Transition from alluvial to coastal deposits (Permian–Triassic) on the Island of Mallorca, western Mediterranean

Abstract

Non-marine redbeds (Permian and Triassic) in the island of Mallorca consist of a 0.4 km-thick alluvial succession that passes upwards into siliciclastic-carbonate coastal deposits. Tectonics and sealevel changes have been the main influences in their evolution. Low in this succession (the 'Areniscas y lutitas de Port des Canonge* unit) sandstone sheets with lateral accretion surfaces (macroscale inclined strata) and mudstones with frequent exposure structures are interpreted as the products of a sinuous alluvial system and floodplain. Climatic fluctuations are considered to be responsible for some significant up-section changes in the evolution of the alluvial deposits. Low-angle or horizontally stratified sandy units, interpreted as the result of flash floods, alternate upwards with point-bar deposits in the 'Areniscas de AsS'. The hydrological response to minor climatic changes was evidently nearly instantaneous due to the lack of significant vegetation cover.During accumulation of mudstones and sandstones of the overlying 'Lutitas y Areniscas de Son Serralta' unit, the interpreted environment of deposition changed from a distal braidplain, mainly constructed by superposition of sandy bedforms with straight or linguoid crestlines in low sinuosity river channels, into a coastal plain with evidence of both continental and marine influences. The overlying carbonate platform (Muschelkalk) marks the development of a more homogeneous marine environment resulting from the Tethyan transgressive event that affected the whole peri-Mediterranean realm during the Anisian (middle Triassic).

Reworked calcretes: their significance in the reconstruction of alluvial sequences (Permian and Triassic, Minorca, Balearic Islands, Spain)

“…Small laterally restricted, fl at bases or chan nelized bodies are probably crevasse-splay deposits that often contain reworked ca1crete clasts resulting from the erosion of the levees . The occurrence of reworked ca1crete clasts in conglomerate lag deposits, lining the scours of major channels, indicate that they were derived from the soils contained in blocks of fl oodplain deposits that collapsed from the cutbank, as described by Ramos (1995).…”

“…Ramos (1995) also interpreted the Permian redbeds of Majorca Island as deposited in a meandering fl uvial system. The mudstone beds represent the vertical accretion sediments deposited during periods of over bank fl ooding, and reduced sedimentation rate within the fl oodplain favoured the development of the cal cretes.…”

“…1), belong to the Alpine system and form part of the Betic-Balearic domain. The structure of this domain is the result of two major tectonic processes that operated in the western Mediterranean during the Neogene: the building of the Betic thrust system, during the Oligocene-Middle Miocene, and the opening of the Algerian basin, during the Middle Late Miocene (Fonbote et aI., 1990;Ramos, 1995).…”

“…The area that became the Balearic Islands fo rmed after the Early Permian unifi cation of the Pangaea supercontinent (Ramos, 1995). The initial stages of rifling took place during the Late Permian and even the Triassic (Sopefi a et aI., 1988), when Africa and Europe moved apart Wl der a sinistral transtensional regime, allowing the development of a network of graben systems (Rarnos,1 995 Lithostratigraphic section of the Pennian of northern Minorca (modifi ed from Rosell et aI., 1988).…”

Stratigraphical and palaeogeographical significance of the continental sedimentary transition across the Permian–Triassic boundary in Spain

“…The middle Buntsandstein facies sediments of Iberia mainly consist of red sandstones and are represented by the Cafiizar or Rillo Formations in the Iberian Ranges or its equivalent Eramprunya Formation (Marzo, 1980) and Asa Formation (Ramos, 1995) in the Catalonian Ranges and Balearic Islands, respectively (Fig. 4).…”