bluuebunny/crossref_metadata_2025_split huggingface dataset:
New perspective on the nineteenth-century golden pumice deposit of Kīlauea Volcano
Authors: Biass Sébastien , Swanson Donald A. , Houghton Bruce F. 
Published: October 2019

ABSTRACT
The golden pumice deposit (unit K1) represents one of the latest episodes of Hawaiian fountaining in the Keanakāko‘i Tephra and is the product of the first high fountaining eruption at Kīlauea summit in ~300 yr, since the caldera formed in ca. 1500 CE. We present a new physical characterization of the deposit based on over 200 field sites, all affected by severe erosion, alteration, and silicic encrusting. We detail the deposit geometry, stratigraphic and structural relationships, and componentry to constrain its volume and reconstruct the eruptive sequence. The deposit is then discussed and set against other young episodes of high fountaining at Kīlauea.
We interpret the golden pumice as the product of a days-long eruptive sequence with a source located inside a caldera much deeper than that of today. The eruption probably started along a NE-SW–oriented fissure and migrated toward a single vent in the southwestern part of the caldera, where at least two high Hawaiian-style fountains produced a tephra deposit of ~6 × 106 m3. Stratigraphic contacts reveal that erosion occurred not only between, but also during the fountaining episodes, suggesting heavy rainfall during deposition. Field observations during this study also led to the discovery of the first stratigraphic evidence that the eastern pumice postdates the golden pumice, which contributes to the new definition of the stratigraphy of the Keanakāko‘i Tephra presented in this volume.
Large hydromagmatic eruption related to Fernandina Volcano’s 1968 caldera collapse—Deposits, landforms, and ecosystem recovery
Authors: Howard* Keith A. , Simkin† Tom , Geist Dennis J. , Merlen Godfrey , Nolf§ Bruce 
Published: October 2019

ABSTRACT
The hydromagmatic eruption that immediately preceded the 1968 caldera collapse of Fernandina Volcano, Galápagos, which had a volcano explosivity index (VEI) of 4, offers a case study of powerful eruptions where basaltic magma interacts with caldera-ponded water. The 4-d-long hydromagmatic eruption sequence records an early stage and a small fraction of the volume of magmatic withdrawal that led the caldera floor to lower 350 m over the next 10 d. Erupted tephra was lithic-rich. The small proportion of juvenile basaltic glass included blocky fragments, Pele’s tears, and Pele’s hair. Pyroclastic density currents swept across the western summit plateau 600–700 m above the vent and deposited dunes, cross-bedded and rubbly breccia deposits, imbricated lag blocks, and ash plasters, and toppled trees. Blocks ejected out of the caldera formed impact craters on the volcano’s flank &gt;600 m higher and &gt;1 km away. Ejected blocks are mostly basalt but include cumulate olivine gabbro. The vent area enlarged by 300 × 106 m3 during the eruption. A small adjacent fault-bounded block subsided after the eruption. Lake water and groundwater confined within the caldera by ring dikes were available to interact with hot rocks and magma. In our interpretation, this water helped to trigger and feed the eruption by interacting with rocks above a lowering magma column. Ecosystems recovered rapidly on the tephra. Eruptions have not diminished the island’s biodiversity despite Fernandina’s high rate of volcanic activity, including the massive resurfacing in 1968. Stratigraphic evidence suggests that the 1968 eruption may be only the latest in a series of explosive eruptions from the caldera.
U-Pb zircon geochronology of calc-alkaline ash-flow tuff units in the Mogollon-Datil volcanic field, southern New Mexico
Authors: Rentz Shannon P. , Michelfelder Gary S. , Coble Matthew A. , Salings* Emily 
Published: October 2019

ABSTRACT
The Mogollon-Datil volcanic field is a 40–24 Ma cluster of calderas that formed during ignimbrite flare-up eruptions in southern New Mexico associated with sub-duction, and possible delamination, of the Farallon plate beneath the North American plate. This study uses magmatic zircon sampled from four ignimbrites from a nested caldera system and an additional ignimbrite located outside of the nested system to compare the processes and timing of magma accumulation in southern New Mexico. These ignimbrites include: the Whitewater Tuff, the Cooney Canyon Tuff, the Davis Canyon Tuff, and the Shelley Peak Tuff from the Mogollon Mountains and the Bell Top 4 Tuff from the Uvas volcanic field. The ignimbrites range from crystal-poor, high-silica rhyolite to crystal-rich, low-silica rhyolite. We compare previous 40Ar/39Ar sanidine eruption ages to new U-Pb crystallization ages and trace-element compositions of zircon. Weighted mean zircon ages define two magmatic groups. Group one includes the Bell Top Tuff (34.5 ± 0.5 Ma), the Cooney Canyon Tuff (34.8 ± 0.8 Ma), and the Whitewater Creek Tuff (36.2 ± 0.4 Ma). The second group includes the Davis Canyon Tuff (28.7 ± 0.5 Ma) and the Shelley Peak Tuff (29.6 ± 0.5 Ma). Weighted mean zircon ages are within published 40Ar/39Ar ages, with the exception of the Shelley Peak Tuff, which is ~1 m.y. older. Hafnium contents and Th/U and Yb/Gd ratios suggest the dominant mechanism that produced eruptible melt was rejuvenation or remobilization of a crystal mush accompanied by minimal partial melting of the continental crust.
Numerical basin modeling of the Laptev Sea Rift, NE Russia
Authors: Brandes Christian , Franke Dieter , Piepjohn Karsten , Gaedicke Christoph 
Published: October 2019

ABSTRACT
The Laptev Sea Rift in the East Siberian continental margin plays an important role in the geodynamic models for the opening of the Eurasia Basin. The active Gakkel Ridge, which also represents the boundary between the North America and Eurasia plates, abruptly meets the continental margin of the Laptev Sea. On the continental shelf in the prolongation of the Gakkel Ridge, a rift developed since the Late Cretaceous/Early Cenozoic with the formation of five roughly north-south trending depocenters. To better understand the evolution of this rift, a basin modeling study was carried out with PetroMod® software. The modeled sections used in this study were developed on the basis of depth-converted reflection seismic sections. The sections cover the Anisin Basin in the north and the southeastern margin of the Ust´ Lena Rift in the south. The numerical simulations are supported by tectonic and sedimentological field data that were collected in outcrops during the CASE 13 expedition to the New Siberian Islands in 2011. For the Anisin Basin different scenarios were modeled with rift onsets between 110 Ma and 66 Ma. The results show that the present-day temperature field in the area of the Anisin Basin and at the southeastern margin of the Ust´ Lena Rift is characterized by horizontal, seafloor-parallel isotherms. Geohistory curves extracted from the 2D simulations indicate a twofold rift evolution with a stronger initial subsidence in the Late Cretaceous to Early Paleogene and a moderate subsidence in Late Paleogene and Neogene times. Based on the modeling results, an early rift onset around 110 Ma seems to be more realistic than a later one around 66 Ma.
Tonian and Silurian magmatism in Nordaustlandet: Svalbard’s place in the Caledonian orogen
Authors: McClelland* William C. , von Gosen* Werner , Piepjohn* Karsten 
Published: October 2019

ABSTRACT
The Nordaustlandet terrane of Svalbard plays a critical role in evaluating strike-slip displacements in the Caledonian orogen. Comparison of Silurian and Tonian magmatism in Nordaustlandet, East Greenland, and the Pearya terrane on Ellesmere Island provides a means to evaluate models of large-scale versus minimal displacements. Augen gneiss with an emplacement age of 972 ± 5 Ma demonstrates that the Tonian granite suite is coeval with the calc-alkaline Kap Hansteen volcanic rocks. Zircon from Silurian leucosomes, leucogranites, and granites is dominated by xenocrystic components, making it analytically difficult to isolate magmatic versus inherited age domains. Zircon systematics from a relatively undeformed Silurian granite (431 ± 5 Ma) resemble those of similar granites interpreted to be Tonian in age (e.g., Kontaktberget granite). Assuming less deformed granites of Nordaustlandet are Silurian, synemplacement or syntectonic deformation of Tonian augen gneiss and volcanic rocks is no longer required. Tonian magmatic rocks of Svalbard share a common origin with basement rocks of the Pearya terrane within a continental arc system, but are distinctly older than Tonian igneous and metamorphic rocks of East Greenland. Migmatite complexes and granite intrusions in Nordaustlandet, with ages ranging from 440 to 425 Ma, are coeval with granites in East Greenland that record the combined effects of subduction beneath Laurentia and mid-crustal melting. Migmatites in East Greenland are juxtaposed with low grade rocks by syn-contraction normal faults whereas migmatites show gradational contacts into lower grade rocks on Nordaustlandet. These differences in basement age and structural setting preclude proximity of the Nordaustlandet terrane with East Greenland during the 440–400 Ma continent-continent collision phase (Scandian) of the Caledonian orogen. Similarly, differences in depositional, magmatic, and metamorphic history between the Pearya terrane basement and Nordaustlandet terrane argue against simple offset of crustal fragments. The Pearya and Nordaustlandet terranes likely were not involved in the main phase of crustal thickening directly related to collision of Baltica and Laurentia, but rather resided on a convergent boundary north of the Scandian continent-continent collision zone, consistent with models of Gee and Teben’kov (2004) and Johansson et al. (2005).
Defining tectonic boundaries using detrital zircon signatures of Precambrian metasediments from Svalbard’s Southwestern Caledonian Basement Province
Authors: Ziemniak Grzegorz , Kośmińska Karolina , Schneider David A. , Majka Jarosław , Lorenz Henning , McClelland William C. , Wala Virginia T. , Manecki Maciej 
Published: October 2019

ABSTRACT
Detrital zircon provenance studies of Precambrian metasedimentary rocks in Wedel Jarlsberg Land and Sørkapp Land, Svalbard’s Southwestern Caledonian Basement Province, were conducted to evaluate local stratigraphic correlations and the role of long-distance strike-slip displacements in assembling the basement of the Arctic Caledonides. The detrital zircon U-Pb age spectra of the late Mesoproterozoic to Neoproterozoic metasediments revealed mainly Mesoproterozoic to Paleoproterozoic age signatures characteristic for a Grenville–Sveconorwegian orogen provenance. These results confirmed a stratigraphic correlation between basement units of southern Sørkapp Land and the Isbjørnhamna Group of Wedel Jarlsberg Land and suggest relocation of the tectonic boundary between the Eimfjellet Complex and the Isbjørnhamna Group above the Eimfjellbreane Formation. Moreover, the results support the Vimsodden Kosibapasset Shear Zone (VKZ) as a major tectonic boundary and highlight the inhomogeneity in the Southwestern Caledonian Basement Province. The detrital zircon age signatures south of the VKZ bear similarities with coeval metasediments of the Northwestern Caledonian Basement Province of Svalbard and other localities in the Greenland and Scandinavian Caledonides. In contrast, the detrital zircon age spectra north of the VKZ are comparable with the high Arctic Neoproterozoic sediments of Baltican affinity. In conjunction with previous studies, the results suggest that the basement units may continue across the traditional boundaries of the Svalbard’s Caledonian basement provinces.
Late Cretaceous–Paleogene burial and exhumation history of the Southwestern Basement Province, Svalbard, revealed by zircon (U-Th)/He thermochronology
Authors: Barnes* Christopher J. , Schneider David A. 
Published: October 2019

ABSTRACT
We apply zircon (U-Th)/He low-temperature thermochronology to metasedimentary sequences of the Southwestern Basement Province of Svalbard to investigate the shallow crustal tectonics of Svalbard and the High Arctic. We resolve Cretaceous through Paleogene time-temperature histories for four areas of the province: Sørkapp Land, Wedel Jarlsberg Land, Oscar II Land, and Prins Karls Forland. Results indicate peak Late Cretaceous temperatures of ~175–185 °C in the south (Sørkapp Land, Wedel Jarlsberg Land) and &gt;200 °C in the north (Oscar II Land) as a consequence of maximum burial and an elevated geothermal gradient (&gt;40 °C/km). Late Cretaceous cooling affected all areas during regional exhumation related to initial rifting in the Eurasian Basin to the north. A subsequent heating event (recorded at Wedel Jarlsberg Land and Oscar II Land) from ca. 53–47 Ma is interpreted to result from tectonic burial during Eurekan deformation and development of the West Spitsbergen Fold-and-Thrust Belt. Our thermal models reveal a subsequent cooling event (47–34 Ma) corresponding to a shift in tectonic regime from compression to dextral strike-slip kinematics during Eurekan deformation; exhumation of the West Spitsbergen Fold-and-Thrust Belt coincided with strike-slip tectonism. Throughout Eurekan deformation, Prins Karls Forland resided at temperatures &gt;200 °C and records cooling during post-34 Ma extension. Our models indicate 2.5–3.5 km of unroofing in Wedel Jarlsberg Land and Oscar II Land, and &gt;4 km of unroofing of Prins Karls Forland, which is a deeper structural level of the West Spitsbergen Fold-and-Thrust Belt than other exposures on Spitsbergen. The results of this study document elevated heat flow in the Late Cretaceous, extend spatial resolution of Late Cretaceous crustal cooling documented across Svalbard, and illustrate the temporal and thermal evolution of the West Spitsbergen Fold-and-Thrust Belt, which is necessary for an improved understanding of Arctic geodynamics.
Coal rank data and tectonic structure of Mesozoic and Paleogene sediments in North Greenland
Authors: Paech Hans-Jürgen , Estrada Solveig 
Published: October 2019

ABSTRACT
Vitrinite reflectance (Rr) data, combined with structural field evidence, allow insights into the thermal and tectonic history of North Greenland. During the tectonism at the Cretaceous–Paleocene boundary, the thermal imprint varies considerably, mostly controlled by active fault zones. The Upper Cretaceous sequences along the Harder Fjord Fault Zone show Rr values between ~3.2% (Frigg Fjord area) and ~2.1% (Depotbugt area). Along the Trolle Land Fault Zone, Rr varies between 1.3% and 2.9% in the Herlufsholm Strand area, and between 1.6% and 2.2% in the Kilen area. These maturity variations along regional fault zones are connected with varying deformation intensity and explained by unequal conductive heat flow. In the Kap Washington Group, the high coal rank attaining 5.4% Rr is associated with ductile deformation, and is additionally influenced by magmatic activity, i.e., convective heat flow. The coalification is low in regions a greater distance away from active faults, e.g., in Lower Cretaceous sediments of Herluf Trolle Land with ~0.5% Rr. The Paleogene Thyra Ø Formation was deposited following deformation and thermal imprint at the Cretaceous–Paleogene boundary. It remained undeformed and shows a reduced Rr of ~0.55%, reflecting burial thermal imprint. A later thermal event (known from the literature) that affected Mesozoic sediments, and possibly also locally Paleogene sediments close to the continental margin, is assumed to be related to heat flow from the active plate boundary between northeast Greenland and Svalbard.
Based on detailed geochemical and mineralogical studies, thin, yellowish jarosite-bearing, clayey horizons within the Thyra Ø Formation are interpreted to probably originate from volcanic ashes erupted during the first stage of the opening of the North Atlantic.
Episodic tectonics in the Phanerozoic succession of the Canadian High Arctic and the “10-million-year flood”
Authors: Embry* Ashton , Beauchamp Benoit , Dewing Keith , Dixon James 
Published: October 2019

ABSTRACT
We have identified 57 large-magnitude, sequence boundaries in the Phanerozoic succession of the Canadian High Arctic. The characteristics of the boundaries, which include angular unconformities and significant changes in depositional and tectonic regimes across the boundaries, indicate that they were primarily generated by tectonics rather than by eustasy. Boundary frequency averages 10 million years throughout the Phanerozoic and there is no notable variation in this frequency.
It is interpreted that each boundary was generated during a tectonic episode that lasted two million years or less. Each episode began with uplift of the basin margins and pronounced regression. This was followed by a rapid subsidence and the flooding of the basin margins. Each tectonic episode was terminated by a return to slow, long-term subsidence related to basin forming mechanisms such as thermal decay. The tectonic episodes were separated by longer intervals of tectonic quiescence characterized by slow subsidence and basin filling.
The tectonic episodes are interpreted to be the product of changes in lithospheric stress fields with uplift being related to increased, compressional horizontal stress and the following time of rapid subsidence reflecting a decrease in such stresses or an increase in tensional stresses. Conversely, the longer intervals of tectonic quiescence would reflect relatively stable, horizontal stress fields. The episodic changes in stress fields affecting the Canadian High Arctic throughout the Phanerozoic may be a product of intermittent, plate tectonic reorganizations that involved changes in the speed and directions of plate movements. The longer intervals of tectonic quiescence would occur during times of quasi-equilibrium in the plate tectonic mosaic.
The tectonic episodes that generated the sequence boundaries were governed by nonlinear dynamics and chaotic behavior, and there is a one-in-10-million chance that a tectonic episode will be initiated in the Canadian High Arctic in any given year. Thus, the major transgression associated with each episode can be referred to as a “10-million-year flood.”
Detrital zircon U-Pb and Lu-Hf analysis of Paleozoic sedimentary rocks from the Pearya terrane and Ellesmerian Fold Belt (northern Ellesmere Island): A comparison with Circum-Arctic datasets and their implications on terrane tectonics
Authors: Malone* Shawn J. , McClelland* William C. , Gosen* Werner von , Piepjohn* Karsten 
Published: October 2019

ABSTRACT
Detrital zircon U-Pb and Hf isotopic data from Ordovician to Devonian–Carboniferous sedimentary rocks sampled from the Pearya terrane and adjacent areas, northern Ellesmere Island, record temporal variation in detrital zircon signature on the northeastern Arctic margin of Laurentia. Ordovician to Silurian clastic sediments deposited on the Pearya terrane record a provenance signal from before terrane accretion. This signal is dominated by Ordovician arc material and grains derived from recycling of Proterozoic metasedimentary and metaigneous basement. This pattern is similar to Neoproterozoic detrital zircon spectra from the Svalbard and East Greenland Caledonides, supporting the exotic nature of the Pearya terrane and links between Pearya and the Arctic Caledonides. Sedimentary rock deposited in the late Ordovician and early Silurian deep water basin of the Clements Markham fold belt likewise record a recycled source containing abundant early Neoproterozoic and Mesoproterozoic aged zircon. This contrasts with similarly aged units on Franklinian shelf, which contain much more abundant Paleoproterozoic zircon ages.
The provenance of the late Devonian–Carboniferous(?) Okse Bay Formation is dominated by sediment reworked from the units exposed in Pearya or the East Greenland Caledonides, with new sources derived from Paleoproterozoic domains of the Canadian-Greenland shield and late Devonian igneous rocks documented in Ellesmere and Axel Heiberg Islands, and Arctic Alaska. In contrast, detrital zircon age spectra from Devonian sedimentary rocks in the western Ellesmerian Clastic Wedge and northern Cordilleran clastic wedge of the Mackenzie Mountains contain abundant zircon grains yielding ages characteristic of the Caledonian and Timanian Orogens. This contrast suggests that the northeastern and northwestern sectors of the Paleozoic Laurentian Arctic margin received sediments from different terranes, with the northeast being dominated by reworked Caledonide terrane and Laurentian craton detritus, and the northwest likely receiving sediment from elements of Arctic Alaska–Chukotka. These detrital zircon data indicate that the Pearya terrane was isolated from northern Laurentia until after the late Silurian. The accretion of the Pearya terrane is constrained between the late Silurian and middle Devonian by stratigraphy, detrital zircon provenance shifts indicating a Laurentian cratonic source by the early Carboniferous, metamorphism in the orthogneiss basement observed between ca. 395 and 372 Ma, and the emplacement of the Cape Woods post-tectonic pluton at 390 Ma.
Triassic history of the Tanquary High in NE Sverdrup Basin, Canadian Arctic Archipelago
Authors: Embry* Ashton 
Published: October 2019

ABSTRACT
The Tanquary High is a positive tectonic feature that was identified on the southern margin of the far northeastern portion of Sverdrup Basin. A sequence stratigraphic analysis of the Triassic succession of northern Ellesmere Island, involving 27 measured sections and one well section, has allowed the geometry and evolution of the high in the Triassic to be elucidated. The Triassic succession occurs within five second-order sequences, and each sequence boundary reflects the occurrence of a tectonic episode that included basin margin uplift and basinward movement of the shoreline.
The Tanquary High was uplifted during these tectonic episodes, which occurred in the latest Permian, latest Early Triassic, latest Middle Triassic, latest Carnian, and latest Norian. Each sequence is truncated toward the crest of the high where Rhaetian strata now overlie Cambrian strata. Isopach and facies data for each sequence reveal that, at the times of maximum uplift of the Tanquary High, the subaerially exposed part of the high extended 100–150 km down its northwest-trending axis and up to 150–200 km down each flank. Rapid subsidence completed each tectonic episode and initiated the development of a new sequence. The Tanquary High was completely drowned at these times. It is hypothesized that the tectonic episodes were generated by changes in horizontal stress fields driven by plate tectonic reorganizations.
The facies and isopach maps of the latest Triassic to early Early Jurassic (Rhaetian-Sinemurian) second-order sequence demonstrate that the Tanquary High ceased to exist following the first order, latest Norian sequence boundary. A complete reversal of source areas and the initiation of the Amerasia rift basin coincided with the demise of the Tanquary High.