Calcified root cells in Miocene pedogenic carbonates of the Madrid Basin: evidence for the origin of Microcodium b

Alonso-Zarza, Ana María; Sanz, Montserrat; Calvo, J.P.; Estévez, Pilar

doi:10.1016/s0037-0738(97)00077-8

Cited by 69 publications

(39 citation statements)

References 23 publications

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“…Stringers of original host mudstone remain, and fractures cross-cut earlier micritic nodules. The sub-horizontal fractures superficially resemble rhizogenic calcretes formed by calcretization in, or around, root mats within the soil profile (Wright et al 1995;Alonso-Zarza et al 1998a;Alonso-Zarza 1999). In thin section, the RCF horizontal fractures comprise micritic cements, but with no obvious cellular structure, a rhizogenic origin cannot be proven.…”

Section: Calcretesmentioning

confidence: 96%

The Ridgeway Conglomerate Formation of SW Wales, and its implications. The end of the Lower Old Red Sandstone?

Hillier

Williams

2007

Geological Journal

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The Devonian Old Red Sandstone Ridgeway Conglomerate Formation crops out in Pembrokeshire, SW Wales. It was deposited as part of a dryland alluvial fan, axial fluvial valley deposystem. It conformably overlies the mid Lochkovian Freshwater West Formation and probably predates deposition of the Lower Cosheston Group Mill Bay Formation indicating an Early Devonian (latest Lochkovian to earliest Pragian) age, rather than a Middle Devonian age as suggested by previous workers. It therefore represents the youngest preserved formation of the Milford Haven Group south of the Ritec Fault. The Formation thickens drastically into the Ritec Fault, indicating its control on sedimentation. The half-graben topography initiated deposition of a hangingwall alluvial fan that was sourced from a southerly Lower Palaeozoic/Precambrian provenance within the present-day Bristol Channel. The Formation is heterolithic in nature, with deposits on the fan reflecting a mixture of processes. Conglomerates were deposited primarily by laterally extensive sheetfloods, and as bars in low-relief, laterally accreted channels. Sandstones were also predominantly deposited by sheetfloods. Gritty mudrocks in comparison demonstrate deposition by cohesive debris flows.The fan prograded northward and interfingered with a low-gradient, high-sinuosity fluvial channel system dominated by inclined and non-inclined heterolithic stratification. Thinly laminated mudstone and sandstone interbeds were deposited in ephemeral fan-toe and axial valley lakes that may have developed during sub-humid climatic episodes. The lacustrine heterolithic association has associated matgrounds and possible 'algal roll-up' structures. Calcretized peetee structures and root traces comprise a lake margin calcrete association.Fan gravels prograded into the axial fluvial valley during periods of increased sediment flux that may represent semi-arid conditions and/or episodes of tectonic activity. Calcretes of varying development were established in both the fan and axial valley zones. Calcretes with lower stages of development are more proximal to the Ritec Fault reflecting decreased soil residence times and high deposition rates within the axial valley. More strongly developed soil profiles on the fan may indicate sequence boundaries associated with low sediment flux, or increased soil residence time due to active fan-channel migration (the pedofacies concept). Groundwater calcretes have sharp-based and layer-bound calcrete profiles. Gully-bed cements are locally developed within the fan gravels.

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Section: Calcretesmentioning

confidence: 96%

The Ridgeway Conglomerate Formation of SW Wales, and its implications. The end of the Lower Old Red Sandstone?

Hillier

Williams

2007

Geological Journal

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“…However, some biogenic microstructures found commonly in paleosols and at paleo-exposure surfaces lack reliable modern analogs, and consequently, their origin is highly controversial (e.g., Verrecchia et al 1995Verrecchia et al , 1996Freytet et al 1997;Wright et al 1996;Wright et al 1997;Wright et al 1998;Alonso-Zarza et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Microcodium Revisited: Root Calcification Products of Terrestrial Plants on Carbonate-Rich Substrates

Košir¹

2004

Journal of Sedimentary Research

155

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Microcodium is a problematic calcitic microfeature of many calcretes and calcareous paleosols in the Cretaceous and Tertiary continental and marine successions of the peri-Tethyan realm. The main controversy about the Microcodium structures is their origin and possible relation with calcified plant roots. Microcodium and rhizogenic (root-formed) microfabrics were studied in calcrete profiles within the Paleocene shallow-marine carbonate succession in southwestern Slovenia. The prominent laminar calcrete horizons contain abundant calcite aggregates, 150 m to 1 cm in size, with perfectly preserved structural details of plant root tissues. Morphology and structure of these aggregates indicate that they formed through biologically controlled precipitation of calcium carbonate within the root cortical cells. The morphologies intermediate between the typical Microcodium aggregates, composed of a single layer of individual, elongate pyramidal or prismatic crystals of calcite (measuring 100-500 m in length and 20-70 m in width) and calcified roots with multilayer arrangement of isodiametric cells were observed, and this supports previous rhizogenic interpretations of Microcodium structures. Intermediate forms show that the typical Microcodium aggregates formed through morphological transformation of the root tissue by growth of the calcite within the cortical cells, which distorted the cell shape. Calcification of roots and the creation of Microcodium structures can be explained as an effective nutrient-acquiring mechanism used by certain types of terrestrial plants inhabiting nutrient-poor calcareous substrates. The widespread occurrence of Microcodium in almost unaltered shallowmarine limestones indicates that its formation took place during early stages of paleosol development, probably reflecting specific types of vascular plants of a pioneer community that were able to colonize carbonate substrates during the early phases of subaerial exposure.

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“…Calcrete is a near-surface, terrestrial accumulation of predominantly calcium carbonate (Wright and Tucker 1991;Alonso-Zarza et al 1998;Alonso-Zarza 2003). Calcretes which were formed only when evaporation exceeded precipitation, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…Two kinds of Microcodium were defined by Esteban (1972): 'Microcodium a' refers to typical Microcodium, consisting of prismatic calcite crystals; whereas 'Microcodium b' was defined by its smaller grain size and subquadrangular sections of its prisms (atypical Microcodium). Based on a large number of reports, the original interpretation of Microcodium as siphonaceous alga or any other phototrophic microorganism has been rejected; however, the process of Microcodium formation still remains unsolved (Klappa 1978;Alonso-Zarza et al 1998;Košir 2004;Kabanov et al 2008). Microcodium was interpreted as a calcification product of a mycorrhizae-cortical root cell association by Klappa (1978).…”

Section: Introductionmentioning

confidence: 99%

“…Microcodium was interpreted as a calcification product of a mycorrhizae-cortical root cell association by Klappa (1978). Alonso-Zarza et al (1998) suggested that 'Microcodium b' formed through calcification of root cells. Similarly, Košir (2004) stated that morphology and structure of the typical Microcodium aggregates indicate that they formed through biologically-controlled precipitation of calcium carbonate within the root cortical cells.…”

Section: Introductionmentioning

confidence: 99%

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Pedogenic calcrete records in southern Transdanubia, Hungary: A brief review with paleoenvironmental and paleogeographic implications

Varga

Raucsik²

2014

Central European Geology

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In the Hungarian part of the Tisia Block, four occurrences of rhizolith-bearing pedogenic calcrete have been published, three of which are located in southern Transdanubia. Nodular calcrete with beta fabrics was documented from the lower Permian (Cisuralian) continental Korpád Sandstone Formation where the subaerial exposure section was developed on a strongly altered, volcanic shard-rich siliciclastic substrate. Additionally, two locations with Microcodium-bearing calcrete developed on a lower Jurassic carbonate substrate were published in the last few years. The scope of this study is to briefly summarize pedogenic calcrete records known from the Permian to the Cenozoic of southern Transdanubia (Tisia Block, Hungary), and to highlight their regional paleoenvironmental and paleogeographic importance.

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Calcified root cells in Miocene pedogenic carbonates of the Madrid Basin: evidence for the origin of Microcodium b

Cited by 69 publications

References 23 publications

The Ridgeway Conglomerate Formation of SW Wales, and its implications. The end of the Lower Old Red Sandstone?

The Ridgeway Conglomerate Formation of SW Wales, and its implications. The end of the Lower Old Red Sandstone?

Microcodium Revisited: Root Calcification Products of Terrestrial Plants on Carbonate-Rich Substrates

Pedogenic calcrete records in southern Transdanubia, Hungary: A brief review with paleoenvironmental and paleogeographic implications

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