Faizan Sabir TahirKheli is sedimentary geologist interested in reconstructing paleoclimate evolution, recent glacial-interglacial events, physical sedimentology processes, and understanding related stratigraphic record.
Faizan’s research will focus on recent glacial and interglacial episodes by applying physical sedimentology techniques on deepwater sediments. His project will consider the complete depositional history of sediment from source to sink and link past climate trends with current/future global warming patterns. Faizan will center his work on core samples and data from IODP Exp 400 (NW Greenland Margin).
Faizan has a BS in Paleontology and Advanced Stratigraphy and a MPhil degree specializing in Sedimentology. His background includes extensive research on carbonate and siliciclastic rocks, including microfossil studies and diagenesis analysis using thin sections. Faizan’s broader experience spans sedimentology-stratigraphy, geo-mapping, groundwater surveys, and lab work involving sediment analysis and thin sections from various sedimentary rocks.
In addition to his academic and professional work, Faizan enjoys collecting rocks to prepare tumble stones and studying fossils and grains in rock sections under the microscope.
Welcome to the Sedimentary Systems Research Group Faizan!!
Congratulations to (now former) SSR graduate student Michala Puckett on successfully defending her thesis in May 2024 and officially graduating from the program and obtaining her M.S. degree! Michala, originally from Mooresville, North Carolina and a graduate of Appalachian State University, joined the SSR group in August 2022 and worked on a project as part of the Chile Slope Systems research program for her master’s thesis.
Michala’s thesis, titled Variability of sedimentary texture in deep-marine channel sandstones: Insights from petrographic characterization of Cretaceous Tres Pasos Formation, Chile, leveraged spectacular outcrops of submarine channel deposits we’ve studied for many years in the Upper Cretaceous Tres Pasos Formation in the Magallanes Basin. Multiple Ph.D. and M.S. projects from over the years provided the stratigraphic and architectural context for Michala’s work, which focused on micro-scale texture (specifically grain size and sorting).
Michala analyzed 57 samples of the medium- to thick-bedded structureless sandstone facies that is dominant in the channel-fill deposits. The samples were organized into transects of several well-documented channel-fill exposures with the idea to investigate trends and patterns in grain size and sorting that aren’t quantifiable through field observation alone. The results are intriguing and we are designing a follow-up study to characterize the composition of these sandstones in more detail.
It was such a pleasure having Michala in the group and we will miss seeing her in the lab. A master’s degree goes so fast! Michala has already landed a job in the environmental consulting industry in North Carolina. Congratulations Michala!
The first bit of news in this update is to congratulate Dr. Natalia Varela on successfully completing her Ph.D.! Natalia passed her defense in December 2023 and submitted the dissertation and officially finished the degree in January 2024. Natalia’s research focused on sediment samples and data from two International Ocean Discovery Program (IODP) expeditions: Exp 374 in the Ross Sea (which I sailed on in 2018) and Exp 396 along the Norwegian margin (which Natalia got to participate on in 2021).
Stay tuned for some fantastic papers in the coming year led by Natalia and based on her dissertation research, including the Pliocene-Pleistocene history of turbidite sedimentation offshore West Antarctica. Natalia is now at University of Virginia (just ‘up the road’ from Blacksburg) to continue her work on Antarctic margin sedimentation as part of a post-doctoral fellowship in Dr. Lauren Miller‘s lab.
I’d like to also acknowledge Natalia’s contributions to the department’s education mission. Natalia was not only an excellent TA for several different courses and levels, but was instrumental in helping design and develop a brand new course, an introductory paleoclimate course for any major/year called Climate History. Natalia won a much-deserved teaching award from the department in 2023 acknowledging these achievements. It’s been such a privilege to work with Natalia these past years, we miss her already!
Last month, I traveled to southern Chile to co-lead a field workshop for the sponsors of our Chile Slope Systems project. I realized that this year is my 20th anniversary of first visiting these amazing outcrops (my first field season as a new Ph.D. student in 2004). Time flies! We had a small, but enthusiastic, group for this year’s field workshop. Along with the co-directors of CSS, Lisa Stright (Colorado State Univ) and Steve Hubbard (Univ of Calgary), and SSR alum Sebastian Kaempfe, we showed off some of the ‘classic’ Tres Pasos Formation submarine channel-fill outcrops as well as sharing some of our newest results.
Although she didn’t make the trip to Patagonia this year, we presented results from Michala Puckett‘s M.S. thesis research, which examines the grain-scale textural characteristics of these sandstones. Michala is on track to finish her master’s in the next several weeks. Below is a photo of Michala presenting her research at the department’s Geoscience Student Research Symposium (GSRS) event a couple of weeks ago.
Finally, I’m very pleased that our research on the response of deep ocean circulation in the North Atlantic to significant climate change at the Eocene-Oligocene Transition (EOT; ~34 Ma) is now out in Paleoceanography and Paleoclimatology. This study goes back several years, starting with Kristin Chilton (M.S., 2016) with the foundational work on Site U1411 and then Drew Parent (Ph.D., 2022) generated data from a second site (Site U1406) and led the integrated analysis. We applied the terrigenous grain-size proxy ‘sortable silt’ to the fine-grained contourite drift deposits on the Newfoundland ridges to investigate the physical bottom-current history during this pivotal transition in Earth’s climate. The samples for this work came from IODP Exp 342, which I sailed on back in 2012. I’ll also note that this new work with sample-based proxy data is an appropriate follow-up to the regional seismic-stratigraphic research of these drift systems led by Patrick Boyle (M.S., 2014), summarized in our 2017 paper in Marine Geology.
Congrats to Drew, Kristin, and the rest of the author team!
What has the Sedimentary Systems Research group been up to lately? This post provides an update on the activities and accomplishments of the current and recently-finished SSR students and a bit about what I’ve been doing and have planned.
Ph.D. student Natalia Varela is on her way back from the 2023 Urbino Summer School in Paleoclimatology in Italy. This school is for doctoral students and focuses on …
… past climate dynamics with special emphasis on the analysis of long-term carbon cycling and its implications in the understanding of present and future climates. USSP integrates lectures, symposia, field trips, and exercises on the many different areas of paleoclimatology including biogeochemical cycling, paleoceanography, continental systems, and all aspects of deep-time climate modelling. These techniques and systems are explored through interactive discussions of Cretaceous OAEs, P/E hyperthermals, the Greenhouse-Icehouse transition, Neogene and Quaternary climate dynamics.
This content and training is a fantastic addition to Natalia’s strong background in sedimentology, stratigraphy, and basin analysis and sets her up nicely to make scientific contributions in deep-time paleoclimate research going forward. Natalia will be wrapping up her Ph.D. and her time at Virginia Tech later this year, so stay tuned for updates about exciting next steps in her career.
M.S. student Michala Puckett has finished her first year in the program (time flies!) and is busy this summer working on her thesis research. Michala joined the Chile Slope Systems team for the 2023 field season in southern Chile in February-March. In addition to helping out other students with field work and attending the sponsor’s field workshop, Michala collected more than 50 sandstone samples from submarine channel deposits of the Tres Pasos Formation for her thesis project. Here’s Michala at one of the sampling transects along Alvarez Ridge.
Michala will be generating quantitative grain size and sorting data from thin sections to investigate textural variability as a function of channel architecture. Additionally, we plan to make her photomicrographs and size/sorting data available to use as a ‘benchmark’ data set for emerging automated workflows and other image-analysis methods. Michala’s thin sections (pictured below) arrived a couple weeks ago and she’s now getting to work on the characterization.
SSR alum Sebastian Kaempfe (Ph.D., 2022) participated in this year’s field season, helping the team immensely with data collection, field planning and logistics, and as a translator and liaison with the local communities. Sebastian also has the first (of three) dissertation chapters submitted and currently in review (at Sedimentology). This first paper focuses on submarine channel architecture of the Tres Pasos Formation and will hopefully be out and available this fall. The next chapter will be submitted soon!
One of the chapter’s of the dissertation of SSR alum Drew Parent (Ph.D., 2022) is now submitted and in review at Paleoceanography & Paleoclimatology. This study summarizes our work on reconstructing the bottom-current history of the Newfoundland Ridges contourite drifts (using cores from IODP Exp 342) with an emphasis on addressing the long-standing question: Did North Atlantic circulation intensify in response to the Eocene-Oligocene Transition? This work goes back several years, including initial work on one of the sites by SSR alum Kristin Chilton (M.S., 2016) and in collaboration with Tim van Peer, Paul Wilson, Steve Bohaty, and several others working on these questions. I’m very excited to get this work out to the Cenozoic paleoceanography community, stay tuned for updates.
As for me, I’m currently on research leave, and the first of two major activities was a five-week visit at the University of Geneva (Switzerland) in June and early July working with my host Sebastien Castelltort, colleagues, and students. Sebastien and I had collaborated on a source-to-sink review paper several years ago, but haven’t had the opportunity to collaborate more closely since then. Thus, my visit was aimed at revisiting key ideas about signal propagation in source-to-sink sedimentary systems and thinking about what work has been done over the past several years, where we are, and next steps. As part of this, we organized and ran a two-day workshop (pictured below) with other sedimentary system researchers in Europe and with a focus on the Ph.D. students participating in the S2S Future program. It was really fantastic to see the amazing work these students are doing.
During this time I was able to make some progress on a long-languishing paper that includes Sebastien (among others). Time for deep focus on a single research task is exceedingly rare at this point in my career, so I was very happy to be able to regain momentum on several ideas for papers and future proposals. Many thanks to Sebastien for being a fantastic host and to the Swiss National Science Foundation for funding. Additionally, we made sure to visit the Alps for both geology and fun while there.
My second major activity during this research leave is participating as a shipboard scientist on IODP Expedition 400 (NW Greenland Margin), which departs Reykjavik on August 12th. I’m sailing on the core description team and very excited about the sediment cores we hope to recover. More about this expedition in a future post.
It’s January 2023 and everyone is playing with language generating model ChatGPT. If you’re reading this post from the 2030s or later and want to reminisce about the quaint days of AI, before it caused and/or worsened all sorts of societal problems, this post is what you’re looking for. We don’t know what happens from here. I’m not even going to attempt to make predictions or discuss the possibilities (there’s already enough of that out there). I was curious and simply wanted to see what it was like. Below are several separate chats, all with a geoscience foundation. My questions/prompts are in bold italics and the program’s answers are in normal text. Some of the chats have follow-up questions. I’ve put some additional commentary (not part of the chat) in red italic text below each segment of the chat.
What are the most important uncertainties to consider when reconstructing past climate change from the sedimentary record?
There are several important uncertainties to consider when reconstructing past climate change from the sedimentary record:
Age control: Establishing the age of sedimentary deposits is critical for determining the timing of past climate events. This can be challenging, especially for older deposits, as the available dating techniques become less precise.
Stratigraphy: The layering of sedimentary deposits can be disrupted by geological processes, making it difficult to accurately reconstruct the original sequence of events.
Diagenesis: Physical and chemical changes that occur to sedimentary deposits after they are deposited can alter the original record of past climate conditions.
Sample size: The amount of sedimentary material available for study may be limited, which can make it difficult to accurately reconstruct past climate conditions.
Proxy data: Different types of sedimentary materials (such as fossil shells or pollen) can be used as proxies for past climate conditions. However, the accuracy of these proxies depends on the accuracy of the assumptions used to interpret them.
Spatial and temporal resolution: The resolution of the sedimentary record is limited by the spacing and duration of sedimentary deposits. This can make it difficult to accurately reconstruct fine-scale changes in past climate conditions.
First thing I notice is how the program repeats the question in the first part of the answer. This seems to be a fundamental part of the behavior, as it occurs in all the answers (in various ways). It reminds me of student answers to written exam questions. The list the program provides is really quite good!! I might edit this slightly, but it captures the main issues. Impressive. The below question/answer is a follow-up question to the above.
What are some examples of the layering of sedimentary deposits being disrupted by geological processes?
There are several geological processes that can disrupt the layering of sedimentary deposits:
Erosion: The removal of sediment by wind, water, or ice can disrupt the layering of sedimentary deposits.
Burial: Sedimentary deposits can be buried by newer deposits, making it difficult to accurately reconstruct the original sequence of events.
Deformation: Tectonic forces can deform sedimentary deposits, causing them to fold or fault. This can disrupt the original layering of the deposits.
Metamorphism: High temperatures and pressures can cause sedimentary rocks to undergo metamorphism, which can alter the original layering of the rocks.
Diagenesis: Physical and chemical changes that occur to sedimentary deposits after they are deposited can alter the original layering of the deposits.
Bioturbation: The actions of burrowing animals can mix and disturb sedimentary deposits, disrupting the original layering.
My follow-up question requested some more detail about one of the items in the list in the first answer. Again, a pretty good summary! However, check out #2 (“Burial”). The program is not comprehending the concept of stratigraphy. Stratigraphy is created by burial! A sequence of events (of sediment deposition at the surface of the Earth) is generated through burial. Layers being buried is, in fact, how we conceptualize the sequence of events (processes). Another nuance is how it uses “original layering” in each item. That phrase works perfectly well for some of those, but less so for others. For example, diagenetic change more commonly alters the composition (mineralogy, isotope geochemistry, etc.) of the sedimentary material, not really the “layering”. What does this all mean? 🤷🏼♂️
What was the Earth’s climate like in the Eocene?
The Eocene was a geological epoch that lasted from about 56 to 34 million years ago. During this time, the Earth’s climate was generally warm and humid, with temperatures ranging from subtropical to tropical. This warmth was due to high levels of atmospheric carbon dioxide, which acted as a greenhouse gas, trapping heat in the Earth’s atmosphere. The Eocene was also a time of high sea levels, as melting polar ice caps caused the oceans to rise. This led to the creation of shallow seas and the expansion of shallow-water habitats, which supported a diverse array of plant and animal life. The Eocene is also known for the proliferation of mammals and the evolution of modern whales and primates.
Like a good student, the program kicks off its answer with some basic info about the Eocene. I guess it’s programmed to provide definitions of some terminology before discussing it (?). Pretty good summary for only a paragraph, it covers the general state, the proposed cause, and then the state of various sub-systems of the Earth system. If I asked this question on an quiz in my Climate History (intro paleoclimate for non-science majors) course, I would mark it as correct! Follow-up question/answer below.
Why was atmospheric CO2 so high in the Eocene?
There are several factors that may have contributed to the high levels of atmospheric carbon dioxide during the Eocene. One factor may have been the high levels of volcanic activity during this time, which released large amounts of carbon dioxide into the atmosphere. Another factor may have been the warm temperatures of the Eocene, which could have caused the oceans to release more dissolved carbon dioxide into the atmosphere through a process called outgassing. The warm temperatures may also have caused increased decomposition of organic matter, releasing more carbon dioxide into the atmosphere. It is also possible that there were other, unknown factors that contributed to the high levels of atmospheric carbon dioxide during the Eocene.
Nice. After talking about volcanic CO2 it then gets into several amplifying feedbacks.
By how much would current CO2 levels need to increase to match those of the Eocene?
The atmospheric carbon dioxide concentrations during the Eocene were much higher than they are today. It is estimated that atmospheric carbon dioxide concentrations during the Eocene ranged from about 1,000 to 2,000 parts per million (ppm), while current atmospheric carbon dioxide concentrations are around 415 ppm. To match the atmospheric carbon dioxide concentrations of the Eocene, current atmospheric carbon dioxide concentrations would need to increase by more than double their current level. This would have significant implications for the Earth’s climate and the life forms that inhabit it.
It is important to note that the high levels of atmospheric carbon dioxide during the Eocene were not caused by human activities, such as the burning of fossil fuels. Today, human activities are the primary driver of increasing atmospheric carbon dioxide concentrations, and the Intergovernmental Panel on Climate Change (IPCC) has warned that continued increases in atmospheric carbon dioxide concentrations could lead to significant and potentially catastrophic changes to the Earth’s climate.
Bonus points for the second paragraph. I asked a fairly straightforward question, but the program “decided” to provide additional information to further elaborate on how Eocene climate might be relevant to modern climate change.
How did AABW (Antarctic Bottom Water) formation respond to climate change over the past 4 million years?
Antarctic Bottom Water (AABW) is a type of cold, dense water that forms in the Southern Ocean around Antarctica and flows northward along the ocean floor. The formation of AABW is influenced by several factors, including the temperature, salinity, and density of the water in the region, as well as the mixing of water masses and the movement of the Earth’s crust.
Over the past 4 million years, the climate of the Earth has undergone many changes, including multiple ice ages and warmer periods. During ice ages, the formation of AABW may have been enhanced due to increased sea ice formation around Antarctica, which leads to increased brine rejection and increased density of the water. During warmer periods, the formation of AABW may have been reduced due to decreased sea ice formation and reduced density of the water.
It is difficult to say exactly how the formation of AABW has responded to climate change over the past 4 million years, as the climate has changed in complex ways and the mechanisms that control the formation of AABW are not fully understood. However, it is likely that the formation of AABW has varied in response to changing climate conditions, and that it will continue to do so in the future as the Earth’s climate continues to change.
So, this is a question we are actively working on! Our NSF-funded project is led by Ph.D. student Natalia Varela (2018-2023) and is focused on sediment samples and data from IODP Site U1524 in the Ross Sea (which I sailed on in 2018). Again, note how the program dutifully provides a definition and explanation of what AABW is before addressing our question. The third and final paragraph is a classic “it’s complicated” response that all of us are used to giving. We were happy that there wasn’t a clear answer (we’ve done our homework to identify a problem to work on).
What does the current scientific understanding say about how AABW is responding to very recent climate change (over the past few decades)?
The current scientific understanding is that the formation and properties of Antarctic Bottom Water (AABW) have been changing in response to recent climate change.
One of the main factors that has been affecting the formation of AABW is the warming of the Southern Ocean, which is caused by anthropogenic greenhouse gas emissions. As the ocean warms, the sea ice around Antarctica melts, which leads to a decrease in the salinity and density of the water, making it more difficult for AABW to form. Additionally, research indicates that the amount of AABW being formed is decreasing as well as its volume and temperature of the water is also increasing.
The ocean circulation is also impacted due to the climate change, where it is expected that the density of the water in the Southern Ocean will decrease, resulting in the reduction of the sinking rate of the dense water and thus less of the deep and bottom water formation. This is expected to lead to a slowdown of the global ocean circulation and potential impacts on the ocean ecosystems and global climate.
Several studies have been conducted that support the above mentioned change, for example one study using observations and models suggests that the AABW formation is declining due to warming and freshening of the Southern Ocean. Another study using the ocean observation data since the 1960s also shows that the rate of the AABW formation has decreased.
In summary, current scientific understanding indicates that the recent climate change is having a significant impact on the formation and properties of Antarctic Bottom Water (AABW) and is leading to a decrease in the amount and density of AABW being formed, as well as an overall warming trend, which in turn is affecting the ocean circulation and having potential consequences for the global climate and marine ecosystem.
The above was a follow-up to the first question about AABW, so it did not need to provide me a definition of AABW, which makes it feel conversational. If I were reviewing/editing/grading this text I would recommend junking that first sentence, not necessary. I don’t focus on the modern behavior of AABW (I don’t keep up on all that literature), so I’m not able to rigorously evaluate what it’s saying, but it seems reasonable given what I do know. I was intrigued (and impressed!) when it mentioned “several studies” and “one study” in the example provided, so I asked the below follow-up:
Thanks … can you provide links or detailed citation information for these studies you mentioned above?
I’m sorry, but as an AI language model, I do not have the ability to provide specific links or detailed citation information for studies. However, I can help you with some general guidance on finding research papers that have looked at the impacts of recent climate change on the formation and properties of Antarctic Bottom Water (AABW).
Here are a few keywords that may be helpful in searching for relevant studies:
Antarctic Bottom Water
Southern Ocean
Climate change
Warming
Freshening
Ocean circulation
You can use these keywords to search for papers in scientific databases such as Web of Science, Scopus, or Google Scholar. It is also worth checking the websites of organizations that conduct research on oceanography, such as the National Oceanic and Atmospheric Administration (NOAA), the National Science Foundation (NSF), or the European Space Agency (ESA).
Alternatively, you can look into studies that were recently published on journals such as Journal of Climate, Nature Communications, or Global Biogeochemical Cycles which are the common venue for the Oceanography or Climate science research studies.
Please let me know if you have any other question or need help with your research.
Disappointing. I already know how to use GoogleScholar with keywords, we all do this everyday and have gotten pretty good at it. So, this program gets its information from what humans have written to guide it’s language generation, but it can’t connect to specific writing in a direct way. The text in the segment above says “for example one study using observations and models suggests …” yet it does not know what that one study is? Anyway, I presume the ability for this type of auto-generating text program to be able to integrate with specific info that is accessible (or, at a minimum provide a reference) will happen in the next few years 🤷🏼♂️. Okay, now for a couple of fun ones:
Can you describe the Paleocene-Eocene Thermal Maximum in the style of Kendrick Lamar?
I’ll note that it starts composing the text mere seconds after I hit ‘Enter’ to ask the question. It’s fast. I’ve listened to some Kendrick Lamar, but I must admit I haven’t listened to him so much that I have a solid feel for his lyrical style. The above seems pretty generic to me, but that’s consistent to all of the program’s answers in my small amount of interaction. Has a meteor impact been proposed to be the trigger for the PETM? I don’t think so, but I could be wrong, I’ve never focused on the PETM interval itself. I do appreciate the final two lines, a nice articulation of why it’s important and valuable to reconstruct past climates!
Can you describe the Pleistocene ice ages in the style of Shakespeare?
Fantastic stuff. I would’ve liked to have seen a stanza about orbital forcings (Milankovitch cycles) but I suppose I didn’t ask for the cause of the ice ages, just a description. To what extent I’ll actually use this to help me work (instead of merely experimenting), I’m not sure yet. If this “evolves” to be able to help me find specific information within journal articles then I would use all the time. For example, “Briefly summarize and point me to a handful of papers that include measurements of velocity for dense shelf water cascading processes in high latitudes.” Even if it didn’t return all or the most relevant papers, this would be a useful way to narrow down the search. We shall see what happens next!
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 (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!!
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!!
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.
What is rare? Is a recurring event that happens once every decade rare or common? Is an event that occurs once a century rare? Looking to the dictionary we can find that “rare” is “an event, situation, or condition that does not occur very often.” It depends, of course, on the temporal frame of reference. Someone who has well-developed timefulness skills may respond “Duh, of course it depends on the timescale of investigation.” But, would the student new to geoscience (or other areas of inquiry that work in longer timescales) or the person in your family or community who rarely thinks beyond the timescale of their lived experience consider this obvious and trivial?
In our lived experience we can naturally shift our understanding of what is ‘frequent’ versus ‘rare’ based on the timescale. For example, if you do some activity (go for a jog, a bicycle ride, etc.) once a week, this might be quite frequent for some people or contexts but infrequent for others. We’ll add phrases like “which is a lot for me” or “which is pretty rare for us” as a way to communicate the temporal reference. Or, if we don’t add that, someone will ask “So, is that often for you?”. The point is that, in the context of the range of timescales we experience, we are pretty good at incorporating the temporal reference without thinking about it too much.
Coupled with how common or rare an event is over time is the significance or ‘size’ of the event (i.e., frequency-magnitude relationship). Humans have internalized this in numerous contexts. For example, as I write this post (April 2021) the pandemic is still affecting the globe, to varying degrees, and a phrase we find ourselves saying is “this is a once-in-a-century event!”. Implicit in such a statement is that this event we are experiencing is both rare and of significant magnitude. In turn, we often link this to some vague idea of probability — because an event is significant and infrequent it’s likely not to happen again for a long time.
We can consider these ideas for timescales longer than the human lived experience and for ‘prehistorical’ times (before the collective memory or spoken/written record of humans). While this may not come as naturally to us, it’s a skill we can develop. While thinking about this, I was reminded of this 1967 paper from Gretener that I read many years ago (as part of a grad-level stratigraphy course). I won’t summarize the details of this paper here, I encourage you to read it.
Gretener’s main point, which I’ve highlighted in the image of the Abstract above, is that, given enough time, an event that is exceedingly rare becomes probable if not certain. We could apply this notion to the huge range of timescales represented in Earth history. For example, a rare event at the scale of 100,000 years might be considered ‘common’ when viewing 10,000,000 years. How can this stretching of time and the associated frequency-magnitude relationships help us think about and cope with the ‘rare’ events in our society?
Another thought-provoking paper along these lines is this 1989 paper from Kenneth Hsu. This paper focuses on extinction events but the message is very similar to the Gretener paper.
Why is this important? Related to these ideas is the notion of shifting baselines, or a gradual change in what is considered a “normal” range of conditions due to lack of memory and/or knowledge of past conditions. The idea of shifting baselines has been discussed in the context of environmental issues for decades and, more recently, for climate change. And the relationship to hazards and how we collectively assess risk (e.g., “a 100-year flood”) is particularly relevant. As geoscientists, we make the case that the enhanced temporal perspectives gained from studying Earth history provides insight into contemporary challenges. In addition to the technical insights, I think we can also highlight the development of temporal reasoning itself.
As the previous posts in this series (clock time and event time and what is an event?) discussed, my motivation in thinking about timefulness is to move towards developing activities/assignments in my courses that are more explicit about temporal reasoning. One way to do this is develop specific activities centered on temporal reasoning as the primary learning objective. And/or it could be embedded within activities/assignments that have other learning goals, but it would be highlighted and intentionally discussed as part of the activity (a temporal reasoning ‘check’).
In the context of this post, a bunch of potential ideas — e.g., analyze the frequency/magnitude relationships of well-dated sedimentation events and include a class discussion (even just 5 minutes) or reflection question about the dependency of terms like ‘rare’ versus ‘frequent’. If such temporal reasoning ‘checks’ occur many times throughout the course there could then be a more lengthy summary-style activity near the end of the semester to tie them together. 🤔