Miocene Tuffs Research Articles

Middle Miocene marine flooding: New 40Ar/39Ar age constraints with integrated biostratigraphy on tuffs from the North Croatian Basin

In the North Croatian Basin which is located in the southwestern part of the Pannonian Basin System, Miocene tuff deposits have been observed at several localities in the area of Banovina, Medvednica Mt. and Slavonia. Here we present new 40Ar/39Ar age results obtained from volcanic glass from the Laz tuff (15.42 ± 0.15 Ma) intercalated with lacustrine freshwater/brackish deposits, the Jovac tuff (15.10 ± 0.06 Ma) intercalated with lacustrine freshwater deposits, the Čučerje tuff (14.81 ± 0.08 Ma) and the Nježić tuff (14.40 ± 0.03 Ma) both deposited in a marine environment. Fossil data (calcareous nannofossils/foraminifera) from the underlying and overlying beds of the tuffs from Čučerje and Nježić match the geochronological data i.e. NN5 zone and M6 zone were determined. Integration of biostratigraphic and geochronological data enable a better understanding of the NCB sedimentary evolution and constrain the Middle Miocene marine flooding event in the marginal areas of the western part of the NCB at ~15 Ma i.e. early/middle Badenian boundary. These results together with the existence of lower Badenian marine sediments in the Sava depression (in the southern part of NCB) suggest it is possible to conclude that during the early Badenian in the NCB, freshwater lacustrine and marine environments coexisted.

Miocene tuffs from the Dinarides and Eastern Alps as proxies of the Pannonian Basin lithosphere dynamics and tropospheric circulation patterns in Central Europe

Tuffaceous layers are regularly preserved in Miocene carbonate and siliciclastic sediments of the Dinarides and Eastern Alps in southeastern and central Europe. Detailed mineralogical and geochemical analyses of 13 tuffs of known ages acquired from sedimentary successions of the intramontane Dinarides basins and the southwestern Pannonian Basin were carried out to infer on plausible source areas, relative strengths of volcanism, and ash distribution patterns. Studied tuffs were altered to various degrees with illite–smectite and smectite as dominant phases while volcanic glass, carbonates and other silicates are minor constituents. Tuffs’ compositions range from andesite through trachyandesite to rhyolite and trachyte. Trace-element-based correlation with regional data reveal that Lower Miocene (LM) and Lower Middle Miocene (LMM) tuffs (17.0–14.0 Ma) likely originated in the Western Carpathians (the Bükkalja volcanic field) while source areas of Upper Middle Miocene (UMM) tuffs (13.8–12.5 Ma) were in the Apuseni Mountains and/or Eastern Carpathians. The spatial relation of LM/LMM and UMM tuffs with respect to their source areas (the Bükkalja volcanic field and Apuseni Mountains, respectively) is most consistent with tropospheric easterly trade winds that carried ash hundreds of kilometres to the SW toward an azimuth of c. 200–250°. Supplementary material: Annotated X-ray diffractograms of the global and clay fraction of studied tuffs and AFM classification diagram are available at https://doi.org/10.6084/m9.figshare.c.5429592

40AR/39AR GEOCHRONOLOGY USING HIGH SENSITIVITY MASS SPECTROMETRY: EXAMPLES FROM MIDDLE MIOCENE HORIZONS OF THE CENTRAL PARATETHYS

40Ar/39Ar radio-isotopic dating of volcanic tuffs intercalated in sediments can provide high accuracy age control on the deposition of sedimentary rocks. State-of-the-art mass spectrometers such as the ARGUS VI+ are able to acquire highly precise ages for relatively small single grains (~90-250 μm for Miocene samples). Single grain measurement can provide insight into the sometimes complex age distributions within volcanic tuffs. The results show that 40Ar/39Ar ages based on multiple grain fusions will not necessarily reflect eruption ages, which can lead to (slight) overestimation of the depositional age. The paper compares multiple and single grain data from different Miocene tuffs in the Central Paratethys, which plays an important role in the establishment of a geological time frame for this area. The examples come from three middle Miocene tuff horizons that span from the Badenian transgression to the Badenian-Sarmatian Extinction Event. The new ages obtained from the Quellgraben section in the Styrian Basin (14.31±0.27 Ma and 14.03±0.04 Ma) are much younger than the previous dating and together with the new data from the Bernhardsthal-4 well, Vienna Basin (15.12±0.19 Ma) indicate, that the Badenian (Langhian) marine flooding did not reach this area before 15.2 Ma. The new weighted mean age of 12.56±0.10 Ma from the Kamenica nad Hronom section in the Danube Basin dates the transition from marine to terrestrial setting, which is possibly connected with a sea level lowstand at the beginning of the Sarmatian.

New 40Ar/39Ar, fission track and sedimentological data on a middle Miocene tuff occurring in the Vienna Basin: Implications for the north-western Central Paratethys region

Abstract The Kuchyňa tuff is found on the Eastern margin of the Vienna Basin and was formed by felsic volcanism. The Ar/Ar single grain sanidine method was applied and resulted in an age of 15.23±0.04 Ma, which can be interpreted as the age of the eruption. The obtained numerical age is in accordance with the subtropical climate inferred by the presence of fossil leaves that originated in an evergreen broadleaved forest. Furthermore, the described volcanism was connected with the syn-rift stage of the back-arc Pannonian Basin system. The sedimentological data from the underlying sandy mudstones indicate alluvial environment what confirms terrestrial conditions during deposition. Moreover, the tuff deposition probably occurred shortly before the Badenian transgression of the Central Paratethys Sea.

A perched, high-elevation wetland complex in the Atacama Desert (northern Chile) and its implications for past human settlement

AbstractA previously undocumented type of wetland is described from the Atacama Desert in northern Chile (3000 m above sea level), sustained exclusively by direct precipitation and perched above the regional water table. Geomorphological mapping, pedostratigraphy, geochemistry, and analysis of contemporary vegetation is used to understand wetland formation and dynamics during historical and present time periods. The paleowetland deposits overlie a Miocene tuff that acts as an impermeable barrier to water transfer and creates conditions for local shallow ground water. These deposits include several paleosols that were formed during periods when precipitation increased regionally at 7755–7300, 1270, 545, and 400–300 cal yr BP. The similarity in timing with other palaeohydrological records for the Atacama implies that paleosols from this wetland are proxies for reconstructing past changes in local and regional hydrological cycle. Archaeological investigations have revealed the presence of two small farms from the Late Intermediate period, i.e., during the earliest wetter phase represented by the paleosols. Both farms are located near the paleowetland deposits, which suggests that local inhabitants exploited these water sources during late pre-Hispanic times. Results of this study improve knowledge of settlement patterns during this and earlier cultural periods.

Intercalibration and age of the Alder Creek sanidine 40Ar/39Ar standard

Abstract The accuracy of 40Ar/39Ar geochronology relies in large part on precise and accurate calibration of the ages and K-Ar isotopic compositions of standards. A widely used standard for Quaternary samples, the ∼1.2 Ma Alder Creek sanidine (ACs), has published ages spanning a range of ∼2%. New measurements of ACs co-irradiated with the Fish Canyon sanidine (FCs) standard and sanidines from astronomically dated Miocene tuffs in Crete and Morocco yield results that enable both (i) a direct calibration of ACs relative to FCs, and (ii) stepwise calibrations between these two standards employing the Miocene intermediaries. Results are summarized by the parameter R F C s A C s , defined as the ratio of (40Ar*/39ArK) of ACs to FCs, which embodies the fundamental age relationship between these standards that is independent of systematic variables such as decay constants or absolute ages of standards. Our new measurements, executed using three mass spectrometers and various irradiation and analytical protocols, yield a weighted mean R F C s A C s = 0.041702 ± 0.000014 (σ). This result can be combined with previously published determinations of R values for ACs relative to the Miocene tuffs and to FCs to yield a recommended interlaboratory value of R F C s A C s = 0.041707 ± 0.000011. The weighted-mean age of ACs using this interlaboratory value, based on astronomically-calibrated ages of FCs and the Miocene intermediary sanidines, is tACs = 1.1848 ± 0.0006 Ma (±0.05%). Applying this result to the most precise published 40Ar/39Ar data for the Matuyama-Brunhes geomagnetic polarity reversal yields tMBB = 780.1 ± 0.8 ka. In addition, these new data for ACs support previous conclusions that U-Pb zircon ages from the Alder Creek rhyolite incorporate ∼13 ka of pre-eruptive residence time.

Magmatic provenance and diagenesis of Miocene tuffs from the Dinaride Lake System (the Sinj Basin, Croatia)

This study presents new insights on the provenance, genesis, and post-depositional history of the Miocene pyroclastic tuffaceous layers (~18 and ~15 Ma) preserved in argillaceous sediments and interbedded within the lacustrine sedimentary succession of the Sinj Basin in central Dalmatia (Dinaride Lake System, Croatia). Analysed tuffs are classified as smectitic tuffs composed of three main lithotypes: (a) vitriclastic tuffs, (b) altered vitriclastic tuff, and (c) tuffaceous clays. The high field strength element (HFSE) contents of the tuffs, as well as the major- element chemistry of the vitric glass, suggests that parental magmas were high-K calc-alkaline trachyandesites. This is consistent with the distinctive heavy-mineral assemblages including clinopyroxene, zircon and apatite, identified in less evolved parental magmas, and biotite in more evolved ones. The regional geological data imply the placement of the parent volcano(es) outside the Dinaric Alps region, most probably in an area corresponding to the present-day southern margin of the Pannonian Basin where volcanic rock suites of analogous age and geochemistry are reported. Minor compaction and high permeability of coarse ash-sized pyroclastic material allowed for extensive in situ diagenetic clay mineral formation dominated by smectite. Following discrete smectite formation, the illite-smectite mixed-layering took place as a result of mica/illite alteration or surface illitization processes. On the basis of the very-low grade alteration of volcanic materials, it is suggested that diagenesis operated in an open hydrologic system of a lacustrine environment.

Comparison between middle Miocene Tuffs in the Kii Peninsula, Japan: insights from whole-rock chemical composition analyses.

Comparison between middle Miocene Tuffs in the Kii Peninsula, Japan: insights from whole-rock chemical composition analyses.

Felsic tuff from Rutland Island — A pyroclastic flow deposit in Miocene-sediments of Andaman-Java subduction complex

The bedded felsic tuff exposed in Rutland Island, Andaman, consists of two facies: white massive tuff with ill-defined bedding contacts (facies-A) and dominantly green tuff exhibiting well-developed turbidite sequence with up-section change from a massive unit to plane laminated units to ripple drift lamination (facies-B). The felsic tuff is vitric to crysto-vitric in nature and contains broken crystals of quartz, feldspar, biotite and glass shards of different shapes and sizes. The bulk chemistry indicates trachyte to dacite compositional range, and high values of Zr relative to Nb and Y suggest convergent margin tectonic setting of the tuff. Dominance of cuspate shards rather than blocky shards in both the facies indicates subaerial eruption of the pyroclasts. Recurrence of turbidites as well as good sorting of crystals and glass suggest that subaerially erupted ash was transported in subaqueous condition. The bed pattern supports rapid deposition of facies-A from high concentration turbidity flow whereas facies-B could be produced by decrease in grain size and suspended-load fallout rate of turbidity current. Regional correlation suggests that felsic volcanism in Sumatra was the source for such early Miocene to middle Miocene tuff.

Large‐fruited Salicaceae s.l. from the Miocene tuff of the Eichelskopf, northern Hessen, Germany

AbstractReexamination of Saccoglottis kayseri (Schindehütte) Kirchheimer from the Miocene tuff of the Eichelskopf southeast of Homberg an der Efze in northern Hessen, Germany, indicates that the species was incorrectly attributed to Humiriaceae. The large ovoid fruits are 6‐ and 7‐valved capsules bearing numerous seeds in parietal position. The outer surface is hexagonally or heptagonally ridged. Each valve of the capsule bears a broad, ventral longitudinal band that is densely punctate indicating the position of numerous seeds. These characters point to affinities with the Salicaceae s.l. (incl. most former Flacourtiaceae), and match particularly well with Itoa L., which is distributed today in southern China and eastern Malesia. However, the fruit valves appear to separate only from the apical end, rather than both from base and apex which is a feature of fruits in the Itoa‐Carrierea‐Poliothyrsis group. We treat the fruits as a new genus of Salicaceae, Schindehuettea gen. nov. under the binomial Schindehuettea kayseri (Schindehütte) Manchester. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Zeolites and Coexisting Authigenic Minerals in Miocene Tuffs of the Alaçatı (Çeşme) Area, Turkey

AbstractThe zeolites and coexisting minerals of the silicic vitric tuffs in the Alaçatı (Çeşme) area, west of İzmir (Turkey), were studied. Mordenite is the most abundant zeolite in tuffs of the Alaçatı area and usually coexists with clinoptilolite-heulandite, smectite and calcite. Opal-CT was identified by means of its crystal morphology and EDX spectrum. Scanning electron microscopy (SEM) revealed the relative age relationships between the zeolites and coexisting minerals, namely mordenite, clinoptilolite-heulandite, smectite, calcite, and, in addition, opal-CT. Smectite consistently crystallized earlier than any of the zeolites, and it occasionally coats the outer walls of some of the vitric material. The zeolites are commonly located on the smectite, although some mordenites were observed to be in direct contact with glass shards that lacked a smectite coating. Clinoptilolite-heulandite formed after smectite and before mordenite. Opal-CT is seen to postdate both smectite and needle-shaped mordenite. Calcite was probably the latest mineral to crystallize in the Alaçatı tuffs. The zeolites in the tuffs of the Alaçatı area formed by dissolution of silicic vitric tuffs by Na- and Ca-rich thermal waters which passed through the fracture zone. The appearance of zeolites together with smectite along this zone may be attributed to a semi-open system which subdivided into smaller closed systems. Small changes in the pH and chemical composition of the thermal waters during alteration produced the corrosion effects observed by SEM. Small amounts of clinoptilolite-heulandite were corroded prior to crystallization of coexisting mordenite. The different compositions of the thermal waters were probably inherited from water that resulted from mixing of thermal and groundwaters.

Mammal bearing late Miocene tuffs of the Akkaşdağı region; distribution, age, petrographical and geochemical characteristics

Mammal bearing late Miocene tuffs of the Akkaşdağı region; distribution, age, petrographical and geochemical characteristics

Statistical Review of Major Element Data from the Miocene Tuffs in Hungary.

Statistical Review of Major Element Data from the Miocene Tuffs in Hungary.

Silicate diagenesis in deep-sea sediments from the Tonga forearc (SW Pacific): a strontium and Rare Earth Elements signature

87Sr/ 86Sr isotopic ratios, strontium and Rare Earth Element concentrations obtained on volcano-sedimentary rocks and separated clay mineral and zeolite fractions reveal a formation by pore water–volcanic rock interaction for most of the hydrous silicate minerals of the Site 841 ODP collected from the Tonga forearc. Unusual strontium concentrations and isotopic ratios recorded in the Miocene tuffs associated with specific REE patterns indicate that the formation of these hydrous silicates does not follow a simple burial diagenesis model, but was related to the cooling of intruding basaltic sills in the Miocene volcano-sedimentary series. Migration of strontium into the pore water in response to the heat flow induced the formation of Sr-bearing zeolites such as clinoptilolite, heulandite and chabazite. No evidence of any influence of a further thermal pulse in the Eocene rhyolitic tuffs could be found. As recorded by the chemistry of their clay mineral fraction, the rhyolitic tuffs developed a polyphasic diagenetic process, which might have been influenced by a possible circulation of a fluid into structurally weak areas. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS Tonga / silicates / strontium / Rare Earth Elements / diagenesis / heat flow

Weathering rate of mudstone and tuff on old unlined tunnel walls

The mechanisms and rate of weathering of soft sedimentary rocks exposed along unlined tunnel walls were investigated using mineralogical, chemical and physical methods. Tunneling occurred several decades ago within the Kakinokidai Formation (middle Pleistocene) and the Kiwada Formation (lower Pleistocene) of the Kazusa Group of Chiba Prefecture, as well as within the Fukuda Formation (Miocene) of Saitama Prefecture in Japan. Since then, the walls of the tunnels have been desiccated by ventilation, sulfuric acid has been generated by pyrite oxidation, calcite and glass have been dissolved by sulfuric acid, and gypsum has crystallized on the surface of the tunnel walls. The oxidized zone was formed on the surface of the walls by the weathering. The formation of this zone and weathering rates (determined as rates of movement of the oxidation fronts) in the vadose zone are explained by the diffusion of oxygen from the surface of the tunnel walls. The relationship between the depth of the oxidation front ( l cm) and the number of years since excavation ( t year) was expressed by l=R oxi t . The R oxi values from the tunnels ranged among 5 for the middle Pleistocene sandy mudstone, 2–4 for the middle Pleistocene mudstone, 0.3 for the lower Pleistocene mudstone and 1–3 for the Miocene tuff. R oxi depends on the diffusion coefficients of oxygen and the chemical composition of rocks. The diffusion coefficients of oxygen ( D e), calculated using the R oxi and chemical compositions of the four kinds of rock above, were 10 −5 cm 2/s, 10 −7–10 −5 cm 2/s, 5×10 −8 cm 2/s and 4×10 −7–3×10 −6 cm 2/s, respectively, depending on the air permeabilities of the rocks that correlate closely with the coefficient of water permeabilities ( K). The relationship for the mudstone was log D e (cm 2/s)=0.91 log K (cm/s)−0.71. The values of D e for the tuff were smaller than for the mudstone due to the smaller air porosities of 0.01–0.04.

Formation temperatures of clays from the volcaniclastic series of Site 841 ODP: an oxygen isotopic record of a paleothermal flux into the Tonga forearc

Oxygen isotopic compositions of clay minerals were determined on representative samples of the volcano-sedimentary series from Site 841 ODP (Tonga forearc). This isotopic study has demonstrated an abnormally high crystallisation temperature of the clay minerals with respect to temperature expected in burial diagenesis. Formation temperatures obtained using 18O reach up to 200 °C in a Fe-chlorite-corrensite paragenesis found in the vicinity of basaltic andesite sills intruded into the Miocene tuffs. The paleothermal flux resulting from the cooling of the sills has produced very low grade contact metamorphism in the Miocene Tonga forearc deposits. The consequence of this was the formation of a large amount of hydrous silicates characterised near the sills by a Fe-clays-analcime mineralogical association.

Thermal diagenesis of clay minerals within volcanogenic material from the Tonga convergent margin

Clay minerals are examined in detail in the sediment from the Tonga Trench margin at Site 841 (Leg 135 ODP). The changes in amount and nature of secondary clays with depth provide an alternative explanation for the intensive alteration of volcanogenic material at convergent margins. A characteristic distribution of clay minerals with depth shows four distinct zones unexplainable by simple burial diagenesis processes. These are named the upper, reactive, lower and rhyolitic zones. The reactive zone is intercalated with numerous sills and is characterized by the dominant iron-rich clays such as saponite, corrensite and chlorite associated with analcime. The occurrence of such iron-rich clays, mostly associated with a large amount of analcime, yields chemical and mineralogical evidence for thermal diagenesis. The required heat for the diagenetic process was transferred from recently intruded basaltic andesite sills. In the vicinity of these intrusions, the iron-rich clay minerals may have formed at temperatures up to 200°C. A zoning with respect to clay and zeolite minerals indicates that the influence of the palaeoheat flow decreased with the distance from the intrusion. The formation of interlayered I/S, illite, kaolinite and aluminous chlorite, which are recognized as major secondary minerals within the rhyolitic complex, was mainly controlled by both early diagenesis at moderately elevated temperatures, and since the Eocene by burial diagenesis at low temperatures. The occurrence of a steam zone in an early stage of the intrusion is restricted to Miocene tuffs and has overprinted the early alteration of the volcanogenic material within the tuffs and has changed the originally pristine composition of the pore fluids.

Fission Track Age of Miocene Kn-3 Tuff in Central Japan: Towards Better Age-Control on Magneto-Biostratigraphic Time Scale.

A fission track age for a Miocene tuff (Kn-3) in the late Cenozoic sedimentary sequence in the Boso Peninsula, central Japan, was determined in an effort to gain an age control for the biozone boundary. The obtained age of 15.0 ± 0.5 Ma (error: 1σ) represents the N.9/N.10 boundary of the planktonic foraminiferal zones, as the Kn-3 Tuff is located near the first occurrence of Globorotalia peripheroacuta which defines the N.9/N.10 boundary. Our age determination supports most of the recent estimates for the N.9/N.10 biozone boundary which until now has not been dated directly, but inferred based on speculative assumptions.

40Ar/ 39Ar geochronology of biostratigraphically controlled Miocene tuffs from central Japan: Comparison with Italy and age of the Serravallian-Tortonian boundary

Two volcanic tuffs of the Tomioka area (central Japan) were selected from a fossiliferous marine succession of Late Serravallian age (Miocene) and dated using the incremental heating 40Ar/ 39Ar technique. The Kitamura Tuff, located 10 m below the regional first occurrence (FO) of the planktonic foraminifera Globigerina nepenthes, yielded a biotite age of 11.79 ± 0.08 Ma. The Baba Tuff, located 180 m above the previous one, yielded ages of 11.26 ± 0.09 Ma (biotite),11.29 ± 0.12 Ma (sanidine) and ∼ 11.3 Ma (plagioclase). Isochron ages are similar to the plateau ages. The FO of G. nepenthes is estimated to have an age of 11.76 ± 0.10 Ma in Japan. Similarly precise results obtained from the Central Apennines (biotite: 11.48 ± 0.13 Ma) lead to an age estimate of 11.53 Ma for the same FO in an Italian section. The age difference between sections is of the same magnitude as the analytical errors. However, the potential diachronism of the biostratigraphic signal has been independently estimated at 0.25 Ma. The FO of G. nepenthes and FO of Neogloboquadrina acostaensis are commonly taken as index for the beginning of N14 and end of N15 foraminiferal biozones, respectively. In the Italian section, the time interval between the two signals — i.e. the duration of the two biozones — may be estimated at 0.3 Ma. The Serravallian-Tortonian boundary located near the dated layers can be estimated to have an age of ∼ 11.25 ± 0.20 Ma.

Ion Exchange and Dehydration Effects on Potassium and Argon Contents of Clinoptilolite

AbstractZeolite-rich Miocene tuffs are an important part of the principal hydrochemical barrier to water-borne radionuclide transport from a potential high-level nuclear waste repository at Yucca Mountain, Nevada. The timing of zeolitization is an issue that relates to paleohydrology, permeability, zeolite stability, and unsaturated-zone geochemical processes. Exploratory K/Ar dating of clinoptilolite, the most abundant and widespread zeolite, shows a striking and consistent pattern of increasing apparent ages (2–13 Ma) with depth. Only the isotopic ages from the saturated zone are compatible with geologic evidence suggesting an age >10 Ma for most of the zeolites.Factors that may be responsible for the young apparent ages in the unsaturated zone were investigated. Cation exchange with recharge water and Ar diffusion under unsaturated conditions (processes that may be characteristic of the unsaturated zone) were evaluated experimentally for their effects on K/Ar systematics. Cation exchanging a natural clinoptilolite with Ca-, Cs-, K-, and Na-chloride solutions showed minimal effects on radiogenic Ar content. However, clinoptilolite heated at 2007deg;C for 16 hours in air lost a significant amount of its radiogenic Ar compared with minimal losses from clinoptilolite heated in water at 100°C for over 5 months. The preliminary results indicate that Ar loss from incompletely hydrated clinoptilolite may be a major factor contributing to the young apparent ages of clinoptilolite in the unsaturated zone at Yucca Mountain.