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Eight sites with geological (including palaeontological and geomorphological) interest (geosites) representative of the Lower and Middle Miocene carbonate deposits near Albufeira in central Algarve (southern Portugal) have been selected based on our extended working experience. The sites can be visited by hiking in a 1-day field trip. A virtual 3D tour of the georeferenced sites was produced using augmented reality technique and geoinformatic tools which integrate thematic digital layers such as geological maps and orthophotos. Every stop in the tour includes descriptive and graphic elements that can be viewed in free virtual globes (e.g. Google Earth) combined with diagrams, photographs and information sheets that quantitatively assess the cultural-touristic, educational and scientific value of the geosites. A virtual flight itinerary compatible with video formats in the new free technologies (smartphones, tablets and iPads) is also presented. [ABSTRACT FROM AUTHOR]

The Pennsylvanian phylloid algal mounds exposed in the Cervatina Limestone of the Cantabrian Zone (NW Spain) developed during the highstands of high-frequency shallowing-upward cycles and lack evidence of subaerial exposure at their tops. Mound core facies are composed of massive bafflestones with variable amounts of calcite cements and anchicodiacean phylloid algae with cyathiform thalli preserved in growth position. Through standard petrographic, isotopic (δO and δC), major and trace element (Ca, Mg, Fe, Mn, Sr) and cathodoluminescence analyses, five calcite cement phases (cement 1 (C1)-cement 5 (C5)) have been identified filling primary and secondary pores. Early marine diagenesis is represented by micritization and non-luminescent to mottled-dull luminescent high-Mg calcite fibrous marine cement (C1). A dissolution phase then occurred and created vuggy and moldic pores. Based on the absence of field or petrographical or geochemical evidence of exposure, it is inferred that dissolution occurred in near-surface undersaturated marine waters with respect to aragonite related to progressive organic matter oxidation. Secondary porosity was subsequently filled by dull-bright-dull bladed high-Mg calcite (C2), which precipitated in the early shallow burial from marine-derived pore waters. Remaining porosity was occluded by shallow-burial precipitates consisting of non-luminescent scalenohedral low-Mg calcite (C3) followed by non-ferroan dull luminescent calcite spar (C4). Latter phases of calcite spar exhibiting non- and dull luminescence (C5) are associated with burial calcite veins. Low δO values (around −8‰), moderately depleted δC values (around 0.5‰) and the homogeneity of trace element contents of carbonate matrix, cements and vein-filling calcites suggest burial isotopic re-equilibration and recrystallization, probably in Early Permian times during post-thrusting orocline formation. [ABSTRACT FROM AUTHOR]

The new species Archaeolithophyllum asymmetricum nov. sp., from the Bachende Formation (Pennsylvanian, Cantabrian Zone, NW Spain), is described herein using cathodoluminescence microscopy. Under plane-polarized light, A. asymmetricum occurs as elongate and arcuate sheets preserved as calcitic mosaics of tiny anhedral to subhedral crystals. Cathodoluminescence has revealed that skeletal walls are composed of dull-bright (locally bright) luminescent calcite that contrasts sharply with the nonluminescent cements filling the intraskeletal pores. Skeletal walls are currently composed of low-Mg calcite (0.5-2 mol % MgCO) with low Sr content (average 415 ppm). A. asymmetricum shows a strong asymmetry of the thallus organization. The internal tissue is well differentiated into a thick medullar hypothallus and a thin upper cortical perithallus, the latter being composed of nearly rectangular cells arranged in rows perpendicular to the external surface. Cell fusions commonly occur in the perithallial tissue whereas conceptacles exhibit a highly arched geometry lacking any preserved aperture. A. asymmetricum accumulations display a growth pattern similar to that reported from Late Paleozoic 'phylloid algae', and also resemble Miocene frameworks of the corallinacean Mesophyllum. These accumulations of A. asymmetricum formed micrite-rich bioherms with abundant shelter porosities, which are filled up with radiaxial-fibrous calcite (originally high-Mg calcite) and subsequent blocky spar. They constructed a rigid framework that was basically a combination of the foliaceous growth form, crust fusion and division, and synsedimentary marine cementation. Paleontological and sedimentological evidence suggests that A. asymmetricum thrived in an outer platform environment with relative quiet conditions. The exceptional preservation of these algae was favored by a rapid cementation of the intraskeletal pores under oxidizing conditions in a marine phreatic environment, protecting skeletons from early dissolution and recrystallization. Although the resulting neomorphic microsparite fabric suggests an aragonite precursor, the morphological similarities (especially reproductive organs) between Archaeolithophyllum and Recent calcitic corallinaceans, and the similar trace element composition of the algal thalli and the surrounding high-Mg radiaxial-fibrous cements, suggest that originally, Archaeolithophyllum was probably composed of high-Mg calcite. Based on the morphologic features, framework strategies (crust fusion and division) and growth modes, it is suggested that Archaeolithophyllum might be phylogenetically related to the modern coralline algae. [ABSTRACT FROM AUTHOR]

O3, TiO2, Zr, and Nb abundances in shales from all the units, strongly suggest a gradual compositional change within this sedimentary succession. Together with the petrological data, the chemical results do not reveal any obvious coeval volcanic contribution to the sediments. On the basis of the chemical data, a comparison is made with other European zones containing detrital sediments composed of reworked crustal components. [ABSTRACT FROM AUTHOR]

The Lower–Middle Miocene Lagos-Portimão Formation at Portimão, southern Portugal, consists of three main heterozoan carbonate facies: mollusc-rich rudstone in a matrix of skeletal packstone/grainstone (MR), fine-to-medium skeletal packstone/grainstone (SPG), and quartz-rich skeletal packstone (QSP). These facies occur in different arrangements and indicate deposition on a wave-dominated open shelf with a well-established heterozoan fauna, most likely related to increased trophic resources where continent supply and upwelling contributed nutrients. These facies form belts inferred to have lain roughly parallel to the strike lines of the shelf, with the MR occupying the more landward, shallower areas and the SPG and QSP extending progressively offshore on the open shelf. Bryozoan abundance in the QSP facies indicates a deep setting on the middle/outer shelf, whereas the absence of rhodalgal components is attributed to a combination of temperature decrease and seafloor eutrophication during the late Langhian and Serravallian, coeval with the "Middle Miocene climatic cooling". The large photosymbiont-bearing foraminifers and the absence of calcareous algae and zooxanthellate corals point to deposition under warm-temperate conditions. Two main orders of cyclicity are present. Small-scale sequences, 40–60 cm thick, may represent minor sea-level changes related to fifth-order sequences modulated by (~ 100-kyr) eccentricity forcing. Six large-scale sequences, 3–9 m in thickness, are recognized. Based on LAD and FAD of planktic foraminifers and the occurrence of two erosive surfaces related to major sea-level falls (Lang2/Ser1 and Ser4/Tor1), five Miocene sequences (Bu, L1, S1, S2, and S3) are correlated with third-order eustatic cycles. [ABSTRACT FROM AUTHOR]