Category Archives: news and updates

Welcome new M.S. student Michala Puckett

I’m very happy to welcome Michala Puckett to the VT Sedimentary Systems Research group. Michala arrived in August 2022 as an M.S. student.

Michala is from Mooresville, North Carolina and received a Bachelor’s in Geology from Appalachian State (in Boone, NC) in May 2022. She found the idea of using geology to make interpretations of the past to be fascinating, which is why Michala’s undergrad research dealt with geoarcheology, to look at humans’ past, and now her graduate research will focus on sedimentology, to reconstruct aspects of the Earth’s past.

Michala’s master’s research will be supported by the Chile Slope Systems project (which is nearing a decade of continuous funding!) and will focus on micro-scale (thin section-scale) characterization of sedimentary texture in deep-marine sedimentary rocks. After many years of field mapping and observation, we can now address questions such as: How does grain size, sorting, grain shape, etc. vary as a function of submarine channel stratigraphic architecture? Michala’s work will also evaluate recent advancements in photomicrographic image-analysis techniques. 

We are excited to have her on board. Welcome Michala!

Congratulations to Sebastian Kaempfe on successfully finishing his Ph.D.!

Congratulations to (now former) SSR graduate student Sebastian Kaempfe on successfully defending his dissertation in May 2022 and officially graduating from the program and obtaining his Ph.D.! Sebastian (who is originally from Punta Arenas, Chile) and I first met back in 2014, when he approached us asking if he could be a field assistant for the Chile Slope Systems research group. Sebastian joined us each February-March the next couple of field seasons, both helping us out and learning about the work we were doing. The result of this interaction was Sebastian coming here to Blacksburg, VA in January 2016 to start a Ph.D. and develop research projects on the geology of a region he grew up exploring.

Sebastian’s dissertation is titled Multi-scale deep-marine stratigraphic expressions in the Cretaceous Magallanes Basin, Chile: Implications for depositional architecture and basin evolution, comprising three chapters that span a range of scales, from detailed (bed-scale) sedimentology to basin-scale paleogeography. All three projects involved extensive field work in the Cerro Toro and Tres Pasos Formations of southern Chile:

(1) The Stratigraphic Expression of Early Channel-fill Deposits During the Evolution of Submarine Slope Channels in the Upper Cretaceous Tres Pasos Formation, Magallanes Basin, Chile

This work summarizes Sebastian’s work on a truly unique and exceptional outcrop exposure of submarine channel system deposits. While the outcrop belt that this location is part of contains abundant quality exposures of sandstone-rich channel-fills that our group has worked on for many years, this particular location reveals details of dominantly fine-grained elements of the system (mud-filled channels and levee overbank) that are typically poorly constrained in outcrops. Sebastian collected a tremendous amount of detailed sedimentological data over a few field seasons. In this paper, which we plan to submit very soon, we present ideas about how stacking patterns in submarine channel systems change through time and also share results about deposits associated with channels in their “young” phase, which are rarely preserved.

(2) Stratigraphy and Syn-Depositional Faulting of an Overbank Succession in a Large Submarine Channel-Levee System, Upper Cretaceous Cerro Toro Formation at El Chingue Bluff, Southern Chile

This chapter presents new findings about another outcrop in the Magallanes Basin that has been visited numerous times over the years, but lacked sufficient amount and type of data to be fully understood. The ~500 meter-thick exposure of dominantly fine-grained and thin-bedded turbidites also contains numerous normal faults that had previously been interpreted to be syn-sedimentary in nature. Sebastian generated an amazing field data set that integrated sedimentological information with structural measurements (e.g., fault orientation/attitude) to finally test these ideas. These new data, combined with previously published age control from our group, suggest that most of this succession is part of a slope system associated with the overbank of the very large Cerro Toro channel-levee system. The paper that summarizes this study discusses the possible controls of this depositional-deformational interaction and will be submitted later this year, so look for it in 2023!

(3) Deciphering the Depositional Age of Coarse-Grained Deep-Marine Sedimentation in a Previously Undocumented Location in the Magallanes Foreland Basin, Southern Chile

Sebastian’s final chapter ‘zooms out’ in scale and considers regional paleogeography of generally similarly aged depositional units in the region south of Puerto Natales, Chile, which was essentially frontier territory (geologically speaking). The relationship to the better-studied units to the north had been assumed for decades based on large-scale geologic mapping, but there wasn’t any actual age control. Sebastian led multiple excursions to this very-difficult-to-access location to collect samples for detrital zircon geochronology. Due to the relatively high abundance of nearly contemporaneous zircons in Magallanes Basin strata, we’ve been able to constrain depositional ages of stratigraphic units much more accurately than previously known. Sebastian’s work shows that the conglomeratic deposits that make up the bulk of this location are actually younger than similar-looking units to the north and, therefore, likely represent a wholly different sediment-routing system.

As I mentioned in the recent post about Drew Parent finishing, it’s always so bittersweet — when graduate students succeed, that means they leave! I am so happy to have worked with Sebastian on these projects and look forward to future collaborations (and getting these papers out!). Sebastian has moved back to Chile and will be working on numerous interesting educational, public outreach, and research projects as an independent consultant. Congratulations Sebastian!!

Sebastian and Brian in the field (2015) and then following Sebastian’s PhD defense (2022).

Congratulations to Drew Parent on successfully finishing his Ph.D.!

This post is coming many months after it should, but better late the never! Congratulations to SSR graduate student Drew Parent on successfully defending his dissertation in December 2021 and officially graduating from the program and obtaining his Ph.D. in January 2022! Drew’s dissertation is titled Deep-marine depositional systems of the western North Atlantic: Insights into climate and passive-margin evolution, comprising three chapters that span a diverse range of approaches and topics, including experimental sedimentology, paleoceanography, and source-to-sink analysis, with applications focused on the North Atlantic Ocean and eastern margin of North America:

(1) Comparative analysis of flume experiments and natural systems: Implications
for application of sortable silt to deep-sea bottom-current reconstruction

This work summarizes Drew’s contributions to a collaboration we had with Kyle Strom and his Fluid & Sediment Dynamics group in Civil and Environmental Engineering here at Virginia Tech. This project aimed to test aspects of the widely used physical paleoceanographic proxy known as ‘sortable silt’ in an experimental flume. Our first paper, which summarizes the experimental design and basic results, was published in Sedimentology in 2021. Drew’s chapter about this research focuses on the implications to the usage of sortable silt for paleoceanography, including quantitative comparison with published data from the literature. We plan to submit this manuscript later this year.

(2) Eocene-Oligocene intensification of the Deep Western Boundary
Current in the North Atlantic Ocean

This chapter applies the sortable silt proxy (mentioned above) to a ~9 million-year-long succession of deep-sea contourite drift deposits on the Newfoundland ridges that includes the Eocene-Oligocene Transition (EOT; ~34 Ma). The EOT is the most significant climate transition of the past ~60 million years of Earth history and is characterized by significant global cooling and rapid expansion of land ice on Antarctica. Drew’s research built on data collected by former SSR student Kristin Chilton (M.S., 2016) and investigates the long-standing hypothesis that North Atlantic deep circulation intensified during the EOT. Drew’s work suggests that deep ocean circulation did indeed intensify over this time, but gradually over million-year timescales. This manuscript will be submitted this summer (once our co-authors give it a thorough review!).

(3) Sediment routing system connectivity of the mid-Atlantic U.S. margin
during the Early Cretaceous: Insights from detrital zircon geochronology

This final chapter is focused on the western part of the North Atlantic Ocean and continental margin of eastern North America. While this work also highlights deep-marine sediments and processes, it’s distinct from chapters 1 and 2 in that it ventures further back in time and applies different methods. Drew generated new detrital zircon geochronology data in a proximal-distal transect for the Early Cretaceous as a way to examine the linkage of onshore (fluvial) depositional systems to offshore (turbidite fan) systems, which has implications for broader landscape reconstructions and evolution.

Graduate students finishing is such a bittersweet event — when they succeed that means they leave! I am so happy to have worked with Drew on these projects and look forward to getting this science out to the community and working on new collaborations in the future. Drew also TA’d several times during his time here becoming a talented educator and mentor in addition to researcher. Drew is now working as a geoscientist at Shell in Houston, Texas. Congratulations Drew!!

Summer 2021 Update

This post provides an update on the activities of the Sedimentary Research Group over the last year or so. Despite the challenges that the COVID-19 pandemic has caused — most notably, the inability to travel for field work, sample collection, and some lab work — the group is thriving and making advancements in our research. Also, SSR director Brian Romans is looking for a new graduate student to join the group (starting in August 2022) at either the M.S. or Ph.D. level. Please contact Brian to learn more (contact info here).   

SSR Group Member Activities:

PhD student Drew Parent presented preliminary results from his project on detrital zircon geochronology along the U.S. Atlantic passive margin at the virtual GSA 2020. (See a video recording of this talk here.) This work is part of a broader collaboration with students and faculty at UT-Austin as well as SSR alum Cody Mason, ultimately aimed at reconstructing the evolution of sediment dispersal systems during and after the rifting of Pangea. Drew worked as an intern with the Clastic & Seismic Stratigraphy group at Chevron this summer and will be starting full-time at Shell in Houston, TX in January 2022.

PhD student Sebastian Kaempfe will be presenting some of his research at the SEG-AAPG IMAGE conference in September 2021. His presentation is titled “Early-stage slope-channel fill deposits preserved at the base of an interval levee succession, Late Cretaceous Tres Pasos Formation, Chile” and will summarize some of the results from his research in southern Chile as part of the Chile Slope Systems program. This specific project is one chapter of Sebastian’s dissertation and presents new insights into deposits interpreted to have accumulated in an active sediment pathway that was subsequently abandoned, thus preserving a phase of channel development that is commonly observed in modern seafloor, but not in the stratigraphic record. 

PhD student Natalia Varela participated in two virtual conferences this past summer (2021 SEPM ISGC Virtual Student and Early Career Sessions and the U.S. Scientific Conference Antarctic Research [SCAR]) where she shared her work on the sedimentology of the turbidite record on the levee of the Hillary Canyon, a submarine channel that is a conduit for Antarctic Bottom Water (AABW) formation in the Ross Sea, Antarctica. This research is part of IODP Exp 374, which Brian Romans sailed on in early 2018, and focuses on ocean and ice-sheet interactions in the Pliocene-Pleistocene. All the SEPM talks, including Natalia’s, can be viewed on their YouTube channel. Natalia is right now in the North Atlantic Ocean participating as a shipboard scientist on IODP Exp 396 (Mid-Norwegian Continental Margin Magmatism) — the photo below was taken aboard the JOIDES Resolution drillship a few days after they left port to begin the expedition.

New Publications From the SSR Group:

PhD student Drew Parent and SSR director Brian Romans are co-authors on a new paper out in Sedimentology summarizing a collaborative study with Kyle Strom and students in the Civil & Environmental Engineering department to test the physical paleoceanographic proxy known as ‘sortable silt’. Our study generated grain-size data from deposits produced in a controlled setting (laboratory flume) and shows that mean sortable silt (10-63 µm) correlates well with flow velocity (see figure below), suggesting that under certain conditions this proxy is a reliable indicator of bottom-current speed. We have a follow-up paper, led by Drew Parent, in the works that dives into more details about how our experimental results compare to studies that measured bottom currents and grain size in natural systems. Stay tuned!

Brian Romans is a co-author on a new paper out Frontiers in Earth Science titled Times Associated with Source-to-Sink Propagation of Environmental Signals During Landscape Transience that proposes a common conceptual language and definition for aspects related to how signals (e.g., climate, tectonic, anthropogenic) are transferred and preserved in stratigraphic archives. We focus on the various temporal aspects and hope to engage with different Earth science disciplines involved in these ideas (e.g., geomorphologists, hydrologists, sedimentologists, climatologists, and more). For example, the figure below discusses how signals associated with specific grain-size (hydraulic) fractions may have different signal arrival times, which could impact how we interpret stratigraphic archives.    

Sediment recycling from strontium isotope ages of reworked fossils

Sedimentary Systems Research group alum Neal Auchter (Ph.D. 2016) has a new paper out in Geology based on one of his dissertation chapters.

In this study, we use strontium isotope stratigraphy on reworked fossil fragments from the Cretaceous Tres Pasos Formation (southern Chile) to document sediment recycling. Strontium isotope stratigraphy is an established method to determine numerical ages of primary calcium carbonate from the 87Sr/86Sr ratio. This works better in some periods of Earth history than others, and the Late Cretaceous is one of those periods. Check out this 2012 review by McArthur and co-authors to learn all about this method.

However, we apply strontium isotope stratigraphy in a different way. Instead of determining 87Sr/86Sr from shelly fossils found in situ (e.g., in growth position), we made this measurement on fossil fragments found in coarse-grained turbidite deposits. In other words, the fossils were eroded, transported, and deposited some time after they formed. The conceptual diagram below (Fig. 1 from the paper) puts into context our use of strontium isotope ages with commonly used zircon (U-Pb) dating methods. The important difference between detrital zircon and detrital strontium, however, is that the latter helps constrain recycling from within the marine basin.

Over the course of a few field seasons, Neal and others in the Chile Slope Systems team collected shell-fragment samples from across the ~100 km-long Tres Pasos outcrop belt. The figure below (Fig. 3B from the paper) summarizes the detrital strontium isotope stratigraphy data (n=94 ages). The samples are organized on the horizontal axis by sample sets (L1-L13), which represent stratigraphic units whose depositional age generally youngs southward (to the right). The gray rectangles are maximum depositional age ranges as defined by our published detrital zircon work. The strontium ages are color/symbol-coded by specimen type (inoceramid, oyster, gastropod, and bivalve).

The primary observation in the data plot above is that very few of the strontium ages are within the gray rectangles. In other words, most of the strontium ages are older than depositional age and, in some cases, >10 Myr older. We interpret these fossil fragments to have been recycled during Tres Pasos deposition. For example, downcutting by a submarine canyon could have tapped into the underlying older deposits that were then transported further into the basin via turbidity currents. Considering the tectonically active setting, even minor uplift along the basin margin, could have contributed to the exhumation of shallowly buried deposits then available to be reworked further into the basin.

Although there is uncertainty about the exact mechanism (or combination of mechanisms) that led to the recycling we emphasize that with this method we can (1) document that intrbasinal recycling is occurring and (2) constrain the residence time of shelly fossils between initial calcium carbonate precipitation and eventual deposition. The figure below (Fig. 4 from the paper) depicts the regional stratigraphy and our interpretation of how proportions of specimen type (namely, inoceramid versus oyster) represent intrabasinal source terranes. Check out the paper — it’s open access! — for all the details.

Congrats to Neal on getting this work out there! It can take a lot of effort to get a thesis/dissertation chapter refined, submitted, and eventually published after graduate school is officially done (for example, when life events and new opportunities become the priority).

Summer 2019 Update

It’s been an exciting several months since the last update. The Sedimentary Systems Research group and collaborators are busy working on a bunch of different projects.

First off, some papers that have been published so far in 2019:

We have a couple other papers currently in review and several others in the pipeline for 2020.

Here’s a brief update of what we’ve been up to so far in  2019 (this is just a sampling):

Sebastian Kaempfe (PhD student) had another successful field season in southern Chile in February-March, collecting loads of data for all three chapters of his PhD dissertation. He presented a poster at the AAPG Annual Meeting in San Antonio in May 2019 as well as presenting an update to the sponsors of the Chile Slope Systems program. The biggest highlight of the past several months for Sebastian is successfully passing his PhD preliminary examination, congrats SK!!

Natalia Varela (PhD student) had another busy spring semester, taking multiple classes and TAing our department’s “Resources” course for non-majors. During the semester and into this summer, she has been hard at work in our lab processing samples from IODP Exp 374 (West Antarctic Ice Sheet History, Ross Sea) and generating grain-size data. Natalia also attended the Antarctic Core Workshop in June 2019 organized by IODP and held at Texas A&M University.

Drew Parent (PhD student) is juggling multiple research projects this summer, making significant progress on finalizing the data set of terrigenous grain-size data from Newfoundland contourite drifts (IODP Exp 342), which we are using to reconstruct the history of deep-ocean circulation in the North Atlantic in response to the Eocene-Oligocene Transition. Additionally, he and Brian Romans visited the Maryland Geological Survey in May 2019 to sample cores of Early Cretaceous sandstones for detrital zircon work. Drew visited Danny Stockli’s (UT Austin) lab in August 2019 to generate U-Pb ages from detrital zircons from U.S. Atlantic continental margin sandstones.

Brian Romans (director of SSR) finished the second half of a speaking tour for the IODP Discovery Lecture Series in the early part of 2019 with visits to Scripps Institution of Oceanography, University of Cincinnati, Colorado School of Mines, University Texas Austin, University Nebraska-Lincoln, and University of Arkansas. In the spring semester, Brian led a graduate student seminar on deep-marine depositional systems where eleven students chose topics, readings, gave a presentation, and led a discussion. Thanks to the enthusiasm and efforts of the participating students we also ran a field trip to outcrops in the region to view sediment gravity flow deposits in Paleozoic strata.

Winter 2019 Update

It’s been quite a while since I provided an update on what the Virginia Tech Sedimentary Systems Research group is up to. Here’s a rundown of our activities over the past several months:

First, although it’s always sad to see a member of the group leave, I am also filled with joy to see them move on to the next stage. Former PhD student and post-doc of the group, Cody Mason, is now an Assistant Professor at the University of Western Georgia. Cody finished up his post-doc in summer 2018 and started at UWG that fall. We have some results from detrital zircon studies of the Amazon submarine fan we shared in this EarthArXiv pre-print, with the peer-reviewed paper (hopefully) coming very soon. I’m looking forward to collaborating with Professor Mason in the years to come!

Ph.D. student Natalia Varela has finished her first full year in the program and has hit the ground running. In summer 2018, Natalia attended the IODP Petrophysics Summer School in Leicester, UK and, later that summer, participated in the IODP Expedition 374 sampling party at the Gulf Coast Repository at Texas A&M University. Natalia’s dissertation research is focused on Miocene through Pleistocene continental slope deposits recovered during IODP Exp 374 in the Ross Sea, Antarctica (read the Exp 374 Preliminary Report). In addition to her research activities, Natalia has also been a teaching assistant for Sedimentology-Stratigraphy and Natural Resources courses.

Ph.D. student Sebastian Kaempfe is in southern Chile right now for his third field season. His dissertation research is part of the industry-funded Chile Slope Systems project, a multi-institution collaboration with colleagues and students at the University of Calgary and Colorado State University. Sebastian presented preliminary results of the first chapter of his dissertation work at the AAPG Annual Convention and Exhibition in May 2018 and also participated in the annual Chile Geological Congress in Concepcion, Chile in November 2018. Sebastian TA’d the Sedimentology-Stratigraphy course in fall 2018.

Ph.D. student Andrew Parent has been quite busy both leading and contributing to various different projects. A lot of progress was made in generating a late Eocene-mid Oligocene terrigenous grain-size record from IODP Site U1406 (Newfoundland Ridge drifts) to complement former SSR student Kristin Chilton’s record from Site U1411. Drew presented a poster with these new data at the AGU Fall Meeting in Washington, D.C. in December 2018. Drew and I have also been collaborating with researchers in the Civil & Environmental Engineering department on an American Chemical Society-funded grant on ‘sortable silt’ flume experiments. CEE master’s student Jeff Culp presented a poster of our preliminary results at AGU. Finally, Drew worked with collaborators in the Mining Engineering department to help with seismic stratigraphic characterization of the South Carolina Trough for a Dept. of Energy-funded project to characterize offshore carbon storage potential.

As for me, I’ve been traveling around the U.S. as one of the IODP distinguished lecturers for the 2018-2019 academic year. I’m honored to be among the six lecturers for this year and have been having tons of fun sharing our IODP science. My talk summarizes our work on the Newfoundland drifts (Exp 342) and previews the research to come from the Ross Sea (Exp 374). Here’s a 4-minute video that science communicator Kim Kenney produced as both a summary and advertisement of the talk:

Welcome new Ph.D. student Natalia Varela

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!

New paper on catchment-fan system erosion rates during Pleistocene climate change

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’).

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.