Calcareous Sandstone Research Articles

Structural engineering and geology applied to the static problems of the Etruscan “Tomba dell’Orco” (Tarquinia, Central Italy)

Abstract The Etruscan Tomba dell’Orco was discovered in 1868. However, soon after discovery, part of its ceiling collapsed. An investigation was thus conducted with a view to assessing its safety conditions and permitting visitors’ access. Petrographic and physico-mechanical features of the local weak sandstones and mechanically more resistant calcareous sandstones “macco” were determined. Field mapping, drill-holes and geophysical prospecting helped reconstruct the stratigraphy of the volume where the tomb was excavated. The stability of the tomb basement is given by a thick macco layer. A few dm macco layer was identified above the ceiling. A model was then prepared with the Plaxis 2D V8.6 software. The safety coefficients calculated along two cross-sections of the tomb indicated that the margins for the tomb stability are reasonable.

The geology of the Corallian ridge (Upper Jurassic) between Gilling East and North Grimston, Howardian Hills, North Yorkshire

SUMMARY The northern edge of the Howardian Hills, running for 25 km from Gilling East to North Grimston, North Yorkshire, comprises a near-continuous ridge of Oxfordian limestones and calcareous sandstones, here termed the Corallian ridge. These strata rise gently from the Vale of Pickering up to a steep scarp face which overlooks underlying Oxford Clay to the south. The limestones and sandstones belong to the Corallian Group, which in the Howardian Hills includes the Lower Calcareous Grit, Coralline Oolite and Upper Calcareous Grit formations. The Lower Calcareous Grit Formation comprises a succession of fine-grained, calcareous or spicular, siliceous sandstones, and forms a prominent feature. The Coralline Oolite Formation underlies gently rolling hills leading down to the Vale of Pickering, and is composed of a series of oolitic and fine-grained limestones with subordinate calcareous sandstones and sandy limestones. The Upper Calcareous Grit is represented here largely by calcareous strata, the North Grimston Cementstone, and is only exposed in faulted inliers to the south. The sequence was laid down in a tectonically active area, and movement of faults during deposition of the strata in the Mid Oxfordian led to marked changes in thickness and lithology across the area. Complications caused by these penecontemporaneous movements have meant that, though the outcrop has been investigated by numerous geologists over the last 150 years, the exact sequence of strata present and its correlation with the Corallian sequence on the north side of the Vale of Pickering have long presented problems. Much that was uncertain about the geology of the area has been resolved through detailed mapping of the area west of Malton.

Palaeoenvironments and Quaternary foraminifera in the Elx coastal lagoon (Alicante, Spain)

During the Quaternary, different palaeoenvironments characterised the Elx coastal lagoon (‘Albufera d'Elx’) located in the easternmost sector of the Betic Ranges (SE Spain). Micropalaeontological and sedimentological analysis of three drilled cores allowed characterization of different sedimentary environments, including alluvial, restricted lagoon, lagoon with marine connection, shoreface, foreshore, backshore, swamp, washover fan, and back-barrier flat. A model of the evolution of this region during Marine Isotope Stage (MIS) 7 is proposed, based on chronostratigraphic correlation between the cores. Up to six transgressive episodes can be recognised, mostly represented by calcareous sandstones deposited in different sub-environments of the littoral zone. Holocene shoreface beds comprise unconsolidated sands. The occurrence of planktonic foraminifera at depths than 18 m indicates the existence of Pliocene marine beds beneath the Quaternary deposits. The data demonstrate that coastal lagoon systems have existed in this area of SE Spain since to at least the Middle Pleistocene.

A nautiloid from Middle Eocene beds at Grdoselo in Istria, Croatia

Treated are remains of a stone core of phragmocone of an Eocene nautiloid of species Aturia cf. ziczac (Sowerby, 1812) from Grdoselo in central Istria, western Croatia. Remains of Aturia occur in a calcareous sandstone horizon of the Pazin flysch basin megasequence. In these beds occur abundant sea urchins of genera Ecinolampas and Cyclaster, and much less frequent specimens of genera Macropneustes and Conoclypus. Of mollusks are normally found only their stone cores. The relatively modest diversity of sea urchins, high numbers of individual species and total absence of corals might indicate that organisms of this locality most probably remained near their original living environment, without a sign of allochthonicity.

A NEW WIDE‐GAUGE SAUROPOD TRACK SITE FROM THE LATE CRETACEOUS OF MENDOZA, NEUQUÉN BASIN, ARGENTINA

Abstract: Agua del Choique is a new Late Cretaceous sauropod track site from Mendoza Province, Neuquén Basin, Argentina. It is situated in the Loncoche Formation, late Campanian – early Maastrichthian in age, and is one of the youngest sauropod tracks site recorded in the world. Agua del Choique represents a lake setting and river‐dominated delta deposits, and comprises at least 160 well‐preserved tracks, located on a calcareous sandstone bed. A new ichnotaxon, Titanopodus mendozensis ichnogen. et ichnosp. nov., is erected for the footprints of this track site. Titanopodus mendozensis exhibits the following association of features: (1) wide‐gauge trackway (manus and pes trackway ratios of 18–22 and 26–31 per cent respectively), (2) pronounced heteropody (manus‐pes area ratio of 1:3), (3) outer limits of trackway defined, in some cases, by the manus tracks, and (4) manus impression with an asymmetrical crescent contour and acuminate external border. Titanopodus mendozensis is an excellent case study of the wide‐gauge style of locomotion produced by Late Cretaceous derived titanosaurs that have no impression of manual phalanges. These features, and the fossil record from the Loncoche Formation, suggest that the trackmakers were, probably, middle size saltasaurine or aeolosaurine titanosaurs (14–16 m long).

Sedimentology, sequence stratigraphy and syn-rift model of younger part of Washtawa Formation and early part of Kanthkot Formation, Wagad, Kachchh basin, Gujarat

The 600 m thick prograding sedimentary succession of Wagad ranging in age from Callovian to Early Kimmeridgian has been divided into three formations namely, Washtawa, Kanthkot and Gamdau. Present study is confined to younger part of the Washtawa Formation and early part of the Kanthkot Formation exposed around Kanthkot, Washtawa, Chitrod and Rapar. The depositional architecture and sedimentation processes of these deposits have been studied applying sequence stratigraphic context. Facies studies have led to identification of five upward stacking facies associations (A, B, C, D, and E) which reflect that deposition was controlled by one single transgressive - regressive cycle. The transgressive deposit is characterized by fining and thinning upward succession of facies consisting of two facies associations: (1) Association A: medium - to coarse-grained calcareous sandstone - mudrocks alternations (2) Association B: fine-grained calcareous sandstone - mudrocks alternations. The top of this association marks maximum flooding surface as identified by bioturbational fabrics and abundance of deep marine fauna (ammonites). Association A is interpreted as high energy transgressive deposit deposited during relative sea level rise. Whereas, facies association B indicates its deposition in low energy marine environment deposited during stand-still period with low supply of sediments. Regressive sedimentary package has been divided into three facies associations consisting of: (1) Association C: gypsiferous mudstone-siltstone/fine sandstone (2) Association D: laminated, medium-grained sandstone - siltstone (3) Association E: well laminated (coarse and fine mode) sandstone interbedded with coarse grained sandstone with trough cross stratification. Regressive succession of facies association C, D and E is interpreted as wave dominated shoreface, foreshore to backshore and dune environment respectively. Sequence stratigraphic concepts have been applied to subdivide these deposits into two genetic sequences: (i) the lower carbonate dominated (25 m) transgressive deposits (TST) include facies association A and B and the upper thick (75m) regressive deposits (HST) include facies association C, D and E. The two sequences are separated by maximum flooding surface (MFS) identified by sudden shift in facies association from B to C. The transgressive facies association A and B represent the sediments deposited during the syn-rift climax followed by regressive sediments comprising association C, D and E deposited during late syn-rift stage.

The Albian–Cenomanian boundary at Eggardon Hill, Dorset (England): an anomaly resolved?

Re-examination of the classic exposures of the Eggardon Grit (topmost Upper Greensand Formation) at Eggardon Hill, Dorset shows that the upper part of this unit has a more complex stratigraphy than has been previously recognised. The Eggardon Grit Member, as described herein, is capped by a hardground and associated conglomerate, and is entirely of Late Albian age. The hardground is probably the lateral equivalent of the Small Cove Hardground, which marks the top of the Upper Greensand succession in southeast Devon. The conglomerate is overlain by a thin sandy limestone containing Early Cenomanian ammonites. This limestone is almost certainly the horizon of the Early Cenomanian ammonite fauna that has previously been attributed to the top of the Eggardon Grit. The limestone is regarded as a thin lateral equivalent of the Beer Head Limestone Formation (formerly Cenomanian Limestone) exposed on the southeast Devon coast. The fauna of the limestone at Eggardon suggests that it is probably the age equivalent to the two lowest subdivisions of the Beer Head Limestone in southeast Devon, with a remanié fauna of the Pounds Pool Sandy Limestone Member combined with indigenous macrofossils of the Hooken Nodular Limestone Member. The next highest subdivision of the Beer Head Limestone in southeast Devon (Little Beach Bioclastic Limestone Member), equates with the ammonite-rich phosphatic conglomerate of the ‘Chalk Basement Bed’, which caps the Beer Head Limestone at Eggardon, and which was previously regarded as the base of the Chalk Group on Eggardon Hill.Petrographic analysis of the Eggardon Grit shows that lithologically it should more correctly be described as a sandy limestone rather than sandstone. The original stratigraphical definition of the unit should probably be modified to exclude the softer, nodular calcareous sandstones that have traditionally been included in the lower part of the member.Without the apparently clear evidence of unbroken sedimentation across the Albian–Cenomanian boundary, suggested by the previous interpretation of the Eggardon succession, it is harder to argue for this being a prevalent feature of Upper Greensand stratigraphy in southwest England. Correlation of the Eggardon succession with successions in Dorset and southeast Devon reveals a widespread regional break in sedimentation at the Albian–Cenomanian boundary. The sand-rich facies above this unconformity represent the true base of the Chalk Group, rather than the ‘Chalk Basement Bed’ of previous interpretations.Selected elements of regionally important Upper Greensand ammonite faunas previously reported from Shapwick Quarry, near Lyme Regis, and Babcombe Copse, near Newton Abbot, are newly figured herein.

Late Jurassic (Kimmeridgian) larger benthic Foraminifera from Santiago Coatepec, SE Puebla, Mexico

A micropaleontologic study was carried out from samples collected along a section that crops out in the Santiago Coatepec Stream, located in the southeast of the state of Puebla, Mexico. The sedimentary sequence begins with a reddish conglomerate. Above, thick and thin layers of grey-greenish sandstones that continue in fine-grained, calcareous sandstones, and, finally, in limestones. The reddish conglomerate may represent a continental environment, and the marine transgression began with the sandstone deposit that contains a marine association of Invertebrates such as Trigonids ( Myophorella sp.), and other Mollusks such as Trichites sp., Ostreids and Gastropods, Echinoderms, and Sponges as Cladocoropsis mirabilis. This sequence also provides a rich assemblage of larger Foraminifera as well as Algae, which is reported for the first time in this site. The larger agglutinated Foraminiferal assemblage is composed of Alveosepta jaccardi, Pseudocyclammina lituus, Everticyclammina virguliana, Rectocyclammina chouberti, Choffatella cf. Ch. tingitana, Mesoendothyra croatica, Nautiloculina oolithica, Freixialina planispiralis, Audienusina fourcadei, Placopsilina sp., Pseudocyclammina sp., Meandrospira sp. and Lenticulina sp. All those taxa were adapted to special paleoecological conditions, such as a continuous terrigenous input. The Algae are Marinella lugeoni, Pseudoepimastopora jurassica, Permocalculus sp., and Halimeda sp. The stratigraphic distribution of the larger benthic Foraminifera allow us to propose a Kimmeridgian age for the studied sequence. The opening of the Atlantic Ocean permitted the colonization of its margins by the larger Foraminifera during this time. The data provided by the larger Foraminifera, the Algae, and the lithology may suggest an internal platform environment of warm shallow water. This foraminiferal association is constituted by cosmopolitan species which are frequent in the Tethyan Realm.

High energy transgressive deposits from the Late Jurassic of Wagad, Eastern Kachchh, India

The whole sedimentary succession (ca 600 m thick) of Wagad area ranging in age from Callovian to Early Kimmeridgian has been divided in to three Formations namely Washtawa, Kanthkot and Gamdau in ascending order. Prograding Kanthkot Formation was frequently interrupted by transgressions. Field and petrographic investigations revealed that the Kanthkot Formation represents three fossiliferous marker beds corresponding to Transgressive sequence I; Transgressive sequence II and Transgressive sequence III. These transgressive sequences are composed of two lithounits: medium to coarse grained/gritty, graded to massive, sheetlike, fossiliferous calcareous sandstone (storm lag unit I) and fossiliferous mudrocks (swell lag unit II). The thickness of the unit I varies from 5 to 75 cm and contains mostly convexly oriented shell fragments and whole shell of Pelecypods, Cephalopods and Brachiopods. Unit II (5–15 cm) is distinguished by sheetlike, massive or laminated, yellowish colour, soft fossiliferous mudrocks. This unit is intercalated with moderately bioturbated sandy siltstone. Unit I is dominant over Unit II in the sequences. Study suggests that the transgressive units were deposited close to wave base by high energy storm flows followed by low energy marine swells during transgression. The intense storms played a major role in the distribution of siliciclastics and nonclastic materials. Storms are evidenced by the occurrence of two distinctly different types of units (storm lags and swell lags). High energy levels are characterized by sand dominated sequence, abundance of reworked sediment particles, high proportion broken shells with convex up orientation and erosional and sharp nature of basal contacts of units together with well preserved bioclasts. Sudden short term changes from high to low energy during transgression are explained by the occurrence of medium to coarse grained siliciclastics interbedded with moderately bioturbated mudrocks. Moderately bedded individual strata, high content of coarse clastics along with polished granule size quartz and abundance of comminuted shells indicate a significant change in depositional setting, possibly closure approach of the source of terrigenous fraction or source uplift. Synrift sedimentation in the present study is documented by an abundance of coarse clastics and an over all aggradational nature of transgressive sequences.

Mineralogy and organic petrology of oil shales in the Sangkarewang Formation, Ombilin Basin, West Sumatra, Indonesia

The Ombilin Basin is filled by late Eocene to early Oligocene marginal fan deposits (Brani Formation) and lacustrine shales (Sangkarewang Formation), unconformably overlain by a late Oligocene to early Miocene fluvial sequence (Sawahlunto and Sawahtambang Formations) and capped by an early to mid-Miocene marine sequence (Ombilin Formation). Significant oil shale deposits occur in the Sangkarewang Formation, intercalated with thin laminated greenish-grey calcareous sandstones. X-ray diffraction shows that the sediments consist mainly of quartz, feldspar, carbonates and a range of clay minerals, together in some cases with minor proportions of sulphides, evaporites and zeolites. Feldspar and non-kaolinite clay minerals decrease up the sequence, relative to kaolinite, suggesting a changing sediment source as the basin was filled. Calcite, thought to be mainly of authigenic origin, is also more abundant in the middle and upper parts of the sequence. The organic matter in the oil shales of the sequence is dominated by liptinite macerals, particularly alginite (mainly lamalginite) and sporinite. Cutinite also occurs in some samples, along with resinite and traces of bituminite. The dominance of lamalginite in the liptinite components suggests that the material can be described as a lamosite. Samples from the Sangkarewang Formation have vitrinite reflectance values ranging between 0.37% and 0.55%. These are markedly lower than the vitrinite reflectance for coal from the overlying Sawahlunto Formation (0.68%), possibly due to suppression associated with the abundant liptinite in the oil shales. Fischer assay data on outcrop samples indicate that the oil yield is related to the organic carbon content. Correlations with XRD data show that, with one exception, the oil yield and organic carbon can also be correlated directly to the abundance of carbonate (calcite) and inversely to the abundance of quartz plus feldspar. This suggests that the abundance of algal material in the lake sediments was preferentially associated with carbonate deposition. High yields of oil are noted in some samples, as a percentage of the organic carbon content. This may indicate that partial generation of hydrocarbons from the material has already taken place, in association with thermal maturation of the Sangkarewang succession.

The geology of the Neoproterozoic Swakop-Otavi transition zone in the Outjo District, northern Damara Orogen, Namibia

Research Article| March 01, 2008 The geology of the Neoproterozoic Swakop-Otavi transition zone in the Outjo District, northern Damara Orogen, Namibia Tom N. Clifford Tom N. Clifford School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa, e-mail: cliffordt@geosciences.wits.ac.za Search for other works by this author on: GSW Google Scholar Author and Article Information Tom N. Clifford School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa, e-mail: cliffordt@geosciences.wits.ac.za Publisher: Geological Society of South Africa First Online: 09 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2008, The Clay Minerals Society South African Journal of Geology (2008) 111 (1): 117–140. https://doi.org/10.2113/gssajg.111.1.117 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Tom N. Clifford; The geology of the Neoproterozoic Swakop-Otavi transition zone in the Outjo District, northern Damara Orogen, Namibia. South African Journal of Geology 2008;; 111 (1): 117–140. doi: https://doi.org/10.2113/gssajg.111.1.117 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract The Neoproterozoic succession in the Outjo District of northern Namibia is a mainly sedimentary sequence that was deposited in the time-interval of approximately 800 to 600 Ma ago and was deformed and suffered mild greenschist facies regional metamorphism during Damaran times ca. 550 Ma ago. The map area occupies the lithofacies and tectonic transition from the highly deformed more eugeoclinal Swakop Group sequence to the south to the coeval, uniformly southward-dipping, miogeoclinal Otavi Group of the Fransfontein Ridge to the north. The oldest unit is a largely sandstone and biotite-muscovite phyllite succession tentatively equated with the volcanogenic Naauwpoort Formation (Nosib Group) that pre-dates the Swakop Group in the Summas Mountains to the southwest. The overlying Saturn Formation comprises two distinct but coeval lateral carbonate facies: a 300 m thick sequence of bedded dolomite with a 20 m thick median limestone; and massive biohermal dolomite of undetermined thickness. The conformably overlying Landeck Formation comprises a lower succession of interbedded sandstone, phyllite and local carbonate rocks, a distinctive middle iron formation marker horizon with rather rare overlying dolomite, followed by a siliciclastic-carbonate sequence. The combined succession is up to 450 m in thickness, and glacial diamictite is recorded at 30+ localities sited below, within and above the iron formation. However, in the more distal parts of the Landeck Formation in the Saturn Dome, glacial diamictictite has not been identified, the iron formation is overlain by a distinctive dolomite, and the uppermost 200 to 300 m of the Landeck Formation is characterized by four horizons of siliciclastic sediments with three intervening horizons of blue limestone that reflect the concordant transition to the overlying Bergfriede Formation. New chemical analyses are reported for graphitic dolomite, magnetite-calcite schist, iron formation, ferruginous limestone, dolomitic sandstone and biotite-muscovite phyllite of the Landeck Formation. The Bergfriede Formation consists almost entirely of limestone and dolomite and is characterized by major changes in facies and thickness, and five lateral facies end-members are recognized: I. Hankow Facies, a five-fold succession of limestone, dolomite and calcarenite up to 500 m thick; II. Tsuwandes-Zuwitsaub Facies, a three-fold sequence of limestone-dolomite-limestone >300 m thick; III. Uranus Facies, entirely dolomite generally 150 m thick; IV. Belina-Sophienhof Facies, a limestone-dolomite sequence, with a distinctive arenaceous limestone at the top, 100 to 400 m thick; and V. Mooilagte-Mooihoek Facies, largely dolomite-chert-limestone ≥1500 m thick, that is transitional to the dolomite-dominated upper Otavi Tsumeb Subgroup of the Fransfontein Ridge to the north. The overlying Okaua Formation is composed of a >3000 m thick sequence of muscovite-chlorite phyllite and calcareous sandstone that occupy, inter alia, the troughs of the regional Ugab and Uranus-Neuland Synclines; it is most likely correlative with the Mulden Group of the Otavi Mountainland. The Damaran regional structure of area is characterized by: D1 an early phase of southward-directed gravity nappes; D2 the regionally dominant northeast-southwest to east-west trending tight compressional upright or northward-verging folds, and local thrusts; and D3 late strike-slip faulting. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Lizard eggs from Upper Cretaceous Lameta Formation of Jabalpur, central India, with interpretation of depositional environments of the nest-bearing horizon

A nest with eleven relatively large-sized eggs of lacertilian affinity has been recovered from the Lower Limestone horizon exposed at the type section of the Lameta Formation, Jabalpur (Madhya Pradesh, India). Morpho-structurally, the eggs probably represent a new family as they share common features with the eggs of the living varanid lizard Varanus indicus and a shell microstructure described for geckonids. The close association of a lizard nest and titanosaurid (Sauropoda) eggs raises interesting questions regarding the egg-laying strategies of these differently-sized reptiles. Sedimentological data suggest that the Lower Limestone of Lameta Ghat was deposited in an alkaline lagoon that was connected to a marine embayment by channels. The massive limestone, sandy limestone, and calcareous sandstone lithofacies forming coarsening upward sequence represents sedimentation from deeper to marginal parts of the lagoon that were densely vegetated. Pre-burial meteoric diagenesis of the sediments indicates humid climate. Such conditions might have provided a suitable habitat supporting a large variety of terrestrial life.

The Pliocene Pleshet Formation near Khassif, southern Israel, and its shallow marine ostracode fauna

Neogene sediments, several hundred meters thick, are exposed in the Gaza - Be’er Sheva Canyon, southern Israel. Isolated Khassif sections at the edge of the canyon south of Ofaqim are only up to 12m thick. A micropaleontological study undertaken on more than 40 samples reveals, in addition to benthonic foraminifers, a diversified fauna of 31 species of ostracodes belonging to 22 genera. Representatives of the genus Aurila are the most common forms. Nearly all taxa are stenohaline, shallow marine species. The occurrence of the euryhaline Cyprideis cf. torosa marks a shallowing event in the middle parts of both sections. Other sea level changes are evidenced in the exposures by erosional unconformities, as well by changing lithologies of calcareous sandstones and marls versus conglomerates. A Pliocene age is attributed to the sections based on the distribution of common ostracodes inMediterranean region. The stratigraphic ranges of Cistacythereis robusta and Oblitacythereis mediterranea suggest an Early Pliocene age for these exposures.Marine Pliocene ostracodes are described in the present study for the first time from Israel. The age and lithology of the Khassif sections allow their correlationwith the sediments of the Pleshet Formation from the Gaza - Be’er Sheva Canyon.

Hydrocarbon source potential of the Santiago Formation, Oriente Basin, SE of Ecuador

The Santiago Formation (Late Hettangian–Sinemurian), described in the area of Santiago in the Oriente Basin of eastern Ecuador, consists of three distinct sedimentary members. The Santiago River Member is composed of limestones and calcareous sandstones. The Yuquianza Member is a monotonous sequence of black shales. The Patuca Member consists of a sequence of sandstones, greywackes, and shales, intercalated with lava flows and dikes. The fine-grained sediments of the three members are characterized by a high content of particulate organic matter (POM). Palynofacies and rock-eval analyses indicate the predominance of kerogen types II and III, with HI values that indicate a moderate to low source potential. At the type locality, the organic matter is thermally mature and locally overmatures.

Gold and platinum group metals in skarns of the Ol’ginsk and Dal’negorsk ore districts of Primorye and some issues of metallogeny of the southern Sikhote Alin region

The Triassic‐Jurassic carbonaceous sequence of Sikhote Alin includes metalliferous sediments represented by siliceous‐rhodochrosite rocks and their metamorphosed analogues [3, 4], siliceous rocks with pyrophanite (“brown cherts”), tin‐iron ores, “ilmenite‐ biotite‐feldspar” (metamorphosed clayey) rocks, and “itabirites.” They are characterized by high contents of Au, Ag, Pt, and Pd [2] and the ubiquitous presence of minerals of these elements. Hydrothermally altered sandstones, as well as siliceous‐clayey and siliceous rocks, which are associated with syngenetic metalliferous rocks, contain grains of gold, silver, argentite, platinum, Pd-platinum, itenbohaardite, and other minerals of noble metals. It should be mentioned that identifications of all minerals mentioned in this paper have been confirmed by microprobe analyses. Another type of hydrothermal ores is represented by Mn-rich amphibole‐pyroxene rocks that contain native gold, silver, Pdplatinum, and other minerals of gold, silver, and platinum group metals (PGM). Hydrothermal ores are products of the regeneration of metalliferous rocks due to the evolution of Late Cretaceous granitoid massifs. The amphibole‐pyroxene rocks formed after calcareous sandstones, which are probably of Late Triassic age [3]. The southern Sikhote Alin region incorporates numerous Late Cretaceous skarn and vein (cavity-filling) deposits of lead, zinc, silver, tin, tungsten, and iron. Skarns are characterized by high concentrations of Mn derived from manganese rocks [1]. Similarly as other metalliferous rocks, the manganese rocks are enriched in Pb, Zn, Ag, Sn, W, and Fe. Hydrothermal deposits of these metals define the metallogenic profile of the southern Sikhote Alin region. Manganese and other metals mentioned above were probably derived from metalliferous rocks of the Triassic‐Jurassic carbonaceous sequence. The metalliferous rocks and associated hydrothermal rocks contain Au and PGM. For example, these metals are concentrated in amphibole‐pyroxene rocks of the Shirokaya Pad area of the Ol’ginsk district. These rocks are analogues of the adjacent manganiferous

Fe Skarn, Iron Oxide Cu-Au, and Manto Cu-(Ag) Deposits in the Andes Cordillera of Southwest Mendoza Province (34 -36 S), Argentina

Several Fe, Fe-Cu, and Cu-Ag prospects hosted by Mesozoic carbonate-rich sedimentary rocks that were intruded by diorite stocks define an approximately 20 × 200 km belt along the Andes Cordillera of southwest Mendoza province, Argentina (34°–36°S). This belt includes the Hierro Indio and Vegas Peladas Fe skarns, Las Choicas, and several other Cu-(Ag) prospects. The main features of the Fe skarns include: association with mantle-derived middle Miocene (~15–11 Ma) diorite stocks and sills; widespread alteration including epidote ± amphibole ± magnetite endoskarns, and zoned garnet (Grs0–66 Adr32.5–100) ± magnetite ± pyroxene (Di24–50 Jo2–9 Hd74–41) exoskarns formed from oxidized, saline, high-temperature brines (530°–660°C; 60–70 wt.% NaCl equiv.); and magnetite-hematite orebodies associated with quartz ± epidote ± calcite ± actinolite formed at lower temperatures (290°–436°C) from saline fluids (32–50 wt.% NaCl equiv.) of magmatic origin. West of the Fe skarn belt, the Valle Hermoso district covers more than 300 km2 and hosts several poorly known Cu-(Ag) prospects (estimated 30 Mt with 1.5% Cu and 20 g/t Ag). These prospects share many characteristics with the iron oxide copper-gold-type systems and manto-type Cu deposits of northern and central Chile. One of the prospects (Las Choicas) is located at the apex of a regional 015°-trending anticline, along the contact of stratified calcareous sandstone and limestone (Neocallovian-Oxfordian) with a diorite pluton. This pluton has positive Ta and Nb anomalies (on normalized diagrams) and a high Ti content, features uncommon in Miocene diorites associated with Fe skarns and of magmas derived from sub-arc mantle sources. Alteration at Las Choicas includes early widespread chlorite + calcite ± albite ± scapolite ± ilmenite or titanite ± apatite, and local actinolite ± hematite ± biotite alteration of diorite and sedimentary rocks along contacts. Later Cu mineralization (1%–10% Cu) is associated with calcite ± albite ± quartz alteration in fractures, vein networks, and crackle breccias. Mineralization is zoned from bornite ± chalcopyrite ± millerite with Zn, As, Mo, Ag, and U anomalies in the main orebody, through chalcopyrite-rich breccias with Zn anomalies, and chalcopyrite ± tetrahedrite vein networks with Sb, As, Ag, and Zn anomalies in the uppermost zone, to a Cu-depleted pyrite-rich envelope with Co anomalies, and finally to late, barren calcite veins in distal zones.

An Upper Llandovery Konservat–Lagerstätte in a depositional context: the Pentland Hills Eurypterid Bed, Midlothian

Synopsis Re-excavation and detailed logging of the sedimentary sequence which includes the Eurypterid Bed on the Gutterford Burn, Pentland Hills, Midlothian, has clarified the depositional setting of this Silurian Konservat–Lagerstätte. The relative positions of the Gutterford Burn limestones, beds yielding dendroid graptolites and the Eurypterid Bed itself have been identified. Clay bands occur at a number of horizons throughout the 23 m of logged section, but the most important of these enclose the distinctive lithology of the Eurypterid Bed. Exceptionally preserved fossils typically occur within a volcanic ash-rich claystone which was deposited below storm wave-base in a fully marine setting. Depositional style, presence of in situ corals and the presence of volcaniclastic input all indicate similarity to the sequence exposed around the Deerhope Coral Beds. The stratigraphy of the North Esk Inlier is revised t o take into account these new findings. The boundary between the Reservoir Formation and the overlying Deerhope Burn Formation is defined as lying at the base of the first calcareous sandstone on the Gutterford Burn section.

Complex volcanic facies architecture of the Forest Reefs Volcanics near Cadia, New South Wales, associated with prolonged arc-related volcanism

The Ordovician to Lower Silurian Forest Reefs Volcanics in the Cadia – Neville region, northeastern Lachlan Orogen, represent the product of at least two shoshonitic volcanic centres intercalated with a volcaniclastic apron. The two episodes of shoshonitic volcanism in the Forest Reefs Volcanics are separated by between 15 and 20 million years. The Forest Reefs Volcanics are informally divided into lower and upper parts, separated by an inferred unconformity that broadly coincides in age with a limestone-forming hiatus in volcanism (449 – 447 Ma) and emplacement nearby of medium-K calc-alkaline dacitic intrusions (448 – 445 Ma). The lower part includes shoshonitic basaltic andesite, feldspar-rich sandstone, volcanic lithic breccia and lesser black mudstone; polymictic volcanic conglomerate with sandstone matrix and calcareous sandstone are important near the top. The basaltic facies association occurs near the base of the lower Forest Reefs Volcanics and could represent a submarine basaltic volcano at least 12 km in diameter. A major change in provenance for the upper Forest Reefs Volcanics is reflected in the increased abundance of ferromagnesian crystals and coarse mafic volcanic fragments, particularly in the mafic volcanic sandstone, polymictic volcanic conglomerate with coarse volcanic matrix and polymictic hornblende andesite breccia. The trachyandesite facies association records another episode of shoshonitic volcanism that probably occurred late in the accumulation of the upper Forest Reefs Volcanics and could represent an intrusive complex or the initial, largely shallow intrusive stages of a cone volcano. Highly porphyritic basalt to basaltic andesite intrusions were emplaced as sills before the volcaniclastic succession was lithified. The final magmatic activity generated coarsely equigranular, mafic to intermediate intrusions. The trachyandesite facies association, the highly porphyritic basalt to basaltic andesite intrusions and the coarsely equigranular intrusions were emplaced successively in a relatively short time (about 443 – 439 Ma). The complex facies architecture of the Forest Reefs Volcanics thus represents the product of prolonged broadly arc-related shoshonitic volcanism, separated by limestone deposition and the subsequent emplacement of medium-K calc-alkaline dacitic intrusions.

Rock petrophysics v. performance of protective and consolidation treatments: the case of Mt Arzolo Sandstone

Abstract The petrophysical characteristics of a building stone used in the city of Pavia, northern Italy, are analysed in the light of stone conservation through the application of water repellent and consolidant products. The research focuses on the modification of petrophysical properties as a function of the applied products, and on the critical assessment of the performances of fluorinated and siloxane resins as a function of the variable nature of the same lithotype. The studied material is a calcareous sandstone (Mt Arzolo Sandstone), Late Miocene-Early Pliocene in age, extensively employed as a building material during the 11th and 12th centuries. Experimental investigations on samples from historic quarries were performed before and after application of treatments: i.e. petrographical and fabric analyses; ultrasonic measurements; mercury porosimetry; abrasion resistance measurements; contact angle measurements; capillary and low-pressure water absorptions; water vapour permeability; and colour measurements. Two main lithotypes of Mt Arzolo Sandstone were recognized according to their petrophysical features: the open porosity being similar, differences exist concerning their fabric. These differences influence the physical-mechanical properties of the material and consequently the performances of the applied products. In particular, the difficulties in penetration of products when sandstone of smaller pore size is treated can lead to a significant reduction of the overall performances, which is more evident for products containing organic solvent with high molecular weight.

Foraminiferal response to an active methane seep environment: A case study from the Adriatic Sea

It has been analysed the taxonomic structure and isotopic composition of the cytoplasm and tests of living (Rose Bengal stained, protoplasm-full) and dead (empty tests) benthic foraminifera (> 63 μm) in surface sediments from sites with and without methane seepage at water depths of about 25 m water in the northern Adriatic Sea, and compared these data to isotope analyses of carbonate rocks at the same locations. Foraminiferal density is higher in seep samples than in control ones, despite the low oxygen and high sulphide contents in sediments. The δ 13C values in foraminiferal cytoplasm at the seep sites are lower than those in cytoplasm of the same species in control samples, suggesting that Beggiatoa may be a food source for the foraminifera, and explaining the higher foraminiferal density at the seep site. In contrast, the δ 13C values of tests of living and dead benthic foraminifera at seep sites were not significantly different from those in tests of the same species collected at the control sites. Therefore, the carbon isotope values of foraminiferal tests in this area do not reflect the ones of the methane seepage, although the authigenic carbonate in calcareous sandstones of the methane seepage area is significantly negative and indicates the contribution of methane seepage. The similar carbon isotope values measured in the foraminiferal tests from shallow settings of the north-eastern Adriatic Sea seem therefore to be independent of methane seepages.