Euhedral sparitic calcite in buried surface horizons in lake basins, southwestern Kalahari, Namibia

Mees, Florias; Ranst, Éric Van

doi:10.1016/j.geoderma.2011.04.009

Cited by 4 publications

(2 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4). This suggests a period of stable environmental and geological conditions, which promoted low nucleation density and slow growth of calcite as already suggested for different buried soils of the Kalahari Desert (Mees and Van Ranst 2011).…”

Section: Formation Of Ck Bauxites: Insights From Mineralogy and Geochemistrysupporting

confidence: 71%

Karst bauxite formation during Miocene Climatic Optimum (central Dalmatia, Croatia): mineralogical, compositional and geochronological perspectives

Brlek

Gaynor

Mongelli

et al. 2021

Int J Earth Sci (Geol Rundsch)

View full text Add to dashboard Cite

The Miocene Climatic Optimum (MCO) represents a global warm period (approximately 17-14.7 Ma) interrupting a longterm period of Cenozoic cooling. To elucidate if bauxitization took place in southeastern European mid-latitude areas during the MCO, we studied a section of undated massive karst bauxite (Crveni Klanac, CK) in central Dalmatia, Croatia, hosted in Upper Cretaceous limestones and overlain by Miocene Sinj Basin lacustrine deposits. Integrated mineralogical, morphological and geochemical analyses indicate the predominant mineral phases of the homogenous bauxite matrix are authigenic, subhedral to euhedral kaolinite and gibbsite. The in-situ mineralization was a consequence of pedogenic processes, indicating the CK bauxites formed autochthonously. In situ U-Pb zircon ages of the lower, middle and upper parts of the CK bauxite are very similar, dominated by Miocene and Oligocene ages, indicating that they all share similar protolith(s). Subsequent high-precision chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) analyses indicate a maximum depositional age (MDA) for the pre-bauxitic material of 16.9576 ± 0.021 Ma (2σ uncertainty, incorporating decay constant uncertainty). This MDA, a maximum age of autochthonous bauxitization, coincides with the onset of the MCO. Based on currently available geochronological constraints, the maximum timeframe for CK bauxitization was less than ~ 700 ka, which matches the records of the MCO in paleo-mid-latitude Europe. The potential imprint of pre-17 Ma bauxitization and contribution of older (i.e., Upper Paleogene) bauxite deposits resedimented to the CK profile, as well as degree of potential parautochthonous origin of the CK bauxites, is yet to be investigated. More than simply aligning with regional and local reconstructions of continental climatic conditions during the onset and the early stages of the MCO, the high degree of autochthony of the CK bauxites provide a precise climatic constraint. For in-situ bauxitization to occur in the southeastern parts of mid-latitude continental Europe, paleoclimatic and paleoenvironmental conditions must have had mean annual temperature greater than 17-22 °C and mean annual precipitation of more than 1100-1200 mm.

show abstract

Section: Formation Of Ck Bauxites: Insights From Mineralogy and Geochemistrysupporting

confidence: 71%

Karst bauxite formation during Miocene Climatic Optimum (central Dalmatia, Croatia): mineralogical, compositional and geochronological perspectives

Brlek

Gaynor

Mongelli

et al. 2021

Int J Earth Sci (Geol Rundsch)

View full text Add to dashboard Cite

show abstract

“…Pan soils are solonchaks, with shallow leptosols, regosols and arenosols in fringing areas (De Wit and Nachtergaele, 1990;Wang et al, 2007) which can become calcified in areas immediately surrounding the pans (Mees and Van Ranst, 2011;Ringrose et al, 2005;White and Eckardt, 2006). Pan sediment is clay-rich and mixed with salts derived from shallow near-surface water, as well as deeper brines dominated by NaCl and Na 2 CO 3 (Department of Environmental Affairs and Centre for Applied Research, 2010;Gould, 1986).…”

Section: Study Sitementioning

confidence: 99%

Seasonal differences in soil CO2 efflux and carbon storage in Ntwetwe Pan, Makgadikgadi Basin, Botswana

et al. 2014

View full text Add to dashboard Cite

The carbon cycle in salt pans is complex and poorly understood. Field-based data are needed to improve regional estimates of C storage and land-atmosphere CO 2 fluxes from dryland environments where pans are prevalent. This paper provides a first estimate of C stores and CO 2 efflux within the salt pan, grassland and woodland of Ntwetwe Pan in the Makgadikgadi Basin, Botswana. C fluxes and stores associated with cyanobacteria-salt crusts are also determined. Total C stores are approximately an order of magnitude greater than on neighbouring Kalahari Sands at 675 ± 41, 760 ± 94 and 274 ± 15 tons ha −1 to 1 m depth in the woodland, grassland and salt pan respectively. Most of the C is found as carbonate, with organic C comprising 4.6-10% of total C. CO 2 efflux increased with temperature and also increased for a few hours after flooding of the pan surface. Crusts were a small net contributor to CO 2 efflux in the dry season but could be a net CO 2 sink in the wet season. The biogeochemistry of the sediment is likely to facilitate rapid conversion of organic C from aquatic organisms, biological crusts and algal mats into inorganic carbonates. Although further work is required to improve estimates of the spatial and temporal distribution of C, our data have demonstrated the substantial C store with the Makgadikgadi environment and the important role of biological crusts in the C cycle.

show abstract

Palaeoenvironmental reconstruction of Kathu Pan, South Africa, based on sedimentological data

Lukich

Cowling

Chazan

2020

Quaternary Science Reviews

View full text Add to dashboard Cite

Euhedral sparitic calcite in buried surface horizons in lake basins, southwestern Kalahari, Namibia

Cited by 4 publications

References 18 publications

Karst bauxite formation during Miocene Climatic Optimum (central Dalmatia, Croatia): mineralogical, compositional and geochronological perspectives

Karst bauxite formation during Miocene Climatic Optimum (central Dalmatia, Croatia): mineralogical, compositional and geochronological perspectives

Seasonal differences in soil CO2 efflux and carbon storage in Ntwetwe Pan, Makgadikgadi Basin, Botswana

Palaeoenvironmental reconstruction of Kathu Pan, South Africa, based on sedimentological data

Contact Info

Product

Resources

About