Lake-islands: A distinct morphology of river systems

Abstract The Palaeoproterozoic Hekpoort Formation of the Pretoria Group is a lava-dominated unit that has a basin-wide extent throughout the Transvaal sub-basin of South Africa. Additional correlative units may be present in the Kanye sub-basin of Botswana. The key characteristic of the formation is its general geochemical uniformity. Volcaniclastic and other sedimentary rocks are relatively rare throughout the succession but may be dominant in some locations. Hekpoort Formation outcrops are sporadic throughout the basin and mostly occur in the form of gentle hills and valleys, mainly encircling Archaean domes and the Palaeoproterozoic Bushveld Complex (BC). The unit is exposed in the western Pretoria Group basin, sitting unconformably either on the Timeball Hill Formation or Boshoek Formation, which is lenticular there, and on top of the Boshoek Formation in the east of the basin. The unit is unconformably overlain by the Dwaalheuwel Formation. The type-locality for the Hekpoort Formation is the Hekpoort farm (504 IQ Hekpoort), ca. 60 km to the west-southwest of Pretoria. However, no stratotype has ever been proposed. A lectostratotype, i.e., the Mooikloof area in Pretoria East, that can be enhanced by two reference stratotypes are proposed herein. The Hekpoort Formation was deposited in a cratonic subaerial setting, forming a large igneous province (LIP) in which short-termed localised ponds and small braided river systems existed. It therefore forms one of the major Palaeoproterozoic magmatic events on the Kaapvaal Craton.

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Mio-Pliocene Palaeogeography, Uplands And River Systems of the Sunda Region Based on Mapping Within a Framework of Vim Depositional Cycles.

10.29118/ipa.0.16.506.g ◽

2018 ◽

Cited By ~ 1

Author(s):

Robert J Morley

Keyword(s):

River Systems ◽

Depositional Cycles

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Terrane provenance and amalgamation: examples from the Caledonides

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1990.0092 ◽

1990 ◽

Vol 331 (1620) ◽

pp. 599-609 ◽

Cited By ~ 13

Keyword(s):

Sedimentary Basins ◽

Fault Zones ◽

River Systems ◽

Pan African ◽

Basin Formation ◽

Laurentian Margin

The Scottish Caledonides have grown by the accretion of terranes generated somewhere along the Laurentian margin. By the time these terranes had been emplaced along the Scottish sector, they were structurally truncated then reassembled to form an incomplete collage of indirectly related tectonic elements of a destructive margin. The basement to some of these tectonic elements and the basement blocks belonging to the previously accreted Precambrian are of uncertain provenance and a source in the Pan-African craton is possible. As terranes migrate along the orogen they generate in the fault zones and on their periphery a reservoir of mature sediment. This mature sediment is produced because of the recycling produced during the generation and destruction of sedimentary basins developing during terrane translation. At each period of recycling the mature sediments are mixed with less mature sediments yielded from local uplifts generated by the new basin formation. If a large part of the orogen suffers orthogonal closure, giant river systems may form and disperse sediment across terranes. This is likely to have happened during the Devonian-Carboniferous of parts of N. Europe.

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Typologies of collaborative governance for scaling nature-based solutions in two strategic South African river systems

AMBIO ◽

10.1007/s13280-021-01531-z ◽

2021 ◽

Author(s):

Stephanie J. E. Midgley ◽

Karen J. Esler ◽

Petra B. Holden ◽

Alanna J. Rebelo ◽

Sabine I. Stuart-Hill ◽

...

Keyword(s):

South African ◽

Collaborative Governance ◽

River Systems

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Landscape controls on riverine export of dissolved organic carbon from Great Britain

Biogeochemistry ◽

10.1007/s10533-021-00762-2 ◽

2021 ◽

Author(s):

Jennifer L. Williamson ◽

Andrew Tye ◽

Dan J. Lapworth ◽

Don Monteith ◽

Richard Sanders ◽

...

Keyword(s):

Land Use ◽

Great Britain ◽

Population Density ◽

Organic Carbon ◽

Dissolved Organic Carbon ◽

Forest Cover ◽

River Systems ◽

C Cycle ◽

Global Land ◽

Doc Export

AbstractThe dissolved organic carbon (DOC) export from land to ocean via rivers is a significant term in the global C cycle, and has been modified in many areas by human activity. DOC exports from large global rivers are fairly well quantified, but those from smaller river systems, including those draining oceanic regions, are generally under-represented in global syntheses. Given that these regions typically have high runoff and high peat cover, they may exert a disproportionate influence on the global land–ocean DOC export. Here we describe a comprehensive new assessment of the annual riverine DOC export to estuaries across the island of Great Britain (GB), which spans the latitude range 50–60° N with strong spatial gradients of topography, soils, rainfall, land use and population density. DOC yields (export per unit area) were positively related to and best predicted by rainfall, peat extent and forest cover, but relatively insensitive to population density or agricultural development. Based on an empirical relationship with land use and rainfall we estimate that the DOC export from the GB land area to the freshwater-seawater interface was 1.15 Tg C year−1 in 2017. The average yield for GB rivers is 5.04 g C m−2 year−1, higher than most of the world’s major rivers, including those of the humid tropics and Arctic, supporting the conclusion that under-representation of smaller river systems draining peat-rich areas could lead to under-estimation of the global land–ocean DOC export. The main anthropogenic factor influencing the spatial distribution of GB DOC exports appears to be upland conifer plantation forestry, which is estimated to have raised the overall DOC export by 0.168 Tg C year−1. This is equivalent to 15% of the estimated current rate of net CO2 uptake by British forests. With the UK and many other countries seeking to expand plantation forest cover for climate change mitigation, this ‘leak in the ecosystem’ should be incorporated in future assessments of the CO2 sequestration potential of forest planting strategies.

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