The Interpretation of Some Basic Calcrete Types

Netterberg, F

doi:10.2307/3888287

Cited by 71 publications

(31 citation statements)

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“…GroWl dwater ca1cretes are non-pedogenic carbo nates whose fo rmation is related to shallow aquifer systems (Netterberg, 1969;Mann and Horwitz, 1 979). They were initially referred to as "valley calcretes" (Butt et aI., 1977) to describe the massive carbonate bodies associated with drainage channels.…”

Section: Groundwater Calcretesmentioning

confidence: 99%

Palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record

Alonso-Zarza¹

2003

Earth-Science Reviews

498

321

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Section: Groundwater Calcretesmentioning

confidence: 99%

Palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record

Alonso-Zarza¹

2003

Earth-Science Reviews

498

321

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“…Based on the type of authigenic minerals, several varieties of duricrusts have been recognized, namely, calcrete, dolocrete, ferricrete, silcrete, gypcrete, phoscrete and alcrete (Lamplugh, 1902;Goudi, 1973). The occurrence and genesis of dolocretes and calcretes have been studied by many workers (Nagtegaal, 1969;Netterberg, 1969;Goudie, 1972;Watts, 1977;Mann and Horwitz, 1979;Arakel and McConchie, 1982;Esteban and Klappa, 1983;Semeniuk and Searle, 1984;and Khalaf, 1987;1990).…”

Section: Introductionmentioning

confidence: 99%

Dedolomitization of dolocrete deposits in Kuwait, Arabian Gulf

Khalaf

Abdal

1993

Geol Rundsch

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Dedolomitization of a dolocrete profile hosted in Mio-Pleistocene siliciclastic deposits in the area of Kuwait City, Arabian Gulf was investigated. Dolocrete dolomite crystals vary considerably in size, shape and internal structure; however, they are mostly zoned. Zonation is usually due to the alteration of cloudy and clear zones. The cloudy zones, which are mostly formed of disordered metastable dolomite, are more susceptible to dedolomitization than the stable, well ordered clear zones. Two modes of dedolomitization were recognized; the first involves complete dissolution of the metastable dolomite followed by precipitation of intracrystalline cavity-filling calcite. The second is a pseudomorphic replacement of dolomite by calcite. This replacement takes place by the simultaneous dissolution of dolomite and precipitation of calcite in such a manner that the original dolomite fabrics are inherited in the dedolomite. Exposed and near-surface dolocrete profile (less than 5 m deep) are almost completely dedolomitized and altered to secondary calcrete whereas subsurface profiles are slightly dedolomitized. Dedolomitization of the sub surface dolocrete profiles may indicate the effect of flushing by fresh groundwater; which flows from west to east, whereas the alteration of the exposed dolocrete profile could be attributed to be an effect of meteoric water. A new mode of calcrete genesis by dedolomitization and/or complete calcitization of precursor dolocrete is suggested.

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“…This type of enrichment did not result in the formation of nodules, in contrast to the early stages of calcite precipitation in soils (e.g. Gile et al, 1966;Netterberg, 1969).…”

Section: Nature Of the Depositsmentioning

confidence: 81%

“…Some of these profiles can be assumed to have developed in lacustrine deposits, in view of their fossil content (e.g. Netterberg, 1969Netterberg, , 1978Netterberg, , 1980, although this is only rarely explicitly stated (Netterberg, 1982). Calcareous or diatomaceous lacustrine deposits have been identified in various parts of southern Africa, including the Namib (e.g.…”

Section: Introductionmentioning

confidence: 99%

The nature of calcareous deposits along pan margins in eastern central Namibia

Mees

2002

Earth Surf Processes Landf

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In a region along the western margin of the Kalahari in eastern Namibia and western Botswana, many pan basins have mainly calcareous deposits along part of their margins. These are typically lined by low vertical scarps. In Namibia, these pans are mainly located in dry river beds. The petrographical study of these deposits demonstrates that they consist of lacustrine sediments that have to a varying extent been affected by early-diagenetic processes and by the formation of late-diagenetic features.The original composition of the deposits ranges from highly calcareous sediments, typically with ostracod, diatom and charophyte remains, to entirely non-calcareous diatomites. The deposits generally show an upward increase in total carbonate content, which is mainly a synsedimentary feature. The early-diagenetic processes that affected the deposits include the formation of orthic siliceous nodules. At a later stage, secondary calcite enrichment occurred, leaving only the silica-impregnated sections unaffected. This enrichment partly accounts for the upward increase in total carbonate content in some profiles and often resulted in the development of a highly calcareous surface horizon. Sepiolite and amorphous silica that are part of the groundmass of the deposits may also partly have formed at this stage. Late-diagenetic features include various forms of secondary calcite and silica.This study of pan basins in eastern central Namibia indicates that a lacustrine rather than purely pedogenic origin should also be considered for calcareous deposits that commonly occur along pan margins in other parts of southern Africa.

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The Interpretation of Some Basic Calcrete Types

Cited by 71 publications

References 1 publication

Palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record

Palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record

Dedolomitization of dolocrete deposits in Kuwait, Arabian Gulf

The nature of calcareous deposits along pan margins in eastern central Namibia

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