Research

“Stratified rocks with their entombed fossils form a manuscript in stone and are the source of much of our knowledge of the past history of the world.” - C.O. Dunbar, 1960, Historical Geology

 Earth’s protracted history is written in the universal languages of math, physics, and chemistry in a palimpsest “manuscript of stone” that is scattered across the globe. Through my research I try to develop new techniques to translate these languages from the sedimentary record to make sense of Earth’s past to realize Earth’s future. My research group is interested in using sedimentary rocks to understand the timing and mechanisms driving ancient mountain belt growth and the climatic feedbacks such topography can create. However, in a continental-scale game of telephone, this tectonic and climatic information can undergo sequential modification as rivers and oceans transport sediment from the mountain sources to their sedimentary basin sinks. Thereby our group develops new sediment tracking tools by studying sedimentary systems across the world from Argentina to Iceland and California to Romania, which will provide a better understanding on how Earth-surface processes observed today can be preserved in sedimentary rocks deposited millions of years ago.

updated: August, 2024

Tectonics of Sedimentary Basins

Resolving thin-skinned and basement-involved deformation within a seismically active broken foreland region, San Juan, Argentina

In Collaboration with: Dr. Chelsea Mackaman-Lofland (U. TenNesseE); Dr. Margo Odlum (UCSD); Gustavo Ortiz (Universidad Nacional San Juan)

Students Involved: Chloe Weeks (UCSD); Zoey Plonka (UNLV)

Publications: Capaldi et al., 2020; 2021; Horton, Capaldi et al., 2022a; 2022b; Plonka, Capaldi et al., 2023

Tectonic stresses associated with flat slab subduction have driven deformation 800 km inboard across the broken foreland of west-central Argentina. Ongoing shortening accommodated within the overlapping thin-skinned and basement-involved structural provinces makes this broken foreland region one of the most seismically active places on Earth. However, there is no consensus on the structural or kinematic links between the thin-skinned Central Precordillera, the Sierras Pampeanas basement uplifts, or the enigmatic thrust front of the Eastern Precordillera structural domain. We aim to resolve the temporal and kinematic relationships among structures by (1) determining the timing and magnitude of deformation in the Eastern Precordillera thrust front and (2) interrogating how spatial patterns in exhumational cooling and subsidence coincide with predictions based on the various structural geometries and kinematics proposed for the region. Our research plan will integrate geologic and structural mapping, basin analysis, geo-/ thermochronology, and flexural thermokinematic modeling to discriminate between hypothesized structural models. Evaluating spatial-temporal relationships among the seismically active, structural domains in Argentina will inform models of subsurface structural geometries, how shortening transfers from lower to upper crustal levels, and the long-term interactions between frontal thrust structures and foreland-basin sedimentation. New results will quantify the effects of enhanced mechanical coupling between the subducting and overriding plate during flat slab subduction, which dictates the thermo-tectonic evolution of orogenesis and topographic growth and decay of mountain belts.

Tectonic Evolution of the Antler Orogeny in Nevada and California Recorded in Multi-mineral Geochronology

In Collaboration with: Dr. Michelle Gevedon (Colorado College)

Students Involved: James Duncan (UNLV)

The Antler orogeny was the first in a series of mountain building events that occurred along the western margin of the North American continent in present day Nevada, California, and Idaho. The Devonian-Mississippian (~325-375 million years ago) Antler Orogeny led to westward growth of the continent by the accretion of allochthonous crustal material to the continental margin. The allochthon’s origin and mechanisms for accretion remain the subject of intense debate between a native versus exotic origin of the allochthon rocks, and several broad tectonic models of accretion: (1) non-collisional retroarc thrusting, (2) arc-continent collision, or (3) transform margin. Previous studies of the Antler Orogenic system predominantly rely on detrital zircon geochronology for dating and tracking geologic events. Although detrital zircon methods are useful for tracking intermediate-to-felsic arc magmatism and high temperature metamorphism, they have been shown to exhibit lithologic and fertility bias. Thereby, detrital zircon geochronology is an incomplete recorder of mafic magmatism and lower temperature metamorphic events that are critical for discriminating between end member models of the Antler orogeny. This research will test the various tectonic models by establishing new constraints on the timing and duration of proposed mafic magmatism, low-temperature metamorphism, and erosion.

Stratigraphic response to collapse of the sevier-laramide orogeny

In Collaboration with: Dr. Ryan Anderson (Idaho State University)

Students Involved: Ian Gillette (UCSD)

This research seeks to provide insights into Earth surface responses to changes in tectonic regime, namely the onset of extension following the cessation of Sevier and Laramide shortening, which are recorded in a series of Eocene to modern basin deposits in the Northern Basin and Range of Utah, Idaho, and Wyoming. We use field sedimentology that involves measuring stratigraphic sections, paleoflow analysis, conglomerate clast composition measurements, and sampling for sandstone petrography, detrital zircon U-Pb geochronology, and optically stimulated luminescence. Integration of these new sedimentary datasets allows us track changes in depositional environment and sediment source areas during the Eocene tectonic mode shift, and Oligocene to Pleistocene extensional basin development.

Sediment Provenance in Quaternary Systems

Extracting Climate and Tectonic Signals from Fluvial-Eolian Continental-Scale Drainage Systems

In Collaboration with: Dr. Eduardo Garzanti (università di milano bicocca); Dr. Alfonsina Tripaldi (Ciudad Universitaria, Buenos Aires)

Publications: Capaldi et al., 2019; Garzanti, Capaldi et al., 2021; 2022

Continental drainage systems are a fundamental component of Earth systems linking surface processes, lithospheric dynamics, and climate cycles. Understanding the sediment transfer dynamics in terrestrial systems impacts our understanding of linked continental margin stratigraphy, which has implications for paleoclimate reconstructions and paleogeography. These drainage networks are integrated sedimentary systems characterized by three main process domains (1) denudation/erosion zones in higher-relief sediment-source regions, (2) sediment transfer zones that are assumed to be neither net-denudational nor net-accumulative over longer timescales, and (3) regions of accumulation and deposition in either temporary or long-term sedimentary sinks. Sediment routing systems archive crucial processes such as variation in rock uplift and source area relief (driven by tectonics), precipitation and glaciation (driven by climate), areal extent of river drainage networks, sediment source lithology, and subsidence. Our work investigates sedimentary systems where there are two competing sediment transport mechanisms: wind and water, to understand how distal eolian systems impact preservation of tectonic and climatic signals in continental-scale drainage systems. We assessed how modern-historical to Quaternary eolian systems in central Argentina drive either sediment removal/remobilization or sediment storage of Andean river sediment, which feeds or starves down-system Atlantic margin accumulation zones. To quantify eolian transport influence in continental drainage systems we employ: (1) multiple sediment fingerprinting methods (detrital zircon U-Pb geochronology, sandstone petrology, heavy mineral analysis), (2) incorporate novel sediment mixing models, and (3) correlate the findings to the sedimentary record.

Variable thermal histories across the Pyrenees orogen recorded in modern river sand

In Collaboration with: Dr. Margo Odlum (UCSD); Dr. Maggie Curry (North Carolina State University)

Publications: Capaldi et al., 2022

To understand how do orogens grow and decay we investigated the modern sedimentary record of magmatism, metamorphism, and exhumation using multi-mineral detrital thermochronology, and compared results with thermo-kinematic Pecube modeling. Using modern river sand we can efficiently samples large areas of bedrock sources to help assess the timing and pattern of exhumation across the entire eroding landscape. We applied this workflow to constrain the contrasting thermo-tectonic evolution between the Northern and Southern Pyrenees in France and Spain, a classic doubly-vergent orogenic system.

Tracking sediment mixing from the Carpathians to the Black Sea

In Collaboration with: Dr. Cornel Olariu (UT Austin); Dr. Iulian Pojar (GeoEcoMar Romania)

Publications: Pojar, Capaldi et al., in review

We use detrital zircon U-Pb geochronology as a sediment provenance tracer in modern river sands to resolve tectonic, climatic, and anthropogenic forcings that control sediment transport dynamics of the Carpathian to Black Sea source to sink system. Our findings show that anthropogenic factors can either amplify or diminish environmental signals along the Danube River system. Tributary river catchments that have experienced significant land use change from forest to more erodible farmlands are interpreted to enhance the sediment provenance signatures. Whereas tributary river systems with high density of dam structures exhibit diminished sediment contributions to the main trunk Danube River. This summary dataset provides the groundwork for future inquiry across the Carpathian to Black Sea sediment transfer system in both space and time.  

Developing new sediment proveance tools

Students Involved: Odinaka Okwueze (UNLV); Clay Barlow (Utah State University)

Publications: Capaldi et al., 2017; Capaldi et al., 2022a; 2022b; Okwueze et al., in revision

Provenance studies incorporating the composition and geochronology of clastic sediments are fundamental to reconstructions of tectonic, paleogeographic, and paleodrainage histories. Detrital zircon (DZ) U-Pb geochronology has become utilized as a proxy for contributions from continental crustal rocks, with U-Pb age distributions providing constraints on sediment provenance and depositional age. Nevertheless, interpretations of DZ provenance for ancient systems are far from routine, as they involve numerous unknowns and assumptions regarding source-to-sink processes, which commonly relate to issues of source characterization, drainage network morphology, zircon fertility, erosional variability, and the effects of proximal-distal mixing (Capaldi et al., 2017), and zircon inherit bias towards felsic magmatism (Capaldi et al., 2022b). In an attempt to establish a provenance tool to track mafic magmatism, I have begun to leverage Ar-Ar dating of detrital basaltic groundmass from Iceland rivers to track variations in mafic volcanism (Okwueze et al., in revision). Additionally, because quartz is the most ubiquitous detrital mineral in the sedimentary record we have leveraged quartz OSL sensitivity coupled with sediment petrography as a potential robust sediment provenance tool to track sediment mixing in depositional settings (Capaldi et al., 2022a).