Tuffaceous Conglomerate Research Articles

Characteristics of Mengger Formation’s volcaniclastic in Cisaat River, Brebes, Central Java, Indonesia

The Cisaat River in Brebes Regency, Central Java, is one of the sites on Java Island where vertebrate fossils were found. Mengger Formation, composed of volcaniclastics material such as tuff and pumice fragments, contains these fossils. The presence of vertebrate fossils along with volcanic deposits has remained unclear of its deposition history. This research characterizes the volcaniclastic rocks in Mengger Formation based on geological field observation and petrography analysis. The study aims to identify and distinguish its primary and secondary volcaniclastic depositional processes. The measured stratigraphic sections reveal that the formation has 7 lithofacies from older to younger, namely grain-supported conglomerate, sandstone, siltstone, sandy mudstone, matrix-supported conglomerate, tuffaceous sandstone, and tuffaceous conglomerate. The primary volcaniclastic materials comprise pumice clast, plagioclase, pyroxene, hornblende, quartz, biotite, lithic fragments, and volcanic glass. In contrast, secondary volcaniclastic or epiclastic-sedimentary materials contain lithic fragments, quartz, plagioclase, pumice clast, and clay matrix. The origin of the resedimented volcaniclastic material was probably derived from a large volume of ignimbrite near the volcano. From the deposit and measurement section, it can be concluded that the type of the Mengger volcaniclastic.

Lithofacies architecture and paleoenvironment of a Paleoproterozoic volcano-sedimentary sequence: Insight into rift-related volcanism during supercontinent assembly

The greenschist to lower-amphibolite facies, Proterozoic (Orosirian: ca. 1883–1848 Ma) Aillik Group in Labrador, Canada, comprises a well-preserved example of subaqueous to intermittently subaerial volcanism and sedimentation. The group consists of interlayered sedimentary, volcaniclastic, pyroclastic and bimodal volcanic units that exhibit well-preserved depositional and structural relationships. Cumulatively, these lithofacies significantly demonstrate the evolution of Paleoproterozoic volcanism during the assembly of the supercontinent Nuna. A minimum stratigraphic thickness of 14.9 km of the Aillik Group is exposed along the coast of Labrador and is divided into two successions. The western stratigraphic succession consists of subaerial to subaqueous sandstone, siltstone, conglomerate, resedimented tuffaceous sandstones, and tuffaceous conglomerate with lesser rhyolite flows and felsic tuff. The eastern stratigraphic succession is dominated by felsic tuff and rhyolite, lesser pillowed to massive mafic lavas, and in situ and resedimented mafic tuff. Mafic rocks are basaltic, whereas felsic rocks comprise high-silica rhyolites and tuffs. Primary subaqueous pyroclastic deposits are indicative of explosive activity, an observation also supported by the presence of accretionary lapilli and an abundance of lithic fragments in epiclastic deposits. The volcano-sedimentary lithofacies of the Aillik Group are consistent with that observed in modern intra-arc or arc-rift settings, and the succession is interpreted to have formed in a localized back-arc rifting environment within an overall complex convergent margin.

Petrografická charakteristika spodnokarbonských ryolitových tufitů z vrtů v lomu Výkleky (moravické souvrství, kulmská pánev Nízkého Jeseníku)

Two layers of volcanoclastic rock with thickness 40 and 210 cm were identified in core-samples, obtained by exploration drilling in the Výkleky quarry which was established in Lower Carboniferous sediments of the Moravice Formation (Moravo-Silesian Culm basin in the Nízký Jeseník Mts.). The volcanoclastics are represented by tuffaceous sandstones to tuffaceous conglomerates. These tuffites consist of a mixture of pyroclastic and epiclastic material, mainly fragments of strongly carbonatised porphyritic rhyolite, less of quartz shards, argillitised feldspars (K-feldspar and albitised plagioclase), chloritised biotite leaflets and muscovite. Lithic and mineral fragments are surrounded by lutitic matrix. Volcanic glass was completely replaced by mixture of quartz, alkali feldspars, chlorite and “clay micas” (phengitic illite-muscovite). Chemical composition of albite from rhyolite fragments and tuffite matrix is similar (An01 - 04), chlorite chemically corresponds to chamosite (XMg = 0.39 - 0.47; Si = 2.72 - 3.08 apfu). Pyrite and carbonates (calcite and side-rite to Mg-rich siderite) often fills cracks in the rock. Studied volcanoclastic rocks represent products of extrabasinal Lower Carboniferous terrestrial explosive volcanism whose activity probably culminated during the sedimentation of the Moravice Formation.

Geodynamic setting of Ediacaran and Permian–Triassic plagiogranites of the Ust-Bel’sky and Algansky terranes, West Koryak fold belt, NE Russia: insights from U–Pb geochronology and geochemistry

ABSTRACTEdiacaran and Permian‒Triassic stages of plagiogranite magmatism are distinguished for the Ust-Bel’sky and Algansky terranes of the West Koryak fold belt, NE Russia. The U‒Pb ages of Ediacaran plagiogranites are 556 ± 3 Ma (SIMS data) and 538 ± 7 Ma (LA–ICP–MS data), respectively, and 235 ± 2 Ma (SIMS data) for the Permian‒Triassic plagiogranites. The Ediacaran and Permian‒Triassic plagiogranites are low-K igneous rocks. Sr‒Nd isotopy and REE patterns of both plagiogranite suites allow suggesting their formation via partial melting of primary mantle material or fractional crystallization of basaltic magma. Ediacaran plagiogranites were formed in the oceanic arc setting contemporaneously with the volcanic-sedimentary complex of Otrozhnaya slice, Ust-Bel’sky terrane. Tuffaceous conglomerates in the lower part of this complex contain Ediacaran zircons with a peak age of 571 Ma. Formation of the Permian‒Triassic plagiogranites took place within the Ust-Bel’sky segment of the Koni‒Taigonos arc via partial melting of melanocratic ophiolite material in the accretionary structure of this arc or fractional crystallization of basaltic magma, melted from such substrate.

The Cerro Rajón Formation—a new lithostratigraphic unit proposed for a Cambrian (Terreneuvian) volcano-sedimentary succession from the Caborca region, northwest Mexico

A new mappable rock unit, the Cerro Rajón Formation, is proposed for the Cambrian succession of the Caborca region, Sonora, México. Formerly Unit 1 of the Puerto Blanco Formation, the Cerro Rajón Formation is interpreted as a volcano-sedimentary succession deposited along the coast of a passive margin that was impacted by rift-related volcanism. At its proposed type locality, in Cerro Rajón, the Cerro Rajón Formation consists of 270–285 m of tuffaceous conglomerate, metabasalt, mafic tuff, mafic lapillistone, mafic agglomerate, and quartzite with minor siltstone, limestone, and dolostone- and quartzite-dominated conglomerate. The unit contains a major disconformity near its base, where m-to dm-thick conglomerate locally replaces the fine-grained clastics that make up the base of the Cerro Rajón Formation. δ13C chemostratigraphy and biostratigraphy of the Rajón and its bounding strata limits Rajón deposition to the Fortunian Stage of the Terreneuvian Series. Volcanic rocks in the Cerro Rajón Formation are represented by mafic to ultramafic flows, including picrobasalts and metabasalts with hydrothermal alteration characteristics, evidenced by replacement of clinopyroxenes by chlorite, actinolite, and epidote. The mineral paragenesis of these volcanic rocks suggests the succession experienced greenschist grade metamorphism. Basalt geochemistry is consistent with low silica (34.32–48.21%) magmatism with high TiO2 concentrations (3.63–7.52%), related to continental rift volcanism with OIB characteristics. This volcanism could represent the last southern evidence of the rifting process that occurred along the western margin of Laurentia or could be related to volcanic rift deposits further afield.

Early Cambrian alkaline volcanism on the southern margin of Laurentia: evidence in the volcaniclastic units from the Puerto Blanco Formation in the Caborca block, NW Mexico

ABSTRACTVolcaniclastic units are exposed at the base of the Puerto Blanco Formation in the Caborca region, northwestern Mexico. The lower unit reveals the presence of Early Cambrian mafic volcanism in this region. It consists of a volcano-sedimentary sequence represented by tuffaceous conglomerates, agglomerates, lapillistones, tuffs, and altered mafic volcanic flows. Petrographic analysis classified the volcanic clasts as albite-sphene-calcite-actinolite granofels, with a moderate to intense hydrothermal alteration, precisely characterized by EPMA analysis. Albite-actinolite geothermometry indicates temperatures from 400 to 500°C, suggesting metamorphic conditions in the upper temperature greenschist facies. Geochemistry analysis shows a high TiO2 basic–ultrabasic volcanism that originated the volcanic clasts. Rock protoliths were studied using immobile trace elements, which classified them as OIB-type alkaline basalts with the characteristic spider hump-shaped pattern, situated in an anorogenic intracontinental tectonic setting with enriched mantle signatures. 40Ar/39Ar geochronology shows metamorphic ages of 52.58 ± 2.0 and 91.67 ± 0.55 Ma, consistent with the emplacement of Laramidic granitoids identified in the region. Possible correlations of this alkaline volcanism include the Southern Oklahoma Aulacogen and the late stages of the rifting of north western Laurentia represented in western United States.

Rock Physical Experimental Research in Tanan Volcanic Rock Reservoir

Under the condition of simulated formation temperature and pressure, the compression and shear wave velocity of the tuffaceous conglomerates and rock-fragment sandstones of the reservoirs in K1t, k1n group of Cretaceous system in Tanan are measured. The effects of lithology, mineral content, density, porosity, shale content, and water saturation on the acoustic velocity of the athrogenic rock are studied. Within the limits of our observation, some rules are found: (1) the velocity of the fine tuffaceous conglomerates is remarkably greater than that of the tuffaceous rock-fragment sandstones with good physical property; (2) the compression velocity increases with fragment content, and decreases with quartz and feldspar content in the mud; (3) the compression velocity increases with density, especially, in tuffaceous rock-fragment sandstones, the velocity keeps a good relation with density in form of power function; (4) compression and shear wave velocity decreases with porosity and shale content, velocity of the tuffaceous rock-fragment sandstones keeps a good relation with porosity and shale content in form of negative linear function, but effects of shale content is only 1/5 to 1/10 of that of the porosity, hence can be neglected; (5) with porosity increases, compression wave velocity is relatively sensitive to fluid alternation, and the rang in which velocity varies keeps positive correlation with porosity. The result provides a foundation for the research of seismic and logging data evaluation approaches in athrogenic rock reservoirs, Haita basin.

Petrography characteristic and tectonic setting of Chau Thoi formation, Viet Nam

The Late Paleozoic – Early Mesozoic sedimentary formations in the South – eastern region have exhumed incomplete, and they have more complex geological characteristics, related to the closure process of the Paleo-Tethys ocean and the Indosinian orogeny occured from late Permian to late Trias. Sedimentary sequences in this period were classifed to Ta Not, Hon Quan, Song Sai Gon and Chau Thoi formations. The results from researches on petrography at areas of Chau Thoi formation such as Chau Thoi, Buu Long, Minh Duc, Loc Thanh have indicated that the pyroclasic rocks such as tuff, agglomerate, tuffaceous conglomerate, tufaceous sandstone conglomerate, sandstone, siltstone… are also present with the mainly lithological component of formation as conglomerate, sandstone, siltstone... Reseach on the lithological composition and geochemical content from the number of rock samples of the Chau Thoi formation show that the Chau Thoi formation is formed in rift setting as backarc basin type.

Tuffaceous Conglomerates: Syn-Eruptive Resedimented Debris Flow and Hyperconcentrated Flow Deposits from the "Rhyodacitic Formation", Gutai Mountains, Eastern Carpathians

The first volcanic products from Gutâi Mts, Eastern Carpathians belong to the Rhyodacitic Formation. The physical constituents of this formation are as follows: pyroclastic deposits (ignimbrites and fall tuffs), syn-eruptive resedimented volcaniclastic deposits, volcanogenic and non-volcanogenic sedimentary deposits. The tuffaceous conglomerates belong to the syn-eruptive resedimented volcaniclastics and represent the coarsest deposits. They outcrop in Baiţa area, west from Baia-Mare, being underlain by Lower Badenian (15.4±0.6 Ma) ignimbrites and overlain by Lower Sarmatian claystones. The main components of the conglomerates are boulders and cobbles of sedimentary and metamorphic rocks in a tuffaceous matrix. Scarse blocks eroded from the lower ignimbrite unit are present. In the frame of the study of the Rhyodacitic Formation, the conglomerates have been investigated using facies analysis. The facies model concludes that the studied deposits have been emplaced from debris flows and hyperconcentrated flows. They derived from subaerial channelized ignimbrite flows, which underwent strong flow separation while jumping in submarine basin and settling in deep water, below wave base. Such conditions, above the lower subaerial ignimbrite unit, were determined by the subsidence of Sasar-Dealu Crucii compartment, contemporaneously developed with the conglomerates emplacement.

The Iwato Slide Has Characteristics of both Shear Zone Slide and Hydrothermal Alteration Zone Slide

The 1986 Iwato slide occurred during November 1986, at Iwato, situated in the southwestern part of Ikutahara Town, northeastern Hokkaido, Japan. This slide took place over an area at the foot of an ancient slide configuration that was approximately 140 m wide and 100 m long. The dimensions of the 1986 Iwato slide were approximately 25 m wide and 45 m long.The geology in the vicinity of the Iwato slide area consists of the Lower Cretaceous-Eocene Hidaka Supergroup, Upper Miocene Ikutawara Formation, Neogene rhyolite and basalt dikes, as well as Quaternary river terrace deposit, slide deposit, alluvial fan deposit and Alluvium.Hydrothermal alteration is mainly characterized by smectitization (smectite ± quartz ± opal-CT ± pyrite), zeolitization (mordenite+heulandite-clinoptilolite series mineral ± smectite ± quartz ± opal-CT ± pyrite), propylitization (quartz + albite + chlorite ± smectite ± calcite ± pyrite), illitization (quartz + illite + pyrite ± chlorite) and Kfeldsparization (quartz+adularia+pyrite ± illite ± chlorite).The bedrock of the slide area is reconsolidated crushed shale of the Hidaka Supergroup in a crush zone . The shale is believed to have been subjected to hydrothermal smectitization. The slide, therefore, can be characterized as both shear zone slide and hydrothermal alteration zone slide. The slide deposit consists chiefly of debris, such as sand or silt mixed with rubble that consists primarily of shale fragments of the Hidaka Supergroup and tuffaceous conglomerate fragments of the Ikutawara Formation, and is approximately 6 to 7 m in thickness. The displaced material moved along a curved surface. The movement of the 1986 Iwato slide was a slump.In addition, the slip surface is estimated to be inside the debris, or the detritus. Thus the slide can also be characterized as a debris slump, or a detritus slump.

Slides Occurring in Hydrothermal Alteration Zones

The geology in the catchment area of the Nitappugawa River consists primarily of the Upper Miocene Ikutahara Formation and Late Miocene rhyolite, andesite, and basalt dikes, as well as the Quaternary System. The Ikutahara Formation is widely distributed in the area and is composed of tuffaceous conglomerate, sandstone and mudstone, lapilli tuff, tuff breccia, tuff, rhyolite lavas, and andesite lavas. The clastic and volcaniclastic rocks occupy the valley and hillside whereas the rhyolite or andesite lavas cap the peaks of the mountains. The rocks of the Ikutahara Formation and a part of the rhyolite dikes were intensely affected by hydrothermal alteration related to the Ryuo epithermal gold-silver mineralization of the Late Miocene Age. The hydrothermal alteration related to an ancient neutral-type geothermal system is primarily characterized by smectite, zeolite, interstratified illite/smectite, illite, and adularia.Seven ancient slide configurations are distributed on the interstratified illite/smectite and smectite zones. The Yasukuni slide and three slide configurations are closely related to the interstratified illite/smectite zone occurring abundantly in interstratified illite/smectite, which is a swelling clay mineral. The other three slide configurations are closely related to the smectite zone characterized by smectite, which is also a swelling clay mineral.These facts are useful when evaluating contemporary slide hazards and constructing hazard maps of ancient hydrothermal fields.

Slides Occurring in Hydrothermal Alteration Zones: An Example from the Kanehana

The geology of the Kanehana slide areas consists primarily of the Cretaceous-Paleocene Yubetsu Group, Upper Miocene Ikutahara and Yahagi Formations, Late Miocene andesite and rhyolite dikes, Lower Pliocene Hakugindai Lava, and Quaternary System. The Ikutahara Formation is distributed in the eastern part of the areas, and consists primarily of tuffaceous conglomerate, lapilli tuff, tuff, and rhyolite lavas. The Yahagi Formation is distributed in the western part of the areas, and consists primarily of tuffaceous conglomerate, sandstone and mudstone, pumice-tuff, and rhyolite lavas. The Hakugindai Lava unconformably covers the rocks of the Ikutahara and Yahagi Formations. In particular, the rocks of the Ikutahara and Yahagi Formations and andesite dikes were affected to various extents by hydrothermal alterations related to the Late Miocene epithermal gold-silver mineralizations of the Muka and Kunihana deposits.Hydrothermal alterations are divided into two stages. The stage I neutral-type alteration zones consist of K-feldspar, illite, interstratified illite/smectite, chlorite, zeolite, and smectite zones, while the stage II acid-type zones include kaolinite, veined 7 A halloysite-kaolinite, and veined smectite-kaolinite zones.Seven ancient slides and the Kanehana-toge slide occurred in hydrothermal alteration zones. The smallestscale Kanehana-toge slide and four intermediate-scale slides were closely related to the veined smectitekaolinite and smectite zones, respectively. Two large- and intermediate-scale slides were also closely related to the smectite zone, to the zeolite zone containing a relatively large amount of smectite, and/or to the kaolinite zone.The largest-scale ancient slide configuration was approximately 1, 450 m in width of displaced material, and approximately 1, 550 m in total length, and was of the “Concave Poly-Hill type” consisting of roughly twelve parts. On the other hand, the smallest-scale slide was approximately 20 m wide and approximately 70 m long. The small- and intermediate-scale slides were of the “Concave Hill type”.These data are useful for evaluating the degree of hazard of slides and for making a hazard map of slides in the hydrothermal alteration zones.

Ferromanganese deposits from the Gulf of Alaska Seamount Province: mineralogy, chemistry, and origin

Ferromanganese-oxide deposits dredged from four seamounts (Welker, Miller, Murray, and Patton) in the Gulf of Alaska Seamount Province include poorly crystallized microlaminated crusts on basalt substrate, well-crystallized Mn-oxide veins in epiclastic sedimentary rocks, and crystalline Mn-oxide layers and micronodules in phosphorite. The principal rock types dredged are alkali-basalt pillow fragments and tuffaceous conglomerate and sandstone. The glassy rims of pillow fragments, the glassy goundmass of large volcanic clasts, and the tuffaceous component of the sediment are altered to palagonite. Other low-temperature alteration products include phillipsite, smectite, and carbonate-apatite.Thick (10–50 mm) Fe–Mn crusts consist mainly of δ-MnO2; straight and cuspate growth laminae indicate variable growth rates and periods of nondeposition. A larger number of detrital particles toward the top of thick crusts record the increasing influence of active volcanoes of the Aleutian arc during northwestward movement of the Pacific plate. Thick crusts on basalt substrate have higher Mn/Fe ratios and lower Co content than Fe–Mn crusts from low-latitude seamounts of the central Pacific region. Thin (< 10 mm) crusts on volcaniclastic substrate contain todorokite and birnessite and have higher Mn/Fe ratios, Ni, and Cu and lower Fe and Co than thick Gulf of Alaska crusts.Veins of todorokite and cryptomelane with complex internal structure occur in altered tuffaceous sandstone and conglomerate from Miller Seamount. Fibrous todorokite has a composition similar to those of other marine examples but may contain up to 7% Mn2+ in M2 sites. Microprobe analysis of the marine cryptomelane indicates a composition that is approximately (K,Ba)1–2(Mn4+,Co)7–8O16∙x(H2O).A third type of Fe–Mn deposit in phosphorite is an intimate mixture of todorokite (and minor δ-MnO2)-bearing layers and micronodules, carbonate-apatite, and phillipsite that encloses grains of altered volcanic glass and lithic fragments.The microlaminated structure, mineralogy (predominantly δ-MnO2), and composition (Mn/Fe ratio and transition metal, rare earth element, U, and Th contents) of the thick crusts are characteristic of hydrogenetic Fe–Mn crusts elsewhere in the Pacific. Conversely, the crystallinity and chemical composition of the Mn-oxide veins and thin crusts indicate formation during diagenesis of the volcanogenic sediment substrate. Mn and other transition metals are mobilized during low-temperature oxidative alteration (palagonitization) of basaltic volcanic glass; the oxidation of Fe2+ to Fe3+ during palagonitization and the dissolution of the dilute biogenic fraction of the sediment combine to lower the Eh of ambient pore fluid and enhance the mobility of Mn2+. Diagenesis in the phosphatic sandstone from Patton Seamount involves organic-rich sediment and pore waters elevated in phosphorus owing to upwelling above a large volcanic edifice.

A Green Mineral from Iron-Sand Layers in Tuffaceous Conglomerate Bed near Enkyo, Yamanasi Prefecture

A Green Mineral from Iron-Sand Layers in Tuffaceous Conglomerate Bed near Enkyo, Yamanasi Prefecture