The Pescadero Basin Complex, southern Gulf of California: structure, tectono-stratigraphic evolution and magmatism

2021 ◽  
Author(s):  
Ronald M. Spelz ◽  
Néstor Ramírez-Zerpa ◽  
Juan Contreras ◽  
Ismael Yarbuh ◽  
Antonio González-Fernández ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Autonomous Underwater Vehicle ◽  
Geochemical Data ◽  
Kinematic Modeling ◽  
Cross Sectional ◽  
Incremental Strain ◽  
Seismic Reflection Profiles ◽  
Stratigraphic Evolution ◽  
Seismic Images ◽  
Highly Evolved

<p>The Pescadero Basin Complex (PBC) in the southern Gulf of California comprises three distinctive stretched rhomboid pull-apart basins separated by several short transforms. Multibeam and Autonomous underwater vehicle (AUV) bathymetry data collected at 40-m and 1-m resolution, respectively, combined with the processing and interpretation of three 2-D high-resolution multichannel seismic reflection profiles, were used to characterize the architecture of the entire PBC, as well as the internal structure of the northern Pescadero basin. Detailed mapping and cross-sectional kinematic modeling based on multichannel seismic images of the northern Pescadero basin reveals a highly evolved pull-part geometry, characterized by a well-defined ~1.8 km wide axial graben stretching ~32 km in an NNE-SSW direction. Both finite and incremental strain analyses carried out in this study point out that the PBC developed under sustained transtensional deformation, where the relative motion of the crustal blocks is oblique and divergent to the transforms or principal displacement zones (PDZ's), and subsidence is likely being accommodated by one of more décollement layers located at the bottom of a broad negative flower structure. We also present new geochemical data of lava flows with a N-MORB composition outcropping on the NE segment of the northern Pescadero axial graben, and lava-flow samples of E-MORB composition from an uplifted sediment hill on the western margin of the southern Pescadero basin. MORB samples from the PBC represent the northernmost surface flows known in the Gulf of California, highlighting that the PBC has evolved beyond being a pull-apart complex to having initiated seafloor spreading with new oceanic crust formation in response to the opening of the Gulf of California.</p>

A new Method for Fault-Scarp Detection Using Linear Discriminant Analysis (LDA) in High-Resolution Bathymetry Data From the Alarcón Rise and Pescadero Basin, Gulf of California.

2021 ◽  
Author(s):  
Luis Angel Vega Ramirez ◽  
Ronald Michael Splez Madero ◽  
Juan Contreras Perez ◽  
David Caress ◽  
David A. Clague ◽  
...  
Keyword(s):  
High Resolution ◽  
Gulf Of California ◽  
Autonomous Underwater Vehicle ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Fault Scarp ◽  
Fault Line ◽  
Cross Sectional ◽  
Linear Discriminant ◽  
Automated Method

<p>The mapping of faults and fractures is a problem of high relevance in Earth Sciences. However, their identification in digital elevation models is a time-consuming task given the resulting networks' fractal nature. The effort is especially challenging in submarine environments, given their inaccessibility and difficulty in collecting direct observations. Here, we propose a semi-automated method for detecting faults in high-resolution gridded bathymetry data (~1 m horizontal and ~0.2 m vertical) of the Pescadero Basin in the southern Gulf of California, which were collected by MBARI's D. Allan B autonomous underwater vehicle. This problem is well suited to be explored by machine learning and deep-learning methods. The method learns from a model trained to recognize fault-line scarps based on key morphological attributes in the neighboring Alarcón Rise. We use the product of the mass diffusion coefficient with time, scarp height, and root-mean-square error as training attributes. The method consists of projecting the attributes from a three-dimensional space to a one-dimensional space in which normal probability density functions are generated to classify faults. The LDA implementation results in various cross-sectional profiles along the Pescadero Basin show that the proposed method can detect fault-line scarps of different sizes and degradation stages. Moreover, the method is robust to moderate amounts of noise (i.e., random topography and data collection artifacts) and correctly handles different fault dip angles. Experiments show that both isolated and linkage fault configurations are detected and tracked reliably.</p>

scholarly journals Volcanic record of the arc-to-rift transition onshore of the Guaymas basin in the Santa Rosalía area, Gulf of California, Baja California

Geosphere ◽  
2020 ◽  
Vol 16 (4) ◽  
pp. 1012-1041
Author(s):  
Cathy Busby ◽  
Alison Graettinger ◽  
Margarita López Martínez ◽  
Sarah Medynski ◽  
Tina Niemi ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Baja California ◽  
Sedimentary Basin ◽  
Volcanic Rocks ◽  
Seafloor Spreading ◽  
Geochemical Data ◽  
Normal Faults ◽  
Guaymas Basin ◽  
The North ◽  
Santa Rosalia

Abstract The Gulf of California is an archetype of continental rupture through transtensional rifting, and exploitation of a thermally weakened arc to produce a rift. Volcanic rocks of central Baja California record the transition from calcalkaline arc magmatism, due to subduction of the Farallon plate (ca. 24–12 Ma), to rift magmatism, related to the opening of the Gulf of California (<12 Ma). In addition, a suite of postsubduction rocks (<12 Ma), referred to as “bajaites,” are enriched in light rare-earth and other incompatible elements (e.g., Ba and Sr). These are further subdivided into high-magnesian andesite (with 50%–58% SiO2 and MgO >4%) and adakite (>56% SiO2 and MgO <3%). The bajaites correlate spatially with a fossil slab imaged under central Baja and are inferred to record postsubduction melting of the slab and subduction-modified mantle by asthenospheric upwelling associated with rifting or slab breakoff. We report on volcanic rocks of all three suites, which surround and underlie the Santa Rosalía sedimentary rift basin. This area represents the western margin of the Guaymas basin, the most magmatically robust segment of the Gulf of California rift, where seafloor spreading occurred in isolation for 3–4 m.y. (starting at 6 Ma) before transtensional pull-apart basins to the north and south ruptured the continental crust. Outcrops of the Santa Rosalía area thus offer the opportunity to understand the magmatic evolution of the Guaymas rift, which has been the focus of numerous oceanographic expeditions. We describe 21 distinct volcanic and hypabyssal map units in the Santa Rosalía area, using field characteristics, petrographic data, and major- and trace-element geochemical data, as well as zircon isotopic data and ten new 40Ar-39Ar ages. Lithofacies include lavas and lava domes, block-and-ash-flow tuffs, ignimbrites, and hypabyssal intrusions (plugs, dikes, and peperites). Calcalkaline volcanic rocks (13.81–10.11 Ma) pass conformably upsection, with no time gap, into volcanic rocks with rift transitional chemistry (9.69–8.84 Ma). The onset of rifting was marked by explosive eruption of silicic ignimbrite (tuff of El Morro), possibly from a caldera, similar to the onset of rifting or accelerated rifting in other parts of the Gulf of California. Epsilon Hf zircon data are consistent with a rift transitional setting for the tuff of El Morro. Arc and rift volcanic rocks were then juxtaposed by normal faults and tilted eastward toward a north-south fault that lay offshore, likely related to the north-south normal faults documented for the early history of the Guaymas basin, prior to the onset of northwest-southeast transtenional faulting. Magmatism in the Santa Rosalía area resumed with emplacement of high-magnesian andesite lavas and intrusions, at 6.06 Ma ± 0.27 Ma, coeval with the onset of seafloor spreading in the Guaymas basin at ca. 6 Ma. The 9.69–8.84 Ma rift transitional volcanic rocks underlying the Santa Rosalía sedimentary basin provide a maximum age on its basal fill. Evaporites in the Santa Rosalía sedimentary basin formed on the margin of the Guaymas basin, where thicker evaporites formed. Overlying coarse-grained clastic sedimentary fill of the Santa Rosalía basin and its stratiform Cu-Co-Zn-Mn sulfides may have accumulated rapidly, coeval with emplacement of 6.06 Ma high-magnesian andesite intrusions and the ca. 6 Ma onset of seafloor spreading in the Guaymas basin.

Some aspects of Tertiary acid magmatism in NE Ireland

1984 ◽  
Vol 48 (348) ◽  
pp. 351-363 ◽  
Author(s):  
I. G. Meighan ◽  
D. Gibson ◽  
D. N. Hood
Keyword(s):  
Northern Ireland ◽  
Central Complex ◽  
Geochemical Data ◽  
Igneous Province ◽  
Granitic Intrusions ◽  
Isotope Evidence ◽  
County Antrim ◽  
Geochemical Studies ◽  
Basic Rocks ◽  
Highly Evolved

Abstract Geochemical data (including REE determinations) are presented for all five Mourne Mountains granites and three Northern Ireland rhyolites. These confirm (1) the extremely fractionated nature of some of the rocks (Sr and Ba < 10 ppm, Rb > 400 ppm, Eu/Eu* < 0.1, and K/Rb < 100), and (2) a major revision to the outcrops of the E. Mourne granites G1 and G2 in which much of the former is reclassified as G2. Combined petrographic and geochemical studies have also indicated that magmatic pulses were involved in the emplacement of Mourne intrusions G2 (Revised)-G5 inclusive. The N. Ireland Tertiary acid rocks exhibit general geochemical similarities to their analogues elsewhere in the British Tertiary Igneous Province (in which Sr is generally < 100 ppm and CeN/YbN generally < 8 with Eu/Eu* often < 0.6), but as a suite the Mourne granites are enriched in Rb and some other LIL elements relative to their N. Arran counterparts. The more fractionated acid magmas of NE Ireland are believed to have evolved from primitive granitic parent liquids by crystal fractionation at depth which involved major and accessory phases (including zircon and allanite). In the Mourne (and County Antrim) areas the primitive acid compositions lie at the ends of basaltic (tholeiitic) differentiation series, and in the Mourne central complex there is a complete geochemical sequence from basic rocks through intermediate members to primitive and ultimately highly evolved, subalkaline, granitic intrusions. It is concluded that the data are consistent with the Mourne granites and Northern Ireland rhyolites being essentially basaltic differentiates, although Sr isotope evidence indicates some (probably minor) crustal involvement.

scholarly journals The Bortoluzzi Mud Volcano (Ionian Sea, Italy) and its potential for tracking the seismic cycle of active faults

Solid Earth ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 741-763 ◽  
Author(s):  
Marco Cuffaro ◽  
Andrea Billi ◽  
Sabina Bigi ◽  
Alessandro Bosman ◽  
Cinzia G. Caruso ◽  
...  
Keyword(s):  
Active Faults ◽  
Mud Volcano ◽  
Geochemical Data ◽  
Helium Isotope ◽  
Accretionary Wedge ◽  
Seismic Cycle ◽  
Ionian Sea ◽  
Mud Volcanoes ◽  
Seismic Reflection Profiles ◽  
Sea Area

Abstract. The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African–Adriatic plates in the Mediterranean. This area is seismically active with instrumentally and/or historically recorded Mw>7.0 earthquakes, and it is affected by recently discovered long strike-slip faults across the active Calabrian accretionary wedge. Many mud volcanoes occur on top of the wedge. A recently discovered one (called the Bortoluzzi Mud Volcano or BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). High-resolution bathymetric backscatter surveys, seismic reflection profiles, geochemical and earthquake data, and a gravity core are used here to geologically, geochemically, and geophysically characterize this structure. The BMV is a circular feature ≃22 m high and ≃1100 m in diameter with steep slopes (up to a dip of 22∘). It sits atop the Calabrian accretionary wedge and a system of flower-like oblique-slip faults that are probably seismically active as demonstrated by earthquake hypocentral and focal data. Geochemistry of water samples from the seawater column on top of the BMV shows a significant contamination of the bottom waters from saline (evaporite-type) CH4-dominated crustal-derived fluids similar to the fluids collected from a mud volcano located on the Calabria mainland over the same accretionary wedge. These results attest to the occurrence of open crustal pathways for fluids through the BMV down to at least the Messinian evaporites at about −3000 m. This evidence is also substantiated by helium isotope ratios and by comparison and contrast with different geochemical data from three seawater columns located over other active faults in the Ionian Sea area. One conclusion is that the BMV may be useful for tracking the seismic cycle of active faults through geochemical monitoring. Due to the widespread diffusion of mud volcanoes in seismically active settings, this study contributes to indicating a future path for the use of mud volcanoes in the monitoring and mitigation of natural hazards.

scholarly journals The Bortoluzzi Mud Volcano (Ionian Sea, Italy) and its potential for tracking the seismic cycle of active faults

2018 ◽  
Author(s):  
Marco Cuffaro ◽  
Andrea Billi ◽  
Sabina Bigi ◽  
Alessandro Bosman ◽  
Cinzia G. Caruso ◽  
...  
Keyword(s):  
Sea Water ◽  
Active Faults ◽  
Mud Volcano ◽  
Geochemical Data ◽  
Helium Isotope ◽  
Accretionary Wedge ◽  
Seismic Cycle ◽  
Ionian Sea ◽  
Mud Volcanoes ◽  
Seismic Reflection Profiles

Abstract. The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African-Adriatic plates in the Mediterranean. This area is seismically active with instrumentally/historically-recorded Mw > 7.0 earthquakes and it is affected by recently-discovered long strike-slip faults across the active Calabrian accretionary wedge. Many mud volcanoes occur on top of the wedge. A recently-discovered one (here named Bortoluzzi Mud Volcano, BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). Bathymetric-backscatter surveys, seismic reflection profiles, geochemical and earthquake data as well as a gravity core are here used to geologically, geochemically, and geophysically characterize this structure. The BMV is a circular feature ≃22 m high and ≃1100 m in diameter with steep slopes (up to a dip of 22°). It sits atop the Calabrian accretionary wedge and a system of flower-like oblique-slip faults that are probably seismically active as demonstrated by earthquake hypocentral and focal data. Geochemistry of water samples from the seawater column on top of the BMV shows a significant contamination of the bottom waters from saline (evaporite-type) CH4-dominated crustal-derived fluids similar to the fluids collected from a mud volcano located in the Calabria main land over the same accretionary wedge. These results attest for the occurrence of an open crustal conduit through the BMV down to at least the Messinian evaporites at about −3000 m. This evidence is also substantiated by Helium isotope ratios and by different geochemical data from three sea water columns located elsewhere in the Ionian Sea. Conclusions are drawn on the origin of the BMV and on the potential of this type of structures for tracking the seismic cycle of active faults. Due to the widespread diffusion of mud volcanoes in seismically active settings, this study may contribute to indicate a potential and feasible future path for the use of these ubiquitous structures in favor of the mitigation of natural hazards.

scholarly journals The stratigraphic evolution of a submarine channel: linking seafloor dynamics to depositional products

2020 ◽  
Vol 90 (7) ◽  
pp. 673-686
Author(s):  
Stephen M. Hubbard ◽  
Zane R. Jobe ◽  
Brian W. Romans ◽  
Jacob A. Covault ◽  
Zoltan Sylvester ◽  
...  
Keyword(s):  
Turbidity Currents ◽  
High Concentration ◽  
Bounding Surface ◽  
Cross Sectional ◽  
Genetic Link ◽  
Submarine Channel ◽  
Time Space ◽  
Stratigraphic Evolution ◽  
Geomorphic Surfaces ◽  
The Relationship

ABSTRACT We investigate the relationship between the cross-sectional geomorphic expression of a submarine channel as observed on the seafloor and the stratigraphic product of long-lived erosion, bypass, and sediment deposition. Specifically, by reconstructing the time–space evolution of an individual channel fill (i.e., channel element) exposed in outcrop, we establish a genetic link between thick-bedded channel-element-axis sandstone to thinly interbedded channel-element-margin deposits. Although the bounding surface between axis sandstone and margin thin beds is sharply defined, it is composed of a series of geomorphic surface segments of various ages; as such, the composite stratigraphic surface (∼ 17 m relief) was formed from numerous incision events that repeatedly sculpted the conduit. By demonstrating the origin of the stratigraphic surface, we conclude that geomorphic surfaces with 2–7 m of erosional relief were largely responsible for the observed intra-channel-element architecture (and ultimately, the composite 17-m-thick element). The widely documented channel element axis-to-margin architecture is a product of submarine-channel thalweg dynamics, primarily recording interactions between the seafloor and the basal high-concentration layers of channelized turbidity currents.

Kinematics and Hydrodynamics of Mobuliform Swimming: Oscillatory Winged Propulsion by Large Pelagic Batoids

2017 ◽  
Vol 51 (5) ◽  
pp. 35-47 ◽  
Author(s):  
Frank E. Fish ◽  
Haibo Dong ◽  
Joseph J. Zhu ◽  
Hilary Bart-Smith
Keyword(s):  
Strouhal Number ◽  
Autonomous Underwater Vehicle ◽  
Underwater Vehicle ◽  
The Body ◽  
Body Posture ◽  
Optimal Range ◽  
Cross Sectional ◽  
Oscillatory Frequency ◽  
Pectoral Fins ◽  
Biomimetic Approach

AbstractLarge, pelagic rays (family Myliobatidae) that swim by flapping movements of wing-like pectoral fins use the mobuliform mode of swimming. These rays have pectoral fins with a triangular planform and streamlined cross-sectional geometry that would minimize drag. Thrust is produced by vertical oscillations of the fins with spanwise and chordwise flexibility. The thrust is derived from lift generated by the fins. Speed is modulated by changes in oscillatory frequency, whereas the amplitude of heave remains relatively constant with speed. Mobuliform swimming is considered to be a highly efficient means of propulsion. The Strouhal number for different species of myliobatoid rays is within the optimal range for efficient propulsion, except at low swimming speeds. The design of the body, posture of the pectoral fins, and mode of swimming provide a stable platform to resist external and internal perturbations, while permitting maneuverability. The advantages of mobuliform swimming can be exploited through the biomimetic approach to develop a bioinspired autonomous underwater vehicle.

scholarly journals The role of phyllosilicate partial melting in segregating tungsten and tin deposits in W-Sn metallogenic provinces

Geology ◽  
2021 ◽  
Author(s):  
Panlao Zhao ◽  
Xu Chu ◽  
Anthony E. Williams-Jones ◽  
Jingwen Mao ◽  
Shunda Yuan
Keyword(s):  
Partial Melting ◽  
Geochemical Data ◽  
Dehydration Melting ◽  
Metasedimentary Rocks ◽  
Partial Melt ◽  
Tin Deposits ◽  
Higher Temperature ◽  
Biotite Dehydration Melting ◽  
Highly Evolved

Most tungsten (W) and tin (Sn) deposits are associated with highly evolved granites derived from the anatexis of metasedimentary rocks. They are commonly separated in both space and time, and in the rare cases where the W and Sn mineralization are part of a single deposit, the two metals are temporally separate. The factors controlling this behavior, however, are not well understood. Our compilation of whole-rock geochemical data for W- and Sn-related granites in major W-Sn metallogenic belts shows that the Sn-related granites are generally the products of higher-temperature partial melting (~800 °C) than the W-related granites (~750 °C). Thermodynamic modeling of partial melting and metal partitioning shows that W is incorporated into the magma formed during low-temperature muscovite-dehydration melting, whereas most of the Sn is released into the magma at a higher temperature during biotite-dehydration melting; the Sn of the magma may be increased significantly if melt is extracted prior to biotite melting. At the same degree of partial melting, the concentrations of the two metals in the partial melt are controlled by their concentration in the protolith. Thus, the nature of the protolith and the melting temperature and subsequent evolution of the magma all influence the metallogenic potential of a magma and, in combination, helped control the spatial and temporal segregation of W and Sn deposits in all major W-Sn metallogenic belts.

scholarly journals Thick deltaic sedimentation and detachment faulting delay the onset of continental rupture in the Northern Gulf of California: Analysis of seismic reflection profiles

Tectonics ◽  
2013 ◽  
Vol 32 (5) ◽  
pp. 1294-1311 ◽  
Author(s):  
Arturo Martín-Barajas ◽  
Mario González-Escobar ◽  
John M. Fletcher ◽  
Martín Pacheco ◽  
Michael Oskin ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Gulf Of California ◽  
Deltaic Sedimentation ◽  
Seismic Reflection Profiles ◽  
Detachment Faulting
Sign in / Sign up

Export Citation Format

Share Document