Uncategorized

John O. Ajayi, Organic Geochemist

jenebauerLeave a comment

Tell us a little bit about yourself. Hello, I am John Ajayi, currently a Ph.D. student at the University of Connecticut (UConn). Prior to joining UConn, I obtained a Bachelor of Technology degree in Applied Geology from the highly reputable Federal University of Technology, Akure (FUTA) in Nigeria. I am a huge football fan (soccer in the U.S.), spending my free weekends watching top games in the English Premier League, Spanish La Liga, and some Major League Soccer (I do not really have a favorite football club I support, I just enjoy each game, wishing the better team luck and enjoying the upset drama that occurs in sports). A good part of my week is spent reading books written by top-selling authors on different aspects of life, career, economics, finance, psychology, family, and some biographies. This also determines the kind of movies I watch. I mostly find documentaries interesting. I also spend time visiting friends and colleagues. It is one of the ways I provide and get support as a graduate student far away from my home country. 

Background has blue sky with clouds and a layered rock wall with vegetation. The foreground has an individual with a hat and camera in front of a fence.
John standing across one of the sedimentary succession in Taiwan.

What kind of scientist are you and what do you do? As an organic geochemist, I explore geochemical patterns of organic biomarkers to study different Earth processes. The approach to my studies is very interdisciplinary, combining knowledge and techniques of geology, chemistry, biology, and geographic information systems (GIS). These allow me to integrate these data to reconstruct the history of the Earth’s environment, and some changes in the Earth’s dynamics. I prepare rock and soil samples for organic biomarker extraction and subsequent compound-specific isotopic analysis. I use the Isotope Ratio Mass Spectrometer to analyze the Hydrogen (δ2H) and Carbon (δ13C) isotope ratio of organic compounds (such as alkanes, and fatty acids) produced by plants and preserved in sedimentary archives. These are utilized as proxies to reconstruct paleohydrology, paleoclimate, and other paleoenvironmental changes that might have occurred during a given geologic time either due to an external or internal driving process. My current study involves reconstructing the paleoelevation of a tropical mountain currently growing due to an ongoing collision between two tectonic plates. 

Background is a wetland with grassy vegetation, water cutting through and rocks scattered around. Foreground is an individual in a hat with a camera and back pack scrambling up a bank.
Getting samples may involve some rugged terrain, climbing steep surfaces, but the science is worth it.

What is your favorite part about being a scientist, and how did you get interested in science? I chose to study Geology in college specifically because I am very adventurous, I love being outdoors, exploring nature and travel. In fact, I was almost going to train to become a pilot with the dream to travel round the world and view scenic landscape and geomorphic features from the cockpit. This ambition metamorphosed to a closer interaction with the Earth, studying the processes that shaped the landscapes and reconstructing the history of our dynamic planet. During my third year in college, I enrolled in a Geochemistry class which exposed me to different aspects of this subdiscipline of Earth Sciences. What I find most fascinating about geochemistry is the idea that every process leaves a geochemical signal that if studied critically can be uncovered and reconstructed. Thus, I see geochemistry as a versatile tool to tackle any problem, ranging from environmental pollution to hydrology (and groundwater hydrology), energy and mineral exploration (such as in petroleum exploration, and metallic ore deposit exploration), and paleoclimate reconstruction. This informed the decision to become a geochemist. I have also become interested in studies related to the origin of life, particularly exploring the chemosynthetic pathway. This could provide more clues for the exploration of life on other planets in our solar system. I follow scientific discoveries from the International Ocean Discovery Program (IODP) expeditions which explore scientific curiosities below the seafloor.

Background is a hazy cloudy sky with heavily vegetated mountains with a river cutting through them. Foreground is an individual on a bridge overlooking the landscape.
Enjoying the beautiful landscape of Taiwan on a suspension bridge with the mountains in the background.

How does your work contribute to the betterment of society in general? My current study on reconstructing the paleoelevation of mountain belts is fundamental to various aspects of the Earth’s dynamic systems. To simply state it, the topography of a mountain represents a dynamic balance between deep Earth mantle processes driving plate tectonics, rock exhumation and surface uplift, and surface processes of weathering, erosion, and denudation which cause a reduction/change in surface elevation due to re-distribution of mass, these two major components are modulated by a third major component- climate. Silicate weathering in tandem with carbonate precipitation in the marine environment has been shown to facilitate CO2 drawdown in geologic time. Therefore, generating records of past topography will allow us to constrain the feedback among these (tectonics, erosion, and climate). We can estimate how much CO2 has been introduced into the atmosphere due to the exhumation of buried organic carbon in rocks, mantle degassing via volcanoes, and other tectonic processes, and as well estimate the amount of CO2 drawdown as fresh mineral surfaces are exposed to weathering reactions during exhumation and subsequent removal by erosion due to steeper gradient as rocks uplift. The product of the balance between all these is the topography of a mountain. The mountain itself has a considerable effect on both local and regional climates by serving as an orographic barrier, inducing more precipitation on the orographic front of the mountain and aridity on the leeward side, and also causing a change in atmospheric circulation patterns. Records from my studies will be valuable input in paleoclimate modeling, especially as we face an uncertain future of climate change. 

Background is of a generic conference hall. Foreground is a poster on a large display board during what appears to be a poster presentation session at a conference. An individual stands to the right of the poster in a jacket with a folder.
John presenting results from a local study of periglacial features in New England at NE GSA section conference at Virginia, USA.

What advice do you have for up and coming scientists? I will leave two of my favorite quotes to inspire upcoming scientists. “Persistence breaks resistance” (original source unknown) and “Curiosity and perseverance matter” (Ben Cichy). Due to word count constraints, I will not be able to share stories to really explain the lessons these quotes impressed on me in my journey as a scientist. First, be very curious, challenge everything, and ask questions (why, when, how, what if, what about this, is there another way to do what better, any other explanation for why? etc.) According to Thomas Edison- “There is a better way to do it- Find it”, so follow science perseveringly. With thousands of failed experiments, he did not give up, but eventually solved the puzzle, and became one of the greatest inventors. Ben shared the story of his struggles as an engineering student in college, but his curiosity and perseverance as an engineer have helped him land two spacecraft on Mars. As my advisor reiterated countless times to me, there is no right or wrong answer and no one right answer, do not think as a student. Think like a scientist. This is something I wished I had known or understood earlier before starting my graduate program. I encourage everyone to enjoy the process of becoming the kind of scientist they want to be. 

Laboratory setting with a fumehood with glassware set up at the back. The fume hood is half open and an individual is extracting something from a sample wearing a lab coat, and other personal protective gear.
John working on Taiwan rock samples, extracting organic biomarkers for compound specific isotope analysis in the lab.
Background is a laboratory room of people in discussion. Foreground is an individual holding a segment of core up to the person taking the photo.
John at the IODP Gulf Coast Core Repository at College Station, Texas. The core shows a clear  boundary during an impact event which caused one of the major extinction event.

372/375: Creeping Gas Hydrate Slide and Hikurangi LWD, Hikurangi Subduction Margin

AdrianeLeave a comment
Figure 1. The location of New Zealand with respect to the complex tectonic boundaries between the the Pacific plate and the Australian plate (Barnes et al., 2019). Cooler, darker colors represent deeper areas of the ocean, whereas warmer colors represent shallower regions around New Zealand.

New Zealand is tectonically complex, hosting both subduction and strike-slip fault zones associated with the plate boundary between the Pacific plate and the Australian plate. The country is thus geologically active, with many potential natural hazards that require investigation and close monitoring (Figure 1, Barnes et al., 2019). The need for improved mitigation also presents an opportunity to better understand the Earth processes prevalent in active tectonic settings. Between 2017–2018, International Ocean Discovery Program Expeditions 372 and 375 set out to collect data (cores, well logs, and in-situ geophysical measurements) at the Hikurangi Margin in northern New Zealand, with primary goals of better understanding the mechanisms and behaviors of gas hydrate-bearing landslide (Barnes et al., 2019) and slow slip events on subduction faults (Saffer et al., 2019). A combined total of six sites were sampled between the two expeditions, with two in the Tuaheni Landslide Complex (TLC) and four in a transect across the Kermadec Trench near the Hikurangi Margin. 

Submarine landslides are often the byproduct of catastrophic destabilization events like earthquakes. If severe, the resulting slope failure can sometimes significantly displace the seafloor, even causing tsunamis (Harbitz et al., 2014). However, the submarine Tuaheni Landslide Complex in the offshore Hikurangi margin is unusual, showing evidence of slow, continuous downslope movement of sediment rather than discrete events. Furthermore, the onset of landslides seem to correlate with the edge of gas-hydrate, with a general shift in the styles of seafloor deformation above and below the depths where the gas hydrates are stable (Figure 2, Mountjoy et al., 2014). The cores and well logs collected from  Expedition 372 were used to test several hypotheses on how exactly the gas hydrates are related to the observed gradual landslides. 

Figure 2. A seismic subsurface image (Mountjoy et al., 2014) showing the cross section of submarine landslides at the Tuaheni Landslide Complex. The lateral change in deformation style across the locations of gas hydrates (strong amplitude in the seismic section) can be inferred from the different faulting style.

Hikurangi Margin is also well documented for another tectonic phenomenon that is observed along the subduction zones, called slow slip events (SSEs). Unlike the devastating megathrust ruptures that release strong seismic energy from sudden movements along the fault surface, SSEs release energy gradually, over a course of weeks or even months (Saffer et al., 2019). While not necessarily an immediate natural hazard, the phenomenon is a relatively recent finding and garnered increased attention from the research community in the last two decades as the observational techniques improved and densified. Hikurangi margin hosts a region of well-studied SSEs with regular occurrences, where the fault (Pāpaku fault) is at shallow depths, accessible by drilling (Saffer et al., 2019). The goal of Expedition 375 was to reach and sample the fault zone, through coring, wireline logging, and installment of geophysical observatories (Figure 3). 

Figure 3. An interpreted seismic subsurface image (Barker et al., 2019) of the drill location relative to the Papaku fault.

Recent studies have begun to shed light on the mechanisms behind the above phenomena using the core and geophysical data retrieved by Expeditions 372 and 375. For example, the cores from Expedition 375 reveal highly variable lithologies near the slow slip fault surface, ranging from marine clay and carbonates to volcaniclastic and conglomerate rocks (Figure 4). The large variety of material with different compositions and grain-sizes also means different deformational responses to the stress as they are carried into the Earth on the subducting plate, and by extension, the different slip behavior (Barnes et al., 2020). Computer numerical modeling has also previously shown that fault surfaces with variable materials might favor transient slow slips over large, sudden ruptures (Saffer et al., 2015), compatible with the observations made from the borehole data.

References

Barnes, P. M., Pecher, I. A., LeVay, L. J., Bourlange, S. M., Brunet, M. M. Y., Cardona, S., … & Wu, H. Y. (2019). Expedition 372A summary. Texas A&M Univ. https://doi.org/10.14379/iodp.proc.372A.101.2019

Saffer, D. M., Wallace, L. M., Barnes, P. M., Pecher, I. A., Petronotis, K. E., LeVay, L. J., … & Wu, H. Y. (2019). Expedition 372B/375 summary. Proceedings of the International Ocean Discovery Program, 372, 1-35. https://doi.org/10.14379/iodp.proc.372B375.101.2019

Harbitz, C. B., Løvholt, F., & Bungum, H. (2014). Submarine landslide tsunamis: how extreme and how likely?. Natural Hazards, 72, 1341-1374.

Mountjoy, J.J., Pecher, I., Henrys, S., Crutchley, G., Barnes, P.M., and PlazaFaverola, A. (2014b). Shallow methane hydrate system controls ongoing,downslope sediment transport in a low-velocity active submarine landslide complex, Hikurangi Margin, New Zealand. Geochemistry, Geophysics, Geosystems, 15(11):4137–4156. https://doi.org/10.1002/2014GC005379

Barker, D.H.N., Henrys, S., Caratori Tontini, F., Barnes, P. M., Bassett, D., Todd, E., and Wallace, L. (2018). Geophysical constraints on the relationship between seamount subduction, slow slip and tremor at the north Hikurangi subduction zone, New Zealand. Geophysical Research Letters, 45(23):12804–12813. https://doi.org/10.1029/2018GL080259

Barnes, P. M., Wallace, L. M., Saffer, D. M., Bell, R. E., Underwood, M. B., Fagereng, A., … & IODP Expedition 372 Scientists (2020). Slow slip source characterized by lithological and geometric heterogeneity. Science Advances, 6(13), eaay3314.

Saffer, D. M., & Wallace, L. M. (2015). The frictional, hydrologic, metamorphic and thermal habitat of shallow slow earthquakes. Nature Geoscience, 8(8), 594-600.

Figure 4. Core and borehole data from site U1520, showing variable lithology of the material being transported into the plate boundary fault zone (Barnes et al., 2020). On the right panels, numbered 1–8, are images of the cores that were drilled during IODP Expeditions 372/375.