USGS collaboration: Astoria Canyon sediment core processing

As a part of the USGS-UW Cascadia Canyons project, the sediment dynamics group recently traveled down to the USGS Pacific Coastal and Marine Science Center in sunny Santa Cruz for one week of sediment core processing. The cores on the “operating table” this week were 9-meter-long jumbo piston cores collected from the muddy floor of Astoria Canyon between 700 and 1500 m water depth. The complete core processing workflow included CT density scanning, core splitting, photography and subsampling. Once our work was complete, we sealed cores into airtight tubes to be archived in a USGS core repository.

These cores are among the longest sediment records collected from this region of Astoria Canyon, and they have already given us valuable insight into canyon mass transport events (turbidity currents and debris flows) during Holocene sea level highstand. A primary feature of these cores are the turbidite deposits that vary in lithology, thickness, age and frequency from core to core. While the canyon was once thought to rarely experience mass transport during Holocene highstand, this new evidence indicates that several transport events have occurred within the last 300 years.

NSF Cascadia Canyons – Sensor Systems Deployed!

A successful cruise on the R/V Sikuliaq in early April, 2023, has kicked off our year-long experimental program exploring sediment gravity flows on the Cascadia Margin.  We placed moorings and bottom boundary layer tripods in the upper canyon reaches of two systems:  Astoria and Quinault.  These two canyons have very different morphologies and relationships with their modern-day sediment supply, the Columbia River.  With the instrumentation we are hoping to capture a range of sediment gravity flows over the year-long deployment.  Seabed coring of the canyon thalwegs and surrounding continental shelf and slope give us clues as to triggering mechanisms, gravity-flow dynamics and seabed deposits resulting from these flows.  UW Sediment Dynamics group participants: Andrea Ogston, Chief Scientist; Evan Lahr, Tripod Builder and Coring Op Lead; and Sarah Vollero, Coring Ops.

The project is being undertaken through a collaboration with the USGS Pacific Coastal and Marine Science Center (led by Dr. Jenna Hill and Kurt Rosenberger).  In addition, we had the pleasure of being joined on the cruise by a UW Sediment Dynamics alumni, Dr. Emily Eidam, Oregon State University, and graduate students Adrian Heath (OSU) and Jonathan Moore (V Tech).

Fun in False Bay

Mariah Josten has contributed this post about her work this Autumn, as a Research Apprentice at Friday Harbor Labs

False Bay at low tide (credit: MJ)

I spent fall quarter at Friday Harbor Labs conducting an independent research project in the False Bay estuary, on San Juan Island. This bay is super unique because at high tide it’s covered completely by water and during a very low tide, the bay empties and reveals a tide flat brimming with benthic organisms, rotting sea lettuce, and a wide range of sediment grain sizes. The goal of my project was to examine how waves coming through the narrow bay entrance and sediment input from False Bay Creek combine to shape the grain size distribution in False Bay. To do this I collected 52 sediment samples by hand (mostly in the middle of the night) along two transects from shore towards the middle of the bay.

Grain size results

The “delta” transect crossed the intertidal delta created by False Bay Creek and continued into the bay to examine the influence of creek sediment transport. A “tideflat” transect, 250 m away from the creek delta, examined wave influence on grain size. The tideflat transect revealed that at the shore, the there was equal amounts of medium and fine sand and the fraction of medium sand increased towards the middle of the bay. The delta transect began with poorly sorted sandy gravel near the shore and converged in character with the tideflat transect beyond the edge of the delta. Overall, my results suggest that outside the delta itself, wave energy dominates sediment characteristics for the rest of the bay.

False Bay Creek delta and channel

At long last, a return to sea!

After what seemed to be an eternity (ok, about a year), the sediment dynamics group was reunited with the open ocean for data collection in the axis of Astoria Canyon. The cruise departed from Newport, Oregon on the RV Thomas G. Thompson, and arrived at the Marine Sciences Building dock in Seattle a week later. The research goals of the cruise were to 1) collect a suite of sediment cores from Astoria canyon, and 2) service many of the Applied Physics Laboratory‘s instrument moorings such as ChaBa.  ~15 undergraduate students were also aboard the ship, gaining firsthand experience collecting data for these research projects. Both research objectives were successful, although ocean conditions tested our crew with high winds and 20-foot swell.

The sediment dynamics group is especially excited about this recent haul of mud from Astoria Canyon. Our research in Astoria Canyon began in 2019, with a series of cores collected from the uppermost canyon head (see map below), and an instrumented tripod deployment measuring water column processes. In this early study, we observed the potential for down-canyon sediment flushing by sediment-gravity flows, and rapid sediment loading in the canyon head, but these findings raised additional questions about the fate of sediments resuspended in the canyon head. Does the shelf-incised canyon axis act as a permanent sink for small, off-shelf gravity flows? Where is the canyon-axis depocenter? Is it possible to trigger a through-canyon sediment gravity flow with shallow oceanic sediment resuspension? The cores collected on this recent cruise march deeper into the canyon axis, aiming to address these questions. Stay tuned for our analysis of these exciting new cores!

 

Sunset in Newport prior to departure.

A curious seal checks out our coring gear at the head of Astoria Canyon.

Hannah recovering the corer like a boss.

Sediment cores collected from Astoria Canyon in 2021 and 2019.

Recovering a subsurface mooring in calm seas.

The tight squeeze through the Ballard locks on our return to the ocean dock.

Hot off the press

Check out our brand new publication in the Journal of Geophysical Research: Earth Surface about sediment dynamics in the Ayeyarwardy Delta!

Glover, H. E., Ogston, A. S., Fricke, A. T., Nittrouer, C. A., Aung, C., Naing, T., et al. (2021). Connecting sediment retention to distributary channel hydrodynamics and sediment dynamics in a tide-dominated delta: The Ayeyarwady Delta, Myanmar. Journal of Geophysical Research: Earth Surface, 126, e2020JF005882. https://doi.org/10.1029/2020JF005882

And please get in touch if you can’t access the article and would like to read it (hglover@uw.edu).

Sampling along the Bogale River in Sept 2017

Fifteenth Century Floods!

The Sediment Dynamics Group recently returned from a short field mission to the lower reaches of the Columbia River, supporting UW scientists who are searching for and sampling two unknown strata that were emplaced during the fifteenth century. These sedimentary layers are being studied by a paleoseismology research group at UW who aim to piece together the character and precise timing of three geologic events: 1) the Bridge of the Gods dam breach, 2) the eruption of Mount St. Helens, and 3) the T2 subduction zone earthquake. The timing of these events relative to one another is very close, but scientists continue to grapple with the details of their potentially interrelated history, and advances in this realm could yield insights into how our landscape will rapidly change during the next subduction zone earthquake.

Surveying equipment on Wallace Island.

The two key stratigraphic layers in this study are 1) a coarse-silt floodplain deposit emplaced by a flood resulting from the Bridge of the Gods land-bridge failure, and 2) a tephra layer emplaced by a water-rafted debris from a volcanic eruption, likely Mount St. Helens. Field methods included outcrop interpretations (contact analysis, identification of cross-bedding, elevation, etc.), grain size analysis, core C14 geochronology, and core CT scanning. The extent of this deposit has been mapped for >30 km, from Clatskanie to beyond Svensen OR. The canoe is the vehicle of choice for this fieldwork, allowing easy access to the muddy river cutbanks which contain the event layers. This is also “one of those sites” where you’ll be caught in the rising tide if you don’t work quickly (see below)!

All smiles as the tide catches up with us. Only a few samples to go!

 

MSP Is Back!

Rainbow over the Elwha! (Photo credit: C. Williams)

The Marine Sedimentary Processes Research Apprenticeship headed back to the Elwha River last week. In this class, students develop their own research questions related to the Elwha dam removal project, collect data, and write a thesis paper all in one quarter! Phew! This year students are focusing on the interactions between sediment transport and biological communities in the coastal area close to the river. We have the opportunity now, 5 years after dam removal, to now examine the system as it approaches a new equilibrium.

We went on two separate research cruises with 4 students each time (for COVID safety) on the School of Oceanography’s R/V Rachel Carson. The first cruise had spectacularly great weather. Students collected benthic grab samples, CTD profiles of the water column, and collected box cores. The second cruise was a bit choppier! We hit some large waves and had to adapt our sampling plan rapidly. But the students still hung in there and collected amazing data. We even managed to sneak in a quick box core despite the weather.

Over the next few weeks we will focus on processing all this data and analyzing the results. Stay tuned to hear more about the class and their results this fall.

Max and Hannah deploying the shipek (they’re smiling under those masks!)

Pod Dam weathering the rough seas with a smile!

Hannah is sad that the shipek failed to collect a sample

Max, Chris, and Hannah (from Pod Baddies) prep instruments for deployment

Alex recovering the Shipek

Ocean Sciences Meeting 2020 (+ sunshine)

This week the Sed Lab has been in sunny San Diego at the 2020 Ocean Sciences Meeting. Conferences are a great opportunity to share research, hear fresh ideas, and learn about new opportunities. Evan and Andrea presented early results from Astoria Canyon. Robin presented posters for both her education research and the final chapter of her PhD (!!!), which examines particle aggregation and deposition in the Mekong River. Hannah gave two oral presentations, one on building a global scientific community and one on sediment dynamics in the Ayeyarwady River Delta.

Robin presenting her poster

Andrea’s presentation

Conferences are also a wonderful chance to catch up with old friends and make new friends. We hung out with Rip, Dan, and Emily, and heard about their latest research. And, most importantly, we also got a good dose of sunshine after a long PNW winter.

Evan and Rip discussing Astoria Canyon

Hannah’s presentation

Back to Myanmar

This past week the Sediment Dynamics Group was back in Myanmar! Andrea and I presented results at the International Joint Symposium at Pathein University. The focus of the symposium was “Challenges in educational development on agricultural and food resources in tropical Asia”. It was very different from the usual presentations we see! There were lots of talks about rice farming and fishing. But we met up with some old friends and made some new ones too. It’s always exciting to connect with researchers from other countries.

After the symposium we met up with Aaron and Evan, and headed back to Meinmahla Island to collect some new data. For the past 2-3 years, we’ve been investigating sedimentary processes in different types of tidal channels in the island. The island is a mangrove preserve, so we’re able to study processes in a natural environment. There are also agricultural fields along the banks of the river near the island, so we can investigate processes in a modified landscape. It’s an ideal study site! There are also lots of crocodiles, snakes, and centipedes (oh my!).

Even though it’s the rainy season we had amazing weather, and there was only one downpour. We measured water and sediment flow in the tidal channels and surveyed the island. We collected lots of videos of the river banks so that we can understand how the bank shapes change through the island. We also measured the elevation of the island and agricultural fields. It was a long week of hot work, but we got some awesome data!

CERMIT the tripod returns!

This May, the UW Sediment Dynamics Lab deployed a benthic tripod in the head of Astoria Canyon to measure canyon hydrodynamics and sediment flux. Over the summer, our tripod recorded minute-by-minute data, documenting the forces that move sediment through Astoria Canyon and into the deep water sediment record. This fall, it was time to recover our tripod from the seafloor. Andrea and Evan boarded the RV Rachel Carson, steamed out to the deployment site, and sent our tripod a signal to release its recovery float… After sleepless nights worrying about bottom-trawl fishing nets hauling away our tripod, we were relieved to discover it was intact and upright, just where we left it. Recovery went smoothly in low seas, and within the hour, our tripod was on deck. We spent a few hours cleaning sandy mud off its feet, scrubbing “biology” off of its sensors, and downloaded data from its instruments.

CERMIT the tripod, above water for the first time in four months.

This little crab was recovered with our tripod.

Although the tripod was safely on deck, our jobs were far from over–we had also set out to collect seismic profiles and sediment cores from the canyon! The USGS accompanied us aboard the RV Carson, and in collaboration with this project, they created a survey plan to map the geologic structure of Astoria canyon with seismic gear (CHIRP and multichannel). Together, the crew logged ten days of 24-hour seismic data collection, and through all that surveying, we managed to have some fun. We caught salmon and tuna, saw dozens of humpback and pilot whales, and had heated discussions over the best practices in coffee brewing. After returning to port, the USGS crew returned to Santa Cruz, reinforcements from UW’s Sed Lab arrived, and we boarded the vessel yet again for two final days of coring. Over this two day effort, the sediment lab collected 25 box cores in and around the canyon head and shelf rim, coring efficiently in spite of large swell and mechanical difficulties. 

USGS scientists deploy the CHIRP seismic package behind the boat, where it will be towed for the next week. This unit contains both the seismic source and receiver.

Aaron takes in the sunrise while steaming out to the first coring station of the cruise.

All told, three datasets were successfully collected from Astoria Canyon, and this is a big step forward in understanding what phenomena drive sediment from the continental shelf to the deep ocean. We’re excited to begin sharing results!

Aaron enjoying the little things on the ride home.