Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc

Geology ◽  
2020 ◽  
Vol 48 (12) ◽  
pp. 1216-1220
Author(s):  
Drew T. Downs ◽  
Duane E. Champion ◽  
Patrick Muffler ◽  
Robert L. Christiansen ◽  
Michael A. Clynne ◽  
...  
Keyword(s):  
Magma Ascent ◽  
Middle Pleistocene ◽  
Normal Faults ◽  
Northern California ◽  
Spatially Distributed ◽  
Dry Lake ◽  
Eruption Age ◽  
Tectonic Settings ◽  
Back Arc ◽  
Crustal Magma

Abstract Mapping and chronology are central to understanding spatiotemporal volcanic trends in diverse tectonic settings. The Cascades back arc in northern California (USA) hosts abundant lava flows and normal faults, but tholeiitic basalts older than 200 ka are difficult to discriminate by classic mapping methods. Paleomagnetism and chemistry offer independent means of correlating basalts, including the Tennant, Dry Lake, and Hammond Crossing basalt fields. Paleomagnetic analysis of these chemically similar basalts yield notable overlap, with statistical analysis yielding 7 chances in 1,000,000 that their similar mean remanent directions are random. These basalts also have overlapping 40Ar/39Ar ages of 272.5 ± 30.6 ka (Tennant), 305.8 ± 23.9 ka (Dry Lake), and 300.4 ± 15.2 and 322.6 ± 17.4 ka (Hammond Crossing). Chemical and paleomagnetic analyses indicate that these spatially distributed basalts represent simultaneous (<100 yr uncertainty) eruptions, and thus we use 305.5 ± 9.8 ka (weighted mean) as the eruption age. Their vents align on a N25°W trend over a distance of 39 km. Tennant erupted the largest volume (3.55 ± 0.75 km3) at the highest elevation; both factors decay to the south-southeast at Dry Lake (0.75 ± 0.15 km3) and Hammond Crossing (0.15 ± 0.05 km3). We propose vertical magma ascent beneath the Tennant vent area, where the most evolved, high-SiO2 magma erupted, with lateral dike propagation in the brittle crust. Propagation was near orthogonal to east-west extension (0.3–0.6 mm/yr) along north-northwest–trending normal faults.

scholarly journals Supplemental Material: Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc

2020 ◽  
Author(s):  
Drew Downs ◽  
et al.
Keyword(s):  
Neutron Activation Analysis ◽  
Radiometric Dating ◽  
Middle Pleistocene ◽  
X Ray ◽  
Data Table ◽  
Analysis Methods ◽  
Dating Methods ◽  
Location Map ◽  
Back Arc ◽  
Crustal Magma

Table S1 (paleomagnetic analysis methods and data); Table S2 (detailed X-ray fluorescence spectrometry and instrumental neutron activation analysis methods and data); Table S3 and Figures S1–S4 (<sup>40</sup>Ar/<sup>39</sup>Ar experimental results, age spectra, and radiometric dating methods); and Figure S5 (location map of basalts plotted in Figure 2B).<br>

scholarly journals Supplemental Material: Simultaneous Middle Pleistocene eruption of three widespread tholeiitic basalts in northern California (USA): Insights into crustal magma transport in an actively extending back arc

2020 ◽  
Author(s):  
Drew Downs ◽  
et al.
Keyword(s):  
Neutron Activation Analysis ◽  
Radiometric Dating ◽  
Middle Pleistocene ◽  
X Ray ◽  
Data Table ◽  
Analysis Methods ◽  
Dating Methods ◽  
Location Map ◽  
Back Arc ◽  
Crustal Magma

Table S1 (paleomagnetic analysis methods and data); Table S2 (detailed X-ray fluorescence spectrometry and instrumental neutron activation analysis methods and data); Table S3 and Figures S1–S4 (<sup>40</sup>Ar/<sup>39</sup>Ar experimental results, age spectra, and radiometric dating methods); and Figure S5 (location map of basalts plotted in Figure 2B).<br>

scholarly journals Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 117
Author(s):  
Maria Filomena Loreto ◽  
Camilla Palmiotto ◽  
Filippo Muccini ◽  
Valentina Ferrante ◽  
Nevio Zitellini
Keyword(s):  
Seismic Reflection ◽  
Magnetic Data ◽  
Normal Faults ◽  
Sedimentary Sequence ◽  
Initiation Zone ◽  
Arc Setting ◽  
Seismic Reflection Profiles ◽  
Back Arc ◽  
Flower Structures ◽  
Tyrrhenian Basin

The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.

scholarly journals Effusive Monogenetic Volcanism

2020 ◽  
Author(s):  
Hugo Murcia ◽  
Károly Németh
Keyword(s):  
Classification Scheme ◽  
Wide Spectrum ◽  
Lava Flows ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Monogenetic Volcanism ◽  
Future Studies ◽  
Lava Domes ◽  
Tectonic Settings ◽  
Monogenetic Volcanoes

The study of monogenetic volcanism around Earth is rapidly growing due to the increasing recognition of monogenetic volcanic edifices in different tectonic settings. Far from the idea that this type of volcanism is both typically mafic and characteristic from intraplate environments, it occurs in a wide spectrum of composition and geological settings. This volcanism is widely known by the distinctive pyroclastic cones that represent both magmatic and phreatomagmatic explosive activity; they are known as scoria or spatter cones, tuff cones, tuff rings, maars and maar-diatremes. These cones are commonly associated with lava domes and usually accompanied by lava flows as part of their effusive eruptive phases. In spite of this, isolated effusive monogenetic emissions also appear around Earth’s surface. However, these isolated emissions are not habitually considered within the classification scheme of monogenetic volcanoes. Along with this, many of these effusive volcanoes also contrast with the belief that this volcanism is indicative of rapidly magma ascent from the asthenosphere, as many of the products are strongly evolved reflecting differentiation linked to stagnation during ascent. This has led to the understanding that the asthenosphere is not always the place that directly gives rise to the magma batches and rather, they detach from a crustal melt storage. This chapter introduces four singular effusive monogenetic volcanoes as part of the volcanic geoforms, highlights the fact that monogenetic volcanic fields can also be associated with crustal reservoirs, and outlines the processes that should occur to differentiate the magma before it is released as intermediate and acidic in composition. This chapter also provides an overview of this particular volcanism worldwide and contributes to the monogenetic comprehension for future studies.

scholarly journals Correlation of the Rockland Ash Bed, a 400,000-Year-Old Stratigraphic Marker in Northern California and Western Nevada, and Implications for Middle Pleistocene Paleogeography of Central California

1985 ◽  
Vol 23 (2) ◽  
pp. 236-257 ◽  
Author(s):  
Andrei M. Sarna-Wojcicki ◽  
Charles E. Meyer ◽  
Harry R. Bowman ◽  
N. Timothy Hall ◽  
Paul C. Russell ◽  
...  
Keyword(s):  
San Francisco ◽  
Hot Spring ◽  
Temporal Correlation ◽  
Middle Pleistocene ◽  
Northern California ◽  
Central California ◽  
Mohawk Valley ◽  
Glaciofluvial Deposits ◽  
Lassen Peak ◽  
Great Valley

Outcrops of an ash bed at several localities in northern California and western Nevada belong to a single air-fall ash layer, the informally named Rockland ash bed, dated at about 400,000 yr B.P. The informal Rockland pumice tuff breccia, a thick, coarse, compound tephra deposit southwest of Lassen Peak in northeastern California, is the near-source equivalent of the Rockland ash bed. Relations between initial thickness of the Rockland ash bed and distances to eruptive source suggest that the eruption was at least as great as that of the Mazama ash from Crater Lake, Oregon. Identification of the Rockland tephra allows temporal correlation of associated middle Pleistocene strata of diverse facies in separate depositional basins. Specifically, marine, littoral, estuarine, and fluvial strata of the Hookton and type Merced formations correlate with fluvial strata of the Santa Clara Formation and unnamed alluvium of Willits Valley and the Hollister area, in northwestern and west-central California, and with lacustrine beds of Mohawk Valley, fluvial deposits of the Red Bluff Formation of the eastern Sacramento Valley, and fluvial and glaciofluvial deposits of Fales Hot Spring, Carson City, and Washoe Valley areas in northeastern California and western Nevada. Stratigraphic relations of the Rockland ash bed and older tephra layers in the Great Valley and near San Francisco suggest that the southern Great Valley emerged above sea level about 2 my ago, that its southerly outlet to the ocean was closed sometime after about 2 my ago, and that drainage from the Great Valley to the ocean was established near the present, northerly outlet in the vicinity of San Francisco Bay about 0.6 my ago.

Quantitative reconstruction of landscape dynamics and tectonics from sediment calibre and architecture: an example from the Kerinitis megadelta, Gulf of Corinth, Greece

2020 ◽  
Author(s):  
Daniel Hobley ◽  
Alexander Whittaker
Keyword(s):  
Grain Size ◽  
Middle Pleistocene ◽  
Normal Faults ◽  
Sudden Increase ◽  
Level Control ◽  
Data Set ◽  
Accommodation Space ◽  
Gulf Of Corinth ◽  
Climatic Environment ◽  
Climatic History

&lt;p&gt;In tectonically active landscapes, fault movement drives both the creation of accommodation space (i.e., basins), and the production of topography on which geomorphic processes act (i.e., mountains). The action of fluvial processes on those mountains will route eroded sediment into the basins; in many extensional mountain belts, this leads to the deposition of coarse alluvial fans or Gilbert deltas in the hanging-walls of normal faults as they slip and create accommodation space. The stratigraphic architecture and sedimentary characteristics of such deposits clearly respond to and thus in principle can record the tectono-climatic environment controlling the system. This implies that key stratigraphic variables, such as grain size and unit thicknesses, can be quantitatively inverted to recover a tectono-climatic history. However, confounding variables also active in erosional-depositional systems (e.g., far-field base level control, stochastic processes, signal degradation during transport) may complicate attempts to decode this archive and may buffer or shred tectono-climatic signals before they are preserved.&lt;/p&gt;&lt;p&gt;The well-exposed early to middle Pleistocene deltaic stratigraphy of the Corinth Rift, central Greece, provides a rare opportunity to test these ideas quantitatively. Here, we present a preliminary data set attempting to decode the geomorphic and hence tectono-climatic history of a key section of the rift directly from the grain size and architecture of a very large (~500 m thick), fault controlled, and now uplifted Gilbert delta in the Kerinitis valley, located on the southern margin of the Gulf of Corinth. We used a series of high-resolution drone surveys to obtain 27 vertical transects through the incised delta, from which detailed grain size and sediment thickness data were obtained from photogrammetric analyses (~10,000 images). Our data enabled us to produce a highly detailed correlation of stratal horizons within the deltaic package, from which we were able to describe the evolution of grain size trends both downstream and through the ca. 800 ky lifespan of the delta. We are able to resolve a marked acceleration of the driving fault from the delta stratigraphy itself, which is recorded in a sudden increase in downstream fining rate, driven by more rapid extraction of sediment from the river supplying material to the delta. The timing of this increase correlates with independent constraints from stratigraphic form on the onset of &amp;#8220;rift climax&amp;#8221; in this delta. Post fault acceleration, we demonstrate that the fining rates begin to fall back, consistent with transient response to tectonic perturbation in the upstream catchment and with a wave of incision sweeping up through the terrestrial system. Our results demonstrate that sophisticated insights into fault evolution can be drawn from deltaic stratigraphy, and emphasise the importance of transient landscape response in creating rift zone sedimentary archives.&lt;/p&gt;

Tectonic evolution of the Gediz Graben: field evidence for an episodic, two-stage extension in western Turkey

2004 ◽  
Vol 141 (1) ◽  
pp. 63-79 ◽  
Author(s):  
ERDİN BOZKURT ◽  
HASAN SÖZBİLİR
Keyword(s):  
Normal Fault ◽  
Geological Mapping ◽  
Normal Faults ◽  
High Angle ◽  
Western Turkey ◽  
Menderes Massif ◽  
Total Displacement ◽  
Field Evidence ◽  
Back Arc ◽  
Short Time

Western Turkey is one of the most spectacular regions of widespread active continental extension in the world. The most prominent structures of this region are E–W-trending grabens (e.g. Gediz and Büyük Menderes grabens) and intervening horsts, exposing the Menderes Massif. This paper documents the result of a recent field campaign (field geological mapping and structural analysis) along the southern margin of the modern Gediz Graben of Pliocene (∼ 5 Ma) age. This work provides field evidence that the presently low-angle ductile-brittle detachment fault is cut and displaced by the high-angle graben-bounding normal faults with total displacement exceeding 2.0 km. The evolution of the N–S extension along the Gediz Graben occurred during two episodes, each characterized by a distinct structural styles: (1) rapid exhumation of Menderes Massif in the footwall of low-angle normal fault (core-complex mode) during the Miocene; (2) late stretching of crust producing E–W grabens along high-angle normal faults (rift mode) during Pliocene–Quaternary times, separated by a short-time gap. The later phase is characterized by the deposition of now nearly horizontal sediments of Pliocene age in the hanging walls of the high-angle normal faults and present-day graben floor sediments. The evolution of extension is at variance with orogenic collapse and/or back-arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the Aegean-Cyprean subduction zone. Consequently, it is misleading to describe the Miocene sediments exhumed on shoulders of the Gediz Graben as simple graben fill.

scholarly journals Identifikasi Sesar Aktif di Pulau Bali dengan Menggunakan Data Pemetaan Geologi Permukaan dan Morfologi Tektonik

2021 ◽  
Vol 35 (1) ◽  
pp. 45
Author(s):  
Hurien Helmi ◽  
Gayatri Indah Marliyani ◽  
Siti Nur’aini
Keyword(s):  
Hazard Analysis ◽  
Active Faults ◽  
Fault System ◽  
Normal Faults ◽  
Earthquake Hazards ◽  
Digital Elevation ◽  
Shallow Earthquakes ◽  
Lineament Analysis ◽  
Elevation Model ◽  
Back Arc

Pulau Bali dan sekitarnya berada dekat dengan zona subduksi sehingga rawan terhadap bencana gempa bumi. Struktur utama yang menyebabkan gempa bumi di Bali umumnya berada di zona subduksi di bagian selatan dan di zona sesar naik belakang busur di utara yang dikenal dengan sesar naik Flores. Selain potensi gempa dari kedua zona sesar ini, gempa yang berasal dari zona sesar di darat juga bisa menimbulkan bahaya yang signifikan. Penelitian ini bertujuan untuk melakukan pemetaan sesar aktif di darat dengan menggunakan kombinasi antara metode penginderaan jauh dengan survey lapangan. Data yang digunakan sebagai peta dasar adalah data digital elevation (DEM) model DEMNAS beresolusi 8 m serta data DEM beresolusi 0.5 m yang dihasilkan melalui proses fotogrametri dari foto udara. Analisis kelurusan menunjukkan adanya pola berarah baratlaut-tenggara dan timulaut-baratdaya. Validasi di lapangan menunjukkan bahwa kelurusan ini berasosiasi dengan keberadaan sesar-sesar geser, sesar oblique dan sesar turun. Sesar-sesar ini memotong batuan berumur Kuarter hingga endapan masa kini. Selain itu, data sebaran seismisitas menunjukkan adanya zona kegempaan dangkal yang berada pada area di sekitar kelurusan yang dipetakan. Kedua indikator ini menunjukkan bahwa sesar-sesar yang teridentifikasi dalam penelitian ini bisa dikategorikan sebagai sesar aktif. Hasil dari penelitian ini memberikan pemahaman baru mengenai geometri sesar aktif yang ada di Pulau Bali dan potensi kegempaan di masa yang akan datang yang memberikan kontribusi terhadap upaya mitigasi bencana gempa bumi di Pulau Bali. Bali and its surrounding region are located within proximity of the Sunda-Banda subduction zone making it prone to earthquake hazards. The structures that caused earthquakes in Bali are mainly from the front subduction faults and from the back-arc thrust fault known as the Flores Fault. In addition, earthquakes are frequently occur in the inland fault system. This study aims to map the inland active faults in Bali using a combination of remotely-based and field-mapping methods. We use the 8-m resolution digital elevation model (DEM) of DEMNAS and the 0.5 m resolution DEM from photogrammetry processing of aerial photo as our base maps. Our lineament analysis identifies northwest-southeast and northeast-southwest lineaments. Our field observation confirms these lineaments to be associated with strike-slip, oblique and normal faults. These faults dissect Quarternary to recent rock units. In addition, seismicity data indicate the occurrence of shallow earthquakes in the vicinity of these structures. All of these indicate that these structures are active. Results from this study provide a new understanding of the inland active fault geometry in Bali, useful in the seismic hazard analysis and may contribute to the earthquake mitigation efforts in Bali.   

scholarly journals From widespread Mississippian to localized Pennsylvanian extension in central Spitsbergen, Svalbard

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1535-1558
Author(s):  
Jean-Baptiste P. Koehl ◽  
Jhon M. Muñoz-Barrera
Keyword(s):  
Sedimentary Rocks ◽  
Fault Zones ◽  
Normal Faults ◽  
Late Devonian ◽  
Growth Strata ◽  
Tectonic Events ◽  
Basement Rocks ◽  
Field Evidence ◽  
History Of ◽  
Tectonic Settings

Abstract. In the Devonian–Carboniferous, a rapid succession of clustered extensional and contractional tectonic events is thought to have affected sedimentary rocks in central Spitsbergen, Svalbard. These events include Caledonian post-orogenic extensional collapse associated with the formation of thick Early–Middle Devonian basins, Late Devonian–Mississippian Ellesmerian contraction, and Early–Middle Pennsylvanian rifting, which resulted in the deposition of thick sedimentary units in Carboniferous basins like the Billefjorden Trough. The clustering of these varied tectonic settings sometimes makes it difficult to resolve the tectono-sedimentary history of individual stratigraphic units. Notably, the context of deposition of Mississippian clastic and coal-bearing sedimentary rocks of the Billefjorden Group is still debated, especially in central Spitsbergen. We present field evidence (e.g., growth strata and slickensides) from the northern part of the Billefjorden Trough, in Odellfjellet, suggesting that tilted Mississippian sedimentary strata of the Billefjorden Group deposited during active (Late/latest?) Mississippian extension. WNW–ESE-striking basin-oblique faults showing Mississippian growth strata systematically die out upwards within Mississippian to lowermost Pennsylvanian strata, thus suggesting a period of widespread WNW–ESE-directed extension in the Mississippian and an episode of localized extension in Early–Middle Pennsylvanian times. In addition, the presence of abundant basin-oblique faults in basement rocks adjacent to the Billefjorden Trough suggests that the formation of Mississippian normal faults was partly controlled by reactivation of preexisting Neoproterozoic (Timanian?) basement-seated fault zones. We propose that these preexisting faults reactivated as transverse or accommodation cross faults in or near the crest of transverse folds reflecting differential displacement along the Billefjorden Fault Zone. In Cenozoic times, a few margin-oblique faults (e.g., the Overgangshytta fault) may have mildly reactivated as oblique thrusts during transpression–contraction, but shallow-dipping, bedding-parallel, duplex-shaped décollements in shales of the Billefjorden Group possibly prevented substantial movement along these faults.

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