Author Archives: Brian Romans

New paper on timing of deep-marine slope system evolution using zircon geochronology

We are pleased to share our newest publication coming out of the Chile Slope Systems project. This paper is led by Univ. of Calgary Ph.D. student Ben Daniels and is now online in the journal GSA Bulletin.

This study reports >6,600 new U-Pb zircon ages from the Upper Cretaceous Tres Pasos Formation in southern Chile. We’ve been investigating the sedimentology and stratigraphic architecture of these exceptional outcrops of slope strata for many years, but haven’t had a robust understanding of the timing until now.

Ben (with the help of others in the group) collected numerous sandstone samples for detrital zircons as well as two volcanic ash deposits. Together, the new geochronologic data constrain the age of distinct “phases” within the Tres Pasos Formation across a ~100 km long by ~2 km thick outcrop belt. With this framework, we discuss rates of progradation/aggradation, comparison to other well-studied slope/margin systems, and potential external controls on the basin-scale architecture. Additionally, we also include a discussion on the use of detrital zircon to calculate maximum depositional ages (MDAs) that will be of interest to anyone using detrital zircon geochronology for sedimentary system analysis.

The figure below (Fig. 2 from the paper) is a regional stratigraphic cross section showing the large-scale architecture, paleocurrent data, and these new U-Pb ages all in one chronostratigraphic framework.  

Huge congrats to Ben on spearheading this effort!

Welcome new Ph.D. student Drew Parent

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.

Congratulations to Cody Mason on finishing his Ph.D.!

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!

Sedimentology and Scientific Ocean Drilling (Video)

The short (~4 minutes) video below features Pincelli Hull (Yale University) and me discussing the job of a sedimentologist on an IODP (International Ocean Discovery Program) expedition. If you’re interested in learning a bit more about what it would be like to participate in these expeditions, this video is a good introduction.

The video was produced by ScienceMediaNL and includes footage from IODP Expedition 342, which Celli and and I sailed on in 2012.

New paper on Cenozoic history of contourite sedimentation in North Atlantic Ocean

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!

New graduate student Sebastian Kaempfe

I’m very happy to welcome Sebastian Kaempfe to the VT Sedimentary Systems Research group. Sebastian is starting a M.S. degree and his research will be part of the Chile Slope Systems program, which is in the first year of another three-year phase.

Sebastian is from southern Chile (Punta Arenas), not far from the field area that is the focus on this research. He received a Bachelor’s in Geology at the Universidad de Concepción in 2009. Sebastian came to us after finding out from a mentor and friend that we were doing sedimentary geology research in Chilean Patagonia. He approached us a few years ago and asked if he could help out as a field assistant and learn about what we were doing. This relationship grew and he’s now working on his own project in the group.

We are excited to have him on board. ¡Bienvenidos Sebastian!

Congratulations to Kristin, Neal, and Sarah on successful defenses!

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.

sj

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.

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.

Seeking new graduate student to join Sedimentary Systems Research group in August 2017

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.

Presentations at AAPG 2016 in Calgary

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.

aapg

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

Virginia Tech sedimentary geoscience trip to Outer Banks, NC

The broader Virginia Tech sedimentary geoscience group (faculty and graduate students of VT Sedimentary Geochemistry and VT Sedimentary Systems and related disciplines) just returned from a six-day field trip visiting locations in the Outer Banks barrier island system of North Carolina. The trip was the culmination of a grad-student seminar this spring semester on coastal sedimentary environments. The students researched topics of interest, identified appropriate locations, designed field activities, and then led that day of the trip. The nine graduate student participants collaborated to design, write, and produce a field guidebook as well.

Topics of interest included: sediment transport dynamics, facies distribution and stratigraphy, biology/ecology of coastal environments, and anthropogenic effects/activities (e.g., beach nourishment). Field activities included: grain-size analysis (using sieves), beach profiling, trenching, push coring, and lots of primary observation.

Most of us in this group study sedimentary rocks so just getting to watch sediment transport happen before our eyes and make the connection to deposits that (might) get preserved into the rock record was an overarching objective.

In addition to the field locales, we had great visits to the UNC Coastal Studies Institute and the Army Corps of Engineers Field Research Facility. Huge thanks to our hosts, these visits added a lot to our trip.

The photos below summarize just some of the trip.

Day1

Day 1: unnourished beach at Duck; “outcrop” of eolian cross-stratification; beach profiling at Nags Head; eolian ripples/dunes at Jockey’s Ridge State Park

Day 2: Coring the foreshore; Examining coarse layers in foreshore; Coring the back-barrier; Well-developed microbial mat in estuarine deposits

Day 2: Coring the foreshore; Examining coarse layers in foreshore; Coring the back-barrier; Well-developed microbial mat in estuarine deposits

Day 2: Watching sand move on the south side of Oregon Inlet

Day 2: Watching sand move on the south side of Oregon Inlet

Day3

Day 3: Discussing beach-to-overwash-fan transition; Exploring overwash fan; Push coring estuarine sediments; View of barrier island facies tracts from Cape Hatteras lighthouse

Day4

Day 4: Exploring the wetlands and swamps of the coastal plain at Alligator River National Wildlife Refuge.

Day5

Day 5: Exploring Currituck Sound (large estuary behind barrier island) by pontoon boat; Taking salinity and pH measurements; Examining estuarine mud via push cores.

Day6

Day 6: Visit to the Army Corps of Engineers Field Research Facility; Back to Jockey’s Ridge State Park to to examine grain-size trends in eolian landforms.

Here’s the group (minus one grad student) on the final afternoon at Jockey’s Ridge State Park.

group