GeoSciences

Geologica Acta, vol. 23, no. 13, 48 p.

Casas J.M., Díez-Montes A., Pujol-Solà N., Beranoaguirre A., Proenza J.A., S�nchez-García T., �lvaro J.J. & Murphy J.B. (2025).- From the Upper Ordovician unconformity to the core-mantle boundary: A review of the Ordovician events in the Canigò massif, Pyrenees.- We present a review of the stratigraphical, structural, geochemical, isotopic and geochronological data that document Ordovician events in the Canigò massif, eastern Pyrenees. Voluminous felsic magmatism, 15-20my in duration, occurred in the Mid to Late Ordovician, in two magmatic pulses that produced several laccolithic bodies, up to ca. 2000m in thickness, which became the protoliths of the various lithologies of the Canigò gneisses. There is also evidence of coeval basalt (now metabasites) with E-MORB affinities. Mid Ordovician uplift and erosion produced an Upper Ordovician (Sardic) unconformity. Synchronous extensional faults built propagation cleavage-free folds affecting a pre-Upper Ordovician succession and caused the erosion of up to 1500m of the underlying Cambrian-Lower Ordovician succession. Early Late Ordovician synsedimentary normal faults produced significant thickness variations in the Upper Ordovician successions. Compiled data match the Ordovician evolution described in Sardinia, Mouthoumet and Montagne Noire (Occitan Domain), but differs from the evolution of neighbouring areas, such as the Iberian, Armorican and Bohemian massifs, where thermal doming and magmatism developed earlier, in Furongian-Early Ordovician times, linked to the Toledanian unconformity. In the study area, uplift, erosion and extensional tectonics argue for a lithospheric uplift coeval with the development of felsic and basaltic (with E-MORB affinities) magmatism, and strongly suggests Mid to Late Ordovician plume activity beneath this segment of NW Gondwanan. The proposed plume would be one of a cluster of plumes impacting the Gondwana periphery that probably migrated inwards into Gondwana. Plume activity may be related to an early Palaeozoic superplume event, that contributed to the birth and development of the Rheic Ocean throughout the Gondwana margin breakup.
https://doi.org/10.1344/GeologicaActa2025.23.13
Wed, 08 Jul 2026 09:59:24 GMT

Geologica Acta, vol. 23, no. 14, 15 p.

Corradini C., Corriga M.G., Pondrelli M., Spalletta C., Zocchi C. & Corradetti A. (2025).- Record of a sea level drop in the lower Mississippian limestones near Passo di Monte Croce Carnico (Carnic Alps, Italy).- The lower Carboniferous succession of the Carnic Alps represents the best-preserved example of such stratigraphic interval within the Alps, thus providing crucial insights for paleogeographic and paleoclimatic reconstructions. This research focuses on the combined biostratigraphic and sedimentological analyses of a stratigraphic section near Passo di Monte Croce Carnico (central Carnic Alps). The presence of two polygonal sedimentary structure-bearing levels suggests a sea level drop. Conodont biostratigraphy places these events within the lower part of the Gnathodus interregnum, correlating with the latest Tournaisian. These data, combined with insights from coeval sedimentary records within the Carnic Alps and from other basins worldwide, indicate that higher-frequency sea-level fluctuations, superimposed on an overall regressive trend, influenced the late Tournaisian evolution of the Carnic Basin.
https://doi.org/10.1344/GeologicaActa2025.23.14
Wed, 08 Jul 2026 10:05:38 GMT

Geologica Acta, vol. 23, no. 15, 16 p.

Mancini, A., Brandano, M., Gaglianone, G., Mannetta, D. & Ferràndez-Cañadell, C. (2025).- Coralgal buildup in a mixed carbonate-siliciclastic succession of the upper Eocene Sant Martí Xic Formation (Orís, Vic, SE Ebro Basin, Spain).- Coralgal buildups from the mixed carbonate siliciclastic succession of the upper Eocene Sant Martí Xic Formation (Orís, Vic, SE Ebro Basin, Spain) were studied. During the upper Eocene, the sedimentation in the Orís area was strongly influenced by global and local factors associated with the evolution of the Ebro Basin. The stratigraphic series in Orís shows first a transgressive sedimentary sequence characterized by floatstone to rudstone limestone with Discocyclina and Nummulites, which developed in a deeper and oligophotic environment and in a general context of humid climate conditions. The second sequence is formed by progradational deltaic deposits rich in Nummulites and developed under more arid climate conditions. Coralgal buildups occur interdigitated with these deltaic deposits forming two different lens-shaped bioherms that resulted in a coalescent buildup, with coral colonies sparse in a skeletal matrix of different grain-size. Corals grew in the mesophotic zone of the deltaic system affected by light fluctuations during periods of low siliciclastic input. The coralgal buildups of Sant Martí Xic Formation were thus influenced both by climatic changes and by the local detrital input from a deltaic system, associated with the uplift of the Catalan Coastal Range, highlighting the resilience of Eocene corals to environmental change.
https://doi.org/10.1344/GeologicaActa2025.23.15
Wed, 08 Jul 2026 10:05:38 GMT

Geologica Acta, vol. 23, no. 16, 31 p.

Oskay R.G. (2025).- Coal properties of Carboniferous Kurtköy coals (Zonguldak, NW Türkiye): Emphasis on rank, provenance of minerals and hydrocarbon generation potential- Late Carboniferous coal seams in the Zonguldak Basin (NW Türkiye) underwent several tectonic movements after the Late Permian; hence, these seams exhibit rank variations. This study presents initial insights into coal rank, mineralogical compositions, and hydrocarbon generation potential of Serpukhovian-Bashkirian coals within the Alacaagzi Formation from the south-easternmost part of the Basin. The examined seams are of bituminous C rank, and Tmax (442–445°C) and HI (221–288mg HC/g TOC) values indicate that they are at the set of oil generation. However, the low PI (0.01–0.02), BI (0.03–0.06), and QI (2.2–2.9) values and the possible presence of preserved cytoplasm spore-filling within the sporinite grains may indicate that the studied coals have only gas-generation potential. The results also show that the studied coals display relatively lower random vitrinite reflectance (%Rr 0.75–0.82%) and calculated Tpeak values (113–123ºC) using %Rr and micro-Raman spectra than their counterparts in the northern parts of the Basin (%Rr 1.18–1.52% and 173–206ºC). This difference seems to be related to the shallower burial depths of the studied coals or to the fact that they experienced relatively lower maximum attained temperatures than the northern parts of the Basin. Furthermore, the coal petrography and SEM-EDS data also suggest that the post-coalification tectonic deformation in the study area created space for circulating Ca- and Si-rich solutions within the coal seams and controlled epigenetic mineralization. Nevertheless, the redox conditions and clastic influx into the palaeomires also controlled syngenetic mineral formations, similar to the other parts of the Basin.
https://doi.org/10.1344/GeologicaActa2025.23.16
Wed, 08 Jul 2026 10:05:38 GMT