Subordinate Sandstone Research Articles

Exploration of Secondary Deposit to Determine Manganese Ore Body

Manganese ore is one of the most critical mineral commodities and irreplaceable in steelmaking. With the high demand for manganese ore, exploration to find manganese ore deposits is essential before large investments in mine development. The purpose of this study is to determine the content of secondary manganese through exploration in Ladang Sungai Terah Gua Musang with an area of 40.5 hectares. The area is located near the Permian -dominated zone which can be observed during plutonic igneous granites in the southwest and in the presence of phyllite, slate and shale with subordinate sandstone and schist. The significant secondary mineral found is manganese oxide or pyrolusite. The exploration method is by excavating the trial pit (TP) and bore hole (BH) drilling. The location of TP and BH are determined from anomalies data and outcrop and boulders presence at site. Results that obtained from the thirteen TP sampling showed that the deepest TPs are excavated at 4.0 meter depth and the shallowest depth was at 3.6 meter depth. The thickest manganese ore was at 0.4 meter for TP 06. The highest-grade manganese was 54.3% at 3.8 meter depth of TP 01 located at north-west from BH1. The BH soil which obtained at 12.0 meter depth with silt clay and the presence of sand gravel. The BH soil was taken and homogenised prior testing in order to get representative result. The XRF analysis shown that the manganese ore was found at 55.90 % and second highest mineral was silica oxide which was 21.74 % followed by aluminium at 14.32 %. The calculation of manganese ore reserves was estimated at 157,545 tonnes of which the lifespan of manganese mining operations was estimated at only 10.375 months. Even the quality was high but it still not reaching the ore body It can be concluded that this area is not economical for commercial production of manganese ore and by pursuing this area will surely contribute to business risks, negatively impacting on potential profitability. Mining revenue calculated from estimated ore reserved in this area is not expected to cover costs such as the exploration working capital, property acquisition costs, mine development costs including development drilling and infrastructure development such as roads, utilities, plant and equipment costs which include mining equipment, mill and processing equipment and building, structure and many more.

Stratigraphy and depositional environment of a mixed siliciclastic-carbonate platform and slope succession of the Paleogene Nisai Group, Pakistan

We document the stratigraphy, lithofacies and depositional environment of the lower Eocene-lower Oligocene Nisai Group, based on petrographic and micropaleontological analysis, and field observations.We rename the whole sedimentary succession as the Nisai Group and divide it into three formations, from bottom to top; Jabrai, Torkhezhe Tsah and Nisai formations. The Jabrai Formation comprises a thick succession of olive gray mudstone and shales with subordinate sandstone, limestone and quartzose conglomerate, interpreted as deltaic and littoral deposits. The Torkhezhe Tsah Formation comprises calciturbidites in its lower part and periplatform oozes and basinal shales in upper part. The shallow-marine carbonate material of calciturbidites possibly derived from a lost platform which was a narrow delta-top-platform developed over deltaic sediments of the Jabrai Formation. The uppermost unit, the Nisai Formation, comprises thick bedded limestone with subordinate shale and nodular reefoid limestone, and shows a shallowing-up succession overlying the slope and basinal deposits of the Torkhezhe Tsah Formation. The presence of Cr-rich spinels in sandstone of the Jabrai Formation, ultramafic-mafic and quartzite lithoclasts in calciturbidite beds as well as paleocurrent data, suggest that siliciclastic sediments of the Nisai Group derived from the Zhob Valley Ophiolites. Moreover, the presence of quartz, igneous and metamorphic extraclasts, and dolomitic horizons within calciturbidite beds, indicate deposition of these calciturbidites in response to lowering of sea level.We propose that emplacement of Zhob Valley Ophiolites served as a drainage divide and supplied deltaic sediments to the Jabrai Formation to its north and the Ghazij Group to the south.

Fracture Orientation Significance in the Study of Pb-Zn Mineralization of Lower Benue Trough, Abakaliki Se Nigeria

The Lower Benue Trough, in South-eastern Nigeria, hosts several lead-zinc deposits. The mineralization is frequently hosted by Cretaceous black shales that appear to have undergone low grade metamorphism, and subordinate sandstones. Most parts of the deposits have been epigenetically formed, and occur as blocky shaped, discordant veins, fracture, and possibly open-space fillings, of hydrothermal origin. For this reason, structural evaluation constitutes an important criterion for the investigation of the mineralization. In particular, the orientation of fractures occurring at the Pb-Zn deposits can be useful in the differentiation of the relative ages of the mineral vein deposits. A total of one thousand, one hundred and forty-seven fractures around mineralized zones, at the study localities, were measured and analysed. Results indicate that the vein deposits are structurally controlled, have four main orientations, and most likely formed by crack-seal process. The most prominent fracture sets show NW-SE, NNE-SSW to N-S orientations, while the less prominent ones are displayed in the NE-SW and ESE-WNW directions. The NW-SE, NNE-SSW to N-S fracture sets is interpreted as ‘ac’ extension fractures from two different deformation episodes that affected the trough, while the NE-SW, ESE-WNW to E-W sets is the two ‘bc’ tensile fractures, respectively parallel to the axes of F1 and F2 folds which occur in the trough. Small variations of the NNE-SSW and ESE-WNW brought about the occurrences of N-S and E-W sets respectively. Indication are that the two deformation episodes affected the trough: the first episode produce the NE-SW (F1) fold axes, while the second less intensity episode produce the ESE-WNW (F2) folds. The most dominant mineral vein trends in the study area are the NW-SE and NNE-SSW to N-S orientations, in which mineral veins are loaded in the ‘ac’ extension fractures. The less dominant mineral vein trends are the NE-SW and ESE-WNW orientations, which are in the ‘bc’ tensile fractures. At the NW-SE trend, vein minerals mainly occur along 150-160o from N, although it ranges from 135-175o from N. Vein width up to 7.0m can be obtained from both the NW-SE and NNE-SSW directions. The Lower Cretaceous sediments appear to be characterized by the NW-SE (major) and NE-SW (minor) sets of veins, while the upper Cretaceous sequence is most likely characterized by the NNE-SSW (major) and ESE-WNW (minor) vein sets. The widest Pb-Zn vein in the study area is 11.5m wide, located in the Enyigba axes sub-area and trends in the NE-SW direction with evidence of slickensides which indicates faulting.

The Evolution of Diagenetic Fluids and Accumulation Characteristics of Tight Sandstone Reservoir in Upper Paleozoic, Southwestern Ordos Basin

The Upper Paleozoic in the southwestern Ordos Basin has significant potential for natural gas exploration. This study investigated the diagenetic fluid evolution and hydrocarbon accumulation characteristics of He 8 section from Permian Lower Shihezi formation and Shan 1 section from Shanxi formation tight sandstone reservoirs by petrographic observation, scanning electron microscope imaging, fluid inclusion study, and laser Raman spectrum analysis. The results show that He 8 section and Shan 1 section reservoirs are mainly composed of quartz sandstone, subordinate arkose quartz sandstone, and lithic quartz sandstone, with minor lithic sandstone and lithic arkose sandstone. The major pores are intergranular dissolved pores. The main diagenetic minerals include quartz overgrowth, siliceous cement, carbonate cement, illite, montmorillonite, and mixed-layer clay minerals. The overall diagenetic features show strong compaction, multistage siliceous and calcareous cements, and abundant clay minerals, strong dissolution, and well-developed fractures. Two stages of fluid inclusions developed in the He 8 and Shan 1 sections recorded the migration and accumulation of the early-stage and late-stage natural gas, respectively. The reservoir in the study area experienced early and late diagenetic stages, and its formation was simultaneous with or after its densification. The diagenetic environment changed from alkaline to acidic and again into alkaline. There are two stages of fluid activities in the study area, namely, the early diagenetic stage corresponding to hydrocarbon generation and migration and the late diagenetic stage corresponding to hydrocarbon accumulation. This study suggests that Upper Paleozoic natural gas migrated into the reservoir in Weibei Uplift, Yishan Slope, and Tianhuan Depression tectonic units during 220-197 Ma, and the large-scale migration and accumulation occurred in these tectonic units at different times. No natural gas was generated in the west margin of the basin because the temperatures of the hydrocarbon source rocks in the Upper Paleozoic were below the gas window.

Geology, Vein Textures, and Fluid Inclusions of the Cibeber Low-Intermediate Sulfidation Epithermal Au-Ag Orefield, Western Java

DOI:10.17014/ijog.8.2.157-175This paper describes the results of surficial geological and alteration mapping combined with several laboratory analyses, including petrography, ore microscopy, ore geochemistry, and fluid inclusion studies, aimed at establishing the nature of mineralization and alteration in the Cibeber area, West Java, Indonesia, and developing a genetic model. The area forms part of the Bayah Dome Complex, which hosts several gold-silver deposits. It is underlain by andesitic lava, tuff breccia, and subordinate sandstone. Its structural framework consists of joints, normal faults, NE-SW dextral strike slip faults, and NW-SE strike-slip faults. Hydrothermal alteration can be divided into four types, viz. silicification, clay-silica, argillic, and propylitic. Mineralization is mostly hosted in quartz veins showing a variety of textures, including massive, colloform-crustiform, breccia, lattice bladed, comb, and saccharoidal. Ore minerals consist of native gold and silver, pyrite, chalcopyrite, sphalerite, galena, tennantite-tetrahedrite, covellite, malachite, hematite, and goethite, while the gangue minerals quartz, illite, epidote, and calcite. Four stages of mineralization/veining are recognized: early, middle (the main ore forming stage), late, and supergene. The highest obtained metal grades are 8.17 ppm Au, 113.6 ppm Ag, 1.23% Cu, 1.28% Pb, and 1.2% Zn. Fluid inclusions from mineralized veins yielded temperatures of 222 - 280°C and salinities of 0.36 - 1.31 wt.% NaCl eq. The hydrothermal fluids are interpreted to have been largely of meteoric origin with the mineralization having formed at a depth of about 258 - 270 m below paleosurface. Both low-sulphidation and intermediate-sulphidation styles of mineralization are present.

Source-to-sink system of Late Permian post-collisional stream-dominated alluvial fans under humid paleoclimate along the Irtysh-Zaisan suture zone, Central Asian Orogenic Belt

Abstract Because of few reports on the Upper Permian in the NW Junggar terrane, Northwest China, the recently identified Upper Permian Zaya conglomerate in the Saur area can provide insights into tectonics and paleoclimate at that time. The succession consists of predominant composite cobble-pebble conglomerate (~80%) and subordinate (gravelly) sandstone (~20%), showing sedimentary structures of stream-dominated alluvial fans and the unique lithofacies in the Saur area. This conglomerate was originally classified as a part of Lower Carboniferous, but its youngest detrital zircon U-Pb age is 265.3 ± 1.7 Ma and the succession shows the deformational patterns different from those of the Triassic sequences in the West Junggar terrane. Thus the conglomerate was deposited during the Late Permian. The Zaya conglomerate was unconformably deposited upon the Lower Permian volcano-sedimentary strata over the Devonian–Carboniferous Saur Arc (SA) and Saur Forearc Basin (SFB) on the northern margin of the Kazakhstan terrane, which currently juxtaposes with the Devonian Buerjin Accretionary Complex (BAC) on the southern margin of the Altai terrane to north. The contributions of the SFB + BAC and SA to the Zaya conglomerate are 89.6–96.7% and 3.3–10.4%, respectively. The conglomerate clasts are derived from Permian–Carboniferous volcano-sedimentary rocks in the SA, but the sandstones contain not only volcanic materials from the SA and SFB but also metamorphic and ultramafic detritus from the BAC. This is in support of the pre-Permian amalgamation of the Altai-Kazakhstan terranes. Plant fossils and organization of conglomerate would suggest a relatively humid paleoclimate with abundant rainfall.

Petrogenesis and tectonomagmatic updates on the origin of the igneous rocks in the lower Benue rift, southeastern Nigeria

This work presents updates on the tectonomagmatic origin of igneous rocks in the lower Benue rift based on recent available geochemical data. The igneous rocks occur as volcanic and plutonic rock series. The rock types are basalts and basaltic sills, pyroclastic rocks (tuffs and lapilli tuff), trachytes, trachybasalts, gabbros (stocks), dolerite sills, and dioritic rocks (stocks). The rocks were emplaced within folded sedimentary sequence of shales, subordinate sandstones, and siltstone and carbonate rocks of Asu-River and Eze-Aku Group. Most of the rocks are moderately to highly altered, with the pyroclastic rocks showing higher effects of alteration (LOI 3 to 22 %). Incompatible and immobile elements and less altered rocks with LOI < 3% show that the rocks were derived from mantle enriched source and possibly HIMU signatures. The high ratios of (La/Yb)N 4.40 to 31.55 in the basic rocks and 23.59 to 135.35 in the trachytic rocks show alkaline affinity with sparse tholeiites and garnets in the source region. The rocks were formed by plume uprising in a within-plate setting of intra-continental rift system similar to the South Atlantic Ocean rocks and East African rift. The magnesium number (Mg#) and differences of the spidergrams and rare earth patterns indicate that the rocks are cogenetic, and source is heterogeneous. The depletion of K, P, Th, and Rb and formation of calcites and sericites in the rocks show mobilization probably by interaction with calcareous host rocks in prevailing conditions.

Geochemical characterization of shales of the Eocene Disang Group, Kohima Syncline, India: Inferences to hydrocarbon potential and depositional environment

The Kohima Syncline exposes the Eocene Upper Disang Formation in an extensive region that is composed of grey shales with subordinate sandstone and siltstone alterations. The shales contain low to fair amount of organic matters represented by Type IV/Type III terrestrial kerogens. The Biomarkers indicate presence of terrestrial angiosperms and microbially reworked organic matters with some marine phytoplankton. Rock-Eval maturity parameters indicate maturity within a wide range between immature to post mature wet gas window, while the biomarkers show maturity between immature to mid mature. The biomarkers indicate that the Disang shales deposited in an oxic deltaic-terrigenous environment. The trace elements characterize an oxic to suboxic warm and humid depositional environment. Few trace elements point to deposition in a low salinity continental rather than a marine environment. Thus, several biomarker and trace element parameters show that a continental milieu was already established during the deposition of the Upper Disang sediments. It indicates that either the Disang basin, that evolved as a marine basin, suffered rapid shallowing during the deposition of the Upper Disang sediments, or the Lower and Upper Disangs were coeval and Lower Disangs represented deep marine facies while the Upper Disangs represented peripheral shallow marine deltaic facies. Maturity parameters like Tmax and, sterane and hopane isomerization ratios indicate that the organic matters of the Disang Group were affected by sudden short duration thermal events followed by cooling. This is possible in an active tectonic region like the Kohima Syncline that bears many evidences of thrusting and folding.

Discovery of Upper Cretaceous Neo-Tethyan trench deposits in south Tibet (Luogangcuo Formation)

Sedimentary basins within the Transhimalayan arc-trench system provide paleotectonic and paleogeographic information on the evolution of the late Mesozoic–early Cenozoic Neo-Tethyan subduction zone along the southern Asian margin. This paper presents detailed stratigraphic, sedimentologic, petrographic, detrital-zircon geochronologic and Hf isotopic data from the Luogangcuo Formation exposed as part of the Xiukang Mélange in south Tibet. The Luogangcuo Formation was deposited (ca. 88–81 Ma) in a trench environment on a deep-sea fan fed from the Lhasa block through a submarine canyon. Dominant chert and subordinate sandstone and limestone clasts in conglomerate beds indicate recycling from the Neo-Tethyan subduction complex during repeated episodes of gravitational failure. The interbedded turbiditic sandstones were sourced directly from the Gangdese magmatic arc and central Lhasa terrane. Detrital volumes from the active Asian margin increased markedly at ca. 88 Ma as a result of uplift of central Lhasa, leading to deltaic progradation, filling of the Xigaze forearc basin, and bypassing of sediments funneled via canyons across the subduction complex to reach the Luogangcuo trench basin at abyssal depths.

Geochronological and petrogenetic constraints on the regional tectonic evolution of the Guanghua Group in northeastern Jiao-Liao-Ji Belt, China

A sequence of Paleoproterozoic meta-supracrustal rocks, known as the “Guanghua Group”, is exposed to the north of Tonghua City, Jilin Province, China. The composition and ages of formation and metamorphism of the protolith, and the tectonic petrogenesis of the Guanghua Group are poorly understood. Comprehending these rocks are important in constraining the formation and evolutionary history of the northern segment of the Paleoproterozoic Jiao-Liao-Ji Belt. We have studied the petrology and geochemistry of these meta-supracrustal rocks, revealing that the protoliths can be sub-divided into two groups: metavolcanic and metasedimentary rocks. The metavolcanic rocks are mainly amphibolite, biotite-bearing plagiogneiss, and minor biotite leptynites, whose protoliths were basaltic andesite, andesite, and minor rhyolite with both calc-alkaline and tholeiite affinities. Petrogenetic studies indicate that the intermediate-basic rocks were derived from a depleted lithospheric mantle wedge that was metasomatized by slab-derived fluids or melts. The metasedimentary rocks consist of biotite–quartz schist and staurolite-bearing garnet-muscovite schist, together with minor biotite-bearing plagiogneiss and biotite leptynites, with protoliths mainly comprising mudstone with subordinate sandstone and greywacke. The structure, composition, and U–Pb ages of zircon indicate that the protoliths of the metavolcanic and metasedimentary rocks formed at ca. 2.18Ga and 2.03Ga, respectively, and were modified by two stages of metamorphism at ca. 1.90 and 1.85Ga. The protoliths of the metasedimentary rocks were derived mainly from mid-Paleoproterozoic granites, with minor contributions from coeval metabasic rocks and Archean granitic rocks. Based on these findings and existing regional data, we suggest that: (i) the Paleoproterozoic supracrustal rocks of the Guanghua Group are comparable with the Laoling Group in their age of formation, composition, and petrogenesis, and were the products of the same geological event; meaning that rocks of the Guanghua Group should be considered as part of the Laoling Group; (ii) the metabasic and metasedimentary rocks formed in a back-arc basin setting; and (iii) the pre-mid-Paleoproterozoic formation and evolution of the northern segment of the Jiao-Liao-Ji Belt were related to arc–continent collision.

Chapter 1: Integrated, High-Resolution Allostratigraphic, Biostratigraphic and Carbon-Isotope Correlation of Coniacian Strata (Upper Cretaceous), Western Alberta and Northern Montana

ABSTRACT Lower to upper Coniacian rocks in the foredeep of the Western Canada Foreland Basin are dominated by mudstone and subordinate sandstone and were deposited on a very low-gradient, storm-dominated marine ramp. The rocks are organized into several scales of upward-coarsening, upward-shoaling succession, bounded by marine flooding surfaces. Abundant, publicly available wireline log data permit flooding surfaces to be traced for hundreds of kilometers in subsurface. Flooding surfaces can be considered to approximate time surfaces that allow the subsidence history of the basin to be reconstructed. Particularly widely traceable flooding surfaces were chosen, on pragmatic grounds, as the boundaries of 24 informal allomembers, most of which can be mapped along the foredeep for >750 km. Allomembers can also be traced westward into the fold-and-thrust belt to outcrop in the Rocky Mountain Foothills. Some flooding surfaces are mantled with intra- or extrabasinal pebbles that imply a phase of shallowing and, ...

Carboniferous History from Coarse Detritus of the Appalachian-Cahaba System: Conglomerate Clasts from the Upper Pottsville Formation, Cahaba Synclinorium, Alabama

AbstractMeasures of abundance of extraformational conglomerates and clast composition, taken together, can be used to unravel the unroofing history of an orogenic belt. This study develops a new approach in quantifying coarse detritus as a provenance indicator. Known as the “conglomerate measures” in the Cahaba synclinorium, the uppermost Pottsville Formation consists of conglomerates and subordinate sandstone, shale, and coal. These siliciclastic sediments were deposited during the Alleghenian orogeny primarily in braidplain-anastomosis environments in Alabama and Mississippi. The abundance of extraformational conglomerate suggests unroofing of active thrust sheets in the Alleghenian foreland basin, which can be used in deciphering the source of Alleghenian sediments in the southeastern United States. Conglomerate clasts in the upper Pottsville Formation consist mainly of sedimentary lithics (chert, sandstone, and mudstone) and metamorphic lithics (phyllite, schist, and quartzite), with minor volcanic an...

Triassic to Early Jurassic climatic trends recorded in the Jameson Land Basin, East Greenland: clay mineralogy, petrography and heavy mineralogy

AbstractDuring the Early Triassic the Jameson Land Basin (Central East Greenland) was located around 30° N, in the Northern arid belt, but by the Early Jurassic was positioned at a latitude of approximately 50° N. This study examines the record of this transition through a largely continental succession using clay mineralogy, sedimentology, petrography and heavy mineralogy. The Jameson Land Basin is aligned north–south and is 280 km long and 80 km wide. Following an Early Triassic marine phase the basin was filled by predominantly continental sediments. The Early‐to‐Late Triassic succession comprises coarse alluvial clastics (Pingo Dal Formation) overlain by a succession of fine‐grained evaporite‐rich playa/lacustrine sediments (Gipsdalen Formation), indicative of arid climatic conditions. The overlying buff, dolomitic and then red lacustrine mudstones with subordinate sandstones (Fleming Fjord Formation) record reduced aridity. The uppermost Triassic grades into dark organic‐rich, and in places coaly, mudstones and buff coarse‐grained sandstones of lacustrine origin that belong to the Kap Stewart Group, which spans the Triassic–Jurassic boundary, and appear to record more humid climatic conditions. Clay mineralogy analyses highlight significant variations in the kaolinite/illite ratio, from both mudstone and sandstone samples, through the Triassic and into the earliest Jurassic. Complementary heavy mineral analyses demonstrate that the variations recognised in clay mineralogy and sandstone maturity through the Triassic–Early Jurassic succession are not a product of major provenance change or the effect of significant diagenetic alteration. The observed variations are consistent with sedimentological evidence for a long‐term trend towards more humid conditions through the Late Triassic to Early Jurassic, and the suggestion of a significant pluvial episode in the mid‐Carnian.

Mid-Eocene alluvial-lacustrine succession at Gebel El-Goza El-Hamra (Shabrawet area, NE Eastern Desert, Egypt): Facies analysis, sequence stratigraphy and paleoclimatic implications

This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic characteristics of the Mid-Eocene (Bartonian) continental succession exposed at Gebel El-Goza El-Hamra (Shabrawet Area, NE Eastern Desert, Egypt). The studied succession consists of siliciclastic rocks followed upward by carbonate rocks. Detailed field observation and petrographic investigation indicate accumulation in floodplain-dominated alluvial and shallow lacustrine systems. The floodplain-dominated alluvial facies (45m thick) is composed mainly of carbonate nodules-bearing, mottled mudrock with subordinate sandstone and conglomerate beds. The conglomerate and pebbly sandstone bodies interpreted as ephemeral braided channel deposits. The massive, laminated, planner cross-bedded, fine- to medium-grained sandstone bodies interlayered within mudstone reflect sheet flood deposits. The mudrocks associated with paleosols represent distal floodplain deposits. The shallow lacustrine facies (15m thick) is made up of an alternation of marlstone, micritic limestone, dolostone and mudrock beds with charophytes and small gastropods. Both the alluvial and lacustrine facies show evidence of macro-and micro-pedogenic features. Pollen assemblages, stable δ18O and δ13C isotopes, and paleopedogenic features reflect prevalence of arid to semi-arid climatic conditions during the Bartonian.The sequence stratigraphic framework shows an overall fining-upward depositional sequence, consisting of Low- and High-accommodation Systems Tracts (LAST, HAST), and is bounded by two sequence boundaries (SB-1, SB-2). Conglomerate and pebbly sandstone deposits (braided channel and sheet flood deposits) of the lower part of the alluvial facies reflect a LAST. Mudrock and silty claystone facies (distal floodplain deposits) of the upper part of alluvial facies and its overlying lacustrine facies correspond to a HAST. The LAST, HAST and SB were formed during different accommodation-to-sediment supply (A/S) ratio phases. The variation in A/S ratios was mainly controlled by sea-level change as well as by local tectonic subsidence and uplift of the basin coincident with the reactivation of the Syrian Arc System during the Bartonian.

Age, internal stratigraphic architecture and structural style of the Oligocene–Miocene Numidian Formation of northern Tunisia

The stratigraphy of the Numidian Formation of northern Tunisia and its internal organization are updated. Planktonic foraminifera point to a mainly Oligocene–Early Miocene age of this formation in the majority of the sections studied. Some key lithological horizons are recognized within the early Miocene succession, allowing lateral correlation between the outcrops of the Mogod and Kroumirie mountains. These include: (1) a conglomeratic interval, up to 1–2 m thick and rich in reworked glauconitic boulders, limestone fragments of the Tellian (Eocene) and pectinid bivalves; and (2) a relatively continuous glauconitic level. In the new stratigraphic scheme, the Zouza, Ben Metir and Sejnene sections represent the entire Numidian Formation. A lower unit (200–700 m thick), highly pelitic with subordinate sandstone beds was distinguished, overlain by an upper unit which is sandier, especially in its uppermost part (1,000–1,500 m thick). In the present study, these have been stratigraphically dated as Oligocene–Early Miocene p.p. (Rupelian–Chattian; P19–P21 zones) to Aquitanian (N4 Zone) and Miocene (Aquitanian–early Burdigalian; N4–N5 zones), respectively. In the areas studied, the sandy succession assigned to the Kroumirie Member begins with a sandstone unit with an erosional base or a major discontinuity, locally marked by conglomerates made up of various reworked components. It rests generally on a thick shale unit that characterises the upper part of the Zouza Member. The thinner, uppermost succession of the Numidian Formation represents the Babouch Member, dated as Burdigalian (N6–N7 zones). Within the framework of the new proposal, the total stratigraphic thickness of the Numidian Formation in northern Tunisia does not exceed 2,200–2,600 m. Internally, the Numidian Formation is transected by the Intra-Numidian Thrust and back-thrust faults, associated with faulted folds that are recognized in outcrop on different scales and in seismic sections. Along these thrust and/or reverse faults, the middle to upper Eocene deposits have undergone uplift and are exposed at the surface (e.g., Dowar Larmel in Meloula-Tabarka, Gaâret Sejnene and Sidi M’chreg sections).

Storm‐dominated shelf‐edge delta successions in a high accommodation setting: The palaeo‐Orinoco Delta (Mayaro Formation), Columbus Basin, South‐East Trinidad

AbstractPliocene age deposits of the palaeo‐Orinoco Delta are evaluated in the Mayaro Formation, which crops out along the western margin of the Columbus Basin in south‐east Trinidad. This sandstone‐dominated interval records the diachronous, basinwards migration of the shelf edge of the palaeo‐Orinoco Delta, as it prograded eastwards during the Pliocene–Pleistocene (ca 3·5 Ma). The basin setting was characterized by exceptionally high rates of growth‐fault controlled sediment supply and accommodation space creation resulting in a gross basin‐fill of around 12 km, with some of the highest subsidence rates in the world (ca 5 to 10 m ka−1). This analysis demonstrates that the Mayaro Formation was deposited within large and mainly wave‐influenced shelf‐edge deltas. These are manifested as multiple stacks of coarsening upward parasequences at scales ranging from tens to hundreds of metres in thickness, which are dominated by storm‐influenced and wave‐influenced proximal delta‐front sandstones with extensive, amalgamated swaley and hummocky cross‐stratification. These proximal delta‐front successions pass gradationally downwards into 10s to 100 m thick distal delta front to mud‐dominated upper slope deposits characterized by a wide variety of sedimentary processes, including distal river flood and storm‐related currents, slumps and other gravity flows. Isolated and subordinate sandstone bodies occur as gully fills, while extensive soft sediment deformation attests to the high sedimentation rates along a slope within a tectonically active basin. The vertical stratigraphic organization of the facies associations, together with the often cryptic nature of parasequence stacking patterns and sequence stratigraphic surfaces, are the combined product of the rapid rates of accommodation space creation, high rates of sediment supply and glacio‐eustasy in the 40 to 100 Ka Milankovitch frequency range. The stratigraphic framework described herein contrasts strikingly with that described from passive continental margins, but compares favourably to other tectonically active, deltaic settings (for example, the Baram Delta Province of north‐west Borneo).

Nannostratigraphy, nannofossil events, and paleoclimate fluctuations in the lower boundary of Kalat formation in East Kopet Dagh (NE Iran)

The biostratigraphy and the response of calcareous nannofossils to the End Cretaceous warming are investigated in the lower boundary of Kalat formation through the record of species richness, diversity, distribution patterns, and statistical treatments. The Kalat formation comprised of coarse-grained detritus limestone with subordinate sandstone intercalations. In the studied sections, the number of ten samples were taken and prepared with smear slide. In Dobaradar, section 22 species; in Kalat, section 25 species; and in Chahchaheh, section 32 species have been determined. Based on nannoplanktons and as a result of biostratigraphic studies, the nannofossil standard zones (CC25–CC26) were identified in all of sections. According to these zones in all of sections, the age of the studied thickness is Late Maastrichtian–Late Late Maastrichtian. In these sections, the presence of Micula murus at the end of Neyzar formation and the presence of this species at the lower part of Kalat formation indicate that the investigated boundary is Late Maastrichtian in age. The paleoecological results point to warm climate. The presence of warm water indicators (M. murus and Micula prinsii) and the absence of cool water indicators (Ahmuellerella octoradiata, Kamptnerius magnificus, and Nephrolithus frequens) suggest warm surface water conditions in these areas. In the lower boundary of Kalat formation, base on Lithraphidites spp. and Watznaueria barnesae, lowered fertility condition with low productivity at the end of the Maastrichtian were suggested, and the studied area was deposited in shallow marine environment in relatively low latitude.

Investigation of the Boundary between Abderaz and Kalat Formations Based on Calcareous Nannofossils in West Kopet-Dagh (NE IRAN)

The biostratigraphy of calcareous nannofossils of the Cretaceous is investigated in the boundary between Abderaz and Kalat Formations through the record of species richness, diversity and distribution patterns in the west Kopet-Dagh region. The Kalat Formation comprising of coarse-grained detritus limestone with subordinate sandstone intercalations and the Abderaz Formation mainly consists of limestone, Shale and Limy marl. Nannofossils of this boundary in each of studied sections are listed and figured. 21 species in Ghalehzoo section, 29 species in Sheikh section and 19 species in Jozak section have been determined. Boistratigraphy based on calcareous nannofossil allow the identification of nannofossil standard zones CC21 and CC26 in all of sections, According to these zones in all of sections, the age of the studied thickness is Early Late Campanian-Late Late Maastrichtian in these sections.

A new Oligo-Miocene Mammal-Bearing site from a sedimentary intercalation in the trap basalts of Central Eritrea

We report the findings of two proboscideans from a sedimentary intercalation within the Central Eritrea Tertiary Trap basalt succession. These intertrappean sediments can be traced continuously between Tera’emni and Adi Quala in the Mendefera region, and are interbedded between the underlying Asmara/Aiba-Alaji basalts and the overlying Adi Ugri basalt. This intercalation is up to 50 m thick and consists of a predominant intensely pedogenized red, green and gray mudstone and siltstone with subordinate channelized pebbly sandstone. The newly discovered mammal remains come from the coarse-grained deposits in the Mai Gobro section. Available radiometric datings of the host volcanic rocks constrain the age of the fossils between 24.6 and 22.1 Ma, i.e. at the transition between the Oligocene and the Miocene. The fossil vertebrate remains from Mai Gobro represent two proboscidean families, Deinotheriidae and Gomphotheriidae. The morphological grade of the two Mai Gobro proboscideans would suggest a more derived stage than that of representatives of the same families known from other Oligocene African sited (e.g. Chilga, Ethiopia), suggesting a possible Oligo-Miocene age.

Chapter 27 The glaciogenic Bol'shoy Patom Formation, Lena River, central Siberia

Abstract The Bol'shoy Patom Formation (Fm.) is part of the Upper Precambrian Patom Supergroup, which comprises a siliciclastic and carbonate succession divided into (from base to top) the Ballaganakh, Dal'nyaya Tayga and Zhuya Groups (Gr.). The supergroup was deposited within the bay-like passive margins of the Siberian craton. The Bol'shoy Patom Fm. is the lower unit of the Dal'nyaya Tayga Gr. Massive and stratified diamictites with subordinate sandstones, mudstones, siltstones, conglomerates and conglo-breccias form the Bol'shoy Patom Fm. New biostratigraphic (microfossils of Pertatataka type, Ediacaran fossils) and chemostratigraphic data ( 87 Sr/ 86 Sr, δ 13 C) point to a Vendian (Late Cryogenian and Ediacaran) age for the Dal'nyaya Tayga and Zhuya Groups. Unsorted diamictite matrix, a very wide range of size and roundness of dispersed erratic clasts, the presence of glacial grooves on boulders, dropstones and till pellets in laminated mudstones and siltstones are all evidence for intense ice rafting and ice-shelf sedimentation in the northeastern part of the Patom basin during deposition of the Bol'shoy Patom Fm.