Mary McGann
Research Geologist at the USGS Pacific Coastal and Marine Science Center
Science and Products
Heavy mineral analysis for assessing the provenance of sandy sediment in the San Francisco Bay Coastal System
The timing of sediment transport down Monterey Submarine Canyon, offshore California
Geologic history of the summit of Axial Seamount, Juan de Fuca Ridge
Anatomy of La Jolla submarine canyon system; offshore southern California
Integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing the provenance of beach sand in the San Francisco Bay Coastal System
Over 150 million m3 of sand-sized sediment has disappeared from the central region of the San Francisco Bay Coastal System during the last half century. This enormous loss may reflect numerous anthropogenic influences, such as watershed damming, bay-fill development, aggregate mining, and dredging. The reduction in Bay sediment also appears to be linked to a reduction in sediment supply and recent
Arrival and expansion of the invasive foraminifera Trochammina hadai Uchio in Padilla Bay, Washington
The FOBIMO (FOraminiferal BIo-MOnitoring) initiative—Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies
Slip rate on the San Diego trough fault zone, inner California Borderland, and the 1986 Oceanside earthquake swarm revisited
Paleoceanograpic changes on the Farallon Escarpment off central California during the last 16,000 years
Paleoceanographic changes on the Farallon Escarpment off central California during the last 16,000 years
The elusive character of discontinuous deep-water channels: New insights from Lucia Chica channel system, offshore California
Submarine mass transport within Monterey Canyon: Benthic disturbance controls on the distribution of chemosynthetic biological communities
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Heavy mineral analysis for assessing the provenance of sandy sediment in the San Francisco Bay Coastal System
Heavy or high-specific gravity minerals make up a small but diagnostic component of sediment that is well suited for determining the provenance and distribution of sediment transported through estuarine and coastal systems worldwide. By this means, we see that surficial sand-sized sediment in the San Francisco Bay Coastal System comes primarily from the Sierra Nevada and associated terranes by wayAuthorsFlorence L. Wong, Donald L. Woodrow, Mary McGannThe timing of sediment transport down Monterey Submarine Canyon, offshore California
While submarine canyons are the major conduits through which sediments are transported from the continents out into the deep sea, the time it takes for sediment to pass down through a submarine canyon system is poorly constrained. Here we report on the first study to couple optically stimulated luminescence (OSL) ages of quartz sand deposits and accelerator mass spectrometry 14C ages measured on bAuthorsThomas Stevens, Charles K. Paull, William III Ussler, Mary McGann, Jan-Pieter Buylaert, Eve M. LundstenGeologic history of the summit of Axial Seamount, Juan de Fuca Ridge
Multibeam (1 m resolution) and side scan data collected from an autonomous underwater vehicle, and lava samples, radiocarbon-dated sediment cores, and observations of flow contacts collected by remotely operated vehicle were combined to reconstruct the geologic history and flow emplacement processes on Axial Seamount's summit and upper rift zones. The maps show 52 post-410 CE lava flows and 20 preAuthorsDavid A. Clague, Brian M Dreyer, Jennifer B. Paduan, Julie F Martin, William W Jr Chadwick, David W Caress, Ryan A Portner, Thomas P. Guilderson, Mary McGann, Hans Thomas, David A Butterfield, Robert W EmbleyAnatomy of La Jolla submarine canyon system; offshore southern California
An autonomous underwater vehicle (AUV) carrying a multibeam sonar and a chirp profiler was used to map sections of the seafloor within the La Jolla Canyon, offshore southern California, at sub-meter scales. Close-up observations and sampling were conducted during remotely operated vehicle (ROV) dives. Minisparker seismic-reflection profiles from a surface ship help to define the overall geometry oAuthorsC. K. Paull, D.W. Caress, E. Lundsten, R. Gwiazda, K. Anderson, M. McGann, J. Conrad, B. Edwards, E.J. SumnerIntegration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing the provenance of beach sand in the San Francisco Bay Coastal System
Over 150 million m3 of sand-sized sediment has disappeared from the central region of the San Francisco Bay Coastal System during the last half century. This enormous loss may reflect numerous anthropogenic influences, such as watershed damming, bay-fill development, aggregate mining, and dredging. The reduction in Bay sediment also appears to be linked to a reduction in sediment supply and recent
AuthorsPatrick L. Barnard, Amy C. Foxgrover, Edwin P.L. Elias, Li H. Erikson, James R. Hein, Mary McGann, Kira Mizell, Robert J. Rosenbauer, Peter W. Swarzenski, Renee K. Takesue, Florence L. Wong, Don WoodrowArrival and expansion of the invasive foraminifera Trochammina hadai Uchio in Padilla Bay, Washington
Trochammina hadai Uchio, a benthic foraminifera native to Japanese estuaries, was first identified as an invasive in 1995 in San Francisco Bay and later in 16 other west coast estuaries. To investigate the timing of the arrival and expansion of this invasive species in Padilla Bay, Washington, we analyzed the distribution of foraminifera in two surface samples collected in 1971, in nine surface saAuthorsMary McGann, Eric E. Grossman, Renee K. Takesue, Dan Penttila, John P. Walsh, Reide CorbettThe FOBIMO (FOraminiferal BIo-MOnitoring) initiative—Towards a standardised protocol for soft-bottom benthic foraminiferal monitoring studies
The European Community Marine Strategy Framework Directive (MSFD) was established to provide guidelines for monitoring the quality of marine ecosystems. Monitoring the status of marine environments is traditionally based on macrofauna surveys, for which standardised methods have been established. Benthic foraminifera are also good indicators of environmental status because of their fast turnover rAuthorsJoachim Schoenfeld, Elisabeth Alve, Emmanuelle Geslin, Frans Jorissen, Sergei Korsun, Silva Spezzaferri, Sigal Abramovich, Ahuva Almogi-Labin, Eric Armynot du Chatelet, Christine Barras, Luisa Bergamin, Erica Bicchi, Vincent Bouchet, Alejandro Cearreta, Letizia Di Bella, Noortje Dijkstra, Sibelle Trevisan Disaro, Luciana Ferraro, Fabrizio Frontalini, Giordana Gennari, Elena Golikova, Kristin Haynert, Silvia Hess, Katrine Husum, Virginia Martins, Mary McGann, Shai Oron, Elena Romano, Silvia Mello Sousa, Akira TsujimotoSlip rate on the San Diego trough fault zone, inner California Borderland, and the 1986 Oceanside earthquake swarm revisited
The San Diego trough fault zone (SDTFZ) is part of a 90-km-wide zone of faults within the inner California Borderland that accommodates motion between the Pacific and North American plates. Along with most faults offshore southern California, the slip rate and paleoseismic history of the SDTFZ are unknown. We present new seismic reflection data that show that the fault zone steps across a 5-km-widAuthorsHolly F. Ryan, James E. Conrad, C. K. Paull, Mary McGannPaleoceanograpic changes on the Farallon Escarpment off central California during the last 16,000 years
No abstract available.AuthorsMary McGannPaleoceanographic changes on the Farallon Escarpment off central California during the last 16,000 years
New benthic and planktic foraminiferal assemblage census data and Benthic Foraminiferal Oxygen Index (BFOI) values, previously published marine climate proxy data (stable isotopes and Ca/Cd), and unpublished results of total carbon, organic carbon, and calcium carbonate analyses of sediments recovered off central California on the Farallon Escarpment (1605m water depth; 37??13.4???N, 123??14.6???WAuthorsM. McGannThe elusive character of discontinuous deep-water channels: New insights from Lucia Chica channel system, offshore California
New high-resolution autonomous underwater vehicle (AUV) seafloor images, with 1 m lateral resolution and 0.3 m vertical resolution, reveal unexpected seafloor rugosity and low-relief (<10 m), discontinuous conduits over ∼70 km2. Continuous channel thalwegs were interpreted originally from lower-resolution images, but newly acquired AUV data indicate that a single sinuous channel fed a series of diAuthorsK.L. Maier, A. Fildani, C. K. Paull, S.A. Graham, T.R. McHargue, D.W. Caress, Mary McGannSubmarine mass transport within Monterey Canyon: Benthic disturbance controls on the distribution of chemosynthetic biological communities
Documenting mass transport within Monterey Canyon and Fan has been a focus of remotely operated vehicle (ROV) observations, sampling, monitoring, and multibeam mapping studies. These efforts indicate that major mass transport events occur within upper Monterey Canyon (<2 km water depths) with a sub-annual recurrence frequency. However, 14C-stratigraphies indicate that a sand carrying event has notAuthorsCharles K. Paull, B. Schlining, W. Ussler, E. Lundsten, James P. Barry, D. W. Caress, D. E. Johnson, Mary McGann - News