Sandstone Petrofacies Research Articles

New constraints for the western Paleotethys paleogeography-paleotectonics derived from detrital signatures: Malaguide Carboniferous Culm Cycle (Betic Cordillera, S Spain)

Carboniferous sandstone within the Paleo-Mesomediterranean Domain (Malaguide Subdomain), in southern Spain, represents a key detrital mode within the sedimentary budget of convergent plate boundaries during the Variscan s.s. to Paleotethysian orogenic time span (≈420–300 Ma). This Carboniferous detritus corresponds with Culm lithostratigraphic depositional unit, and it covers an important gap of information (paleogeographic, paleotectonic, source areas) to the area located between the Iberian-French massifs and the African Paleo-Atlas, in the western Paleotethys. Sandstone composition is quartzolithic and records an important high-to-medium-low grade metamorphic content. The source area was a lithic and transitional recycled orogen with a signature of volcanic and ophiolitic detritus (≈330 Ma and/or older). These supplies seem to be derived from a mid-crustal deformed and thrusted pre-late Ordovician to Early Carboniferous terrane, involved in the plate convergence (the southern Europe Iberian-French massifs overriding the north African area) southeatwards of the Variscan s.s. orogenic system, rapidly exhumed and uplifted at mid-Late Carboniferoous time. Consequently, in the overriding hinterland (southern Europe: Iberian-French massifs), metamorphic basement should be already structured during middle Carboniferous when thrusting took place and deposition of Culm facies started in the Malaguide Complex, suggesting Proterozoic-Early Carboniferous (most probably, ≈420 to 330 Ma) metamorphic highlands. The presence of serpentinite-like detritus (≈330 Ma and/or older) seems to indicate a metamorphosed oceanic crust being dismantled at that time. Thus, sources from ophiolitic suture (most probably developed at ≈420–330 Ma) zones are tentatively proposed in other northern Gondwana of southwestern Europe. The occurrence of a synsedimentary volcanic activity (andesitic) should be related to a lost magmatic arc (most probably developed at ≈360–330 Ma), reinforcing the idea of a nearby subduction area. Therefore, the thick terrigenous Culm deposits (≈330–300 Ma) from the Malaguide Subdomain could be deposited in a complex foreland system basin connected northward with carbonate platforms and with a crystalline highland uplifted domain from the southern Europe Iberian-French massifs and southward with the African Paleo-Atlas Domain. The studied mid- to late Carboniferous sandstone petrofacies deeply contributes to paleogeographic reconstructions since block fragmentation and spreading, during the Paleotethysian and Alpine orogenies, rearranged the Paleozoic paleogeography now part of the Cenozoic Perimediterranean Chains. After the correlation with the Carboniferous from other western Paleotethys domains, new paleogeographic-paleotectonic constraints are proposed for the transitional area between the Iberian-French massifs and the African Paleo-Atlas Domain.

Diagenesis and petrophysics of Miocene sandstones within southern Apennines foreland, Italy

Deep-marine clastic turbidite beds commonly occur in the Southern Apennines and record the main tectonic phases associated with the structural evolution of the area. Based on variations of detrital compositions through time, the sandstone suites are traditionally subdivided into four petrofacies: (I) quartzolithic (Burdigalian-Langhian), (II) quartzofeldspatholithic (Langhian-Tortonian), (III) quartzofeldspathic (Serravallian-Tortonian), and (IV) arkose (Tortonian-Messinian) sandstones. Since the complexity and diversity of these sandstone petrofacies, we aim to investigate their major diagenetic events and relate them with their detrital modes and physical properties in order to obtain key basic information at a regional scale, to better understand the main controls on petrophysical properties in this and in similar contexts. The petrophysical analysis reveals that the quartzolithic sandstones have the lowest porosity values, with a median of 4.56%. In contrast, porosity increases to median values of 16.75% in the quartzofeldspathic and arkosic petrofacies. The median permeability values range between 4.85 and 236.38 mD, and its distribution is generally poorly correlated with any other petrophysical parameter. The most widespread diagenetic minerals observed are carbonates, clay minerals, Fe-oxides and hydroxides, and less quartz. These sandstones are characterized by high compaction, which is the primary factor controlling porosity loss since the early diagenetic phases. In contrast, the early precipitation of pore-filling carbonate cement is assumed to have partly reduced the effect of compaction in quartzolithic and arkosic sandstones. Nonetheless, variations in petrophysical features among petrofacies can be traced back to the detrital composition, with the highest but less effective porosity associated with the presence of ductile grains, siliciclastic matrix and feldspars. Accordingly, this study reveals how linking detrital modes to the key petrophysical parameters may help obtain significant information about the regional control on the evolution of porosity and permeability in clastic turbiditic wedges of foreland domain settings as a baseline useful to further local and detailed studies.

Sandstone petrology of the Crotone Basin, Calabria (Italy) from well cores

Siliciclastic Serravallian–Tortonian strata of the Crotone Basin, and allochthonous Paleogene siliciclastic strata (Cariati Nappe) were studied in 8 well logs, both onshore and offshore. Compositional and stratigraphical variations along transects of 60 km (N-S) and 27 km (W-E) were undertaken. Modal analysis of buried sandstones testified four distinctive sandstone petrofacies: quartzolithic and quartzofeldspathic composition related to allochthonous terranes of the Cariati Nappe, quartzofeldspathic and quartzofeldspatolithic composition related to the Crotone Basin. Sandstones composition reveals a direct influence of the nearby crystalline (plutonic and metasedimentary rocks) and associated Mesozoic to early Miocene sedimentary source areas (Sila Unit). Detrital modes are intimately related to the tectonic setting evolution of the area. Comparison with southern Apennines regional petrofacies of the Sicilide Complex, and Crotone Basin outcrop petrofacies had shown analogies with buried sandstones, as a consequence of typical setting within foreland basin system.

Sandstone petrofacies, deformational events and the dynamic of the Valle Fértil Lineament during the late Paleozoic (Paganzo Basin, northwestern Argentina)

The behavior during the late Paleozoic of the Valle Fértil Lineament, a first-order structural element placed along the suture between Cuyania and Pampia Terranes in northwest Argentina, is analyzed. The study was undertaken following three different lines of research: 1) the analysis of compositional changes of Carboniferous and Permian sandstones, 2) the interpretation of sizeable soft-sediment deformation, and 3) the analysis of the stratigraphic relationships along and away from the Valle Fértil megashear zone. At the Guandacol Hill, three sandstones petrofacies were recognized in the Carboniferous and Permian Guandacol, Tupe and Patquía formations: quartzolithic (Q-L), quartzofeldspathic (Q-F), and lithic-volcanic (L-V). The vertical distribution of these petrofacies allows distinguishing four stratigraphic intervals. The first, which corresponds to the uppermost part of the Guandacol Formation and the lower Tupe Formation, displays a marked alternation between Q-L and Q-F petrofacies, indicating supply from the metamorphic basement of the local Umango-Maz Block (Q-L) and from granitoids of the Sierras Pampeanas System (Q-F). The second interval, corresponding to the upper Tupe Formation, is widely dominated by Q-F petrofacies owing to the progradation of arkosic wedges from the Sierras Pampeanas System and a limited contribution of the Umango-Maz Block. The third interval, the lower Patquía Formation, shows a sharp change in the composition of the sandstones since they are dominated by acidic and intermediate volcanic fragments (L-V petrofacies), suggesting the establishment of a volcanic field in the area. Finally, the fourth stratigraphic interval, the middle Patquía Formation, is again composed of the Q-F petrofacies indicating a new episode of progradation of arkosic wedges from the Sierras Pampeanas System. Evidence of tectonic activity during the deposition of the Guandacol Formation is also suggested by the presence of different scales of syn-sedimentary deformational structures, from small-scale soft-deformation to large-scale mass transport deposits. This deformational belt only occurs along the Valle Fértil Lineament and is not recorded in other localities of the Paganzo Basin located either to the west or east of the megashear zone. Regional analysis of the late Paleozoic stratigraphy provides additional information about tectonic instability. Firstly, while the contact between the Guandacol and Tupe Formations is concordant throughout the basin, some localities close to the Valle Fértil Lineament show an angular unconformable relationship. Secondly, in the Agua de la Peña creek, located just on the trace of the Valle Fértil Lineament, the Permian Talampaya Formation covers through an angular unconformity the Guandacol Formation, a relation not observed in other areas of the Paganzo Basin. Thirdly, the presence of Carboniferous magmatism, including volcanic rocks in the Guandacol Hill and a granitic intrusion in the Veladero Hill, has been only observed along the Valle Fértil Lineament.

Small-Scale Diagenetic Heterogeneity Effects on Reservoir Quality of Deep Sandstones: A Case Study from the Lower Jurassic Ahe Formation, Eastern Kuqa Depression

The Lower Jurassic Ahe Formation is an important exploration target for deep clastic reservoirs in the eastern Kuqa Depression. The Ahe Formation sandstones show heterogeneous porosity and permeability petrophysical properties. These properties have been poorly understood, limiting forecast of petroleum accumulations and making it difficult to develop the reservoirs. Based on cores, thin sections, SEM, and fluid inclusions, this study examined sandstone composition and texture and diagenetic heterogeneity at the core scale. The aim was to understand the influence of variations in detrital composition and texture on diagenetic and reservoir quality evolution. The Ahe Formation sandstones are dominantly fine- to coarse-grained litharenites, with minor feldspathic litharenites. In fining-up sand beds, detrital grain size determines the degree of mechanical compaction and, consequently, the abundance of porosity through ductile grains and muddy matrix. Local complete calcite cementation is a noticeable exception to this general trend. Three sandstone petrofacies have been defined based on texture and framework composition, detrital matrix, diagenesis, and pore types: (1) ductile-lean sandstone, (2) ductile-rich sandstone, and (3) tightly calcite-cemented sandstone. Different petrofacies experienced contrasting diagenetic and porosity evolution pathways. Ductile-lean sandstones underwent lower degree of compaction relative to ductile-rich sandstones during the eodiagenesis stage, and extensive grain dissolution occurred. The petrofacies remained relatively porous and permeable before early oil arrival. With continued burial, the porosity and permeability in the sandstones were further reduced by cementation. The petrofacies still had moderate porosity and permeability and were substantially charged when late petroleum migrated into the reservoirs. Thus, ductile-lean sandstones constitute effective reservoir rocks in deep reservoirs. By translating petrofacies to signatures of well logs, the effective properties of the reservoir rocks can be forecasted at the well scale.

Detection of flow units of Quseir Formation (Lower Campanian) as a potential reservoir using experimental correlations of capillary pressure derived parameters, Gebel el-Silsila, Egypt

Sandstone surface samples were collected from Quseir Fm., a member of Nubian Sandstone at Gebel el-Silsila and subjected to petrographical investigation using polarizing microscope. X-Ray diffraction was carried out to determine mineralogy. Scanning electron microscope also was utilized for the morphological characterization of the rock components. This sandstone petrofacies is mainly quartz arenite. The depositional environment of the studied sandstones is fluvial to fluvial-marine, and they suffered post-depositional alterations. Alterations include diagenesis (clay infiltration and original detrital grains disintegration), weathering, deterioration phenomena as erosion, voids existence due to dissolution and absence of bound materials. Mineralogical characterization indicated that quartz is the main constituent of sandstone in addition to kaolinite clay mineral as a cementing material. Petrophysically, the studied samples subjected to porosity and permeability measurements. The measurements showed that the samples are highly porous and permeable. Permeability–porosity relation displayed two groups (A and B). Although porosity values are close to great extent, permeability is quite different for the two groups due to the different distributions of pore throats, perhaps as a result of uneven clay distribution within the two groups of samples. Many capillary pressure-derived parameters were calculated using experimental correlations. The results confirmed the presence of two flow groups, macroport group (group A) and megaport group (group B) that is the best in terms of reservoir quality. The two groups reflect the excellent properties for the studied potential reservoir.

Petrofacies prediction and 3-D geological model in tight gas sandstone reservoirs by integration of well logs and geostatistical modeling

Abstract These effective reservoir rocks that can have sufficient porosity and permeability and hydrocarbon accumulations determine economic reserves and high yield of tight oil and gas. Understanding the origin and distribution of these effective reservoir rocks is important for sorting out “sweet spots” in tight reservoirs. Multiple-scale analyses from the microscopic, via drill core to single wellbore have been conducted to examine reservoir heterogeneity of the Upper Paleozoic Shanxi Formation in the southeastern Ordos Basin. Five sandstone petrofacies have been defined in terms of texture and framework composition, detrital matrix, diagenesis and pore types: quartz arenite, tuffaceous quartz arenite, ductile lithic-lean sub-litharenite, ductile lithic-rich sandstone and tightly carbonate-cemented sandstone. The various petrofacies show fundamentally different pathways of diagenetic and reservoir-quality evolutions, due to the complexity of texture and detrital composition in the Shanxi Formation, directly related to the provenance and depositional environment. Quartz arenites and ductile grain-lean sub-litharenites both form effective reservoir rocks. By translating petrofacies to well-log signatures corrected from petrographic and core analysis data, a model based on factor analysis has been built to predict petrofacies at the well scale. For investigating the distribution of each petrofacies at the field scale, sequential indicator simulation method has been used to construct a 3-D petrofacies model with facies conditioning. The isopach maps of quartz arenites and ductile lithic-lean sub-litharenites have been made from the 3-D petrofacies model to quantify their areal distributions, and to define the “sweet spots” by combining isopach maps of these effective reservoir rocks and gas production data from well tests. The concept of reservoir petrofacies is an important tool for the characterization of tight sandstone reservoirs.

Influence of primary composition and diagenetic mineralization on natural gamma-ray and density logs of Carboniferous sandstones of the Dęblin Formation

The Carboniferous sandstone of the Deblin Formation is one of the targets for the petroleum industry in the Lublin Basin in southeastern Poland. The formation’s primary and diagenetic composition makes it difficult to estimate its reservoir properties. Based on a detailed analysis of core and petrographic samples, normalization of gamma-ray and density logs was made with respect to the grain-framework of the rock. Recounted logs were used for distinguishing 4 different sandstone petrofacies. For these petrofacies, ranges of gamma-ray and bulk density values were determined and the impact of primary and diagenetic mineral composition was estimated. The application of this petrofacies method can upgrade the level of reservoir characterization and support the interpretation of uncored intervals.

Early Mesozoic sedimentary‒tectonic evolution of the Central-East Iranian Microcontinent: Evidence from a provenance study of the Nakhlak Group

In Central Iran, the mixed siliciclastic‒carbonate Nakhlak Group of Triassic age is commonly seen to have a Cimmerian affinity, although it shows considerable resemblances with the Triassic Aghdarband Group in far northeastern Iran, east of Kopeh-Dagh area, with Eurasian affinity. The Nakhlak Group is composed of the Alam (Late Olenekian‒Anisian), Baqoroq (Late Anisian‒?Early Ladinian), and Ashin (Ladinian‒?Early Carnian) formations consisting mainly of volcanoclastic sandstone and shale and fossiliferous limestone. The Baqoroq Formation contains also metamorphic detritus. Sandstone petrofacies reflect the detrital evolution from active volcanism to growing orogen and again active volcanism. Textural and modal analyses of volcanic lithic fragments from the Alam Formation reflect the eruption style and magma composition of a felsic to intermediate syn-sedimentary arc activity. The detrital modes of the Baqoroq Formation sediments suggest a recycled orogenic source followed by arc activity in a remnant fore-arc basin. The sandstone samples from the Ashin Formation demonstrate a continuity of felsic to intermediate arc activity. Major and trace element concentrations of the Nakhlak Group clastic samples support sediment supply from first-cycle material and felsic magmatic arc input. The enrichment in LREE, the negative Eu anomalies, and the flat HREE patterns indicate origination from the old upper continental crust and young arc material. The chemical index of alteration (CIA ∼51–70 for sandstone and 64–76 for shale samples) indicates medium degrees of chemical weathering at the source. Petrographical and geochemical evidence together with facies analysis constructed the following depositional conditions for the Nakhlak Group sediments: In the Olenekian, a fore-arc shallow to deep marine depositional basin developed that later was filled by recycled and arc-related detritus and changed into a continental basin in the Anisian. Ladinian extension let to a deepening of the basin. With respect to the similarities between the Nakhlak and Aghdarband (NE Iran) groups and unusual present-day position of the Nakhlak Group with no stratigraphic connection to the surrounding area, the development of first a fore-arc basin and later change into a back-arc depositional basin in close relation with the Aghdarband basin at the southern Eurasian active margin in the Triassic are here proposed. Understanding the basin development recorded in the Nakhlak Group provides constraints on the closure history of Palaeotethys and of the tectonic evolution of early Mesozoic basins at the southern Eurasian margin before the Cimmerian Orogeny.

Provenance and depositional conditions of fluvial conglomerates and sandstones and their controlling processes in a rift setting, mid-Permian lower and upper Quanzijie low order cycles, Bogda Mountains, NW China

This study investigates how provenance lithology, transport distance, and depositional and paleoclimatic conditions had affected the composition and texture of fluvial conglomerates and sandstones in the Middle Permian lower and upper Quanzijie low-order cycles, Bogda Mountains, greater Turpan-Junggar intracontinental rift basin, NW China. Composition and texture of gravels in conglomerates and sandstones define two conglomerate and two sandstone petrofacies, respectively, in Tarlong-Taodonggou area in southern Bogda and Dalongkou area 70km to the north in northern Bogda. Conglomerate Petrofacies I occurs in Tarlong-Taodonggou and is dominated by basaltic gravels, whereas Conglomerate Petrofacies II occurs mainly in Dalongkou and is dominated by sedimentary gravels. Sandstone Petrofacies I occurs in Tarlong-Taodonggou and contains dominantly basaltic lithics, few sedimentary lithics, and minimal quartz. It is compositionally immature and texturally immature to submature. The compositional maturity increases upsection. Conglomerate Petrofacies I and sandstone Petrofacies I both indicate the young Tian Shan arc to the south as the main sediment source and rift shoulders as a local source. Sandstone Petrofacies II occurs in Dalongkou and contains dominantly sedimentary lithics and abundant and well-developed pedogenic clay coats. The petrofacies in Dalongkou indicate older rift sedimentary rocks exposed at rift shoulders as the main sediment source and distant suture zones as a minor source. In summary, the composition and texture of Quanzijie conglomerates and sandstones are mainly controlled by provenance lithology and, secondarily, depositional and paleoclimatic conditions and transport distance. The results substantiate the rift origin of the Turpan-Junggar basin in Middle Permian, which had many half-grabens and grabens and was bordered by a volcanic arc at the southern basin margin.

Interpreting provenance relations from sandstone detrital modes, southern Italy foreland region: Stratigraphic record of the Miocene tectonic evolution

The Southern Italy orogen preserves deep-marine turbitic clastic wedges that record the key tectonic events during structural growing over the Adria margin. The regional tectonic transition from thick-skinned Calabrian accretion and deformation (during Late Paleogene-to-middle Miocene) to thin-skinned Southern Apennines thrusting (since early-middle Miocene) is recorded by diverse contrasting petrofacies in uppermost Paleogene and Miocene sandstones of dominantly turbiditie deposits. Most of these sandstones reflect in time quartzolithic and quartzofeldspathic and arkosic petrofacies derived from growing and unroofing Calabrian terranes. Quartzose petrofacies mainly indicate provenance from cratonal African margin, during Langhian, and/or from lowland internal domains before its deformation, during the Cretaceous to Paleogene. Volcaniclastic sandstone petrofacies also testify active volcanism during the Late Paleogene to early Miocene. These variable compositions indicate strong palaeogeographic constraints for the central-western Mediterranean, during the Neogene, reflecting provenance relationships from differentiate source rocks. These include interplays between ophiolitiferous, uplifted continental shallow to deep crust terranes, volcanic and sedimentary (mostly carbonate) source rocks. Sandstone detrital modes provide an example of the close relations between clastic compositions and growing orogen in southern Italy and may contribute to unravel the geodynamic history of other major orogens.

Geochemistry of the Great Valley Group: an integrated provenance record

Sedimentary geochemistry of fine-grained strata of the Great Valley Group (GVG) in California documents a provenance signal that may better represent unstable, mafic minerals and volcanic clasts within sediment source regions than the provenance signal documented in the petrofacies and detrital zircon analysis of coarser sedimentary fractions. Geochemistry of the GVG provides an overall provenance framework within which to interpret sandstone petrofacies and detrital zircon age signatures. The geochemical signature for all Sacramento Valley samples records an overall continental arc source, with significant variation but no clear spatial or temporal trends, indicating that the geochemical provenance signal remained relatively consistent and homogenized through deposition of Sacramento basin strata. The San Joaquin basin records a distinct geochemical provenance signature that shifted from Early to Late Cretaceous time, with Lower Cretaceous strata recording the most mafic trace element geochemical signature of any GVG samples, and Upper Cretaceous strata recording the most felsic geochemical signature. These provenance results suggest that the early San Joaquin basin received sediment from the southern Sierran foothills terranes and intruding plutons during the Early Cretaceous, with sediment sources shifting east as the southern Sierran batholith was exhumed and more deeply eroded during the Late Cretaceous. The GVG provenance record does not require sediment sources inboard of the arc at any time during GVG deposition, and even earliest Cretaceous drainage systems may not have traversed the arc to link the continental interior with the margin. Because the GVG provenance signature is entirely compatible with sediment sources within the Klamath Mountains, the northern and western Sierran foothills belt, and the main Cretaceous Sierran batholith, the Klamath-Sierran magmatic arc may have formed a high-standing topographic barrier throughout the Cretaceous period.

Petrology and provenance of the Toro Negro Formation (Neogene) of the Vinchina broken-foreland basin (Central Andes of Argentina)

Detrital modes of sandstones and conglomerates of the Toro Negro Formation (Late Miocene-early Pliocene) were used to analyze the evolution of the broken-foreland stage of the Vinchina Basin (28°30′–29°00′ S and 68°30′–68°20′ W) of NW Argentina. This basin located in the Western Sierras Pampeanas is bounded to the west by the Precordillera and to the east by the Famatina System. Three sandstone petrofacies: plutonic-metamorphic, volcanic and mixed petrofacies and three conglomerate lithic associations: basement, sedimentary and volcanic lithic associations were recognized, allowing to establish three source areas: Western Sierras Pampeanas (Toro Negro and Umango Ranges), Cordillera Frontal and Precordillera.During the Late Miocene, the Toro Negro Range (to the north) together with the Cordillera Frontal and Precordillera (to the west) were the main sources for depositional sequences I and II (lower member of the Toro Negro Formation). On the contrary, during the latest Miocene-early Pliocene, Depositional Sequence III (upper member) exhibited a progressive increase in the supply from the eastern Precordillera (to the west) with additional material from the Umango Range to the south. Besides, evidence of synchronic volcanism is recorded in the upper part of Depositional Sequence II and the lower part of Depositional Sequence III.The coexistence of the three source areas and the changing distribution patterns due to re-accommodation of sediment dispersal routes demonstrate that the evolution of this type of basin is much more complex than previously envisaged. Therefore, an integrated analysis using different tools (sedimentary facies, paleocurrent measurements, sandstone petrography and conglomerate composition) is needed for a clearer understanding of broken-foreland basins.

The Aghajari (Upper Fars) Formation in the Folded Zagros Zone, Iran: Insights to Identify Facies, Architectural Elements, Fluvial Systems, Petrography and Provenance

Abstract:The Aghajari Formation, called also the Upper Fars, develops throughout the Folded Zagros Zone and its thickness in the type section in southwest of Iran is 2966 meters. To analyze the sedimentary basin of this Formation, lithofacies, architectural elements and petrofacies of the related deposits in a section in southeast of Sarvestan in Fars Province of Iran with a thickness of 2221.45 meters were examined. Microscopically studying thin sections, the petrography and the occurrence of the deposits were determined. In this section, 16 lithofacies, 10 architectural elements and 2 sandstone petrofacies were identified. The lithofacies were divided into two major and minor groups, in which the major lithofacies consist of coarse‐grained (Gh, Gp, Gt and Gm), medium‐grained (Sh, Sp, St, Sl, Sm, Sr and Ss and fine‐grained ones (Fm, Fl and Fsm), and the minor lithofacies were evaporative and mixed silisiclastic‐carbonate. The identified architectural elements are CH, SB, GB, LA, DA, CR, CS, LV, LS, CH (FF) and FF. By combining evidences from facies analysis and architectural elements together, the Aghajari Formation was divided into three parts in which the related sedimentation environments, from top to bottom, are gravel, gravel‐sand and fine‐grained meandering river respectively. There have also been playas and shoreface in the lower part. Based on petrography, the sandstones of this formation were classified into two groups: litharenite and sublitharenite. The origin of these deposits (sandstones) was appointed to the recycled orogeny and the source of quartz is low and medium to high metamorphic rank. Using the field evidences, the paleocurrent direction was achieved indicating the direction of the paleocurrent from northwest to southeast at the time of deposition. It is hoped that these data can be used in the interpretation of the basin and reconstruction of the paleogeography in the local and regional scales.

Composition of modern sand and Cretaceous sandstone derived from the Sierra Nevada, California, USA, with implications for Cenozoic and Mesozoic uplift and dissection

The California Sierra Nevada represents the roots of a primarily Cretaceous magmatic arc that is presently being dissected extensively in the south and to a lesser degree in the north, where it is covered by Cenozoic volcanic rocks. The Cenozoic magmatic arc built on top of the Cretaceous arc has been dissected concurrently with northward migration of the Mendocino triple junction, south of which the magmatic arc is inactive. A north-to-south transect from the modern Cascade arc along the Sierra Nevada, therefore, acts as a proxy for evolution from an active undissected magmatic arc to a transitional arc to a dissected arc to intensely uplifted basement.Discriminant analysis of Cascade and Sierra Nevada modern alluvial sand defines four compositional groups and clearly distinguishes volcaniclastic undissected-arc and plutoniclastic uplifted-basement end members. Two intermediate compositional groups are primarily volcaniplutoniclastic and metamorphiplutoniclastic. The former group represents Dickinson's (1985) “transitional arc;” the latter represents “dissected arc.” Sand composition in the southern Sierra Nevada reflects significant uplift, resulting from a combination of latest Cretaceous–Paleogene uplift and late Cenozoic Basin and Range extension (footwall uplift of the western rift shoulder), possibly enhanced by mantle–lithosphere delamination. High concentrations of quartz and feldspar, and near absence of aphanitic lithic fragments are typical of the southern Sierra Nevada and are characteristic of Dickinson's “basement uplift.”Cretaceous sandstone petrofacies of the Great Valley Group (GVG) of western California document dissection of the Cretaceous magmatic arc, as well as erosion of residual orogenic highlands (analogous to modern Taiwan) formed during latest Jurassic arc–continent collision (Nevadan orogeny). When Cretaceous petrofacies data are entered into the modern-sand discriminant analysis as unknowns, they are classified into the modern Cascade/Sierra Nevada groups and a group from Taiwan. The results confirm that the lowest GVG petrofacies represent erosion of the Nevadan suture belt and the undissected post-Nevadan arc. Increasing dissection of the arc occurred during the Cretaceous, but most samples represent “transitional arc,” indicating that even by the latest Cretaceous (Laramide) cessation of arc activity in California, dissection of the magmatic arc was less than what we see today in the central and southern Sierra Nevada. No Cretaceous samples have compositions equivalent to the “basement uplift” of the southern Sierra Nevada.The application of actualistic sand(stone) petrofacies in this study provides important constraints on models for the Cretaceous to modern history of the Sierra Nevada, as well as implications for arc evolution in general.

Provenance of the Paleogene Colton Formation (Uinta Basin) and Cretaceous–Paleogene provenance evolution in the Utah foreland: Evidence from U-Pb ages of detrital zircons, paleocurrent trends, and sandstone petrofacies

The fluviodeltaic Colton Formation (Late Paleocene–Early Eocene) forms a lobate depositional system that prograded from the south into the Laramide Uinta Basin of northeastern Utah (United States) with a preserved sediment volume of ∼3000 km3 and a maximum thickness of ∼1000 m. Joint consideration of detrital zircon ages, paleocurrent trends, and sandstone petrofacies permits an assessment of Colton provenance relations in the context of evolving Cretaceous–Paleogene sedimentation in the Utah foreland. Grains with U-Pb ages younger than 285 Ma derived from the Cordilleran magmatic arc form ∼50% of the detrital zircons in arkosic Colton sand, and were transported ∼750 km to the Uinta Basin from the Mojave segment of the arc by the California paleoriver. Colton sedimentation was the Paleogene culmination of a persistent pattern of Cretaceous sediment transport northward, subparallel to the Sevier thrust front, to supplement east-directed sediment delivery to the retroarc foreland from the Sevier thrust belt. The ratio of longitudinally to transversely derived sediment was enhanced in foreland strata after Laramide deformation produced intraforeland uplifts that screened the foreland belt from Sevier sources. The relative abundance of arc-derived detrital zircons that were contributed to strata of the Utah foreland increased in late Campanian time and remained high into Eocene time. Detrital zircon populations in Paleogene forearc strata of southern California are compatible with coeval derivation of arc-derived detritus in the forearc sands and the Colton backarc sand from a common paleodrainage divide crossing the Mojave region to connect hinterland Nevadaplano and Mexicoplano uplands to the north and south.

Unravelling provenance from Eocene–Oligocene sandstones of the Thrace Basin, North‐east Greece

AbstractNew sandstone petrology and petrostratigraphy provide insights on Palaeogene (Middle Eocene to Oligocene) clastics of the Thrace Basin in Greece, which developed synchronously with post‐Cretaceous collision and subsequent Tertiary extension. Sandstone petrofacies are used as a tool to unravel complex geodynamic changes that occurred at the southern continental margin of the European plate, identifying detrital signals of the accretionary processes of the Rhodope orogen, as well as subsequent partitioning related to extension of the Rhodope area, followed by Oligocene to present Aegean extension and wide magmatic activity starting during the Early Oligocene. Sandstone detrital modes include three distinctive petrofacies: quartzolithic, quartzofeldspathic and feldspatholithic. Major contributions are from metamorphic basement units, represented mostly by low to medium‐grade lithic fragments for the quartzolithic petrofacies and high‐grade metamorphic rock fragments for the quartzofeldspathic petrofacies. Volcaniclastic sandstones were derived from different volcanic areas, with a composition varying from dominantly silicic to subordinate intermediate products (mainly rhyolitic glass, spherulites and felsitic lithics). Evolution of detrital modes documents contributions from three key source areas corresponding to the two main crystalline tectonic units: (i) the Variegated Complex (ultramafic complex), in the initial stage of accretion (quartzolithic petrofacies); (ii) the Gneiss–Migmatite Complex (quartzofeldspathic petrofacies); and (iii) the Circum‐Rhodope Belt. The volcaniclastic petrofacies is interbedded with quartzofeldspathic petrofacies, reflecting superposition of active volcanic activity on regional erosion. The three key petrofacies reflect complex provenance from different tectonic settings, from collisional orogenic terranes to local basement uplift and volcanic activity. The composition and stratigraphic relations of sandstones derived from erosion of the Rhodope orogenic belt and superposed magmatism after the extensional phase in northern Greece provide constraints for palaeogeographic and palaeotectonic models of the Eocene to Oligocene western portions of the Thrace Basin. Clastic detritus in the following sedimentary assemblages was derived mainly from provenance terranes of the Palaeozoic section within the strongly deformed Rhodope Massif of northern Greece and south‐east Bulgaria, from the epimetamorphic units of the Circum‐Rhodope Belt and from superposed Late Eocene to Early Oligocene magmatism related to orogenic collapse of the Rhodope orogen. The sedimentary provenance of the Rhodope Palaeogene sandstones documents the changing nature of this orogenic belt through time, and may contribute to a general understanding of similar geodynamic settings.

Petrography and provenance of the Early Permian Fluvial Warchha Sandstone, Salt Range, Pakistan

The Warchha Sandstone of the Salt Range of Pakistan is a continental succession that accumulated as part of a meandering, fluvial system during Early Permian times. Several fining-upward depositional cycles are developed, each of which is composed of conglomerate, cross-bedded sandstone and, in their upper parts, bioturbated siltstone and claystone units with distinctive desiccation cracks and carbonate concretions. Clast lithologies are mainly of plutonic and low-grade metamorphic origin, with an additional minor sedimentary component. Textural properties of the sandstone are fine- to coarse-grained, poorly to moderately sorted, sub-angular to sub-rounded, and with generally loose packing. Based on modal analyses, the sandstone is dominantly a feldspathoquartzose (arkose to sub-arkose). Detrital constituents are mainly composed of monocrystalline quartz, feldspars (more K-feldspar than plagioclase) and various types of lithic clasts. XRD and SEM studies indicate that kaolinite is the dominant clay mineral and that it occurs as both allogenic and authigenic forms. However, illite, illite-smectite mixed layer, smectite and chlorite are also recognised in both pores and fractures. Much of the kaolinite was likely derived by the severe chemical weathering of previously deposited basement rocks under the influence of a hot and humid climate. Transported residual clays deposited as part of the matrix of the Warchha Sandstone show coherent links with the sandstone petrofacies, thereby indicating the same likely origin. Illite, smectite and chlorite mainly occur as detrital minerals and as alteration products of weathered acidic igneous and metamorphic rocks. Based primarily on fabric relationship, the sequence of cement formation in the Warchha Sandstone is clay (generally kaolinite), iron oxide, calcareous and siliceous material, before iron-rich illite and occasional mixed layer smectite–illite and rare chlorite. Both petrographic analysis and field characteristics of the sandstone indicate that the source areas were characterised by uplift of a moderate to high relief continental block that was weathered under the influence of hot and humid climatic conditions. The rocks weathered from the source areas included primary granites and gneisses, together with metamorphic basement rocks and minor amounts of sedimentary rocks. Regional palaeogeographic reconstructions indicate that much of the Warchha Sandstone detritus was derived from the Aravalli and Malani ranges and surrounding areas of the Indian Craton to the south and southeast, before being transported to and deposited within the Salt Range region under the influence of a semi-arid to arid climatic regime.

Role of sandstone provenance in the diagenetic albitization of feldspars: A case study of the Jurassic Tera Group sandstones (Cameros Basin, NE Spain)

The Cameros Basin (Iberian Chain, NE Spain) formed during the latest Jurassic–Early Cretaceous rifting stage in an extensional regime characterized by high subsidence rates. Its sedimentary infill (thicker than 6000 m) has been subdivided into eight depositional sequences (DS) mainly composed of continental sediments. DS 1 and DS 2 represent the first rifting stage (Tera Group, Tithonian), mainly formed by fluvial and lacustrine sediments. Sandstone petrofacies evolved from quartz-sedimentolithic in DS 1 to quartz-feldspathic in DS 2 due to the rifting process. In DS 2, three different types of detrital feldspars (K-feldspars, albites and polysynthetic plagioclases) with similar sodium-rich compositions (mean: Ab 94.0 An 4.5 Or 1.5) can be recognized. Chemically pure nonluminescent albites (Ab > 99%) are common. In DS 2, diagenetic albitization of both plagioclases and K-feldspars is inferred from conventional microscopy observations, cathodoluminescence and electron microprobe analyses. DS 1 contains few plagioclase grains, which show no evidence of transformation into albite. Although the albitization is characterized as diagenetic it seems to be provenance-controlled since it affects the units showing higher original plagioclase/K-feldspar ratio (DS 2), due to the greater influence of plutonic and metamorphic source areas in DS 2. Possible Na sources are: (1) the percolation of moderate to high salinity residual brines from related alkaline lakes developed at top of DS 2 in the eastern sector of the basin, (2) clay mineral reactions (sodium smectite to illite and chlorite) indicated by mudstone composition in the interlayered mudstones, and (3) the replacement of detrital sodium plagioclases by carbonate. These three sources can be complementary.

Oligocene-Miocene basin evolution in the northern Altiplano, Bolivia: Implications for evolution of the central Andean backthrust belt and high plateau

The upper Oligocene to lower Miocene Penas and Aranjuez formations are exposed in north-northwest–trending outcrop belts of the central Andean backthrust belt situated within the central Andean plateau along the boundary between the northern Altiplano and the Eastern Cordillera of Bolivia. Sedimentary lithofacies analyses indicate that these coarse-grained siliciclastic formations were deposited primarily in alluvial fan to braided fluvial environments. An upsection change from principally fine-grained sandstone to cobble conglomerate is consistent with increased proximity to the sediment source with time. Paleocurrent analyses reveal that flow was predominantly directed toward the west-southwest away from Cordillera Real, the elevated core of the Eastern Cordillera. Provenance data from conglomerate clast compositions and sandstone petrofacies suggest derivation from recycled quartz-rich metasedimentary and sedimentary rocks from the Paleozoic section in the Eastern Cordillera. The paleoflow orientations, sediment provenance, and increased proximity of the sediment source suggest that deposition of the Penas and Aranjuez formations was related to surface uplift of the Eastern Cordillera relative to the Altiplano. Growth strata observed in the Aranjuez Formation further indicate that shortening was synchronous with deposition, probably in a hinterland basin. New 40 Ar/ 39 Ar ages from a lowermost exposed igneous unit and interbedded ash-fall tuff beds in the Aranjuez and Penas formations show that synorogenic sedimentation and fold-thrust deformation in the frontal (west-southwestern) zone of the central Andean backthrust belt was concentrated during late Oligocene–early Miocene time. These age results are consistent with previous studies of east-derived sedimentation in the Altiplano and indicate regional uplift of the Eastern Cordillera at this time. Upsection trends in provenance data further suggest a progressively greater contribution from younger Paleozoic strata, possibly due to activation of new thrust faults during west-southwestward propagation of the backthrust belt toward the Altiplano. Such a progression of late Oligocene–early Miocene shortening along the Altiplano–Eastern Cordillera boundary likely reflects significant crustal thickening, potential isostatic uplift, and initial topographic expression of the eastern margin of the central Andean plateau.