Revised biochronology of the Lower Cambrian of the Central Iberian zone, southern Iberian massif, Spain

Jensen, Sören; Palacios, Teodoro; Mus, Mónica Martí

doi:10.1017/s0016756809990677

Cited by 35 publications

(41 citation statements)

References 22 publications

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“…The genus Cupitheca is also found in the lower Cambrian of Antarctica, China, Australia, Spain and Kazakhstan (Mambetov in Missarzhevsky and Mambetov, 1981;Zhou and Xiao, 1984;Bengtson in Bengtson et al, 1990;Wrona, 2003;Malinky and Skovsted, 2004;Kruse et al, 2004;Jensen et al, 2010). Hayden's (1904) levels 2, 4, and 13 have not yielded microfossils described herein, but their position is given for clarity.…”

Section: Biostratigraphymentioning

confidence: 99%

Cambrian microfossils from the Tethyan Himalaya

2016

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Cambrian biostratigraphy of the Indian subcontinent is best documented from the Parahio Formation of the Tethyan Himalaya. Recently established trilobite biostratigraphy shows that the formation encompasses the latest part of unnamed Stage 4 and much of unnamed Stage 5. A variety of small shelly fossils have been recovered via acid digestion of carbonate beds and include tetract and pentact hexactinellid sponge spicules, chancelloriid spicules belonging to Chancelloria sp. and a new species, Archiasterella dhiraji, shells of an helcionelloid comparable to Igorella maidipingensis, a meraspid ptychopariid trilobite, the tubular Cupitheca sp., a poorly preserved hyolith, and an assortment of spinose microfossils of uncertain affinity. These newly recovered microfossils are consistent with the trilobite-based lower and middle Cambrian age determination and do not support a late Cambrian age for the top of the Parahio Formation advocated in some recent literature. The microfossils reported herein significantly expand the known diversity of such fossils from Cambrian strata in the Himalayan region, and allow for comparison of this fauna with others from Gondwanaland and elsewhere. Integration with trilobite data indicate that the stratigraphic ranges of many small shelly fossils described in this study are greater than previously recognized.

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Section: Biostratigraphymentioning

confidence: 99%

Cambrian microfossils from the Tethyan Himalaya

2016

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“…(), from hexactinellids and demosponges. Cambrian‐type trace fossils occur several hundred metres down‐section of the main phosphate‐bearing level, and trilobites, small shelly fossils and archaeocyaths are found near the top of the Río Huso Group (Jensen et al ., ) (Fig. ).…”

Section: Stratigraphy Facies and Diagenetic Featuresmentioning

confidence: 99%

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

et al. 2015

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The late Ediacaran–mid Cambrian occurrences of phosphorites in the western Mediterranean region (West Gondwana) and southern Sweden (north‐west Baltica) are related to the poleward drift of West Gondwana and the northern drift of Baltica. As a result, these regions crossed subtropical and temperate palaeolatitudes of the Southern Hemisphere, in which oceanic upwelling and high organic productivity were the probable sources of phosphorus along their western margins. A parallel south‐west/north‐east migration trend of evaporites and delayed, time transgressive phosphorites point to distal upwelling environments associated with shallower arid conditions. Concentration of hardground‐derived phosphate accumulations took place by repeated alternations of low sedimentation rates and condensation, in situ early diagenetic and microbially mediated precipitation of amorphous and cryptocrystalline, carbonate‐bearing francolite, winnowing and polyphase reworking of previously phosphatized skeletons and hardground‐derived clasts. Thicker phosphorites of economic importance display a spiculate sponge‐thromboid consortium that points to a distinct benthic community developed on suboxic, slope to basinal substrates. For most phosphorite samples an up to ten‐fold enrichment in rare earth element concentration relative to post‐Archaean average Australian shale reflects significant incorporation of rare earth elements and yttrium after deposition. Considerable scavenging took place from anoxic pore waters, following reductive dissolution of iron oxides as evidenced from the medium rare earth element enrichment in most samples. This contrasts with the rare preservation of primary sea water features, such as cerium depletion and yttrium enrichment, in phosphatized thrombolites from the shallower realms (for example, Montagne Noire). The data are consistent with phosphogenesis after upwelling and transgression of nutrient‐rich, suboxic–anoxic, ferruginous waters over more oxygenated, rifting settings and inland portions of an evolving passive margin.

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“…According to Martínez Catalán et al (1992) and Russo & Bechstädt (1994), the western boundary of the WALZ-CZ platforms was situated at the Vivero Fault ( Fig. 1), coinciding with the boundary with the Variscan Central Iberian Zone (for a recent stratigraphic revision of the latter, see Jensen et al 2010). To the west of the Vivero Fault, a basinal deposition probably represents the lateral equivalent of the Vegadeo and Lán-cara formations.…”

Section: West Asturian-leonese and Cantabrian Zonesmentioning

confidence: 95%

Stratigraphic record and palaeogeographic context of the Cambrian Epoch 2 subtropical carbonate platforms and their basinal counterparts inSW Europe, West Gondwana

Álvaro¹,

Monceret²,

Monceret³

et al. 2010

Bull. Geosci.

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The Ibero-Armorican Arc is the main Variscan macrostructure inSWEurope. Its branches preserve the Cambrian record of a continuous margin of West Gondwana, from its southwestern edge (West Asturian-Leonese and Cantabrian zones and their lateral continuity into the Iberian Chains) to its northeastern extension (basement of the Cenozoic Aquitaine basin, Montagne Noire, southern Cévennes, and Sardinia). These Variscan relics allow the reconstruction of a Cambrian Epoch 2 carbonate belt that developed intermittently along West Gondwana. Facies associations show that the main centres of carbonate productivity were nucleated in ooidal and sand shoals, together with microbial and microbial- archaeocyathan reefs, developed in high energy regimes under subtropical arid conditions. Outside the inner carbonate belt, carbonate production was episodic and related to deposition of kerogenous black shales and phosphogenesis in the Central Iberian Zone and northern parts of Montagne Noire and Cévennes. Development of carbonate platforms along the margin was diachronous and discontinuous, due to poleward drifting and tectonically induced drowning and flooding. Biogeographic connection with similar subtropical carbonate platforms from East Gondwana (mainly South China) favoured the migration of equatorial and subtropical trilobite genera, such as Dolerolenus, Eoredlichia, Metaredlichia, Protolenus, Redlichia, and Sardaspis

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Revised biochronology of the Lower Cambrian of the Central Iberian zone, southern Iberian massif, Spain

Cited by 35 publications

References 22 publications

Cambrian microfossils from the Tethyan Himalaya

Cambrian microfossils from the Tethyan Himalaya

Ediacaran–Cambrian phosphorites from the western margins of Gondwana and Baltica

Stratigraphic record and palaeogeographic context of the Cambrian Epoch 2 subtropical carbonate platforms and their basinal counterparts inSW Europe, West Gondwana

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