I’m very happy to welcome Natalia Varela to the VT Sedimentary Systems Research group. Natalia arrived in January 2018 as a Ph.D. student.

Natalia is from Santiago, Chile, and received a Bachelor’s in Geology at the Universidad de Concepción in 2009 and earned her professional degree in 2015. She has participated in several stratigraphy-related projects in central Chile, Patagonia, and Antarctica, studying the organic portion of Cretaceous formations and their correlation with the depositional environment. Natalia also has experience working as a geologist for energy, mining, and environmental companies.

Natalia will be working on IODP Expedition 374 (Ross Sea West Antarctic Ice Sheet History) samples and data for her dissertation research. Specifically, Natalia will use the occurrence and character of thin-bedded, overbank turbidites recovered from a core drilled on a continental rise canyon-channel system to investigate the Antarctic Bottom Water (AABW) production history in the Pliocene-Pleistocene. For another project, Natalia will use downhole logs from a continental shelf site in the Ross Sea to characterize ice-sheet-proximal lithofacies and examine ice sheet advance/retreat history over the past ~17 million years.

We are excited to have her on board. ¡Bienvenida Natalia!

We have a new paper out in Earth and Planetary Science Letters led by former Sedimentary Systems Research group Ph.D. student and current post-doc Cody Mason.

Sediment supply has long been considered an important factor in observed depositional patterns and facies in sedimentary basins. Indeed, accommodation and supply are commonly invoked as the two fundamental controls on stratigraphy. However, directly measuring paleo-sediment supply from the stratigraphic record is a significant challenge. In most cases, sediment supply is estimated in a relative sense. Thus, the aim of this study was to calculate sediment supply, in an absolute sense, from outcropping Pleistocene alluvial and lacustrine deposits using cosmogenic radionuclides. We applied the catchment-integrated denudation (erosion) rate methodology that is typically used for modern river sediments to a succession of now-exhumed catchment-outlet deposits in Panamint Valley, California. This approach allowed us to generate a time series of paleo-erosion rates (which we use as a proxy for sediment supply).

The figure below (Fig. 6 from the paper) is a summary of our results. In order to calculate paleo-denudation rate we needed some constraint on depositional age, which we got using 10Be/26Al burial dating techniques. The ~180 m thick succession we studied ranges from ~1.2 Ma to ~0.3 Ma old (part D of the figure below). 

The resultant denudation rates (part E of figure above) show that the sediment supply out of the catchment varied from as low as ~24 mm/kyr to as high as ~54 mm/kyr with a long-term mean rate of ~36 mm/kyr. In the paper, we discuss the potential controls of glacial-interglacial climatic variability and Mid-Pleistocene Transition on source-to-sink dynamics. Additionally, we present an end-member mixing model to explore how sediment storage and/or landslide processes in the upper catchment may have influenced our paleoerosion rate calculations.

If you cannot access the EPSL version, you can get a freely available version on EarthArXiv (or feel free to email us and we can send you a copy).

Additional thanks to Ron Schott for joining us out in the field area during one our trips to take some beautiful GigaPan images of the outcrop (see the images called ‘Ballarat Delta’).

I’m very happy to welcome Drew Parent to the VT Sedimentary Systems Research group. Drew is starting his Ph.D. in the department and his dissertation research will investigate the history and patterns of deep-sea sedimentation in the western North Atlantic Ocean in response to Cenozoic climate change. Drew will employ multiple methods, including: quantitative grain-size analysis of late Eocene through Oligocene cores from the Newfoundland Ridges obtained from IODP Exp 342, experimental (flume) investigation of fine-grained sediment transport (a collaboration with Dr. Kyle Strom and students from Virginia Tech Civil & Environmental Engineering), and regional seismic stratigraphic mapping of the U.S. Atlantic continental margin.

Drew is from Springfield, Massachusetts and received a Bachelor’s of Science in Geological Sciences from Salem State University in 2015. His undergrad thesis combined seismic sonar, stable isotopes, and radiocarbon dating to reconstruct the late Quaternary paleoenvironment of a glacial lake in northwest Iceland; this geophysical-geological approach fueled his interest in these types of investigations (similar to the research that will make up his Ph.D. here at Virginia Tech). Drew then went on to graduate school at Wright State University in Dayton, OH, where he finished a Master’s of Science in Earth and Environmental Sciences this past April (2017). Drew’s M.S. thesis is titled “Pre-Mt. Simon seismic sequences below west-central Indiana: local interpretation and regional significance”. This research employed regional 2-D seismic reflection and potential field data to assess the composition and deformational history of the poorly understood pre-Mt. Simon below the eastern U.S. mid-continent.

Welcome to the department and Sedimentary Systems Research group Drew! Check out Drew’s website here.

I’m very happy to announce that Ph.D. candidate Cody Mason is now Dr. Cody Mason! Cody successfully defended in late April and submitted his finalized dissertation a few days ago. His research interests are in the interactions of tectonics, climate, and surface processes (erosion and deposition). Cody was co-advised by me and my colleague Jim Spotila (neotectonics, geomorphology) and ended up conducting two stand-alone projects, but both within the overall theme of climate-tectonic-surface process interactions and both projects examining normal-fault-bounded mountain ranges in California.

Cody’s project with Jim Spotila is titled “Two-phase exhumation of the Santa Rosa Mountains: Low- and high-angle normal faulting during initiation and evolution of the southern San Andreas fault system”. In this study, Cody and co-authors used (U-Th)/He thermochronometry combined with geologic mapping to test models about the timing and kinematics for initiation of the southern San Andreas system. This paper was submitted earlier this year and is currently in review.

figure from Mason et al. (in review); Two-phase exhumation of the Santa Rosa Mountains: Low- and high-angle normal faulting during initiation and evolution of the southern San Andreas fault system

The project that Cody and I worked on together is titled “Climate-driven unsteady denudation and sediment flux in a high-relief unglaciated catchment-fan system using 26Al and 10Be, Panamint Valley, California”. In this study, Cody calculated catchment-wide denudation rates from a now-exhumed Pleistocene succession of alluvial-lacustrine deposits at the mouth of a short and steep catchment in the Panamint Valley of California. These cosmogenic radionuclide-derived erosion rates are integrated with sedimentological characterization of the deposits to quantify the magnitude and variability in sediment flux in this catchment-fan system. Such catchment-fan systems are ideal natural laboratories to test hypotheses about the transfer of climate and/or tectonic signals to stratigraphy. Cody and I are currently putting the finishing touches on this manuscript and will be submitting it very soon.

figure from Mason & Romans (in prep); Climate-driven unsteady denudation and sediment flux in a high-relief unglaciated catchment-fan system using 26Al and 10Be, Panamint Valley, California

In addition to the above projects, Cody first-authored a paper that came out in Earth & Planetary Science Letters a few months ago that examines millennial to multi-millennial scale sediment mixing in the Mississippi River sediment routing system.

Fig. 4 from Mason et al. (2017); Climatic and anthropogenic influences on sediment mixing in the Mississippi source-to-sink system using detrital zircons: Late Pleistocene to recent; EPSL

Finally, I’m also happy to announce that Cody will be sticking around the Sedimentary Systems Research group for another couple years as a post-doctoral researcher. We will be applying this source-to-sink approach to the behavior of the Amazon sediment-routing system. More on this project later this summer.

Congratulations to Cody on his Ph.D. and these exciting contributions to geoscience!

I’m excited to announce the publication of a new paper from our group out in Marine Geology titled “Cenozoic North Atlantic deep circulation history recorded in contourite drifts, offshore Newfoundland, Canada”.

This paper is based on the M.S. thesis work of former VT Sedimentary Systems Research graduate student Patrick Boyle. Pat used a grid of 2-D seismic-reflection data tied to nine IODP Exp 342 boreholes (drilled in 2012) that have robust bio- and magneto-stratigraphic age control. The resulting seismic stratigraphic framework is used to document the spatial and temporal distribution of deep-sea contourite drift sediments on the Newfoundland ridges and relationship to deep circulation history in the western North Atlantic Ocean.

The onset of bottom-current-controlled, terrigenous-dominated sediment deposition occurs at ~47 Ma and continues, generally, through the present. Unlike many other areas in the western North Atlantic Ocean, we did not identify a prominent (mappable) seismic horizon corresponding with the Eocene-Oligocene Transition. The paper discusses this and other paleoceanographic implications in more detail. Below is the summary figure of the paper, which puts the mapping of the sedimentary drifts into this broader context.

This paper provides important regional and long-term context for the many higher-resolution paleoceanographic studies based on IODP Exp 342 cores that are in the works. Additionally, this new seismic stratigraphic framework is helping design strategies for future ocean drilling proposals.

Congrats to Pat on getting his thesis published!

Three of the four current graduate students in the Sedimentary Systems Research group defended their theses over the past week.

Kristin Chilton (M.S.)

Thesis title: Terrigenous grain-size record of the Newfoundland Ridge contourite drift, IODP Site U1411: The first physical proxy record of North Atlantic abyssal current intensity during the Eocene-Oligocene Transition

Kristin’s work resulted in generation of an important paleoceanographic record of the Eocene-Oligocene Transition (~34 Ma) in an area (North Atlantic Ocean) where this important global climate shift is typically expressed as a hiatus or erosional unconformity. We will be integrating this record with other paleoceanographic proxy records being generated by collaborators. If you’re going to AGU next week, come by on Friday afternoon to see Kristin’s poster.

Kristin is staying in the department to work on a Ph.D. but is shifting topics to geomorphology with my colleague Jim Spotila.

Sarah Jancuska (M.S.)

Thesis title: Sedimentology and architecture of a partially contained slope deposit, Cerro Solitario, Magallanes Basin, Chilean Patagonia

Sarah’s master’s thesis research was part of the Chile Slope Systems consortium and examined the sedimentology and stratigraphic architecture of a Cretaceous turbidite-dominated succession exposed in the Patagonian Andes. Sarah focused on a 40-60 meter thick package exposed along a ~3 km transect and interpreted the unit to record a partially ‘contained’ (or ‘ponded’) intra-slope setting.

Sarah’s next move is to apply her sed-strat expertise in industry … she is currently talking with a major environmental consulting firm about a potential job opportunity characterizing aquifer stratigraphy.

Figure from Sarah Jancuska’s master’s thesis of part of the Cretaceous turbidite outcrop she studied.

Neal Auchter (Ph.D.)

Dissertation title: Basin evolution and slope system dynamics of the Cretaceous Magallanes Basin, Chilean Patagonia

Neal’s work was also part of the Chile Slope Systems program. Not only did a lot of work for his dissertation, but also spanned multiple disciplines. Although the work is focused on questions related to deep-marine slope sedimentation, he used and developed tools involving structural geology and geochemistry. Sedimentary geoscience is a multi-disciplinary endeavor and Neal’s Ph.D. work is a great example.

Neal has three chapters in his dissertation:

1. Slope readjustment revealed by stratigraphic architecture and evolution of a submarine fan system, Tres Pasos Formation at Cerro Cagula, southern Chile
2. Influence of deposit architecture on intrastratal deformation, slope deposits of the Tres Pasos Formation, Chile [published in Sedimentary Geology in July 2016]
3. Detrital strontium isotope stratigraphy: Applications for basin analysis from the Tres Pasos Formation, Upper Cretaceous Magallanes-Austral Basin, Patagonia

Chapters 1 and 3 will be submitted for publication in early 2017.

Neal will be starting a job with Shell’s geoscience R&D team in Houston, TX next month.

Figure from Neal Auchter’s dissertation showing one of the many exceptional outcrop exposures of submarine fan deposits in southern Chile.

As an advisor, this moment is bittersweet. It’s been very rewarding to mentor and collaborate with Kristin, Sarah, and Neal. I will definitely miss having them around! They have all helped me (a pre-tenured assistant professor) develop my young program to what it is now. The thesis work described above does not capture all the day-to-day interactions and help getting field gear prepared, lab instruments working, procedures and workflows honed, and many other thankless tasks graduate students do.

I wish them all the best and hope to collaborate in the future.

I am looking to admit a new graduate student to the Sedimentary Systems Research group to start in August 2017. This could be either a master’s or a Ph.D.

The project(s) for this incoming student would contribute to our growing research program in Paleogene North Atlantic paleoceanography. Specifically, we are generating terrigenous grain-size records from IODP Exp 342 sediment cores that span the Eocene-Oligocene Transition and early Oligocene (~36-25 Ma). These cores are from deep-sea contourite drifts on the Newfoundland ridges and record the history of ocean-basin-scale bottom current activity.

The Eocene-Oligocene Transition represent the most significant global climate shift of the past ~60 Myr, but the response of deep ocean circulation in the North Atlantic is still poorly understood. This research involves collaborations with geoscientists at Univ of Southampton (UK), Univ of Utah, and Univ of South Carolina who are generating different, but complementary, paleoceanographic records from the same cores. Thus, this work will likely involve working with other graduate students from these institutions.

See below for a recent conference abstract from our group with more details. Note that a future project may not look exactly like this, but this abstract will give you a sense of the type of work and the questions we are interested in.

For prospective students seeking a Ph.D., I’m open to your ideas for additional projects. It’s common for Ph.D. students to have multiple, concurrent projects that end up as separate stand-alone, published papers.

Please contact me if you want to learn more and/or have questions. (Please see this page for information about logistics of applying.)

Brian Romans

Below is an abstract at the AGU Fall Meeting 2016 about this work. A future project may not look exactly like this one in terms of the specifics, but it will be in the general area of North Atlantic paleoceanography:

Terrigenous grain-size record of the Newfoundland Ridge contourite drift, IODP Site U1411: The first physical proxy record of North Atlantic abyssal current intensity during the Eocene-Oligocene Transition

Atlantic Meridional Ocean Circulation (AMOC) is a vital process that helps to regulate global climate and support marine ecosystems. The timing and nature of the shift to modern AMOC, and especially to deep-water formation in the North Atlantic, has been a topic of ongoing study, with the Eocene-Oligocene Transition (EOT, ~34 Ma) being a potential focal point of this shift. However, the role played by abrupt EOT cooling in North Atlantic circulation remains unclear. Improved constraints on Paleogene circulation will provide insight into the sensitivity of AMOC to perturbations in global climate.

We obtained grain-size data from the terrigenous fraction of the mud-rich sediments of the Southeast Newfoundland Ridge contourite drift complex at IODP Site U1411, which is interpreted to have formed under the influence of the Deep Western Boundary Current. We analyzed 195 samples that span 150 m of stratigraphy from 36-26 Ma. The main objective was to use the ‘sortable silt’ fraction (10-63 µm) to generate a record of relative change in bottom-current velocity. These data are complemented with a record of the abundance and size of lithogenic sand (>63 µm).

Here we present U1411 sortable silt data as the first physical proxy record of abyssal current intensity in the North Atlantic, from late Eocene to mid Oligocene. Invigoration of North Atlantic deep circulation occurred gradually (over Myr timescales). We infer that deep circulation in the North Atlantic was not sensitive to the abrupt global cooling and Antarctic glaciation associated with the EOT. Rather, our data suggest that changes in North Atlantic circulation were likely governed by longer-term processes related to the opening of key tectonic gateways (i.e., the Greenland-Scotland-Faeroes Ridge, and the Drake and Tasman Passages). Lithogenic sand is nearly absent in the Eocene and then systematically increases in abundance from the earliest Oligocene through the mid Oligocene, which could represent bottom-current transport of an additional supply of terrigenous sediment during the Oligocene. Our findings have important implications for debate over the mechanisms responsible for carbon cycle perturbation associated with the Cenozoic initiation of sustained Antarctic glaciation.

Here’s a rundown of our group’s talks and posters at the 2016 AAPG conference in Calgary next week. All of this work is associated with the Chile Slope Systems project, which is a multi-institution project involving Virginia Tech, Colorado State University, and University of Calgary.

Monday, June 20, 2016

Talks

4:15-4:35 PM, Improving Stratigraphic Models of Outcropping Slope Channel Fills Using Morphometrics From the Lucia Chica Channel System, Offshore Central California,
Palomino D; A.P. Reimchen*; S.M. Hubbard; L. Stright; B.W. Romans.

7:30-10:00 PM, What can ancient turbidite deposits tell us about turbidity currents? SEPM Deepwater Research Group Meeting, Telus Convention Center, Glen Room 2016 – South Building, Upper Level; S.M. Hubbard

Posters

The Influence of Intra- and Inter-Channel Architecture in Selecting Optimal Gridding for Field-Scale Reservoir Simulation, Exhibition Hall C; C.D. Meirovitz*; L. Stright; S.M. Hubbard; B.W. Romans.

Tuesday, June 21, 2016

Talks

4:35-4:55 PM, Stratigraphic Record of Foreland Basin Dynamics, Cretaceous Magallanes-Austral Basin, Chile and Argentina, Hall B, Room 1; B.W. Romans; N.C. Auchter; A. Bernhardt; J. Covault; B.G. Daniels; A. Fildani; J. Fosdick; S.M. Hubbard; Z.R. Jobe; M. Malkowski; T.M. Schwartz; Z.T. Sickmann; L. Stright; S.A. Graham. (Invited Talk)

Posters

Using Synthetic Seismic Models of Channelized Deepwater Slope Deposits to Inform Stratigraphic Interpretation and Reservoir Modeling, Exhibition Hall C; A. Nielson*; L. Stright; S.M. Hubbard; B.W. Romans

Evolution From Confined to Relatively Unconfined Strata in a Distal Slope Setting, Magallanes Basin, Chilean Patagonia, Exhibition Hall C; S. Jancuska*; B.W. Romans; N.C. Auchter; S.M. Hubbard; L. Stright

Wednesday, June 22, 2016

Posters

The Evolution of Deepwater Slope Systems on Retroarc Foreland Basin Margins: Insights From Detrital Zircon Geochronology, Tres Pasos Formation, Magallanes Basin, Chile, Exhibition Hall C; B.G. Daniels*; N.C. Auchter; W. Matthews; S.M. Hubbard; B.W. Romans; L. Stright

Timing of Slope System Evolution and Intra-Basinal Sediment Recycling in the Magallanes Retroarc Foreland Basin (Chile) From Detrital Strontium Isotope Stratigraphy,
Exhibition Hall C; N.C. Auchter*; B.G. Daniels; S.M. Hubbard; L. Stright; B.W. Romans

Here’s what the Sedimentary Systems Research group is up to in the spring 2016 semester:

Ph.D. candidate Neal Auchter submitted his first paper as part of his dissertation research in January. This paper discusses intriguing deformation features in submarine slope strata of the Upper Cretaceous Tres Pasos Formation in southern Chile. We came upon this outcrop a couple of field seasons ago while mapping and were initially confused about the genesis of small-scale (up to ~meter of offset) extensional and compressional faults. The data Neal collected suggests a mechanism of deformation that occurred soon after deposition (shallow burial), with some component of gravitational influence, rather than a tectonic (e.g., uplift of the outcrop belt long after deposition/burial). Interestingly, the position and scale of deformation features are controlled, at least in part, by the depositional architecture. This manuscript is currently in review for Sedimentary Geology.

Photos of down-slope-influenced deformation (part of a figure for Auchter et al., in review)

M.S. candidate Kristin Chilton is right now analyzing the last set of samples that will make up her complete data set for her master’s project. Kristin is investigating paleo-circulation in the North Atlantic Ocean in response to global climate change at the Eocene-Oligocene transition (~34 Ma) via terrigenous grain-size analysis of deep-sea sediment cores. Preliminary results are intriguing and suggest a transient change in circulation at Oi-1 (Oligocene isotope stage 1), but more work is needed to test this. Kristin presented a poster about this work at GSA in fall 2015, which won best student poster. Congrats to Kristin!

M.S. candidate Sarah Jancuska finished the second of two field seasons down in southern Chile earlier this semester and is now poring over the data. Sarah is examining the sedimentology and stratigraphic architecture of deep-marine deposits at the transition from basin-plain/distal-levee to progradational slope systems. The photo below (taken by a drone) showcases part of the outcrop transect Sarah is working.

Drone photograph of the south face of Cerro Sol, Tres Pasos Formation, southern Chile.

Ph.D. candidate Cody Mason is spending the bulk of his time this semester working on a manuscript related to a thermochronolgy and tectonics study in the Coachella Valley of southern California (see this abstract from AGU 2015 presentation). In addition, Cody is exploring various techniques to better understand his cosmogenic radionuclide results from Pleistocene alluvial deposits in Panamint Valley (e.g., methods in this Balco & Stone paper from 2005). Cody will be in Austin, Texas this summer doing another internship with the Statoil research group.

We also have Virginia Tech Geosciences undergraduate Taylor Sanchez doing research in our group this semester. Taylor is working with Kristin on the Eocene-Oligocene paleoceanography project and is focused on the coarse (sand, >63 µm) fraction of these dominantly muddy deposits. Taylor is acquiring images and then using the image-analysis method of Buscombe (2013) [i.e., we are using this MATLAB routine] to characterize grain size of the sand fraction. The photo below is one of hundreds of images that Taylor has generated so far this semester. Taylor will be continuing this work for part of the summer.

Stereoscope image of Oligocene sand from Newfoundland Ridge

Three of the four graduate students in the group (Neal, Sarah, and Kristin) are all planning on defending in the fall, so things are quite busy around the lab!

We tested out using drone-based photography this field season for the Chile Slope Systems project. There’s a lot of potential with this technology for the high-resolution stratigraphy work we do. Simple, but fundamental, visualization is the most obvious value. Getting a view of impossible-to-get-to outcrop faces is a game-changer.

Here’s a ‘fly by’ video taken of the Rio Zamora outcrops that Ph.D. candidate Neal Auchter is working on. The 2-minute video starts lower in the section highlighting the outcrops in the river canyon and then the drone turns up a side creek to show the overlying strata.