Here you can find descriptions of past and present research projects.

Reconstructing past water balance changes from closed-basin lakes in the central Andes

Satellite imagery of the paleoshorelines (see bath-tub like rings) of Agua Caliente I, northern Chile. Image from Bing Maps.

I am currently reconstructing multiple well-dated records of paleolake level variations from the Altiplano plateau of the central Andes (21°-27°S, 4200-4500 meters above sea level). Our aim is to gain a spatiotemporal understanding of water balance changes associated with late Pleistocene climate change in South America. The now arid deserts of the central Andes are home to various high-altitude (>3800 meters above sea level) closed-basin paleolakes surrounded by well-preserved paleoshorelines that indicate previous intervals of much wetter conditions. By mapping and U/Th dating deposits on these paleoshorelines, such lakes provide unequivocal evidence of lake surface area changes throughout time. Moreover, the simple geometry and relatively small size of these basins makes them amenable to hydrological modeling, allowing us to extract quantitative estimates of past precipitation changes from lake level reconstructions.

Fieldwork associated with this project is supported by a National Geographic Young Explorers Grant awarded in 2016.

Associated Media: [National Geographic] [Oceanus Magazine] [Medill Climate Change News]

Quantitative lake level constraints from tufas and paleoshorelines in Searles Lake, southeast California, U.S.A.

Geologists standing next to thick tufa deposits coating bedrock at Searles Lake, CA.

Searles Lake is presently a dry evaporite basin located in southeastern California and is part of a chain of ancient lakes linked by the Owens River that were supplied by meltwater from the neighboring Sierra Nevada mountains. The abundance and diversity of tufa deposits across a broad elevational range in Searles Lake provides an excellent opportunity to create a tufa-based chronology of lake level variations. At this site, I aim to show the potential power of combining (1) precise U/Th dates on tufa and other carbonate deposits that are (2) interpreted in geologic context at all scales—from outcrop to the microscale—and (3) elevational measurements on paleoshorelines to provide more nuanced insights on paleolake level variability.

In addition, a sediment core extracted from the basin center in 2017 will allow us to correlate the discontinuous tufa-based lake level chronology with continuous geochemical proxy data.

Fieldwork associated with this project is supported by student research grants from the Explorers Club, Geological Society of America, and the American Philosophical Society.

The Lake Junín Drilling Project: A continuous record of late Quaternary tropical climate change

The primary objective of the Lake Junín Drilling Project (Projecto Lago Junín) is to recover the first continuous, high-resolution, accurately-dated record of late Quaternary climate change in the tropical Andes. Lake Junín (Chinchaycocha; 11.0°S, 76.2°W) is located 4000 meters above sea level in the central Peruvian Andes and contains a sediment record spanning several hundreds millenia over multiple glacial cycles. Because these sediments contain high concentrations of authigenic calcite, U/Th measurements can be used to establish the age model of these sediments, extending beyond the range of radiocarbon dating. A deep sediment record from this lake will reveal the history of changes in paleovegetation, megafauna, human activity, hydrological balance, and glaciation in tropical South America.

In July-August of 2015, I was part of an international team of scientists stationed at Lake Junín working around the clock with LacCore, DOSECC, Geotec Peru, and GFZ Potsdam to extract hundreds of meters of sediment core from the lake bottom.

This project is supported by grants from the International Continental Drilling Program (ICDP) and the U.S. National Science Foundation. Lead project PIs are Don Rodbell (Union College), Mark Abbott (University of Pittsburgh), and Pedro Miguel Tapia Ormeño (Universidad Peruana Cayetano Heredia).

Basin-wide elevational survey of Lake Bonneville's highest shoreline using differential GPS

The late Pleistocene Lake Bonneville (Utah, USA) is a natural laboratory for various Quaternary studies, including lithospheric deformation due to surface loading and climate-forced water balanced changes since the Last Glacial Maximum (~21 ka). Due in large part to the semi-arid Holocene climate, Lake Bonneville's paleoshorelines are outstandingly well-preserved, recording a complex history of lake level variations induced by deglacial climate change. The last comprehensive study of the Bonneville paleoshorelines by Currey (1982) collected elevation data before the global positioning system (GPS) became available for civilian use.

Paleoshoreline dGPS elevations as a function of distance from basin center (Chen & Maloof, 2017).

Given that it has been 30 years since Currey (1982) constructed his dataset, we thought it was timely to revisit the elevational measurement of these paleoshorelines. We compiled a new dataset of 176 unique paleoshoreline elevations of the highest Bonneville shoreline all measured using high-precision differential GPS (dGPS) and constructed a new Bonneville lake outline based on dGPS measurements, submeter-resolution aerial imagery, topographic digital elevation models (DEMs), and field observations. The deformation pattern described by these paleoshoreline elevations can help resolve the relative effects of local hydro-isostasy due to the lake load and regional lithospheric deflection due to the Laurentide ice sheet.

This work was conducted as part of my undergraduate senior thesis at Princeton University and was advised by Adam Maloof.

Relevant paper: CHEN, C. Y. & MALOOF, A. C. (2017), Revisiting the deformed high shoreline of Lake Bonneville. Quaternary Science Review, 159: 169-189. doi: 10.1016/j.quascirev.2016.12.019 (see also corresponding supplementary materials and data uploaded to Mendeley Data). [pdf] [data]

Preliminary modeling of deformation due to the Laurentide ice sheet and the lake load was advised by Jeroen Tromp and post-doctoral researcher Hom Nath Gharti.

Insights on Earth's deepest δ13C excursion from paleocanyon structures at Saint Ronan, Beltana Station, South Australia

The Wonoka Formation, a deposit of Ediacaran aged (635-542 million years ago) sedimentary carbonate, holds a record of the `Shuram anomaly', the deepest δ13C excursion observed in Earth history. This isotopic signal, found globally in shallow-water carbonates from the Ediacaran Period, suggests a major disturbance to the global carbon cycle, one that dwarfs humanity's cumulative CO2 emissions. This perturbation has been causally linked to the broadly synchronous radiation of macroscopic multicellular organisms and oxygentation of the deep ocean in the Ediacaran period.

The Wonoka Formation (light-colored), exposed as three cross-sections of a submarine paleocanyon.

We focused on one question: Are the δ13C values of the carbonates acquired during their initial deposition or through post-depositional diagenetic alteration? With Jon Husson, I examined physical and isotopic evidence for a syn-depositional age of the Shuram anomaly by examining paleocanyon structures within the Wonoka Formation at Saint Ronan, Beltana Station (South Australia). The results demonstrated that the δ13C and δ18O values of the carbonates were acquired prior to their brecciation and redeposition in the canyon, precluding the burial diagenesis model for the origin of the excursion.

I conducted this research for an undergraduate junior independent research paper at Princeton University, advised by Adam Maloof and Jon Husson.

Relevant paper: HUSSON, J. M., MALOOF, A. C., SCHOENE, B., CHEN, C. Y., and HIGGINS, J. A. (2015), Stratigraphic expression of Earth's deepest δ13C excursions in the Wonoka Formation of South Australia. American Journal of Science, 315 (1): 1-45. doi: 10.2475/01.2015.01 (see also corresponding cover). [pdf]

I also blogged about my experience as a geologic field assistant (see the road to Oz is paved with limestone) in June-August of 2011. Each post is written to be accessible to a non-scientist audience.