Gian Gabriele Ori | Università degli Studi "G. d'Annunzio" Chieti Pescara (original) (raw)

Papers by Gian Gabriele Ori

Research paper thumbnail of Iron-framboids in the hydrocarbon-related Middle Devonian Hollard Mound of the Anti-Atlas mountain range in Morocco: Evidence of potential microbial biosignatures

Sedimentary Geology

Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, M... more Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, Morocco) have been thoroughly investigated through a combination of techniques, including optical and high resolution scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, Raman microscopy and time-of-flight secondary ion mass spectroscopy. Framboids occur embedded in laminated carbonates of the mound and are precipitated along the veins that crosscut it and served as the conduits for (channeled) reduced hydrocarbon-rich fluids. The morphology, structure, and composition of the framboids contribute to the reconstruction of the complex interplay between the advected fluids and the associated biological and/or abiological processes. A comparison of our dataset with that from modern framboids formed under similar conditions indicates that the Fe-rich framboids represent replaced primary pyrite framboids produced as a consequence of bacterial sulfate reduction and the anaerobic oxidation of methane.

Research paper thumbnail of Terraces and Gilbert-type deltas in crater lakes in Ismenius Lacus and Memnonia (Mars

Journal of Geophysical Research, 2000

Paleolacustrine environments have been widely recognized from landform associations on the surfac... more Paleolacustrine environments have been widely recognized from landform associations on the surface of Mars. In contrast to paleolakes in more open areas, putative crater lakes commonly display well-developed sedimentary landforms, especially wave-formed terraces and Gilbert-type deltas. This study focuses on terraces and deltas of Western Memnonia and Ismenius Lacus. As on Earth, these landforms provide important indications of water dynamics and sedimentary processes. The putative Martian paleolakes must have been active for thousands of years to have permitted the water movement and wave formation necessary to form one or more terraces. Fan-shaped landforms at the mouths of channels entering crater-lake areas may indicate various channel water interaction. Of these, Gilbert-type deltas are particularly informative. Their presence indicates multiple flooding events whereby the inlet channels conveyed coarse-grained sediment to the crater lake. Both terraces and deltaic progradation indicate that the crater lakes of Memnonia and Ismenius Lacus were active for long time periods, at least for thousands of years, during the post heavy bombardment period of the later Martian history. The unequivocal presence of standing bodies of water of relatively long durations indicates that climatic settings very different from those prevailing today must have occurred, at least locally and temporarily, during parts of the Martian planetary history.

Research paper thumbnail of Fluid dynamics of liquids on Titans surface

Planetary and Space Science, 1998

... Fluid dynamics of liquids on Titans surface. Gian Gabriele Ori 1 , Lucia Marinangeli 1 , Anto... more ... Fluid dynamics of liquids on Titans surface. Gian Gabriele Ori 1 , Lucia Marinangeli 1 , Antonio Baliva 1 , Mario Bressan 1 and Robert G. Strom 2. ... Soc. 28 (1996), p. 1130. Coustenis et al., 1995 A. Coustenis, E. Lellouch, JP Maillard and CP McKay, Icarus 118 (1995), pp. 87–104. ...

Research paper thumbnail of A description of surface features in north Tyrrhena Terra, Mars: Evidence for extension and lava flooding

Icarus, 2007

We studied north Tyrrhena Terra, an approximately 39,000 km2 area, located in the transition regi... more We studied north Tyrrhena Terra, an approximately 39,000 km2 area, located in the transition region straddling the Amenthes and Mare Tyrrhenum Mars Chart quadrangles 14 and 22, respectively. The study area comprises ancient terrains with infilled craters, ridges and valleys. Interpretation of orbiter data of ancient terrains is inherently difficult, but valuable information can be obtained using multiple datasets and

Research paper thumbnail of Roles of methane and carbon dioxide in geological processes on Mars

Planetary and Space Science, 2011

Research paper thumbnail of Martian paleolacustrine environments and their geological constrains on drilling operations for exobiological research

Planetary and Space Science, 2000

... 4, 64.3°S, 4°W). 3. Exobiology. Lacustrine deposits are among the best candidates to have har... more ... 4, 64.3°S, 4°W). 3. Exobiology. Lacustrine deposits are among the best candidates to have harbored life on Mars (McKay and Nedall, 1988; Cabrol et al., 1999). ... Cabrol, NA, Grin, EA, Newsom, HE, Landheim, R. and McKay, CP, 1999. ...

Research paper thumbnail of Geological Evolution of the Tyras Vallis Paleolacustrine System, Mars

Journal of Geophysical Research, 2006

1] Using the new High Resolution Stereo Camera (HRSC) data and other Martian data sets, we recons... more 1] Using the new High Resolution Stereo Camera (HRSC) data and other Martian data sets, we reconstructed the hydrological history of an unnamed complex crater in the Xanthe Terra region. The crater hosted a lacustrine basin fed by a dense and centripetal drainage system, developed along its inner rim, and by the Tyras Vallis channel. Where the Tyras Vallis opens into the crater, a prominent delta-like feature is visible, characterized by a central terrace and two small longitudinal scarps. This deposit has been used as sedimentary recorder of the crater lake history and allowed assessment of the overall hydrological evolution. Two major stands of the water level have been inferred at 700 and 550 m above the crater floor, based on the correlation between the morphology and topography of the fan and the crater floor deposits. Our reconstruction reveals a complex sedimentary evolution of the fan, which underwent deltaic and alluvial sedimentation, as a result of the different lake water levels and Tyras Vallis supplies. A dominant erosional evolution of the fan-delta was determined by the interaction between the fluvial characteristics and basin wave regime. Wave height analysis and morphological comparison with terrestrial analogues support this hypothesis. The lacustrine activity could be chronologically placed between the Late Noachian and the Hesperian. The climatic conditions could have allowed the recharge of the regional groundwater system by precipitation and episodic fluvial activity. However, also heating effects of cratering could have affected the system, rejuvenating or accelerating the recharge of the local aquifer.

Research paper thumbnail of Origin of glacial–fluvial landforms in the Azas Plateau volcanic field, the Tuva Republic, Russia: Role of ice–magma interaction

Geomorphology, 2007

The basaltic Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federatio... more The basaltic Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federation. The area was glaciated multiple times, and the field is characterized by the formation of subglacial volcanoes called tuyas, but subaerial volcanoes and lava fields also exist. A combined study of remote sensing and field observations in the vicinity of the tuyas in the southeastern Azas Plateau volcanic field identified landforms that are best explained by the jökulhlaup hypothesis. The landforms include elongated hills, paleochannels, and butte and basin topography. These landforms are hypothesized to have formed by both erosion and deposition caused by high-energy water streams. The triggering for the hypothesized jökulhlaups was either melting of ice by subglacial volcanism and/or destabilization of ice-dammed/subglacial reservoirs. The age estimation of the flood events is difficult, but they probably occurred during the ice ages of the Quaternary, as late as in the Middle-Late Pleistocene.

Research paper thumbnail of Combinations of processes responsible for Martian impact crater ``layered ejecta structures'' emplacement

Journal of Geophysical Research, 2007

We utilized images and stereo-derived topographic data acquired by the High Resolution Stereo Cam... more We utilized images and stereo-derived topographic data acquired by the High Resolution Stereo Camera (HRSC) and Thermal Emission Imaging System (THEMIS) images together with other data in order to study the geology of “layered ejecta structures” associated with relatively pristine Martian impact craters. The geomorphology and morphometric properties indicate their origin as complex combinations of a variety of impact processes.

Research paper thumbnail of Microbial signatures in sabkha evaporite deposits of Chott el Gharsa (Tunisia) and their astrobiological implications

Planetary and Space Science, 2006

This study investigates the geomicrobiological potential of Upper Pleistocene evaporite deposits ... more This study investigates the geomicrobiological potential of Upper Pleistocene evaporite deposits of the Chott el Gharsa, a wide continental sabkha in southern Tunisia. Organic and inorganic-derived biosignatures are mostly contained in microcrystalline, laminated gypsum lithofacies consisting of light/dark alternations of concordant laminae, which have precipitated from high salt concentrated waters. These biosignatures include mineralized microbial-interpreted morphologies, such as mucilage, rods, and microfibers, and dumbbell morphologies in the hollow cores of dolomite crystals that are associated with sulfates. Mineral products that are induced by microbial activity and their organic compounds lead to the formation of lenticular-shaped gypsum crystals, with a high length/width ratio, dolomite precipitation and formation of pyrite framboids. Morphological and structural aspects of these biosignatures, and their composition, in laminated, dolomite-rich sulfate deposits could be detected through microscopic investigations and micro-analyses performed by the instrumentation that is planned for ongoing Mars sample return missions. r

Research paper thumbnail of An ESA study for the search for life on Mars

Planetary and Space Science, 2000

Similarities in the early histories of Mars and Earth suggest the possibility that life may have ... more Similarities in the early histories of Mars and Earth suggest the possibility that life may have arisen on Mars as it did on Earth. If this were the case, early deterioration of the environment on Mars (loss of surface water, decrease in temperature) may have inhibited further evolution of life. Thus, life on Mars would probably be similar to the simplest form of life on Earth, the prokaryotes. We present a hypothetical strategy to search for life on Mars consisting of (i) identifying a suitable landing site with good exobiological potential, and (ii) searching for morphological and biogeochemical signatures of extinct and extant life on the surface, in the regolith subsurface, and within rocks. The platform to be used in this theoretical exercise is an integrated, multi-user instrument package, distributed between a lander and rover, which will observe and analyse surface and subsurface samples to obtain the following information:

Research paper thumbnail of Chemical compositions of impact melt breccias and target rocks from the Tenoumer impact crater, Mauritania

Meteoritics & Planetary Science, 2005

Abstract— The impact melt breccias from the Tenoumer crater (consisting of a fine-grained intergr... more Abstract— The impact melt breccias from the Tenoumer crater (consisting of a fine-grained intergrowth of plagioclase laths, pyroxene crystals, oxides, and glass) display a wide range of porosity and contain a large amount of target rock clasts.Analyses of major elements in impact melt rocks show lower contents of SiO2, Al2O3, and Na2O, and higher contents of MgO, Fe2O3, and CaO, than the felsic rocks (i.e., granites and gneisses) of the basement. In comparison with the bulk analyses of the impact melt, the glass is strongly enriched in Si-Al, whereas it is depleted both in Mg and Fe; moreover, the impact melt rocks are variably enriched or depleted in some REE with respect to the felsic and mafic bedrock types. Gold is slightly enriched in the impact melt, and Co, Cr, and Ni abundances are possibly due to a contribution from mafic bedrock.Evidences of silicate-carbonate liquid immiscibility, mainly as spherules and globules of calcite within the silicate glass, have been highlighted.HMX mixing calculation confirm that the impact melt rocks are derived from a mixing of at least six different target lithologies outcropping in the area of the crater. A large contribution is derived from granitoids (50%) and mica schist (17–19%), although amphibolites (˜15%), cherty limestones (˜10%), and ultrabasites (˜6%) components are also present.The very low abundances of PGE in the melt rock seem to come mainly from some ultrabasic target rocks; therefore, the contamination from the meteoritic projectile appears to have been negligible.

Research paper thumbnail of Neogene palaeoenvironmental evolution in the Atlantic side of the Rifian Corridor (Morocco

Palaeogeography Palaeoclimatology Palaeoecology, 2000

Outcrops of Upper Miocene to Upper Pliocene deposits in the Atlantic side of the Rifian Corridor,... more Outcrops of Upper Miocene to Upper Pliocene deposits in the Atlantic side of the Rifian Corridor, northwest Morocco, provide data that allow an assessment of the palaeoenvironmental evolution of the main seaway that connected the Mediterranean to the Atlantic Ocean, until its final closure at the end of the Miocene. A reconstruction of the sedimentary regimes and palaeobathymetries in the Gharb and Saïss Basins has been carried out from the physical and microfaunal (benthic foraminifera) characteristics of sediments and three sedimentary sequences are distinguished, from the oldest rocks deposited at the opening of the corridor (more than 8 Ma) to the Upper Pliocene sediments (younger than 4 Ma) that ended the marine sedimentation. The maximum palaeodepth recognised (about 500 m) occurs in marly sediments of the coastal area (Bou Regreg composite section) between 8 and 5.9 Ma. This is followed by a tectonically controlled, shallowing phase leading to the establishment of neritic conditions and corresponding to a relative sea-level lowering of about 300 m, that we suggest relates to closure of the passageway and consequent onset of the Mediterranean evaporite deposition. The persistence in the Saïss Basin of middle neritic palaeodepths since the upper Tortonian (about 7.8 Ma) suggests, for this internal basin, a sill physiography. Evidence from the present and previously documented palaeobathymetric reconstructions indicates that the tectonic activity in the Atlantic corridor started from the eastern side and moved to the west. (R. Barbieri) between 5.96 and 5.33 Ma ( Krijgsman et al.,

Research paper thumbnail of Chemosynthetic microbialites in the Devonian carbonate mounds of Hamar Laghdad (Anti-Atlas, Morocco

Sedimentary Geology, 2007

Veins cutting across the Devonian conical mounds of the Hamar Laghdad Ridge (eastern Anti-Atlas, ... more Veins cutting across the Devonian conical mounds of the Hamar Laghdad Ridge (eastern Anti-Atlas, Morocco) were the carriers of geofluids. Although not completely determined, the composition of these fluids seems related to hydrothermal and seepage fluxes that were the primary contributors to the establishment of sub-seafloor (cryptic) environments linking deeper fluid sources to the seafloor. The optical and scanning electron

Research paper thumbnail of Iron-framboids in the hydrocarbon-related Middle Devonian Hollard Mound of the Anti-Atlas mountain range in Morocco: Evidence of potential microbial biosignatures

Sedimentary Geology

Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, M... more Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, Morocco) have been thoroughly investigated through a combination of techniques, including optical and high resolution scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, Raman microscopy and time-of-flight secondary ion mass spectroscopy. Framboids occur embedded in laminated carbonates of the mound and are precipitated along the veins that crosscut it and served as the conduits for (channeled) reduced hydrocarbon-rich fluids. The morphology, structure, and composition of the framboids contribute to the reconstruction of the complex interplay between the advected fluids and the associated biological and/or abiological processes. A comparison of our dataset with that from modern framboids formed under similar conditions indicates that the Fe-rich framboids represent replaced primary pyrite framboids produced as a consequence of bacterial sulfate reduction and the anaerobic oxidation of methane.

Research paper thumbnail of Iron-framboids in the hydrocarbon-related Middle Devonian Hollard Mound of the Anti-Atlas mountain range in Morocco: Evidence of potential microbial biosignatures

Sedimentary Geology

Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, M... more Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, Morocco) have been thoroughly investigated through a combination of techniques, including optical and high resolution scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, Raman microscopy and time-of-flight secondary ion mass spectroscopy. Framboids occur embedded in laminated carbonates of the mound and are precipitated along the veins that crosscut it and served as the conduits for (channeled) reduced hydrocarbon-rich fluids. The morphology, structure, and composition of the framboids contribute to the reconstruction of the complex interplay between the advected fluids and the associated biological and/or abiological processes. A comparison of our dataset with that from modern framboids formed under similar conditions indicates that the Fe-rich framboids represent replaced primary pyrite framboids produced as a consequence of bacterial sulfate reduction and the anaerobic oxidation of methane.

Research paper thumbnail of Terraces and Gilbert-type deltas in crater lakes in Ismenius Lacus and Memnonia (Mars

Journal of Geophysical Research, 2000

Paleolacustrine environments have been widely recognized from landform associations on the surfac... more Paleolacustrine environments have been widely recognized from landform associations on the surface of Mars. In contrast to paleolakes in more open areas, putative crater lakes commonly display well-developed sedimentary landforms, especially wave-formed terraces and Gilbert-type deltas. This study focuses on terraces and deltas of Western Memnonia and Ismenius Lacus. As on Earth, these landforms provide important indications of water dynamics and sedimentary processes. The putative Martian paleolakes must have been active for thousands of years to have permitted the water movement and wave formation necessary to form one or more terraces. Fan-shaped landforms at the mouths of channels entering crater-lake areas may indicate various channel water interaction. Of these, Gilbert-type deltas are particularly informative. Their presence indicates multiple flooding events whereby the inlet channels conveyed coarse-grained sediment to the crater lake. Both terraces and deltaic progradation indicate that the crater lakes of Memnonia and Ismenius Lacus were active for long time periods, at least for thousands of years, during the post heavy bombardment period of the later Martian history. The unequivocal presence of standing bodies of water of relatively long durations indicates that climatic settings very different from those prevailing today must have occurred, at least locally and temporarily, during parts of the Martian planetary history.

Research paper thumbnail of Fluid dynamics of liquids on Titans surface

Planetary and Space Science, 1998

... Fluid dynamics of liquids on Titans surface. Gian Gabriele Ori 1 , Lucia Marinangeli 1 , Anto... more ... Fluid dynamics of liquids on Titans surface. Gian Gabriele Ori 1 , Lucia Marinangeli 1 , Antonio Baliva 1 , Mario Bressan 1 and Robert G. Strom 2. ... Soc. 28 (1996), p. 1130. Coustenis et al., 1995 A. Coustenis, E. Lellouch, JP Maillard and CP McKay, Icarus 118 (1995), pp. 87–104. ...

Research paper thumbnail of A description of surface features in north Tyrrhena Terra, Mars: Evidence for extension and lava flooding

Icarus, 2007

We studied north Tyrrhena Terra, an approximately 39,000 km2 area, located in the transition regi... more We studied north Tyrrhena Terra, an approximately 39,000 km2 area, located in the transition region straddling the Amenthes and Mare Tyrrhenum Mars Chart quadrangles 14 and 22, respectively. The study area comprises ancient terrains with infilled craters, ridges and valleys. Interpretation of orbiter data of ancient terrains is inherently difficult, but valuable information can be obtained using multiple datasets and

Research paper thumbnail of Roles of methane and carbon dioxide in geological processes on Mars

Planetary and Space Science, 2011

Research paper thumbnail of Martian paleolacustrine environments and their geological constrains on drilling operations for exobiological research

Planetary and Space Science, 2000

... 4, 64.3°S, 4°W). 3. Exobiology. Lacustrine deposits are among the best candidates to have har... more ... 4, 64.3°S, 4°W). 3. Exobiology. Lacustrine deposits are among the best candidates to have harbored life on Mars (McKay and Nedall, 1988; Cabrol et al., 1999). ... Cabrol, NA, Grin, EA, Newsom, HE, Landheim, R. and McKay, CP, 1999. ...

Research paper thumbnail of Geological Evolution of the Tyras Vallis Paleolacustrine System, Mars

Journal of Geophysical Research, 2006

1] Using the new High Resolution Stereo Camera (HRSC) data and other Martian data sets, we recons... more 1] Using the new High Resolution Stereo Camera (HRSC) data and other Martian data sets, we reconstructed the hydrological history of an unnamed complex crater in the Xanthe Terra region. The crater hosted a lacustrine basin fed by a dense and centripetal drainage system, developed along its inner rim, and by the Tyras Vallis channel. Where the Tyras Vallis opens into the crater, a prominent delta-like feature is visible, characterized by a central terrace and two small longitudinal scarps. This deposit has been used as sedimentary recorder of the crater lake history and allowed assessment of the overall hydrological evolution. Two major stands of the water level have been inferred at 700 and 550 m above the crater floor, based on the correlation between the morphology and topography of the fan and the crater floor deposits. Our reconstruction reveals a complex sedimentary evolution of the fan, which underwent deltaic and alluvial sedimentation, as a result of the different lake water levels and Tyras Vallis supplies. A dominant erosional evolution of the fan-delta was determined by the interaction between the fluvial characteristics and basin wave regime. Wave height analysis and morphological comparison with terrestrial analogues support this hypothesis. The lacustrine activity could be chronologically placed between the Late Noachian and the Hesperian. The climatic conditions could have allowed the recharge of the regional groundwater system by precipitation and episodic fluvial activity. However, also heating effects of cratering could have affected the system, rejuvenating or accelerating the recharge of the local aquifer.

Research paper thumbnail of Origin of glacial–fluvial landforms in the Azas Plateau volcanic field, the Tuva Republic, Russia: Role of ice–magma interaction

Geomorphology, 2007

The basaltic Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federatio... more The basaltic Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federation. The area was glaciated multiple times, and the field is characterized by the formation of subglacial volcanoes called tuyas, but subaerial volcanoes and lava fields also exist. A combined study of remote sensing and field observations in the vicinity of the tuyas in the southeastern Azas Plateau volcanic field identified landforms that are best explained by the jökulhlaup hypothesis. The landforms include elongated hills, paleochannels, and butte and basin topography. These landforms are hypothesized to have formed by both erosion and deposition caused by high-energy water streams. The triggering for the hypothesized jökulhlaups was either melting of ice by subglacial volcanism and/or destabilization of ice-dammed/subglacial reservoirs. The age estimation of the flood events is difficult, but they probably occurred during the ice ages of the Quaternary, as late as in the Middle-Late Pleistocene.

Research paper thumbnail of Combinations of processes responsible for Martian impact crater ``layered ejecta structures'' emplacement

Journal of Geophysical Research, 2007

We utilized images and stereo-derived topographic data acquired by the High Resolution Stereo Cam... more We utilized images and stereo-derived topographic data acquired by the High Resolution Stereo Camera (HRSC) and Thermal Emission Imaging System (THEMIS) images together with other data in order to study the geology of “layered ejecta structures” associated with relatively pristine Martian impact craters. The geomorphology and morphometric properties indicate their origin as complex combinations of a variety of impact processes.

Research paper thumbnail of Microbial signatures in sabkha evaporite deposits of Chott el Gharsa (Tunisia) and their astrobiological implications

Planetary and Space Science, 2006

This study investigates the geomicrobiological potential of Upper Pleistocene evaporite deposits ... more This study investigates the geomicrobiological potential of Upper Pleistocene evaporite deposits of the Chott el Gharsa, a wide continental sabkha in southern Tunisia. Organic and inorganic-derived biosignatures are mostly contained in microcrystalline, laminated gypsum lithofacies consisting of light/dark alternations of concordant laminae, which have precipitated from high salt concentrated waters. These biosignatures include mineralized microbial-interpreted morphologies, such as mucilage, rods, and microfibers, and dumbbell morphologies in the hollow cores of dolomite crystals that are associated with sulfates. Mineral products that are induced by microbial activity and their organic compounds lead to the formation of lenticular-shaped gypsum crystals, with a high length/width ratio, dolomite precipitation and formation of pyrite framboids. Morphological and structural aspects of these biosignatures, and their composition, in laminated, dolomite-rich sulfate deposits could be detected through microscopic investigations and micro-analyses performed by the instrumentation that is planned for ongoing Mars sample return missions. r

Research paper thumbnail of An ESA study for the search for life on Mars

Planetary and Space Science, 2000

Similarities in the early histories of Mars and Earth suggest the possibility that life may have ... more Similarities in the early histories of Mars and Earth suggest the possibility that life may have arisen on Mars as it did on Earth. If this were the case, early deterioration of the environment on Mars (loss of surface water, decrease in temperature) may have inhibited further evolution of life. Thus, life on Mars would probably be similar to the simplest form of life on Earth, the prokaryotes. We present a hypothetical strategy to search for life on Mars consisting of (i) identifying a suitable landing site with good exobiological potential, and (ii) searching for morphological and biogeochemical signatures of extinct and extant life on the surface, in the regolith subsurface, and within rocks. The platform to be used in this theoretical exercise is an integrated, multi-user instrument package, distributed between a lander and rover, which will observe and analyse surface and subsurface samples to obtain the following information:

Research paper thumbnail of Chemical compositions of impact melt breccias and target rocks from the Tenoumer impact crater, Mauritania

Meteoritics & Planetary Science, 2005

Abstract— The impact melt breccias from the Tenoumer crater (consisting of a fine-grained intergr... more Abstract— The impact melt breccias from the Tenoumer crater (consisting of a fine-grained intergrowth of plagioclase laths, pyroxene crystals, oxides, and glass) display a wide range of porosity and contain a large amount of target rock clasts.Analyses of major elements in impact melt rocks show lower contents of SiO2, Al2O3, and Na2O, and higher contents of MgO, Fe2O3, and CaO, than the felsic rocks (i.e., granites and gneisses) of the basement. In comparison with the bulk analyses of the impact melt, the glass is strongly enriched in Si-Al, whereas it is depleted both in Mg and Fe; moreover, the impact melt rocks are variably enriched or depleted in some REE with respect to the felsic and mafic bedrock types. Gold is slightly enriched in the impact melt, and Co, Cr, and Ni abundances are possibly due to a contribution from mafic bedrock.Evidences of silicate-carbonate liquid immiscibility, mainly as spherules and globules of calcite within the silicate glass, have been highlighted.HMX mixing calculation confirm that the impact melt rocks are derived from a mixing of at least six different target lithologies outcropping in the area of the crater. A large contribution is derived from granitoids (50%) and mica schist (17–19%), although amphibolites (˜15%), cherty limestones (˜10%), and ultrabasites (˜6%) components are also present.The very low abundances of PGE in the melt rock seem to come mainly from some ultrabasic target rocks; therefore, the contamination from the meteoritic projectile appears to have been negligible.

Research paper thumbnail of Neogene palaeoenvironmental evolution in the Atlantic side of the Rifian Corridor (Morocco

Palaeogeography Palaeoclimatology Palaeoecology, 2000

Outcrops of Upper Miocene to Upper Pliocene deposits in the Atlantic side of the Rifian Corridor,... more Outcrops of Upper Miocene to Upper Pliocene deposits in the Atlantic side of the Rifian Corridor, northwest Morocco, provide data that allow an assessment of the palaeoenvironmental evolution of the main seaway that connected the Mediterranean to the Atlantic Ocean, until its final closure at the end of the Miocene. A reconstruction of the sedimentary regimes and palaeobathymetries in the Gharb and Saïss Basins has been carried out from the physical and microfaunal (benthic foraminifera) characteristics of sediments and three sedimentary sequences are distinguished, from the oldest rocks deposited at the opening of the corridor (more than 8 Ma) to the Upper Pliocene sediments (younger than 4 Ma) that ended the marine sedimentation. The maximum palaeodepth recognised (about 500 m) occurs in marly sediments of the coastal area (Bou Regreg composite section) between 8 and 5.9 Ma. This is followed by a tectonically controlled, shallowing phase leading to the establishment of neritic conditions and corresponding to a relative sea-level lowering of about 300 m, that we suggest relates to closure of the passageway and consequent onset of the Mediterranean evaporite deposition. The persistence in the Saïss Basin of middle neritic palaeodepths since the upper Tortonian (about 7.8 Ma) suggests, for this internal basin, a sill physiography. Evidence from the present and previously documented palaeobathymetric reconstructions indicates that the tectonic activity in the Atlantic corridor started from the eastern side and moved to the west. (R. Barbieri) between 5.96 and 5.33 Ma ( Krijgsman et al.,

Research paper thumbnail of Chemosynthetic microbialites in the Devonian carbonate mounds of Hamar Laghdad (Anti-Atlas, Morocco

Sedimentary Geology, 2007

Veins cutting across the Devonian conical mounds of the Hamar Laghdad Ridge (eastern Anti-Atlas, ... more Veins cutting across the Devonian conical mounds of the Hamar Laghdad Ridge (eastern Anti-Atlas, Morocco) were the carriers of geofluids. Although not completely determined, the composition of these fluids seems related to hydrothermal and seepage fluxes that were the primary contributors to the establishment of sub-seafloor (cryptic) environments linking deeper fluid sources to the seafloor. The optical and scanning electron

Research paper thumbnail of Iron-framboids in the hydrocarbon-related Middle Devonian Hollard Mound of the Anti-Atlas mountain range in Morocco: Evidence of potential microbial biosignatures

Sedimentary Geology

Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, M... more Iron-framboids in the context of a Middle Devonian, hydrocarbon-seep conical mound (Anti-Atlas, Morocco) have been thoroughly investigated through a combination of techniques, including optical and high resolution scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, Raman microscopy and time-of-flight secondary ion mass spectroscopy. Framboids occur embedded in laminated carbonates of the mound and are precipitated along the veins that crosscut it and served as the conduits for (channeled) reduced hydrocarbon-rich fluids. The morphology, structure, and composition of the framboids contribute to the reconstruction of the complex interplay between the advected fluids and the associated biological and/or abiological processes. A comparison of our dataset with that from modern framboids formed under similar conditions indicates that the Fe-rich framboids represent replaced primary pyrite framboids produced as a consequence of bacterial sulfate reduction and the anaerobic oxidation of methane.