Expanding the toolbox for dating basaltic lava sequences: 40Ar–39Ar dating of silicic volcanic glass from interbeds

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2019-207
Author(s):  
Simone Cogliati ◽  
Sarah C. Sherlock ◽  
Alison M. Halton ◽  
Alena Ebinghaus ◽  
Simon P. Kelley ◽  
...  
Keyword(s):  
Volcanic Glass ◽  
Depositional Environments ◽  
Basaltic Lava ◽  
Content Type ◽  
Additional Tool ◽  
Sample Data ◽  
Stratigraphic Position ◽  
Silicic Volcanic ◽  
Supplementary Material ◽  
Glass Shards

40Ar–39Ar dating of glass shards from silicic tuffs of the Ellensburg Formation (NW, USA) interbedding basaltic lavas yielded accurate, precise, reproducible plateau and isochron ages that are within error at the 2σ level. The age-spectra have flat plateaus and the inverse isochrons have atmospheric 40Ar/36Ar at the 2σ level. Ages of 12.00 ± 0.24, 11.37 ± 0.15, 10.67 ± 0.21 and 10.70 ± 0.18 Ma are consistent with the stratigraphy of four of the dated layers; the age of 10.77 ± 0.18 Ma for a fifth layer is at odds with the stratigraphy. This discrepancy arises due to the effect of glass alteration that induced K- and Ar-loss. There is no evidence of excess 40Ar or 39Ar recoil. The new ages indirectly constrain the timing of eruption of the lavas above and below the ash beds. This demonstrates that volcanic glass from interbeds can be used as an additional tool for indirectly dating basaltic lava sequences, which is independent of the lavas and complementary to other materials. Considering the numerous studies in which volcanic glass failed to provide reliable 40Ar–39Ar ages, additional and supportive constraints are still needed to assess the validity of the ages from glass shards.Supplementary material: A1 – sample location, stratigraphic position and depositional environments; A2 – electron microprobe information with calibration and sample data; A3 – Ar isotopic data of blanks and samples, data reduction software, J values, criteria for age calculation and images of age spectra and inverse isochrons are available at https://doi.org/10.6084/m9.figshare.c.5077705

Carboniferous records of the Zoophycos group of trace fossils from England, Wales, the Isle of Man and the North Sea

2020 ◽  
Vol 63 (2) ◽  
pp. 135-145
Author(s):  
Duncan McLean ◽  
Matthew Booth ◽  
David J. Bodman ◽  
Finlay D. McLean
Keyword(s):  
North Sea ◽  
Trace Fossils ◽  
Depositional Environments ◽  
Common Component ◽  
Content Type ◽  
Clastic Rocks ◽  
Isle Of Man ◽  
The North ◽  
The North Sea ◽  
Supplementary Material

The Zoophycos group of trace fossils is common in Carboniferous to recent marine strata and sediments, and is a common component of ichnofaunas in the Visean and Namurian stages of England and Wales. A review of new and published records indicates that it is often present in limestones and sandstones of Chadian to Arnsbergian age. Thereafter it is less common, and restricted to clastic rocks. There are no known records within Carboniferous strata above the lowest Westphalian. The form is most common and often abundant in limestones of the Yoredale facies in the upper Visean and lower Namurian stages of northern England, particularly so in northern Northumberland. Where detailed sedimentological data exist, they indicate that the organisms responsible for the Zoophycos group burrowed into unconsolidated carbonate substrate that was deposited under low accumulation rates, often affected by storm wave action and where seawater flow provided a nutrient supply. However, in mixed carbonate–clastic settings, the deep-tier nature of Zoophycos may indicate that the organism lived in overlying shallow-marine, clastic-dominated depositional environments and burrowed down into the carbonate substrate. The same may be true of siliciclastic depositional settings where the presence of Zoophycos in some sandstones may reflect the palaeoenvironment of the overlying, finer-grained transgressive marine (prodelta and distal mouth bar) deposits.Supplementary material: A spreadsheet with details of Carboniferous records of Zoophycos group fossils from England, Wales, the Isle of Man and the North Sea is available at https://doi.org/10.6084/m9.figshare.c.4994636

Volcaniclastic deposits and sedimentation processes around volcanic ocean islands: the central Azores

2021 ◽  
pp. SP520-2021-62
Author(s):  
Yu-Chun Chang ◽  
Neil C. Mitchell ◽  
Thor H. Hansteen ◽  
Julie C. Schindlbeck-Belo ◽  
Armin Freundt
Keyword(s):  
Volcanic Glass ◽  
Sedimentary Facies ◽  
Turbidity Currents ◽  
Content Type ◽  
Core Logging ◽  
Supplementary Material ◽  
Geochemical Analyses ◽  
Lithological Composition ◽  
Volcaniclastic Deposits ◽  
Ocean Islands

AbstractGeological histories of volcanic ocean islands can be revealed by the sediments shed by them. Hence there is an interest in studying cores of volcaniclastic sediments that are particularly preserved in the many flat-floored basins lying close to the Azores islands. We analyse four gravity cores collected around the central group of the islands. Three sedimentary facies (F1-F2a, F2b) are recognized based on visual core logging, particle morphometric and geochemical analyses. F1 is clay-rich hemipelagite comprising homogeneous mud with mottled structures from bioturbation. F2a and F2b are both clay-poor volcaniclastic deposits, which are carbonate-rich and carbonate-poor, respectively. More biogenic carbonate in F2a reflects the incorporation of unconsolidated calcareous material from island shelves or bioturbation. Within F2a and F2b we identify deposits emplaced by pyroclastic fallout, primary or secondary turbidity currents by combining multiple information from lithological composition, sedimentary structures, chemical composition of volcanic glass shards and morphometric characteristics of volcanic particles. Primary volcaniclastic sediments were found in all four cores, echoing activity known to have occurred up to historical times on the adjacent islands. These preliminary results suggest that greater details of geological events could be inferred for other volcanic islands by adopting a similar approach to core analysis.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5602176

The effects of basaltic lava flows on the petrophysical properties and diagenesis of interbedded aeolian sandstones: an example from the Cretaceous Paraná Basin, Brazil

2020 ◽  
pp. petgeo2020-036
Author(s):  
G. Bertolini ◽  
A.J. Hartley ◽  
J.C. Marques ◽  
D. Healy ◽  
J.C. Frantz
Keyword(s):  
Lava Flows ◽  
P Wave ◽  
Basaltic Lava ◽  
Petrophysical Properties ◽  
Reservoir Properties ◽  
Content Type ◽  
Paraná Basin ◽  
Supplementary Material ◽  
Parana Basin ◽  
Type 3

An analysis of the petrophysical and diagenetic effects of the emplacement of Cretaceous basaltic lava flows (Serra Geral Formation) on aeolian sandstones (Botucatu Formation) has been undertaken on core samples from the Paraná Basin, Brazil. Between 0.1 to 1 m from the contact zone, acoustic wave velocities and porosities in sandstones show a significantly wider scatter than those located >1m away from the lava contact. Higher P-wave values (av. 3759.3 ms-1) occur between 0.1 to 1 m from the lava contact in contrast to those areas > 1 m away (av. 3376.8 ms-1), whilst the average porosity is 6.5% near the contact (0.1 to 1 m), and 10.7% away from the contact (>1 m). Petrographic evaluation reveals two diagenetic pathways responsible for modification of the petrophysical properties: early hydrothermal Mg-rich authigenesis (Type 1) and early chemical dissolution (Type 2). Type 3 diagenesis occurs away from the lava-sediment contact (>1 m) with the appearance of poikilitic calcite and smectite. The sandstone samples associated with Types 1 and 2 diagenesis display a decrease in porosity and increased acoustic velocities in relation to Type 3, while Type 3 samples show little or no variation in reservoir properties. The lava-induced diagenetic effects at the sandstone-lava contacts (0.1 to 1 m) may form a baffle or seal to fluids around the margins of the sandstone bodies. Therefore, whilst diagenesis associated with lava emplacement may hinder reservoir quality around the margins, the original reservoir properties are preserved within these large sandstone bodies.Supplementary material: Petrophysical and petrographic data is available as annex files. https://doi.org/10.6084/m9.figshare.c.5244473

scholarly journals Coal petrology analysis and implications in depositional environments from upper Cretaceous to Miocene: a study case in the Eastern Cordillera of Colombia

2021 ◽  
Author(s):  
Clara Guatame ◽  
Marco Rincón
Keyword(s):  
Late Cretaceous ◽  
Foreland Basin ◽  
Late Eocene ◽  
Depositional Environments ◽  
Estuarine System ◽  
Eastern Cordillera ◽  
Stratigraphic Position ◽  
San Fernando ◽  
Coal Facies ◽  
Oil Sector

AbstractThe Piedemonte Llanero Basin is located on the eastern side of the Eastern Cordillera of the Colombian Andes. It has been the subject of numerous geological studies carried out for the oil sector, mainly. This study presents the coal-petrographical features of 15 coal seams of four geological formations from Late Cretaceous to Middle Miocene (Chipaque formation, Palmichal group, Arcillas del Limbo formation, and San Fernando formation). Analysis of 33 samples indicates enrichment in vitrinite, while liptinite and inertinite concentrations vary according to the stratigraphic position. Reflectance indicates that the coal range gradually decreases from highly volatile bituminous C (Chipaque formation) to subbituminous C (San Fernando formation). The microlithotypes with the highest concentrations are clarite and vitrinertoliptite. Maceral composition and coal facies indicate changes in the depositional conditions of the sequence. The precursor peat from Late Cretaceous to Late Paleocene accumulated under limnic conditions followed by telmatic in Late Eocene–Early Miocene. The coal facies indices show wet conditions in forest swamps with variations in the flooding surface, influxes of brackish water and good tissue preservation. The tectonic conditions along the Piedemonte Llanero basin is evident, from post-rift to foreland basin, evidenced by oxic and anoxic periods reflected in the maceral composition and its morphology. The coal environment corresponds to an estuarine system started in the Chipaque formation evolving to the lacustrine conditions in the San Fernando formation.

Volcano-sedimentary processes at Las Derrumbadas rhyolitic twin domes, Serdán-Oriental basin, Eastern Trans-Mexican Volcanic Belt

2021 ◽  
pp. SP520-2021-144
Author(s):  
Marie-Noëlle Guilbaud ◽  
Corentin Chédeville ◽  
Ángel Nahir Molina-Guadarrama ◽  
Julio Cesar Pineda-Serrano ◽  
Claus Siebe
Keyword(s):  
Volcanic Belt ◽  
Debris Avalanche ◽  
Density Currents ◽  
Content Type ◽  
Mexican Volcanic Belt ◽  
Wide Range ◽  
Eruptive Episode ◽  
Basin Floor ◽  
Supplementary Material ◽  
Trans Mexican Volcanic Belt

AbstractThe eruption of the ∼10 km3 rhyolitic Las Derrumbadas twin domes about 2000 yrs ago has generated a wide range of volcano-sedimentary deposits in the Serdán-Oriental lacustrine basin, Trans-Mexican Volcanic Belt. Some of these deposits have been quarried, creating excellent exposures. In this paper we describe the domes and related products and interpret their mode of formation, reconstructing the main phases of the eruption as well as syn-and-post eruptive erosional processes. After an initial phreatomagmatic phase that built a tuff ring, the domes grew as an upheaved plug lifting a thick sedimentary pile from the basin floor. During uplift, the domes collapsed repeatedly to form a first-generation of hetero-lithologic hummocky debris avalanche deposits. Subsequent dome growth produced a thick talus and pyroclastic density currents. Later, the hydrothermally-altered over-steepened dome peaks fell to generate 2nd generation, mono-lithologic avalanches. Subsequently, small domes grew in the collapse scars. From the end of the main eruptive episode onwards, heavy rains remobilized parts of the dome carapaces and talus, depositing lahar aprons. Las Derrumbadas domes are still an important source of sediments in the basin, and ongoing mass-wasting processes are associated with hazards that should be assessed, given their potential impact on nearby populations.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5752296

Jurassic–Cretaceous arc magmatism along the Shyok–Bangong Suture from NW Himalaya: Formation of the peri-Gondwana basement to the Ladakh Arc

2021 ◽  
pp. jgs2021-035
Author(s):  
Wanchese M. Saktura ◽  
Solomon Buckman ◽  
Allen P. Nutman ◽  
Renjie Zhou
Keyword(s):  
Late Cretaceous ◽  
Nw Himalaya ◽  
Content Type ◽  
Magmatic Arc ◽  
Basement Rocks ◽  
Ladakh Himalaya ◽  
Accreted Terranes ◽  
Volcaniclastic Rocks ◽  
Supplementary Material ◽  
Depositional Age

The Jurassic–Cretaceous Tsoltak Formation from the eastern borderlands of Ladakh Himalaya consists of conglomerates, sandstones and shales, and is intruded by norite sills. It is the oldest sequence of continent-derived sedimentary rocks within the Shyok Suture. It also represents a rare outcrop of the basement rocks to the voluminous Late Cretaceous–Eocene Ladakh Batholith. The Shyok Formation is a younger sequence of volcaniclastic rocks that overlie the Tsoltak Formation and record the Late Cretaceous closure of the Mesotethys Ocean. The petrogenesis of these formations, ophiolite-related harzburgites and norite sill is investigated through petrography, whole-rock geochemistry and U–Pb zircon geochronology. The youngest detrital zircon grains from the Tsoltak Formation indicate Early Cretaceous maximum depositional age and distinctly Gondwanan, Lhasa microcontinent-related provenance with no Eurasian input. The Shyok Formation has Late Cretaceous maximum depositional age and displays a distinct change in provenance to igneous detritus characteristic of the Jurassic–Cretaceous magmatic arc along the southern margin of Eurasia. This is interpreted as a sign of collision of the Lhasa microcontinent and the Shyok ophiolite with Eurasia along the once continuous Shyok–Bangong Suture. The accreted terranes became the new southernmost margin of Eurasia and the basement to the Trans-Himalayan Batholith associated with the India-Eurasia convergence.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5633162

Geochemical evaluation of the in-situ regolith of Madengi hills of Dodoma, Tanzania. Implication on bedrock mapping and delineating gold mineralization target

2021 ◽  
pp. geochem2021-074
Author(s):  
Godson Godfray
Keyword(s):  
Gold Mineralization ◽  
Early Stage ◽  
Shear Zones ◽  
Soil Geochemistry ◽  
Residual Soils ◽  
Content Type ◽  
Geochemical Evaluation ◽  
Supplementary Material ◽  
Pathfinder Elements

Successful gold exploration projects depend on a piece of clear information on the association between gold, trace elements, and mineralization controlling factors. The use of soil geochemistry has been an important tool in pinpointing exploration targets during the early stage of exploration. This study aimed to establish the gold distribution, the elemental association between gold and its pathfinder elements such as Cu, Zn, Ag, Ni, Co, Mn, Fe, Cd, V, Cr, Ti, Sc, In, and Se and identify lithologies contributing to the overlying residual soils. From cluster analysis, a high similarity level of 53.93% has been shown with Ag, Cd, and Se at a distance level of 0.92. Au and Se have a similarity level of 65.87% and a distance level of 0.68, hence is proposed to be the most promising pathfinder element. PCA, FA, and the Pearson's correlation matrix of transformed data of V, Cu, Ni, Fe, Mn, Cr, and Co and a stronger correlation between Pb and U, Th, Na, K, Sn, Y, Ta and Be shows that source gold mineralization might be associated with both hornblende gneisses interlayered with quartzite, tonalite, and tonalitic orthogneiss. From the contour map and gridded map of Au and its pathfinder elements, it has been noted that their anomalies and target generated are localized in the Northern part of the area. The targets trend ESE to WNW nearly parallel to the shear zones as a controlling factor of Au mineralization emplacement.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5721965

First evidence for tooth-tooth occlusion in a ctenochasmatid pterosaur from the Early Cretaceous Jehol Biota

2021 ◽  
pp. SP521-2021-141
Author(s):  
Chang-Fu Zhou ◽  
Xinyue Wang ◽  
Jiahao Wang
Keyword(s):  
Early Cretaceous ◽  
Feeding Strategy ◽  
Three Dimensional ◽  
Tooth Wear ◽  
First Record ◽  
Jehol Biota ◽  
Content Type ◽  
Dimensional Reconstruction ◽  
Supplementary Material ◽  
Ct Data

AbstractCtenochasmatid pterosaurs flourished and diversified in the Early Cretaceous Jehol Biota. Here, a partial mandible of Forfexopterus is described based on a three-dimensional reconstruction using high-resolution X-ray Computed Tomography (CT) data. The first nine pairs of functional teeth of the rostral dentition revealed along with their replacements. The functional teeth are evenly arranged with a tooth density of 2.2 teeth/cm. The tooth crown is distinctly reduced from its base to the tip, and framed by two weak ridges, possibly as a pair of vestigial carinae. The replacement teeth are sharp and pointed, and have erupted slightly against the medial surface of the functional teeth. Surprisingly, tooth wear is observed in this specimen, the first record of tooth-tooth occlusion in ctenochasmatids. The wear facets exhibit high-angled lingual and lower-angled labial facets, implying a tooth-tooth occlusion in pterosaur clade. This discovery indicates that the Jehol ctenochasmatids possibly employed a more active feeding strategy than other filter-feeding pterosaurs (e.g. Ctenochasma, Pterodaustro, Gnathosaurus).Supplementary material at https://doi.org/10.6084/m9.figshare.c.5722060

Late Cretaceous granitoids of the Sikhote–Alin orogenic belt, southeastern Russia: implications for the Mesozoic geodynamic history of the eastern Asian continental margin

2021 ◽  
pp. jgs2021-109
Author(s):  
Igor V. Kemkin ◽  
Andrei V. Grebennikov ◽  
Xing-Hua Ma ◽  
Ke-Ke Sun
Keyword(s):  
Late Cretaceous ◽  
Pacific Plate ◽  
Orogenic Belt ◽  
Sikhote Alin ◽  
Asian Continent ◽  
Content Type ◽  
Eastern Margin ◽  
Continental Plate ◽  
Supplementary Material ◽  
Cretaceous Magmatism

We present new U–Pb age data for granitoids in the Central Sikhote–Alin orogenic belt in SE Russia, which refute the established opinion about the absence of the Late Cretaceous magmatism at the eastern margin of the Paleo-Asian continent. It was previously thought that a period of magmatic quiescence occurred from 88 to 50 Ma, related to subduction of the Paleo-Pacific Plate under the eastern margin of the Paleo-Asian continent, although this is inconsistent with evidence from the Sikhote–Alin, Sakhalin, and Japan regions. Three suites of plutonic rocks with different ages were identified in this study. The first suite has ages of 105–92 Ma and formed in a syn-orogenic setting. The second (86–83 Ma) and third (ca. 73 Ma) suites formed during the post-orogenic stage of the Sikhote–Alin orogenic belt. The second and third suites were coeval with Late Cretaceous granitoids that formed in a suprasubduction continental arc known as the Eastern Sikhote–Alin volcanic–plutonic belt (ESAVPB). However, the studied rocks are located far inland from the ESAVPB. The ages of the studied granitoids coincide with the timing of a change in the angle of convergence between the Paleo-Pacific Plate and eastern margin of the Paleo-Asian continent. This change in motion of the oceanic plate with respect to the continental plate was probably caused by a rupture in the subducted slab (i.e., a slab tear), followed by asthenospheric upwelling and partial melting of the overlying crust, which ultimately generated post-orogenic intrusive magmatism.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5738616

Iron and sulphur speciation and cycling in the sediments of marine systems located in the arid environment: Case of the northern Red Sea

2021 ◽  
pp. jgs2021-027
Author(s):  
Valeria Boyko ◽  
Jürgen Pätzold ◽  
Alexey Kamyshny
Keyword(s):  
Red Sea ◽  
Water Depth ◽  
Iron Content ◽  
Gulf Of Aqaba ◽  
Earth System ◽  
Content Type ◽  
Reactive Iron ◽  
The Earth ◽  
Sulphur Cycle ◽  
Supplementary Material

High fluxes of iron minerals associated with aeolian dry deposition may result in anomalously high reactive iron content and fast reoxidation of hydrogen sulphide in the sediments that prevents pyrite formation and results in “cryptic” sulphur cycle. In this work, we studied cycling of iron and sulphur in the deep-water (> 800 m water depth) sediments of the Red Sea and its northern extension, Gulf of Aqaba. We found that reactive iron content in the surface sediments of the Gulf of Aqaba and the Red Sea is high, while the content of sulphur-bound iron is very low and decreases with water depth. The presence of pyrite traces and zero-valent sulfur as well as isotopic compositions of sulphate and pyrite, which are consistent with sulphate reduction under substrate-limiting conditions, suggest that cryptic sulfur cycling is likely to be a result of fast reoxidation of hydrogen sulfide rather than microbial sulfate reduction suppression. In the sediments of Shaban Deep, which are overlain with hyper-saline hydrothermal brine, low reactive iron and high organic carbon contents result in a non-cryptic sulphur cycle characterized by preservation of pyrite in the sediments.Thematic collection: This article is part of the Sulfur in the Earth system collection available at: https://www.lyellcollection.org/cc/sulfur-in-the-earth-systemSupplementary material:https://doi.org/10.6084/m9.figshare.c.5508155

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