TY - JOUR A1 - Huck, Stefan A1 - Stein, Melody A1 - Immenhauser, Adrian A1 - Skelton, Peter W. A1 - Christ, Nicolas A1 - Foellmi, Karl B. A1 - Heimhofer, Ulrich T1 - Response of proto-North Atlantic carbonate-platform ecosystems to OAE1a-related stressors JF - Sedimentary geology : international journal of applied and regional sedimentology N2 - Integrated biostratigraphic-chemostratigraphic studies provide evidence that the proto-North Atlantic realm witnessed major changes in carbonate platform production in the run-up of the Early Aptian oceanic anoxic event (OAE) 1a. Whereas pervasive growth of Lithocodium microencrusters represents an early harbinger of OAE1a-related environmental perturbation, the subsequent replacement of oligotrophic rudist-coral-nerineid by mesotrophic orbitolinid-oyster communities was clearly associated with the event itself. In order to test the supra-regional relevance of this major community replacement, two shallow-water sections in the southern Lusitanian Basin (Portugal) are investigated by means of geochemistry (carbon and oxygen isotopes), cement petrography and detailed sedimentological analysis. The focus is on a regional, prominent discontinuity surface (S4) at the transition between oligotrophic and mesotrophic carbonate platform production, which might indicate that the major biotic change could have been associated with a phase of non-sedimentation and possibly erosion. The studied sections (Sao Julia, Crismina) provide evidence that the major Early Aptian biotic turnover was preceded by numerous subordinate but significant changes in platform ecology, which mirrored a series of progressive short-term environmental changes in the course of OAE1. Several transient mass occurrences of orbitolinids indicate repeated phases of ecological stress arguably due to enhanced nutrient input and deepening. Small-scale sea-level changes at parasequence level below the major discontinuity surface are revealed by alternations of rudist assemblages dominated by clinger or recumbent forms as well as intercalated hardground and subaerial exposure stages. Expanded phases of subaerial exposure, however, can be largely ruled out following the geochemical and cement-petrographic data presented here. Enhanced continent-derived siliciclastic input characterising the lower orbitolinid-oyster dominated limestones is in support of a shift to more humid conditions during the middle Early Aptian. This is in line with palaeoclimatic data, which propose a southward movement of the mid-latitude arid climate belt during this time. The documented rapid replacement of oligotrophic assemblages by various environmental-stress adapted carbonate platform communities might be seen as explanation for ongoing Early Aptian proto-North Atlantic carbonate production during a time of widespread platform demise and drowning in the northern Tethyan realm. (C) 2014 Elsevier B.V. All rights reserved. KW - Aptian KW - Oceanic anoxic event 1a KW - Proto-North Atlantic KW - Discontinuity surfaces KW - Carbonate platform response KW - Carbon and oxygen isotopes Y1 - 2014 U6 - https://doi.org/10.1016/j.sedgeo.2014.08.003 SN - 0037-0738 SN - 1879-0968 VL - 313 SP - 15 EP - 31 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Martin-Martin, J. D. A1 - Gomez-Rivas, E. A1 - Bover-Arnal, T. A1 - Trave, A. A1 - Salas, R. A1 - Moreno-Bedmar, J. A. A1 - Tomas, S. A1 - Corbella, M. A1 - Teixell, A. A1 - Verges, J. A1 - Stafford, S. L. T1 - The Upper Aptian to Lower Albian syn-rift carbonate succession of the southern Maestrat Basin (Spain): Facies architecture and fault-controlled stratabound dolostones JF - CRETACEOUS RESEARCH N2 - Syn-rift shallow-marine carbonates of Late Aptian to Early Albian age in the southern Maestrat Basin (E Spain) register the thickest Aptian sedimentary record of the basin, and one of the most complete carbonate successions of this age reported in the northern Tethyan margin. The host limestones (Benassal Formation) are partially replaced by dolostones providing a new case study of fault-controlled hydrothermal dolomitization. The syn-rift sediments filled a graben controlled by normal basement faults. The Benassal Fm was deposited in a carbonate ramp with scarce siliciclastic input. The lithofacies are mainly characterized by the presence of orbitolinid foraminifera, corals and rudist bivalves fauna. The succession is stacked in three transgressive-regressive sequences (T-R) bounded by surfaces with sequence stratigraphic significance. The third sequence, which is reported for the first time in the basin, is formed by fully marine lithofacies of Albian age and represents the marine equivalent to the continental deposits of the Escucha Fm in the rest of the basin. The dolomitization of the host rock is spatially associated with the basement faults, and thus is fault-controlled. The dolostone forms seismic-scale stratabound tabular geobodies that extend several kilometres away from the fault zones, mostly in the hanging wall blocks, and host Mississippi Valley Type (MVT) deposits. The dolostones preferentially replaced middle to inner ramp grain-dominated fades from the third T-R sequences consisting of bioclastic packestones and peloidal grainstones. Field and petrology data indicate that the replacement took place after early calcite cementation and compaction, most likely during the Late Cretaceous post-rift stage of the basin. The dolostone registers the typical hydrothermal paragenesis constituted by the host limestone replacement, dolomite cementation and sulfide MVT mineralization. The Aptian succession studied provides a stratigraphic framework that can be used for oil exploration in age-equivalent rocks, especially in the Valencia Trough, offshore Spain. Moreover, this new case study constitutes a world class outcrop analogue for similar partially stratabound, dolomitized limestone reservoirs worldwide. (c) 2013 Elsevier Ltd. All rights reserved. KW - Aptian KW - Carbonate platform KW - Fault-controlled KW - Dolomitization KW - Maestrat Basin Y1 - 2013 U6 - https://doi.org/10.1016/j.cretres.2012.12.008 SN - 0195-6671 SN - 1095-998X VL - 41 IS - 4 SP - 217 EP - 236 PB - ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD CY - LONDON ER -