@article{SchefflerOberhaensliPourteauetal.2016, author = {Scheffler, Franziska and Oberh{\"a}nsli, Roland and Pourteau, Amaury and Immenhauser, A. and Candan, O.}, title = {Sedimentologic to metamorphic processes recorded in the high-pressure/low-temperature Mesozoic Rosetta Marble of Anatolia}, series = {International journal of earth sciences}, volume = {105}, journal = {International journal of earth sciences}, publisher = {Springer}, address = {New York}, issn = {1437-3254}, doi = {10.1007/s00531-015-1214-y}, pages = {225 -- 246}, year = {2016}, abstract = {Anatolia's high-pressure metamorphic belts are characterized in part by a Neotethyan stratigraphic succession that includes a mid-Cretaceous hemi-pelagic marble sequence. This unit contains, towards its stratigraphic top, dm-to-m-long radiating calcitic rods forming rosette-like textures. Here, we refer to these features as "Rosetta Marble". The remarkable textural similarity of non-metamorphic selenite crystals and radiating calcite rods in the Rosetta Marble strongly suggests that these textures represent pseudomorphs after selenites. Metamorphosed hemi-pelagic limestones, dominated by Rosetta selenite pseudomorphs, are alternating with siliceous meta-sediments containing relictic radiolaria tests. This stratigraphic pattern is indicative of transient phases characterized by evaporites precipitated from basinal brines alternating with non-evaporative hemi-pelagic deposition from normal-marine seawater. The regional distribution of Rosetta Marble exposures over 600 km is indicative of basin-scale evaporitic intervals. High-pressure, low-temperature metamorphism of these rocks is witnessed by Sr-rich (up to 3500 ppm), fibrous calcite pseudomorphs after aragonite and isolated aragonite inclusions in quartz. Peak metamorphic conditions of 1.2 GPa and 300-350 °C are attested by high-Si white mica thermobarometry. The Rosetta Marble case example examines the potential to unravel the complete history from deposition to diagenesis and metamorphism of meta-sedimentary rocks.}, language = {en} } @article{ChristImmenhauserAmouretal.2012, author = {Christ, Nicolas and Immenhauser, Adrian and Amour, Frederic and Mutti, Maria and Preston, Rosalind and Whitaker, Fiona F. and Peterh{\"a}nsel, Arndt and Egenhoff, Sven O. and Dunn, Paul A. and Agar, Susan M.}, title = {Triassic Latemar cycle tops - Subaerial exposure of platform carbonates under tropical arid climate}, series = {Sedimentary geology : international journal of applied and regional sedimentology}, volume = {265}, journal = {Sedimentary geology : international journal of applied and regional sedimentology}, number = {28}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0037-0738}, doi = {10.1016/j.sedgeo.2012.02.008}, pages = {1 -- 29}, year = {2012}, abstract = {The Triassic Latemar platform in the Dolomites, Italy, is the site of several ongoing controversies. Perhaps the most interesting debate focuses on apparent cyclic deposition within the Latemar platform, whose nature and duration are still open to debate. Further disagreement concerns the lack of meteoric diagenesis-related isotope shifts at cycle tops that bear circumstantial petrographic evidence for subaerial emergence. Here, an evaluation of the nature of Latemar cycle tops is presented combining evidence from previous work and new field, petrographic and geochemical data. Cycle tops are ranked according to increasing exposure duration and spatial extent: type I surfaces lacking unequivocal evidence of prolonged supratidal conditions; type II dolomite caps formed in warm, evaporitic, intertidal lagoonal waters followed by exposure of perhaps intermediate duration; type III clastic-rich, red calcareous horizons with some showing platform-wide extent, representing prolonged supratidal conditions, and type IV discontinuities in tepee belts, genetically related to type II and III surfaces, but likely representing shorter-lived exposure stages. Petrographic and geochemical criteria indicate that most diagenesis occurred in the shallow marine and burial domain whilst an extensive meteoric overprint of cycle tops is lacking. This is underlined by the scarcity of meteoric diagenetic fabrics such as gravitational cements that, where present, are here interpreted as marine-vadose in origin. The scarcity of carbon and oxygen isotope signatures commonly assigned to subaerial exposure stages is best explained in the context of mid-Triassic climate. The low latitude, tropical but arid setting of the Latemar, situated in the western extension of the Tethys ocean, its isolation from nearby continental areas and overall short-term emergence episodes are in agreement with a limited degree of meteoric alteration of most cycle tops. High amounts of aeolian clastic material beneath some cycle tops, along with high Fe and Mn elemental abundances argue for intermittent subaerial conditions. This study proposes an enhancement of the classical Allan and Matthews (1982) isotope model for subaerial exposure under strongly arid climates. As the subaerial exposure nature of Latemar cycle tops, and therefore eustasy as the cause for cyclicity, have been previously challenged due to the lack of meteoric-induced isotopic signatures, the outcome of this study is of significance for the ongoing Latemar stratigraphic controversy.}, language = {en} } @article{AgadaChenGeigeretal.2014, author = {Agada, S. and Chen, F. and Geiger, S. and Toigulova, G. and Agar, Susan M. and Shekhar, R. and Benson, Gregory S. and Hehmeyer, O. and Amour, Fr{\´e}d{\´e}ric and Mutti, Maria and Christ, Nicolas and Immenhauser, A.}, title = {Numerical simulation of fluid-flow processes in a 3D high-resolution carbonate reservoir analogue}, series = {Petroleum geoscience}, volume = {20}, journal = {Petroleum geoscience}, number = {1}, publisher = {Geological Soc. Publ. House}, address = {Bath}, issn = {1354-0793}, doi = {10.1144/petgeo2012-096}, pages = {125 -- 142}, year = {2014}, abstract = {A high-resolution three-dimensional (3D) outcrop model of a Jurassic carbonate ramp was used in order to perform a series of detailed and systematic flow simulations. The aim of this study was to test the impact of small- and large-scale geological features on reservoir performance and oil recovery. The digital outcrop model contains a wide range of sedimentological, diagenetic and structural features, including discontinuity surfaces, shoal bodies, mud mounds, oyster bioherms and fractures. Flow simulations are performed for numerical well testing and secondary oil recovery. Numerical well testing enables synthetic but systematic pressure responses to be generated for different geological features observed in the outcrops. This allows us to assess and rank the relative impact of specific geological features on reservoir performance. The outcome documents that, owing to the realistic representation of matrix heterogeneity, most diagenetic and structural features cannot be linked to a unique pressure signature. Instead, reservoir performance is controlled by subseismic faults and oyster bioherms acting as thief zones. Numerical simulations of secondary recovery processes reveal strong channelling of fluid flow into high-permeability layers as the primary control for oil recovery. However, appropriate reservoir-engineering solutions, such as optimizing well placement and injection fluid, can reduce channelling and increase oil recovery.}, language = {en} } @article{ShekharSahniBensonetal.2014, author = {Shekhar, R. and Sahni, I. and Benson, Gregory S. and Agar, Susan M. and Amour, Fr{\´e}d{\´e}ric and Tomas, Sara and Christ, Nicolas and Alway, Robert and Mutti, Maria and Immenhauser, A. and Karcz, Z. and Kabiri, L.}, title = {Modelling and simulation of a Jurassic carbonate ramp outcrop, Amellago, High Atlas Mountains, Morocco}, series = {Petroleum geoscience}, volume = {20}, journal = {Petroleum geoscience}, number = {1}, publisher = {Geological Soc. Publ. House}, address = {Bath}, issn = {1354-0793}, doi = {10.1144/petgeo2013-010}, pages = {109 -- 123}, year = {2014}, abstract = {Carbonate reservoirs pose significant challenges for reservoir modelling and flow prediction due to heterogeneities in rock properties, limits to seismic resolution and limited constraints on subsurface data. Hence, a systematic and streamlined approach is needed to construct geological models and to quickly evaluate key sensitivities in the flow models. This paper discusses results from a reservoir analogue study of a Middle Jurassic carbonate ramp in the High Atlas Mountains of Morocco that has stratigraphic and structural similarities to selected Middle East reservoirs. For this purpose, high-resolution geological models were constructed from the integration of sedimentological, diagenetic and structural studies in the area. The models are approximately 1200 x 1250 m in size, and only faults (no fractures) with offsets greater than 1 m are included. Novel methods have been applied to test the response of flow simulations to the presence or absence of specific geological features, including proxies for hardgrounds, stylolites, patch reefs, and mollusc banks, as a way to guide the level of detail that is suitable for modelling objectives. Our general conclusion from the study is that the continuity of any geological feature with extreme permeability (high or low) has the most significant impact on flow.}, language = {en} }