Folded overthrusts at Aljustrel (South Portugal)

Schermerhorn, L. J. G.; Stanton, William Iredale

doi:10.1017/s0016756800051943

Cited by 29 publications

(12 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The whole succession of the IPB suffered slight regional metamorphism during the Hercynian Orogeny (Munhá 1979(Munhá , 1990Abad et al 2001). Deformation in the IPB has been extensively discussed and a thin-skinned tectonic model is widely accepted that describes the IPB as a southward-verging thrust and fold belt (Schermerhorn and Stanton 1969;Schermerhorn 1971;Ribeiro and Silva 1983;Silva et al 1990;Soriano 1996;Quesada 1998;Onézime et al 2002).…”

Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

et al. 2011

View full text Add to dashboard Cite

International audienceIn the Rio Tinto district of the Iberian Pryrite Belt of South Spain, the weathering of massive sulfide bodies form iron caps, i.e., true gossans and their subsequent alteration and re-sedimentation has resulted in iron terraces, i.e., displaced gossans. To study the stucture and evolution of both types of gossans, magnetic investigations have been carried out with two foci: (1) the characterisation and spatial distribution of magnetic fabrics in different mineralised settings, including massive sulfides, gossans, and terraces, and (2) paleomagnetic dating. Hematite has been identified as the suceptibility carrier in all sites and magnetic fabric investigation of four gossans reveals a vertical variation from top to bottom, with: (1) a horizontal foliation refered to as "mature" fabric in the uppermost part of the primary gossans, (2) highly inclined or vertical foliation interpreted as "immature" fabric between the uppermost and lowermost parts, and (3) a vertical foliation interpreted to be inherited from Hercynian deformation in the lowermost part of the profiles. In terraces, a horizontal foliation dominates and is interpreted to be a "sedimentary" fabric. Rock magnetic studies of gossan samples have identified goethite as the magnetic remanence carrier for the low-temperature component, showing either a single direction close to the present Earth field (PEF) direction or random directions. Maghemite, hematite, and occasionally magnetite are the remanence carriers for the stable high-temperature component that is characterized by non PEF directions with both normal and reversed magnetic polarities. No reliable conclusion can be yet be drawn on the timing of terrace magnetization due to the small number of samples. In gossans, the polarity is reversed in the upper part and normal in the lower part. This vertical distribution with a negative reversal test suggests remanence formation during two distinct periods. Remanence in the upper parts of the gossans is older than in the lower parts, indicating that the alteration proceeded from top to bottom of the profiles. In the upper part, the older age and the horizontal "mature" fabric is interpreted to be a high maturation stage of massive sulfides' alteration. In the lower part, the age is younger and the inherited "imature" vertical Hercynian fabric indicates a weak maturation stage. These two distinct periods may reflect changes of paleoclimate, erosion, and/or tectonic motion

show abstract

Section: Geological Setting Of the Iberian Pyrite Beltmentioning

confidence: 99%

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

et al. 2011

View full text Add to dashboard Cite

show abstract

“…The Barranco do Homem Formation is composed of quartzwackes, siltstones and shales, and forms a terrigenous sequence of regional significance from 2 Stratigraphy and Synsedimentary Tectonism 339 Mertola to Aljustrel. In Aljustrel, it corresponds to what has been described as the Gomes Quartzite Formation (Schermerhorn and Stanton 1969). The unit is highly deformed and its boundary with the PQ Formation is commonly tectonized.…”

Section: Fig2 Selected Stratigraphic Columns Of the Pyrite Beltmentioning

confidence: 99%

Stratigraphy and Synsedimentary Tectonism

Oliveira¹

1990

Pre-Mesozoic Geology of Iberia

120

144

View full text Add to dashboard Cite

“…Quaternary fluvial incision, related to differential tectonic up-lift of the region, resulted in the formation of Quaternary terraces along the Sado and its affluents (Schermerhorn et al 1987). In the northern sector however, due to the abundance of sandy colluviums, fluvial terraces are difficult to identify and a single series of terraces of unknown age is indicated (4).…”

Section: Geographical and Geological Settingmentioning

confidence: 99%

“…A shift from traditional farming practices to large-scale cultivation of wheat in the 19 th century, inspired by government policy, caused widespread erosion of soils and the subsequent silting up of the Sado and its tributaries, particularly in the northern part of the study region (Schermerhorn et al 1987).…”

Section: Geographical and Geological Settingmentioning

confidence: 99%

The Palaeolithic occupation of southern Alentejo: the Sado River Drainage Survey

Burke¹,

Meignen²,

Bisson³

et al. 2011

Trab. prehist.

View full text Add to dashboard Cite

La ocupación paleolítica del Alentejo meridional: investigación en la cuenca del río SadoAriane Burke (*) Liliane Meignen (**) Michael Bisson (***) Nuno Pimentel (****) Virginia Henriques (*****) César Andrade (****) Maria da Conceição Freitas (****) Masa Kageyama (******) William Fletcher (*******) Carla Parslow (********) Dario Guiducci (*) ABSTRACTThe Sado River Drainage Survey project (2004)(2005)(2006)(2007)(2008) was designed to fill a significant gap in our knowledge of the prehistory of Portugal. Southern Alentejo constitutes nearly one third of the total land mass of continental Portugal, but has received comparatively little attention from Palaeolithic archaeologists. Practically nothing was known about the prehistory of the Sado River basin, which includes the southern Alentejo plain, before now. The results of the Sado River Drainage Survey (SRDS) indicate that the Sado River basin was likely occupied at low population densities during the Middle Palaeolithic. There is some evidence for a Lower Palaeolithic presence but little or no evidence of an Upper Palaeolithic occupation. The emerging pattern suggests either an occupational hiatus or a major shift in settlement pattern towards the end of the Middle Palaeolithic. Possible explanations for this pattern, including aridification driven by climate change, are explored here. RESUMEN

show abstract

Folded overthrusts at Aljustrel (South Portugal)

Abstract: SUMMARYThe Upper Palaeozoic rocks in the Aljustrel area of South Portugal suffered strong Hercynian deformation, including isoclinal overturned shearfolding of two important thrust planes bringing sub-Culm strata over Culm.

Cited by 29 publications

References 0 publications

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

A case study of the internal structures of gossans and weathering processes in the Iberian Pyrite Belt using magnetic fabrics and paleomagnetic dating

Stratigraphy and Synsedimentary Tectonism

The Palaeolithic occupation of southern Alentejo: the Sado River Drainage Survey

Contact Info

Product

Resources

About