Upper Ordovician-Lower Silurian transgressive-regressive cycles of the Central Iberian Zone (NE Jaén, Spain)

Abstract

A thick Upper Ordovician shelf sequence was developed in the northern Gondwana margin (southernmost exposures of the Central Iberian Zone). Integrated sedimentologic and stratigraphic studies allow distinction between pedogenetic processes (Facies association C), shoreline deposits (Facies association S), proximal to distal shelf (Facies association L, H 1 , H 2 , H 3 ) and outer shelf zone or open marine environments (Facies association M, Mo). The vertical distribution of facies is characterized by the presence of regressive high frequency sequences (partial shelf progradational sequences), affected by the presence of catastrophic phenomena (storms). These sequences, in turn, can be classified into higher-order transgressive (T)-regressive (R) cycles.Two second-order T-R megacycles (MC. Ord-2 and MC. Sil-1) limited by a major sequence boundary are identified. Traces of emersion (palaeokarsts and palaeosols) are detected along the sequence boundary, and these are related to the eustatic sealevel fall that occurred during the Ashgillian.The MC. Ord-2 and MC. Sil-1 megacycles extend respectively from the Middle Arenig to the Ashgillian and from Late Ashgillian to the Late Llandovery. Major transgressive peaks occurred at the Llanvirn and at the Middle Llandovery (Aeronian). The vertical distribution of the facies delineates successive genetically related units in relation to relative sea-level changes. Within the upper part of the first megacycle (MC. Ord-2) six third-order cycles are proposed (Lla-1, Car-1, Car-2, Car-3, Car-4, Ash-1), in which a transgressive and a regressive interval can be distinguished. Within the lower part of the second megacycle (MC. Sil-1) two transgressive-regressive third-order cycles are proposed (Lly-1, Lly-2).

Metal(loid)s Transport in Hydrographic Networks of Mining Basins: The Case of the La Carolina Mining District (Southeast Spain)

“…Discordantly on the Palaeozoic basement and fossilizing these mineralizations, the posthercynian cover appears, which is subhorizontally arranged. The cover is made up of Triassic materials (red shales and conglomerates), Miocene (marls with levels of sandstones, silts and/or breccia at the base) and quaternaries (silts, sands and gravels associated with the filling of the channels) [18,19,29].…”

Hydrogeochemistry of abandoned Pb sulphide mines: the mining district of La Carolina (southern Spain)

“…The Palaeozoic basement is constituted by a metasedimentary rock succession (essentially shales and quartzites) of Ordovician to Carboniferous age (Azcárate and Argüelles 1971;Fontboté 1982, Lillo 1992Rey and Hidalgo 2004;Rey et al 2005;Ríos 1977 This Palaeozoic succession also consists of Silurian shales, a Devonian alternating of shales/quartzites and Lower Carboniferous grey shales. However, a peculiar characteristic of this area is the presence of a granitoid massif ( Fig.…”

Estimation of the Pb Content in a Tailings Dam Using a Linear Regression Model Based on the Chargeability and Resistivity Values of the Wastes (La Carolina Mining District, Spain)

“…Unlike the Palaeozoic basement and fossilizing these mineralizations, the post-Hercynian cover appears to be arranged subhorizontally. It consists of Triassic (red shales and conglomerates), Miocene (marls with layers of sandstones, silts, and/or breccias at the base), and Quaternary materials (silts, sands, and gravels) [20,21].…”