Mesozoic Units Research Articles

Speculative petroleum systems of the southern Pelotas Basin, offshore Uruguay

The Pelotas Basin of Brazil and Uruguay represents a frontier basin with under-explored hydrocarbon potential. Although oil and gas accumulations have yet to be identified, only 21 exploratory wells have been drilled in an area of more than 330,000 km2, 20 of which are located in the Brazilian portion of the basin. A detailed study of the petroleum system of offshore Uruguay has strong potential to contribute to a better characterization of the capacity of the basin to generate and accumulate hydrocarbons. Three stages have previously been recognized during the evolution of Pelotas basin: (1) a prerift phase which preserved Paleozoic and Mesozoic units of the Paraná Basin; (2) an Early Cretaceous volcano-sedimentary synrift phase; and (3) a Cretaceous to Cenozoic postrift phase deposited during the passive margin stage. In this study, we use sequence stratigraphy methodology to interpret 2D multichannel seismic sections of the southern segment of the Pelotas Basin in the Uruguayan Atlantic margin. This analysis allows us to identify depositional sequences, systems tracts and the distribution of the main elements of the potential petroleum systems. Following our analysis, we propose six speculative petroleum systems (SPS) in the Pelotas Basin. The first SPS is related to the prerift phase and is represented by a Lower Permian restricted marine source rock and reservoirs related to Permian to Upper Jurassic aeolian and fluvial sandstones. The second SPS corresponds to the synrift phase and is constituted by a Barremian lacustrine source rock with reservoirs of alluvial/fluvial sandstones of the same age. The other four proposed SPS are associated with the postrift phase, represented by marine source rocks related to Aptian-Albian, Cenomanian-Turonian and Paleocene transgressions, all of which are identified in the region and interpreted in seismic lines from Uruguay. These postrift SPS have predominantly siliciclastic reservoirs represented by Early Cretaceous aeolian sandstones and Cretaceous to Cenozoic deltaic sandstones and turbidites.

New plays on the Greater East Shetland Platform (UKCS Quadrants 3, 8-9, 14-16) – part 2: newly reported Permo-Triassic intra-platform basins and their influence on the Devonian-Paleogene prospectivity of the area

Despite significant discoveries within Palaeogene-age reservoirs (e.g., Mariner) the East Shetland Platform (ESP) is underexplored, with only ten wells per 1000 km2. Mesozoic units are thin or absent whilst Paleozoic reflectors resemble acoustic basement on legacy seismic. Recent 3D dual-sensor broadband surveys (GeoStreamer) covering 17,200 km2 over parts of Quadrants 3, 8-9, 14-16 have allowed for clearer imaging. Here, this dataset is interpreted, leading to new insights into this large frontier region. The ESP petroleum system comprises multiple proven reservoir and source intervals, with viable play fairways. Up to four regional unconformities are interpreted, merging into fewer erosional surfaces on persistent highs. Elsewhere on the ESP, predominantly subsiding Permo-Triassic depocentres contain a nearly continuous Paleozoic-Mesozoic succession. The most prominent of these, to the south and south-west of the Beryl Embayment, is here referred to as the ‘Crawford-Skipper Basin’. Existing hydrocarbon discoveries on the ESP are in the vicinities (<7 km) of intra-platform Permo-Triassic basin margins. Exploration close to such basins is inherently less risky due to possible positive influences of deep-seated structures on the petroleum system. These include: (1) formation of Meso-Cenozoic closures; (2) Devonian source maturity and presence of simple fault-related migration pathways; (3) viability of sub-Cretaceous reservoir-trap-seal configurations.

New plays on the Greater East Shetland Platform (UKCS Quadrants 3, 8-9, 14-16) – part 1: Regional setting and a working petroleum system

Despite significant discoveries within Palaeogene-age reservoirs (e.g., Mariner) the East Shetland Platform (ESP) is underexplored, with only ten wells per 1000 km2. Mesozoic units are thin or absent whilst Paleozoic reflectors resemble acoustic basement on legacy seismic. Recent 3D dual-sensor broadband surveys (GeoStreamer) covering 17,200 km2 over parts of Quadrants 3, 8-9, 14-16 have allowed for clearer imaging. Here, this dataset is interpreted, leading to new insights into this large frontier region. The ESP petroleum system comprises multiple proven reservoir and source intervals, with viable play fairways. Up to four regional unconformities are interpreted, merging into fewer erosional surfaces on persistent highs. Elsewhere on the ESP, predominantly subsiding Permo-Triassic depocentres contain a nearly continuous Paleozoic-Mesozoic succession. The most prominent of these, to the south and south-west of the Beryl Embayment, is here referred to as the ‘Crawford-Skipper Basin’. Existing hydrocarbon discoveries on the ESP are in the vicinities (<7 km) of intra-platform Permo-Triassic basin margins. Exploration close to such basins is inherently less risky due to possible positive influences of deep-seated structures on the petroleum system. These include: (1) formation of Meso-Cenozoic closures; (2) Devonian source maturity and presence of simple fault-related migration pathways; (3) viability of sub-Cretaceous reservoir-trap-seal configurations.

Evolution of the Carboniferous-Early Cretaceous units of Paraná Basin from provenance studies based on U-Pb, Hf and O isotopes from detrital zircons

U-Pb, Lu-Hf and O isotope data were obtained on detrital zircons from late Paleozoic-early Mesozoic units from White Column, Paraná Basin, southeastern Brazil, in order to characterize the provenance of the sediments, as well as to contribute to the understanding of the evolution of the basin. The studied section includes rocks from 11 stratigraphical units (from base to top), including the Rio do Sul Formation, Rio Bonito Formation (Triunfo, Paraguaçu and Siderópolis members), Palermo, Irati, Serra Alta and Teresina formations, Rio do Rasto Formation (Serrinha and Morro Pelado members) and Botucatu Formation.U-Pb ages of zircons in these units range from 242Ma to 3.4Ga. All units show four main detrital age-groups, Neoarchean, mid-Paleoproterozoic, Grenvillian and Brasiliano-Pan African reflecting the importance of the Precambrian basement bordering the east side of the section such as Dom Feliciano, Kaoko and Namaqua-Natal Belts as source areas. However, the isotopic signatures show that a portion of the mid-Paleoproterozoic zircons (1.9–2.0Ga) are probably from rocks of the presently covered basement, which was exposed until the deposition of the Rio Bonito Formation. The isotopes also show some Grenvillian aged zircons from Argentinian rocks, which implies a long transport distance.The Siderópolis Member is the unit that shows an important change on the sources of the sediments, since it contains a Permian age peak that was not present on the lower units and that persist on the upper units. The isotopic signatures of these Permian grains link them to the Choiyoi igneous province and North Patagonia Massif, sources from Argentina, reaching the basin by long distance travel on subaquatic environmental and not only from the air (ash falls) as is in common acceptance. Other younger age peaks (Ordovician to Carboniferous) found from Palermo Formation to up section are also linked to Argentinian sources, showing the importance of the long travel distance during the filling of the basin.

Cenozoic geology of the Yolomécatl-Tlaxiaco area, Northwestern Oaxaca, Southeastern Mexico: Stratigraphy, structure and regional significance

The Yolomécatl-Tlaxiaco Area, lies in the rugged Sierra Madre del Sur (SMS) of northwestern Oaxaca (YOTLA), southeastern Mexico. Within the area Cenozoic units unconformably overlie metamorphic, clastic and carbonate rock units of Late Paleozoic to Cretaceous ages as well as the Mixteco/Oaxaca Terrane boundary.The Cenozoic sequence, emphasized herein, includes from botton to top: (1) basal, calcilithitic Early Tertiary Tamazulapam Conglomerate, (2) andesitic lava flows of Nduayaco “Group,” (3–4) Epiclastic/pyroclastic strata composing Yolomécatl Formation (∼40.3 ± 1.0 Ma), and Tayata Pyroepiclastics (5) Early Oligocene (∼32.9 Ma), felsic, pyroclastic Nundichi “Group,” (6) Late Oligocene (∼27.7 ± 0.7 Ma) andesitic lava flows of Nicananduta “Group” containing intercalations of unit (7) ?Chilapa Formation (largely lacustrine). Quaternary deposits unconformably overlie the sequence. The structural record includes NNW-SSE folds in the Mesozoic units, and one in Tayata Pyroepiclastics, as well as numerous fractures/faults of diverse types, whose pattern seems to roughly define four geographic/structural domains, NW, SW, S, and E.The Tertiary sequence records four magmatic and six deformational events: Pre-Late Eocene Extension accommodated by the Tamazulapam fault, along which magma of the Nduayaco “Group” moved upward. The next episode is the earliest Late Eocene extension recorded by the Yucuxaco-Santa Cruz Tayata fault was followed by accumulation of Yolomécatl Formation, Tayata Pyroepiclastics, and synsedimentary emplacement of tuff sheets at ∼40.3 ± 1.0 Ma. After this date, left lateral transpression emplaced a Teposcolula Limestone block over Nduayaco “Group” and ?Yolomécatl Formation, whereas the Tayata Pyroepiclastics was folded into an open anticline. Movement along the Yucuxaco-Santa Cruz Tayayata fault suite influenced accumulation of the Nundichi “Group” strata ca. ∼32.9 Ma. Subsequent ENE-WSW extension affected the Nundichi “Group,” partly placing it in contact with Jurassic limestone blocks. Finally, ca. 27.7 Ma, the Nicananduta “Group” was emplaced.The discrimination of YOTLA's Cenozoic magmatic/deformational events correlates well with that of events previously recognized in the SMS, and to the north along the southwestern margin of North America. However, significant differences persist in terms of number, characterization, age and duration of events that cannot be resolved at present. Anyway, differences are expected due to the inherent diachronic nature of magmatism and deformation across SMS, and the fact that the events reported here took place inland, not around the Mixteco/Oaxaca Terranes block, where most events of these kinds occurred.

The Cenozoic fold-and-thrust belt of Eastern Sardinia: Evidences from the integration of field data with numerically balanced geological cross section

Newly collected structural data in Eastern Sardinia (Italy) integrated with numerical techniques led to the reconstruction of a 2-D admissible and balanced model revealing the presence of a widespread Cenozoic fold-and-thrust belt. The model was achieved with the FORC software, obtaining a 3-D (2-D + time) numerical reconstruction of the continuous evolution of the structure through time. The Mesozoic carbonate units of Eastern Sardinia and their basement present a fold-and-thrust tectonic setting, with a westward direction of tectonic transport (referred to the present-day coordinates). The tectonic style of the upper levels is thin skinned, with flat sectors prevailing over ramps and younger-on-older thrusts. Three regional tectonic units are present, bounded by two regional thrusts. Strike-slip faults overprint the fold-and-thrust belt and developed during the Sardinia-Corsica Block rotation along the strike of the preexisting fault ramps, not affecting the numerical section balancing. This fold-and-thrust belt represents the southward prosecution of the Alpine Corsica collisional chain and the missing link between the Alpine Chain and the Calabria-Peloritani Block. Relative ages relate its evolution to the meso-Alpine event (Eocene-Oligocene times), prior to the opening of the Tyrrhenian Sea (Tortonian). Results fill a gap of information about the geodynamic evolution of the European margin in Central Mediterranean, between Corsica and the Calabria-Peloritani Block, and imply the presence of remnants of this double-verging belt, missing in the Southern Tyrrhenian basin, within the Southern Apennine chain. The used methodology proved effective for constraining balanced cross sections also for areas lacking exposures of the large-scale structures, as the case of Eastern Sardinia.

GÖKÇEADA’NIN (ÇANAKKALE) JEOLOJİSİ

The geology and especially the magmatic rocks of Gokceada, which is the biggest island of Turkey and located at 20 km’s west of Biga Peninsula, constitute the subject of this study. Late Ediacaran/Early Paleozoic aged Camlica metamorphics which crop out with a tectonic uplift in a narrow area in northwest of Gokceada are the oldest rocks of the island. Early Eocene aged Karaagac Formation which is formed by submarine fan deposits unconformably overlies Camlica metamorphics. As for the Dagicitepe volcanic member which is formed by rhyolitic lavas, tuff and tuffites emplaced into Karaagac Formation cutting Camlica metamorphics is the oldest volcanic unit of the study area. On Karaagac Formation, Koyunbaba Formation has unconformably been deposited which consists of Middle Eocene shallow marine sediments. Then it has conformably been overlain by Sogucak Formation which consists of SE-NW extending reefal limestone. Middle-Upper Eocene aged Ceylan Formation which conformably overlies the Sogucak Formation and the early Oligocene aged Mezardere Formation which conformably overlies Ceylan Formation have been deposited due to turbiditic currents in deep marine environment. Late Eocene(?) – Oligocene aged subvolcanics which cut Mesozoic and Eocene units and emplaced into Eocene aged sedimentary units in the form of crypto dome and dome form the recent rigid topography of the study area and are the second magmatic phase called the “Gokceada Domes”. Diorite-monzonites porphyry which crystallized in lower zones of subvolcanics on the other hand constitutes Mutludere intrusion. In eastern and southern parts of Gokceada, Late Oligocene Gokceada ignimbrites are located which are observed in the form of pumice flows on Mezardere Formation. These ignimbrites are then overlain by Early Miocene aged Kesmekaya volcanics which are formed by blocky ash flows. Middle Miocene aged Eselek volcanics consisting of lava and pyroclastics with composition basaltic andesite and andesite are observed on a large area in east of Gokceada. Upper Miocene aged Canakkale Formation which is generally formed by the intercalation of poor consolidated conglomerate, sandstone, siltstone and marl crops out in narrow regions at east, southeast and south of Gokceada. Quaternary alluvial deposits and debris composed of loose, unconsolidated sand, silt and other sediments unconformably overlie all previous units and complete the succession. Main tectonic structures of Gokceada are formed by right lateral oblique faults which developed in Neo-tectonic period

Development and application of a robust chronostratigraphic framework in Gulf of Mexico Mesozoic exploration

Renewed interest in Mesozoic exploration, onshore and offshore, in the Gulf of Mexico (GOM) has precipitated a new look at Mesozoic biostratigraphy and how these age-diagnostic bioevents can help to establish a sequence-stratigraphic framework for the basin. We have developed a new chronostratigraphic framework, primarily founded on biostratigraphic age-diagnostic data, specifically developed for Mesozoic strata of the GOM basin. Our goal was to provide a systematic and consistent framework that serves as a reference for the order and timing of depositional sequences and key surfaces in the GOM Mesozoic stratigraphic section. The new chronostratigraphic framework was based on (1) our work delineating significant physical stratigraphic surfaces from seismic and well-log data in the GOM, (2) Mesozoic biostratigraphic data from 202 onshore and offshore wells in the GOM, and (3) published literature from the GOM and other studies. The chronostratigraphic framework was formalized in an online Mesozoic biostratigraphy table and summarized in a Mesozoic stratigraphy chart. The use of the framework was key to our ability to correlate within the GOM basin, and we evaluated several examples of seismic and well-log interpretation using the new chronostratigraphic framework, including onshore-offshore correlation, identification and correlation of source rocks, and interpretation of structural anomalies. These examples illustrated how the chronostratigraphic framework enabled us to reduce uncertainty in identifying and correlating Mesozoic units from land to the deepwater GOM basin. The framework also allowed us to better compare our work with other research groups, within academia and industry, and permitted a higher level of integration of work and comments from various applied industry workers.

Regional constraints of the Sørkapp Basin: A Carboniferous relic or a Cretaceous depression?

The Sørkapp Basin (NW Barents Shelf) contains a comprehensive sedimentary succession that provides insight into regional tectonics and depositional development of the shelf from the Devonian to the Cretaceous. With its location east of the mid-Atlantic spreading ridge and south of Svalbard, the Basin serves as an important link between the offshore and onshore realms.This study subdivides this sparsely studied basin into six main seismic units (three Paleozoic and three Mesozoic). A metamorphic basement together with assumed Devonian sedimentary deposits form the foundation for a chiefly Carboniferous basin. The Basin forms a syncline with infill showing limited fault-influence. Overlying the early infill are Late Carboniferous deposits which show less lateral variation in thickness but also active growth on the few faults showing significant displacement. The overlying platform deposits of the latest Carboniferous and Permian show a change in depositional geometry, with onlapping deposits towards the east probably resulting from uplift of the Stappen High and regional flooding. Subsequent, particularly Late, Triassic sedimentation shows a more distinctly progradational pattern with a dominantly southeastern source for sediments. During this shallow shelf-filling stage, the Sørkapp Basin is sheltered by the Gardarbanken High, blocking the Early Triassic clinoform development. The High was transgressed in the Middle Triassic and the platform-edge progressively approached the present Svalbard coastline.The youngest Mesozoic unit forms a separate saucer-shaped depocenter west of the Sørkapp Basin, where deposits are truncated by the seafloor in a mid-basin position and across the Gardarbanken High. The depositional pattern for this succession correlates with the outcrop pattern of the Adventdalen Group implying a post Middle Jurassic to Cretaceous age. The Sørkapp Basin has been referred to as a Cretaceous feature based in this depocenter. However, the foundations are much older and the Cretaceous depression is located west of the deeper basin. Accordingly, we propose the informal term Sørkapp Depression for the Cretaceous basin.

Crustal recycling through intraplate magmatism: Evidence from the Trans-North China Orogen

The North China Craton (NCC) preserves the history of crustal growth and craton formation during the early Precambrian followed by extensive lithospheric thinning and craton destruction in the Mesozoic. Here we present evidence for magma mixing and mingling associated with the Mesozoic tectonic processes from the Central NCC, along the Trans-North China Orogen, a paleo suture along which the Eastern and Western Blocks were amalgamated at end of Paleoproterozoic. Our investigations focus on two granitoids – the Chiwawu and the Mapeng plutons. Typical signatures for the interaction of mafic and felsic magmas are observed in these plutons such as: (1) the presence of diorite enclaves; (2) flow structures; (3) schlierens; (4) varying degrees of hybridization; and (5) macro-, and micro-textures. Porphyritic feldspar crystals show numerous mineral inclusions as well as rapakivi and anti-rapakivi textures. We present bulk chemistry, zircon U–Pb geochronology and REE data, and Lu–Hf isotopes on the granitoids, diorite enclaves, and surrounding basement rocks to constrain the timing of intraplate magmatism and processes of interaction between felsic and mafic magmas. Our LA-ICP-MS zircon U–Pb data show that the pophyritic granodiorite was emplaced at 129.7±1.0Ma. The diorite enclaves within this granodiorite show identical ages (128.2±1.5Ma). The basement TTG (tonalite–trondhjemite–granodiorite) gneisses formed at ca. 2.5Ga coinciding with the major period of crustal accretion in the NCC. The 1.85Ga age from zircons in the gabbro with positive Hf isotope signature may be related to mantle magmatism during post-collisional extension following the assembly of the Western and Eastern Blocks of the NCC along the Trans-North China Orogen. Our Hf isotope data indicate that the Neoarchean–Paleoproterozoic basement rocks were derived from complex sources of both juvenile magmas and reworked ancient crust, whereas the magma source for the Mesozoic units are dominantly reworked basement rocks. Our study provides a window to intraplate magmatism triggered by mantle upwelling beneath a paleosuture in the North China Craton.

First Evidence of Lamprophyric Magmatism from the Konya Region, Turkey: a Genetic Link to High‐K Volcanism

AbstractIn the vicinity of Konya (Turkey), mafic, micro‐porphyritic sub‐volcanic rocks intrude into the Mesozoic units, which represents the only example of such a rock type in the region. 40Ar/39Ar dating of two whole rock samples from the sub‐volcanics gave ages of 13.72±0.13 and 12.40±0.11 Ma, suggesting temporal association to the Late Miocene‐Pliocene high‐K calc‐alkaline volcanism in the region. The mineral chemistry and geochemical data permit us to classify the rocks as “minette” lamprophyres. They include diopside and phlogopite phenocrysts in a microcrystalline groundmass composed of sanidine, phlogopite, diopside and titano‐magnetite. Segregation and ocelli‐like globular structures occur commonly in the samples. In terms of major elements, the lamprophyres are calcalkaline, and potassic to ultrapotassic rocks. All the lamprophyres display strong enrichments in LILE (Rb, Ba, K, Sr), radiogenic elements (Th, U) and LREE (La, Ce) and prominent negative Nb, Ta, and Ti anomalies on primordial mantle‐normalized trace element diagrams. Geochemical data suggest that the lamprophyres and high‐K calc‐alkaline rocks in the region derived from a subduction‐modified lithospheric mantle source affected by different metasomatic events. Lamprophyric magmatism sourced phlogopite‐bearing veins generated by sediment‐related metasomatism via subduction, but high‐K calc‐alkaline magmas are possibly derived from a mantle source affected by fluid‐rich metasomatism.

멕시코 시나올라주의 지질 및 금속광물자원

멕시코 시나올라(Sinaola)주의 지질은 하부로부터 선캠브리아기 변성암(Sonobari Complex), 두 개의 고생대층(하부: 미분화된 변성암, 상부: 석탄기 퇴적암), 변성화산암, 쇄설암, 탄산염암으로 구성된 5개의 중생대층, 화산암으로 구성된 신생대 암석, 제 4기의 쇄설성 퇴적층과 화산류로 구성되어 있다. 시나올라주는 잠재적으로 금속광물자원이 풍부하며 비금속광물은 적은 편이다. 광상들은 다양한 지질환경과 관련되어 있고 지형학상 시에라 마드레 옥시덴탈(Sierra Madre Occidental)에 부존되어 있는 것이 특징적이다. 주로 알려진 광상은 금과 은이며 뒤를 이어 아연, 연, 동과 일부 철이 분포한다. 시나올라주는 가끔 가행하고 있는 몰리브데늄, 텅스텐, 비스무스 광상도 부존되어 있다. 니켈과 코발트도 부존이 알려져 있으나 단지 소규모로 개발되었음이 보고되고 있다. The geology of Sinaola state consists of Precambrian metamorphic rocks(Sonobari Complex), two Paleozoic units(lower non-differentiated metamorphic rocks and upper Carboniferous sedimentary rocks), five Mesozoic units(metavolcanic, clastic, and calcareous rocks), Cenozoic volcanic rocks, and Quaternary clastic sediments and volcanic flows. The Sinaola state is potentially rich in metallic mineral resources with lower degree of non-metallic mineral resources. They are related to a variety of geological environments and are mainly physiographically located on the Sierra Madre Occidental. Mainly known mineral deposits are of gold and silver followed by zinc, lead, copper and some iron. The state also has deposits of molybdenum, tungsten and bismuth that have been occasionally exploited. There is a reference of nickel and cobalt mineralization, but these deposits have been exploited only at a small scale.

The influence of Mesozoic Palaeogeography on the variations in structural style along the front of the Albanide thrust-and-fold belt

The front of the W-verging Albanide fold-and-thrust belt and its adjacent foreland have been investigated using a grid of seismic reflection profiles, purposely acquired in the Southern Adriatic Sea.This convergent margin is part of the continental collision that extends from former Yugoslavia to North-Western Greece. At the front of the Albanides, both the structural style of the external part of the fold-and-thrust belt, and the evolution of the related foredeep basin, are strongly controlled by the nature of the Mesozoic units that are progressively accreted to the belt, namely the Apulian Platform and its adjacent deep-water basins. Where a thick carbonate platform is accreted (souther Albania) the frontal mountain range presents a high topography, whereas the foredeep basin is relatively shallow. On the other hand, where the basinal domain is accreted (northern Albania), the topography of the fold-and-thrust belt is subdue, whereas the foredeep basin is very deep.

Associations between lithology and land-use in a wine production region (Bairrada region, Portugal)

In this work, we analyze the spatial relationships between land-use and lithology in the wine production region of Bairrada (Portugal) and present a new lithological map (1:50,000) created for the region, highlighting the associations with specific types of land-use. The study was focused on the area of Bairrada that establishes the appellation DOC-VQPRD wines. The region shows a heterogeneous lithology and land-use and it is found that these two variables are not independent. Three different zones with characteristic land-use and geology can be distinguished in Bairrada: a western zone where aeolian sand deposits are associated with coniferous forests; an eastern zone with Precambrian and Paleozoic metasedimentary units associated with broad leaf forests; and a central zone with diversified Mesozoic and Cenozoic units in which most vineyards are placed. There is a clear association between a Jurassic marly and dolomitic unit and an occupation by vineyards, which is particularly obvious when larger vineyards are considered. The vineyards are also common when these Jurassic units are covered by relatively thin siliciclastic sediments.

Organic facies of the Beydalar carbonate platform (Mesozoic), Western Taurus, Antalya, Turkey

Mesozoic carbonates are widespread in the Antalya region of south-west Turkey and have been studied in the outcrop. Mesozoic units include a Jurrasic/Cretaceous sequence that comprises, from bottom to top, the following stratigraphic sequence: BeydaAŸlarA± Formation (Jurrasic-Cretaceous) and CiAŸdemtepe Formation (Senonian). Detailed data from thick Mesozoic carbonates (BeydaAŸlarA± and CiAŸdemtepe Formations) made it possible to construct an organic facies framework using different zonations. Organic matter is composed predominantly of amorphous material, with a minor contribution of allochthonous terrestrial material. Kerogen in the deposite is primarily type II/III, as indicated by organic petrographic observations and Rock-Eval data. Total organic carbon content (TOC) of this deposit is less than 0.5% in different zonations of the BeydaAŸlarA± and CiAŸdemtepe Formations. Tmax values vary between 332 and 535°C, confirming the increase in maturation trends indicated by Rock-Eval data. Both organic petrographic and geochemical maturation parameters place the Mesozoic carbonates of the western Taurides (Antalya-SW Turkey) region within C-CD organic facies. According to this, the different types of kerogen observed fall dominantly in the C facies, with a poor capacity for liquid hydrocarbon generation. When seen in Mesozoic BeydaAŸlarA± carbonates, the organic matter is highly oxidized. Key words: Western Taurus, organic facies, source rock, Mesozoic.

Clay mineralogy of the Paleozoic-Lower Mesozoic sedimentary sequence from the northern part of the Arabian Platform, Hazro (Diyarbakır, Southeast Anatolia)

Clay mineralogy of the Paleozoic-Lower Mesozoic sedimentary sequence from the northern part of the Arabian Platform, Hazro (Diyarbakır, Southeast Anatolia)The Paleozoic-Lower Mesozoic units in the Diyarbakır-Hazro region consist of sandstone (subarkose, quartz arenite), mudstone, shale, coal, marl, dolomitic marl, limestone (biomicrite, lithobiosparite, biosparite with lithoclast, dololithobiosparite, dolomitic cherty sparite) and dolomite (dolosparite, dolosparite with lithoclast, biodolosparite with glauconite). These units exhibit no slaty cleavage although they are oriented parallel to bedding planes. The sedimentary rocks contain mainly calcite, dolomite, quartz, feldspar, goethite and phyllosilicates (kaolinite, illite-smectite (I-S), illite and glauconite) associated with small amounts of gypsum, jarosite, hematite and gibbsite. The amounts of quartz and feldspar in the Silurian-Devonian units and of dolomite in the Permian-Triassic units increase. Kaolinite is more commonly observed in the Silurian-Devonian and Permian units, whereas illite and I-S are found mostly in the Middle Devonian and Triassic units. Vertical distributions of clay minerals depend on lithological differences rather than diagenetic/metamorphic grade. Authigenetic kaolinites as pseudo-hexagonal bouquets and glauconite and I-S as fine-grained flakes or filaments are more abundantly present in the levels of clastic and carbonate rocks. Illite quantities in R3 and R1 I-S vary between 80 and 95 %. 2M1+1Mdillites/I-S are characterized by moderatebcell values (9.005-9.040, mean 9.020 Å), whereas glauconites have higher values in the range of 9.054-9.072, mean 9.066 Å. KI values of illites (0.72-1.56, mean 1.03 Δ2θ°) show no an important vertical difference. Inorganic (mineral assemblages, KI, polytype) and organic maturation (vitrinite reflection) parameters in the Paleozoic-Triassic units agree with each others in majority that show high-grade diagenesis and catagenesis (light petroleum-wet gas hydrocarbon zone), respectively. The Paleozoic-Triassic sequence in this region was deposited in the environment of a passive continental margin and entirely resembles the Eastern Taurus Para-Autochthon Unit (Geyikdağı Unit) in respect of lithology and diagenetic grade.

멕시코 치아파스주의 지질 및 금속 광물자원

The geology of Sinaola state consists of Precambrian metamorphic rocks(Sonobari Complex), two Paleozoic units(lower non-differentiated metamorphic rocks and upper Carboniferous sedimentary rocks), five Mesozoic units(metavolcanic, clastic, and calcareous rocks), Cenozoic volcanic rocks, and Quaternary clastic sediments and volcanic flows. The Sinaola state is potentially rich in metallic mineral resources with lower degree of non-metallic mineral resources. They are related to a variety of geological environments and are mainly physiographically located on the Sierra Madre Occidental. Mainly known mineral deposits are of gold and silver followed by zinc, lead, copper and some iron. The state also has deposits of molybdenum, tungsten and bismuth that have been occasionally exploited. There is a reference of nickel and cobalt mineralization, but these deposits have been exploited only at a small scale.

Structure and evolution of a rocksalt-mudrock-tectonite: The haselgebirge in the Northern Calcareous Alps

The Northern Calcareous Alps are part of the Eastern Alps in Austria and Germany. The Mesozoic units of this fold-and-thrust belt were detached, thrusted and stacked along the evaporitic Haselgebirge Formation. Exposed in salt mines, rocksalt and mudrock form a two component tectonite: The rock type “haselgebirge” consists of 10–70 wt % halite with silt- to gravel- or block-sized components within a halite matrix, and the “kerngebirge” with >70 wt % halite. All rock types studied are fault rocks. By use of a temperature-independent subgrain size piezometer, the paleo-differential stress of halite was calculated at ca. 2.5 MPa in Altaussee and ca. 4.5 MPa in Berchtesgaden. Including data from a grain-size piezometer, temperatures were estimated at ca. 150 ± 20 °C and 110 ± 10 °C. This implies very high strain rates, which are about 10−10–10−9 s−1. During the tectonic movement, the halite deformed, recrystallized, and crystallized as veins in mudrock fractures. We interpret high overpressure of the pore fluid to have significantly contributed to fracturing of the mudrock.

Sand provenance and implications for paleodrainage in a rifted basin: the Tera Group (N. Spain)

Fluvial-fan and fluvial siliciclastic strata, developed during the rifting that generated the Cameros Basin (North Spain), record important provenance changes that reveal source areas compositions and locations, paleodrainage evolution and rift patterns. The Tera Group represents the first rifting stage in the Cameros Basin, containing fluvial-fan sediments at the lower part of the sedimentary fill that evolve to fluvial and lacustrine systems in the upper part of the record. Our quantitative sandstone petrographic analysis evidences the presence of three main petrofacies related closely to the rift basin evolution. At the base of the sedimentary succession, Petrofacies 1 (quartzolithic) indicates that the fluvial-fans source areas included Juras¬sic marine carbonates and older siliciclastic Mesozoic units, as well as metamorphic supplies from the West Asturian Leonese Zone (WALZ). Variscan basement sources of this metamorphic area (WALZ) were more abundant in the upper fluvial record (Petrofacies 2, quartzofeldspathic). Further, the influence of plutonic source areas with a mixed potassic and calcium-sodium composition is also recorded, probably related to the Central Iberian Zone (CIZ). In addition, a local sedimentary input was active during the fluvial and lacustrine stages (Petrofacies 2 and 3, both quartzofeldspathic), as a function of the palaeogeographical position of the Jurassic marine rocks and the level of erosion reached. Plutonic rock fragments have not been observed in the Tera Group sandstones of the western part of the basin. Thus, deeper erosion of the basement in the eastern Cameros Basin is suggested. The provenance evolution from quartzolithic to quartzofeldspathic petrofacies registered in Tera Group siliciclastic deposits is due to the higher influence of transversal supplies during the fluvial-fan stage (quartzolithic) to more important axial inputs during the fluvial stage (quartzofeldspathic). This provenance change represents the evolution from an undissected rift shoulder stage to more advanced stages of rifting (dissected rift shoulder) and during the beginning of a provenance cycle in a rifted basin.

Structural analysis of the Gachsar sub-zone in central Alborz range; constrain for inversion tectonics followed by the range transverse faulting

Analysis of the Gachsar structural sub-zone has been carried out to constrain structural evolution of the central Alborz range situated in the central Alpine Himalayan orogenic system. The sub-zone bounded by the northward-dipping Kandovan Fault to the north and the southward-dipping Taleghan Fault to the south is transversely cut by several sinistral faults. The Kandovan Fault that controls development of the Eocene rocks in its footwall from the Paleozoic–Mesozoic units in the fault hanging wall is interpreted as an inverted basin-bounding fault. Structural evidences include the presence of a thin-skinned imbricate thrust system propagated from a detachment zone that acts as a footwall shortcut thrust, development of large synclines in the fault footwall as well as back thrusts and pop-up structures on the fault hanging wall. Kinematics of the inverted Kandovan Fault and its accompanying structures constrain the N–S shortening direction proposed for the Alborz range until Late Miocene. The transverse sinistral faults that are in acute angle of 15° to a major magnetic lineament, which represents a basement fault, are interpreted to develop as synthetic Riedel shears on the cover sequences during reactivation of the basement fault. This overprinting of the transverse faults on the earlier inverted extensional fault occurs since the Late Miocene when the south Caspian basin block attained a SSW movement relative to the central Iran. Therefore, recent deformation in the range is a result of the basement transverse-fault reactivation.