectacular examples of inverted paleorivers in the Sahara (Giegengack, 1968;Zaki et al, 2018) and Utah deserts (Williams et al, 2007). On Earth, study of inverted channels, where they occur, are a key part of past climate reconstruction because they are coupled with paleodrainage systems (Beresford-Jones et al, 2009;Wang et al, 2015;Matter et al, 2016;Williams et al, 2007;Williams et al, 2009;Zaki et al, 2020). Some of these features also have an economic potential (e.g.…”

Section: Introductionmentioning

confidence: 99%

Global inventories of inverted stream channels on Earth and Mars

Zaki¹,

Pain²,

Edgett³

et al. 2020

Preprint

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Data from orbiting and landed spacecraft have provided vast amounts of information regarding fluvial and fluvial-related landforms and sediments on Mars. One variant of these landforms are sinuous ridges that have been interpreted to be remnant evidence for ancient fluvial activity, observed at hundreds of martian locales. In order to further understanding of these martian landforms, this paper inventories the 107 known and unknown inverted channel sites on Earth; these offer 114 different examples that consist of materials ranging in age from Upper Ordovician to late Holocene. These examples record several climatic events from the Upper Ordovician glaciation to late Quaternary climate oscillation. These Earth examples include inverted channels in deltaic and alluvial fan sediment, providing new analogs to their martian counterparts. This global dataset provides environmental context regarding the formation mechanisms and conditions that accompanied channel formation and inversion. There are five documented processes by which channel sediment and valley fill become consolidated and inverted after adjacent floodplain sediments are eroded away: (1) channel fill cementation during near-surface, early diagenesis; (2) channel fill lithification during burial diagenesis in the subsurface; (3) filling of a channel or valley by extrusive volcanism (lavas, tuffs); (4) channel surface armouring of coarse clasts by aeolian and fluvial processes; (5) compaction of bank-forming peat, which can lead to early inversion without removal of floodplain material. On Earth, early diagenesis (shallow surficial cementation) dominates among inverted fluvial channels (59%), volcanism is an important contributor (23%), and deep burial diagenesis, surface armouring, compaction of bank-forming peat are comparatively minor (11%, 6%, and 1% respectively). Water erosion, wind erosion, and exhumation due to tectonic activity play an important role in removing the surrounding terrain, leaving the channel deposits standing as a ridge. Wind erosion rates involved in causing topographic inversion range from 10 mm/year in the Bodélé Depression, Chad, to 0.21 mm/year in the Kumtagh Desert, China. These observations have important implications for understanding the formation and paleoclimate associated with similar landforms on Mars. Shallow, near-subsurface cementation of channel sediment could be prevalent on Mars due to a favorable climate like that of where they occur on Earth (tropical and subtropical climates), particularly because most Martian examples are not capped by volcanic materials and because tectonism, as compared to Earth, plays a negligible role in returning buried materials to the surface. Studying inverted channels on Mars at the global scale will bring new information on the early climate of Mars, particularly transition from wet to dry conditions. Finally, we propose that inverted deltaic deposits, which occur around the margins of the Pleistocene Tushka paleolake, in Egypt, are an excellent terrestrial analogue for fan-shaped deposits in relief inversion on Mars, particularly the deltaic deposits in Jezero crater, the landing site for NASA’s Mars 2020 rover.

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“…Additional examples have been reported in Africa (Butt & Bristow, 2013; Giegengack & Zaki, 2017; Giegengack, 1968; Zaki & Giegengack, 2016; Zaki et al, 2018); Australia (Kemp & Rhodes, 2010); Europe (Cuevas et al, 2010; Friend et al, 1981); and North America (Williams et al, 2007). Inverted channels have been important in the study of past climate, in relation to paleo‐drainage systems (Williams et al, 2007; Williams et al, 2009; Zaki et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Earthen ridges in coastal sand dunes of the Caribbean coast, Venezuela: Anthropogenic or natural?

et al. 2020

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Earthen ridges that occur in the active Los Médanos de Coro dune fields of the Venezuelan Caribbean coast have been attributed either to anthropogenic or natural origins. Anthropogenic explanations have focused on their location, geometry, structure, and compaction, in the context of archaeological sites and artifacts throughout the dunes, to suggest an origin as causeways built by the extinct Caquetío people and/or their pre‐Hispanic ancestors. To assess this topic, geomorphic, physicochemical, and elemental analyses were carried out on the ridges and interdunal beaches and playas. The configuration, elevation, and composition of the ridges, along with three bulk sediment 14C dates that range 1900–3000 year BP, are here found to be most compatible with a natural origin as exhumed paleochannels. Past human occupants may, however, have used the features as causeways.

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Inverted Channels in the Eastern Sahara—Distribution, Formation, and Interpretation to Enable Reconstruction of Paleodrainage Networks

Cited by 10 publications

References 45 publications

The Oldest Highlands of Mars May Be Massive Dust Fallout Deposits

The Oldest Highlands of Mars May Be Massive Dust Fallout Deposits

Global inventories of inverted stream channels on Earth and Mars

Earthen ridges in coastal sand dunes of the Caribbean coast, Venezuela: Anthropogenic or natural?

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