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.

The 8th (and final) installment of the documentary film series on IODP Expedition 342 is now out. The expedition to drill and recover sediments from the Newfoundland Ridge that contain climate archives going back >50 million years was over three years ago (summer 2012) and much work has been done since.

This episode summarizes the post-cruise science meeting we just had in September 2015 where all the participating scientists get together to share the latest on their research and to re-kindle collaborations.

Ultimately, all this work is strengthened through multi-disciplinary collaborations — this meeting was critical to keeping the momentum going. I’m definitely excited about all the science that will come out of this effort.

To view all the past episodes and the 20-minute documentary, go to this page.

The Sedimentary Systems Research group is quite busy this semester with various research, teaching, and other activities. Here’s what we’re up to:

Ph.D. candidate Neal Auchter is immersed in preparing the first manuscript to come out of his work the past few years. This first paper will highlight the occurrence and style of gravitational deformation features (i.e., faults/folds from down-slope movement) preserved in outcropping stratigraphy. What’s intriguing is the relationship of these deformational features with the stratigraphic architecture. Neal plans to submit this paper by December. Neal is also going to be presenting a poster at AGU in December about work he did during his internship this past summer with the Shell clastic sed/strat research team in Houston.

M.S. candidate Kristin Chilton is crazy-busy taking multiple courses and TAing the undergraduate Sed-Strat course. Even with all of this, she is making progress on her research investigating the response of North Atlantic deep-sea circulation to climate change at the Eocene-Oligocene Transition. Kristin will be presenting a poster at GSA in Baltimore in a few weeks sharing the preliminary results. Undergraduate researcher Shauna Flynn, also a co-author on this poster, is working in our lab this semester focused on characterizing the coarse fraction (>63 microns) of these dominantly muddy deposits.

M.S. candidate Sarah Jancuska is taking courses and working up the wealth of data she collected during the field season in Patagonia back in February-March of this year. Right now, Sarah is focused on compiling statistics from the measured stratigraphic sections (e.g., bed thickness, degree of bed amalgamation, etc.) to test ideas about the degree of large-scale confinement, or ponding, of these turbidite deposits.

Ph.D. candidate Cody Mason is TAing the course I’m teaching this semester, Seismic Stratigraphy, and working on the project he’s doing with Virginia Tech faculty Jim Spotila on the Late Cenozoic tectonic evolution of the Coachella Valley region of southern California. Cody, Jim, and their co-authors will be presenting at AGU in December highlighting some new helium thermochronology data.

Finally, my colleague here at Virginia Tech, Ken Eriksson, and I have a new Basin Research paper in press just this week that estimates sediment flux of a ~325 million-year-old river system sourced in the Alleghanian Orogeny mountain belt (the remnants of which are the Appalachian Mountains). We use a remarkable succession of prodeltaic tidal rhythmites as a high-resolution chronometer and make calculations of sediment load and yield. The figure below (Fig. 8 from the paper) compares our range of estimates with a database of modern rivers (Milliman and Farnsworth, 2011).

Uncertainties in these estimates arises from the true total duration of the stratigraphic interval of interest as well as inferences about the size of the paleo-catchment. However, even with conservative uncertainty ranges incorporated, the paleo-flux of this ancient river system is comparable to modern river systems such as the Fly, Po, and Eel. With the sediment yield estimates we then calculate denudation of the long-gone Alleghanian Mountains, which agrees with denudation estimates from independent methods. We suggest that such paleo-sed flux estimates can, in certain types of systems, provide additional insight into surface process response to tectonics in deep-time archives.