Geology topics

Jared W. Kluesner

Publications and source records attributed to Jared W. Kluesner.

At least 19 recordsLinked to original sources

USGS2026

The Great Salt Lake (Utah, USA) acoustic and sedimentary archive of Wasatch Front earthquakes

As the largest low-relief basin in the western United States, the Great Salt Lake offers an opportunity to explore acoustic and sedimentary archives of earthquake ruptures in a shallow terminal basin. Here, we use subbottom compressed high intensity radiated pulse (Chirp) profiles and sedimentary cores to address questions related to how Great Salt Lake sediments respond to surface rupture and earthquake shaking and whether the lake is sensitive to both Great Salt Lake fault (GSLF) and Wasatch fault zone (WFZ) earthquakes. Chirp profiles reveal laterally continuous seismic stratigraphy with vertically displaced strata, onlap surfaces, and growth stratigraphy produced by GSLF surface ruptures. We identify and date two ruptures on the Fremont Island section and three on the Antelope Island section; temporal overlap of these ruptures supports synchronous rupture of both sections. Combined with previous data, our results yield a record of four Holocene surface-rupturing (M W 6.9−7.3) earthquakes on the GSLF with a mean recurrence of ∼3.2 k.y. Sediment cores include ≤41-cm-thick, massive, homogeneous to normally graded disturbance beds that interrupt laminated bioclastic sediment. Disturbance bed correlations yield four lacustrine earthquake deposits since ca. 1.7 ka; the youngest possibly records the most recent GSLF surface rupture whereas older deposits were likely produced by WFZ earthquakes. Modeled historical earthquakes yield a Great Salt Lake sediment disturbance shaking threshold of MMI ∼VI, controlled in part by the lake-bottom expression of the GSLF scarp. Our integration of primary (fault-related) and secondary (shaking-related) earthquake evidence improves our understanding of sediment disturbance processes and the archival potential of low-relief lake basins.

Utah↗

USGS2026

Widespread abyssal turbidites record megathrust earthquake-triggered landslides and coseismic deformation in the Cascadia subduction zone

Abyssal marine turbidites provide some of the longest and most spatially extensive records of subduction zone earthquake recurrence globally; however, correlation of these deposits over long distances and interpretation of synchronous emplacement requires both an understanding of the turbidite generating systems and precise dating. Here, we present an integrated suite of high-resolution bathymetry, subbottom profiles, and sediment cores from combined autonomous underwater vehicle, remotely operated vehicle, and ship-based studies at a key paleoseismic site in the southern Cascadia subduction zone. We demonstrate how widespread, earthquake-triggered landslides on the lower slope deposit discrete, proximal mass transport deposits (MTDs) that grade offshore into complex, interfingered abyssal turbidites, which correspond to records of megathrust earthquake history. We propose accretion and oversteepening of thrust folds on the lower slope both preconditions the slope to fail and provides a perpetual source of unstable material to fail during every earthquake cycle. Furthermore, we suggest the periodic and pervasive landsliding indicates coseismic deformation of the outer accretionary wedge during megathrust rupture.

California, Oregon↗

USGS2025

Reconstructing late Pleistocene relative sea levels on transgressed shelves: An example from central California

Although prevalent for the late Holocene, relative sea level (RSL) constraints during and immediately after the Last Glacial Maximum (LGM) are sparse. This scarcity of data is particularly pronounced along mid-latitude shelves such as central California, which lack post LGM RSL constraints older than 12 ka. In this study we collected 7 sediment cores and high-resolution seismic data from Estero Bay to constrain RSLs across the central California shelf between ∼9 and ∼16 ka. We reconstructed these RSLs using two sea-level indicators found within our sediment cores: the wave ravinement shell hash burial surface (WRSHBS) and the sedimentary contact between offshore mud facies and ripple cross-laminated sands. To determine the indicative meaning of these two sea-level indicators, we examined the relationship between the local wave regime, modern bathymetric profiles, and the depth of preservation of each sea-level indicator. After correcting for tectonic uplift, we estimated sea levels in central California to have been ∼39 ± 7.5 and 49 ± 7.5 m below present sea level between 9 and 12 ka, in agreement with previous RSL reconstructions along this coast. Between 13.8 and 15.9 ka, we estimate sea levels to have reached ∼86 ± 8–99 ± 8 m below present sea level. Our findings offer a Late Pleistocene RSL reconstruction for central California and develop new methodologies for estimating past RSLs on similar mid-latitude shelves.

California↗

USGS2024

Post-glacial stratigraphy and late Holocene record of great Cascadia earthquakes in Ozette Lake, Washington, USA

Ozette Lake is an ~100-m-deep coastal lake located along the outer coast of the Olympic Peninsula (Washington, USA); it is situated above the locked portion of the northern Cascadia megathrust but also relatively isolated from active crustal faults and intraslab earthquakes. Here we present a suite of geophysical and geological evidence for earthquake-triggered mass transport deposits (MTDs) and related turbidite deposition in Ozette Lake since ca. 14 ka. Comprehensive high-resolution bathymetry data, seismic reflection profiles, and sediment cores are used to characterize the post-glacial stratigraphic framework and examine paleoseismic evidence in the lacustrine sediments. Stacked sequences of MTDs along the steep eastern flanks of the lake appear to grade basin-ward from thick, chaotic, blocky masses to thin, parallel-bedded turbidite beds. The discrete turbidite event layers are separated by fine-grained (silt and clay) lake sedimentation. The event layers are observed throughout the lake, but the physical characteristics of the deposits vary considerably depending on proximity to primary depocenters, steep slopes, and subaqueous deltas. A total of 30–34 event deposits are observed in the post-glacial record. Radiometric dating was used to reconstruct a detailed sedimentation history over the last ~5.5 k.y., develop an age model, and estimate the recurrence (365–405 yr) for the most recent 12 event layers. Based on sedimentological characteristics, temporal overlap with other regional paleoseismic chronologies, and recurrence estimates, at least 10 of the dated event layers appear to be sourced from slope failures triggered by intense shaking during megathrust ruptures; the recurrence interval for these 10 events is 440–560 yr. Thus, Ozette Lake contains one of the longest and most robust geological records of repeated shaking along the northern Cascadia subduction zone.

Washington↗

USGS2024

Characteristics of the fault damage zone From high-resolution seismic imaging along the Palos Verdes Fault, California

The distribution and intensity of fault damage zones provides insight into fault activity and its relationship to fluid flow in the crust. Presently, measures of the in-situ distribution of fault damage remain limited and along-strike studies are rare. This study focuses on an offshore section Palos Verdes Fault damage zone that spans 28 km, near Los Angeles, California. To investigate the previously unresolved shallow (∼400 m below the seafloor) fault damage zone we use densely spaced (∼500 m line separation) newly collected sparker multichannel seismic lines and sub-bottom profiles. The combination of high-resolution acquisition methods and specialized seismic processing workflows provide improved imaging of shallow faulting. We apply a multi-trace similarity technique to identify discontinuities in the seismic data that may be attributed to faults and fractures. This fault detection approach reveals diverse fault damage patterns on adjacent seismic profiles. However, a discernible damage zone pattern emerges by stacking multiple damage detection profiles along strike. We find that peak damage identified in this way corresponds to the active main fault strand, confirmed in this study, and thus the technique may be useful for identifying active fault strands elsewhere. Additionally, we observe that the variable width of the damage zone along strike is controlled by fault obliquity. Furthermore, our observations reveal a correlation between fault damage and seafloor fluid seeps visible in the water column, suggesting that damage plays a role in controlling fluid flow around the fault.

California↗

USGS2024

A comprehensive assessment of submarine landslides and mass wasting processes offshore southern California

It is critical to characterize submarine landslide hazards near dense coastal populations, especially in areas with active faults, which can trigger slope failure, subsequent tsunamis, and damage seabed infrastructure during earthquake shaking. Offshore southern California, numerous marine geophysical surveys have been conducted over the past decade, and high-resolution bathymetric and subsurface data now cover about 60 percent of the total region between Point Conception and the United States-Mexico border from the California coast out to the base of Patton Escarpment ∼200 km offshore. In a comprehensive compilation and interpretive mapping effort, we find evidence of seafloor failure throughout offshore southern California with nearly 1,500 submarine landslide-related features, including 63 discrete slide deposits with debris and >1,400 slide-related scarps. In our analysis, we highlight new mapping of submarine landslides in Catalina Basin, the Del Mar slide, the San Gabriel slide complex, and the 232 km 2 San Nicolas slide, the largest area of any known submarine landslide mass offshore southern California. Analysis of the spatial distribution of submarine landslide features suggests that most mapped slide features are located relatively near coastal sediment sources, particularly during sea-level lowstand conditions, which underscores the importance of sediment supply and sediment accumulation on low-gradient slopes as failure preconditioning processes. Tectonically driven uplift at shelf edges and along basin flanks is another key preconditioning factor, and our results also suggest that earthquakes along active faults trigger mass wasting, especially for repeated, small-scale failures on tectonically steepened slopes.

California↗

USGS2024

Methane seeps on the U.S. Atlantic margin: An updated inventory and interpretative framework

Since the discovery of >570 methane flares on the northern U.S. Atlantic margin between Cape Hatteras and Georges Bank in the last decade, the acquisition of thousands of kilometers of additional water column imaging data has provided greater coverage at water depths between the outer continental shelf and the lower continental slope. The additional high-resolution data reveal >1400 gas flares, but the removal of probable duplicates from the combined database of new flares and those recognized in 2014 yields ∼1139 unique sites. Most of these sites occur in clusters of 5 or more seeps, leaving about 275 unique locations (including 47 clusters) for seepage along the margin. As a function of depth, seep distribution is heavily skewed toward the upper continental slope at water depths shallower than 400 m on the southern New England margin and ∼ 550 m in the Mid-Atlantic Bight, with additional seeps clustered at ∼1100 m and just deeper than ∼1400 m in both sectors. Despite little ongoing tectonic deformation or active faulting on this passive margin, a variety of processes driven from below the seafloor (e.g., migration of fluids along faults or through permeable strata, seepage above diapirs or other pre-existing structures) and from above (e.g., erosion, sapping, unroofing) contribute to the development of seeps in different settings along the margin. In addition, the prevalence of seeps on promontories overlooking shelf-breaking canyons may be directly related to the three-dimensional nature of the hydrate stability zone in these locations. As a function of depth, the parts of the slope at the contemporary landward limit of gas hydrate stability are devoid of seeps, and the upper slope zones with the most concentrated seepage were not within the gas hydrate stability zone even during the Last Glacial Maximum. Thus, if the large number of upper slope seeps is at least partially sourced in gas hydrate degradation, the gas emitted at these seeps must have migrated there from greater depths on the continental slope.

Marine Geology↗

USGS2023

High-resolution geophysical and geochronological analysis of a relict shoreface deposit offshore central California: Implications for slip rate along the Hosgri fault

The Cross-Hosgri slope is a bathymetric lineament that crosses the main strand of the Hosgri fault offshore Point Estero, central California. Recently collected chirp seismic reflection profiles and sediment cores provide the basis for a reassessment of Cross-Hosgri slope origin and the lateral slip rate of the Hosgri fault based on offset of the lower slope break of the Cross-Hosgri slope. The Cross-Hosgri slope is comprised of two distinct stratigraphic units. The lower unit (unit 1) overlies the post–Last Glacial Maximum transgressive erosion surface and is interpreted as a Younger Dryas (ca. 12.85–11.65 ka) shoreface deposit based on radiocarbon and optically stimulated luminescence (OSL) ages, Bayesian age modeling, seismic facies, sediment texture, sediment infauna, and heavy mineral component. The shoreface was abandoned and partly eroded during rapid sea-level rise from ca. 11.5 to 7 ka. Unit 2 consists of fine sand and silt deposited in a midshelf environment when the rate of sea-level rise slowed between ca. 7 ka and the present. Although unit 2 provides a thin, relatively uniform cover over the lower slope break of the older shoreface, this feature still represents a valuable piercing point, providing a Hosgri fault slip rate of 2.6 ± 0.8 mm/yr. Full-waveform processing of chirp data resulted in significantly higher resolution in coarser-grained strata, which are typically difficult to interpret with more traditional envelope processing. Our novel combination of offshore radiocarbon and OSL dating is the first application to offshore paleoseismic studies, and our results indicate the utility of this approach for future marine neotectonic investigations.

California↗

USGS2023

Diving deeper into seep distribution along the Cascadia Convergent Margin, USA

Previous margin-wide studies of methane seep distribution along the Cascadia Subduction Zone indicate peaks in seep density within the landward limit of the of gas hydrate stability zone (GHSZ; ≤500 m depth), suggesting a link between current ocean warming, acceleration of hydrate dissociated, and methane emissions. This inferred connection, however, may not account for regional geologic and/or structural complexities driving methane seepage. Expanding upon an existing seep database by adding new seeps data, we conducted statistical and spatial analyses to determine margin-wide distribution trends and offer a tectonic framework for understanding the tendency toward non-normality and spatial clustering. We then highlight the role of local-scale drivers of seep formation in addition to the first-order tectonic framework, using systematic geologic/geomorphic characterization of seep emission sites in southern Cascadia and case studies using meta-attribute analysis of seismic reflection data.. Seep distribution along the margin is non-random, but instead of clustering along the 500-m isobath, regions of high seep density occur in canyons and topographic highs. New findings from this study conclude that co-location of the outer arc high (OAH) and the landward limit of the GHSZ may explain high concentrations of seeps where deformation is the greatest and hydrates are unstable. Detailed analysis of the spatial relationships between seep sites and geologic-geomorphic features in southern Cascadia reveal a link between seeps and anticlines, with 52% of the seeps found in association with anticlines, 36% found at faults, 16% associated with canyons, and 11% at seafloor failure scarps. Given that a majority of anticlines are located along or seaward of the OAH in the actively deforming outer wedge, we suggest that the location of the OAH is a primary structural control on seep distribution. This scenario is supported by neural network analysis of multichannel seismic data revealing zones of probable fluid migration along vertical pipes, faults, and chimneys in the vicinity of active seep sites on anticlines. Determining linkages between seeps and submarine tectonic geomorphology is a crucial first step for understanding and forecasting the distribution of methane seepage, but also a necessity for evaluating causal relationships between ocean warming and gas-hydrate stability.

California, Oregon, Washington↗

USGS2023

Subaqueous clinoforms created by sandy wave-supported gravity flows: Lessons from the central California shelf

Subaqueous clinoforms are an important yet underappreciated shelf feature. Their origins are typically associated with subaerial deltas but recent work has identified similar features in settings without a significant fluvial source. These other studies have shown that such subaqueous clinoforms, also known as infralittoral prograding wedges (IPWs), are created largely by wave-induced processes. This study uses geophysical, sedimentological, and radiocarbon data to determine the sedimentary characteristics and genesis of a shore-parallel subaqueous clinoform developed far from any significant river on the central California continental shelf; a feature known locally as the Cross Hosgri Slope. Sediment cores through the feature reveal that it is composed of beds with an erosive base, followed by a thin coarsening upward sequence of shelly fine sands transitioning to a fining upward sequence marked by alternating parallel and ripple cross laminated very fine sands. The deposit is often capped by fine silts that are commonly interbedded with thin very fine sand beds. Radiocarbon dating of shells within the cores paired with seismic profiles indicate the subaqueous clinoform initiated progradation ~7 ka, nucleating on an older Younger Dryas relict shoreface. We suggest the CHS was created by winter-storm waves mobilizing sands in water depths up to ~ 70 m that transitioned into wave-supported gravity flows. The wave-supported gravity flows traveled downslope to water depths of up to ~85 m, corresponding to the foot of the subaqueous clinoform. They did not travel beyond this depth as wave influence at these depths is negligible and the shelf slope is insufficient to maintain movement of the load alone. Our work suggests that wave-supported gravity flows can entrain very fine sands and silts and build subaqueous clinoforms, even in the absence of a significant river source. Furthermore, we provide a facies model for sandy wave-supported gravity flow deposits.

California↗

USGS2022

Systematic mapping of the ocean-continent transform plate boundary of the Queen Charlotte fault system, southeastern Alaska and western British Columbia—A preliminary bathymetric terrain model

In 2015, U.S. Geological Survey scientists in collaboration with scientists from other institutions began a study of the Queen Charlotte fault—the first systematic study of the fault in more than three decades. The primary goal of the study was to gain a better understanding of the earthquake, tsunami, and underwater-landslide hazards throughout southeastern Alaska, as well as gather data to develop geologic models that can be applied to similar plate boundaries around the globe, such as the San Andreas fault system in southern California, the Alpine fault in New Zealand, and the North Anatolian fault in Turkey. A bathymetric terrain model was compiled from six different multibeam surveys of the previously unmapped Queen Charlotte fault offshore of southeastern Alaska and Haida Gwaii archipelago.

Alaska, British Columbia↗

USGS2022

High-resolution marine seismic imaging of the Seattle fault zone: Near surface insights into fault zone geometry, Quaternary deformation, and long-term evolution

The Seattle fault zone (SFZ) is a north‐directed thrust fault system that underlies the greater Seattle metropolitan area. Evidence of past land level changes, landslides, liquefaction, and a local tsunami indicate that this 70‐km‐long fault system can host up to M 7–7.5 earthquakes. Both the geometry and earthquake recurrence of the SFZ are debated and surveys of the shallow subsurface have not yet been incorporated into deeper crustal‐scale structural interpretations, especially where the SFZ cuts across marine portions of the Puget Lowland. Here we use a new high‐resolution marine seismic reflection dataset to image fault‐related deformation in Quaternary sediments and Tertiary bedrock throughout Puget Sound and Lake Washington. We use this perspective of shallow geology as a link between existing crustal‐scale geophysical insights into fault geometry at depth and paleoseismological observations of faulting at the surface and propose a refined structural model for the SFZ. We interpret that our new seismic reflection data in the Rich Passage area of Puget Sound images evidence of an inactive, south‐dipping strand of the SFZ, which is overprinted by Quaternary folding and slip along north‐dipping backthrusts within the hanging wall of a blind, south‐dipping fault located 6 km farther north. To explain these results, we propose that the SFZ is a normal sequence fault propagation fold that has stepped northward through time, and we show the plausibility of this model through trishear forward modeling. Growth strata and faulting imaged in Quaternary sediments in Lake Washington and Rich Passage are consistent with the spatial distribution of folding and backthrusting that occurred during an M 7–7.5 earthquake in A.D. 900–930, corroborating existing evidence that the SFZ has been active throughout the Quaternary.

Bulletin of the Seismological Society of America↗

USGS2022

Mega-depressions on the Cocos Ridge: Links between volcanism, faults, hydrothermal circulation, and dissolution

High-resolution bathymetry and 3D seismic data along the Cocos Ridge reveal a 245 km 2 field of ∼1 to 4 km in diameter seafloor depressions. The seafloor depressions are part of a two-tiered honeycomb pattern. The lower-tier depressions have steep faults that truncate strata with chaotic internal reflections consistent with sediment collapse into the depression. These extend into a lens shaped interval just above igneous basement. Overlying these depressions is a second broader set with rough seafloor morphology with gently dipping boundaries defined by pinch-out stratigraphic patterns. Drilling results indicate that the lens-shaped zones that host the deeper depressions represent anomalous regions of high porosity, low velocity, and low density within calcareous rich sediment. Analysis of nannofossils from IODP Site U1414 suggests the collapse structures formed during the late Miocene, whereas the younger shallower depressions likely formed between the early Pliocene and the Pliocene-Pleistocene boundary. Geochemical and petrological analysis at Site U1414 suggests that hydrothermal circulation during the late Miocene led to carbonate dissolution and collapse. Following collapse, focused fluid-flow and bottom current scouring resulted in formation of the overlying set of depressions and a honeycomb seafloor morphology. Similar sets of depressions along the Carnegie Ridge to the south support the hypothesis that two-tiered depressions formed in response to processes that occurred broadly across the Panama Basin between the late Miocene and the Pliocene-Pleistocene transition. Geochemical results at Site U1414, combined with geophysical data, suggest this two-tiered system of depressions currently guides ongoing fluid outflow.

Geochemistry, Geophysics, Geosystems↗

USGS2022

U.S. Atlantic margin gas hydrates

The minimum distribution of gas hydrates on the U.S. Atlantic margin is from offshore South Carolina northward to the longitude of Shallop Canyon on the southern New England margin. Few wells have logged or sampled the gas hydrate zone on this margin, meaning that the presence of gas hydrates is inferred primarily based on seismic data that reveal bottom simulating reflections, mostly at water depths greater than 2000 m. The highest hydrate saturations most likely exist in sandy sediments of the Whale Prospect offshore New Jersey, New York, and the western part of Cape Cod, an area characterized by strong bottom simulating reflections. Such reflections are also imaged on the well-studied Blake Ridge, where fine-grained sediments host lower hydrate saturations that have been constrained by drilling. Within the section of the margin stretching from south of Cape Hatteras to nearly Hudson Canyon, the diagnostic seismic reflections are hard to discern, making inferences about gas hydrate distributions more uncertain. The recognition of as-yet unmapped bottom simulating reflections or top of gas features seaward of the 2000 m bathymetric contour (e.g., Cape Fear Slide, Currituck slide, beneath deepwater gas seeps) within the Mid-Atlantic Bight expands the area of probable gas hydrates on this margin.

Delaware, Maryland, New Jersey, New York, North Ca↗

USGS2022

Using active source seismology to image the Palos Verdes Fault damage zone as a function of distance, depth, and geology

Fault damage zones provide a window into the non-elastic processes of an earthquake. Geological and seismic tomography methods have been unable to measure damage zones at depth with sufficient spatial sampling to evaluate the relative influence of depth, distance, and lithological variations. Here, we identify and analyze the damage zone of the Palos Verdes Fault offshore southern California using two 3D seismic reflection datasets. We apply a novel algorithm to identify discontinuities attributed to faults and fractures in large seismic volumes and examine the spatial distribution of fault damage in sedimentary rock surrounding the Palos Verdes Fault. Our results show that damage through fracturing is most concentrated around mapped faults and decays exponentially to a distance of ∼2 km, where fracturing reaches a clearly defined and relatively undamaged background for all examined depths and lithologies (450 m to 2.2 km). This decrease in fracturing with distance from the central fault strand exhibits similar functional form to outcrop studies. However, here we extend analysis to distances seldom accessible (∼10 km lateral distance). Separating the data by geologic units we find that the damage decay and background level differs for each unit, with the older and deeper units having higher levels of background fracturing and shallower exponential decays of fracturing with distance from the fault. Surprisingly, these differences in damage decay and background level trade-off result in a consistent damage zone width regardless of lithology or depth. We find that the damage zone has similar decay trends on both sides of the fault. When examining the damage zone at shorter (4 km vs 17 km) along strike distances, the damage zone has a more complex decay trend and at least two strands are resolvable.

California↗

USGS2021

Colored shaded-relief bathymetry, acoustic backscatter, and selected perspective views of the northern part of the California Continental Borderland, southern California

The California Continental Borderland is the complex continental margin in southern California that extends from Point Conception southward into northern Baja California (Fisher and others, 2009). This colored shaded-relief bathymetry map of the northern continental borderland in southern California was generated primarily from multibeam-echosounder data collected by the University of Washington in 2016, the Ocean Exploration Trust-Nautilus Exploration Program in 2015–17, and the National Oceanic and Atmospheric Administration in 2017. These datasets were processed in part by the U.S. Geological Survey. Additional smaller amounts of publicly available multibeam-bathymetry data collected by other federal and local agencies, academic institutions, and private firms were also incorporated into this map. Since the production of this map, other multibeam-bathymetry data have been collected in this region.

California↗

USGS2021

In‐situ mass balance estimates offshore Costa Rica

The Costa Rican convergent margin has been considered a type erosive margin, with erosional models suggesting average losses up to −153 km 3 /km/m.y. However, three‐dimensional (3D) seismic reflection and Integrated Ocean Drilling Program data collected offshore the Osa Peninsula images accretionary structures and vertical motions that conflict with the forearc basal erosion model. Here we integrate such data to do an in‐situ accounting of material transfer at the plate boundary across the outermost 10 km of the forearc, characterized by active and inactive megathrusts. Our in‐situ budget finds an approximate balance between sediment recycling via accretion and underplating, 0.7–2.3 km 3 /km/m.y., and basal erosion, 0.7 km 3 /km/m.y., while subducting sediment volumes, 7.8 km 3 /km/m.y., greatly outpace either material transfer volumes. These budget results differ significantly from published estimates based on simple proxies of trench axis deflection and slope subsidence. These budget results are the summation of thin incoming hemipelagic sediments that variably accrete along the deformation front, underplating of hemipelagic sediments on the upthrown‐side and basal erosion on the downthrown‐side of active plate bending faulting landward of the trench axis, and sediment subduction primarily composed of pelagic sediments.

Geochemistry, Geophysics, Geosystems↗

USGS2020

Focused fluid flow and methane venting along the Queen Charlotte fault, offshore Alaska (USA) and British Columbia (Canada)

Fluid seepage along obliquely deforming plate boundaries can be an important indicator of crustal permeability and influence on fault-zone mechanics and hydrocarbon migration. The ~850-km-long Queen Charlotte fault (QCF) is the dominant structure along the right-lateral transform boundary that separates the Pacific and North American tectonic plates offshore southeastern Alaska (USA) and western British Columbia (Canada). Indications for fluid seepage along the QCF margin include gas bubbles originating from the seafloor and imaged in the water column, chemosynthetic communities, precipitates of authigenic carbonates, mud volcanoes, and changes in the acoustic character of seismic reflection data. Cold seeps sampled in this study preferentially occur along the crests of ridgelines associated with uplift and folding and between submarine canyons that incise the continental slope strata. With carbonate stable carbon isotope (δ 13 C) values ranging from −46‰ to −3‰, there is evidence of both microbial and thermal degradation of organic matter of continental-margin sediments along the QCF. Both active and dormant venting on ridge crests indicate that the development of anticlines is a key feature along the QCF that facilitates both trapping and focused fluid flow. Geochemical analyses of methane-derived authigenic carbonates are evidence of fluid seepage along the QCF since the Last Glacial Maximum. These cold seeps sustain vibrant chemosynthetic communities such as clams and bacterial mats, providing further evidence of venting of reduced chemical fluids such as methane and sulfide along the QCF.

Alaska, British Columbia↗