About

Peter G. DeCelles is a professor in the Department of Geosciences at the University of Arizona. His research interests include the regional structural evolution of collisional and cordilleran orogenic belts and sedimentary basins, with specific focus on systems such as the Himalayan, Tibetan, Andean, North American Cordilleran, Pamir, and Alpine-Apennine orogenic systems. He specializes in structural geology of fold-thrust belts, petrology, provenance studies including conventional and geochemical methods, and detrital geo-petro-thermochronology of clastic sediments and sedimentary rocks. Additionally, his work encompasses physical sedimentology and depositional systems across various environments such as fluvial, alluvial, eolian, and marine settings, as well as landscape evolution in orogenic highlands. Dr. DeCelles has made significant contributions to understanding the geological processes shaping mountain belts and sedimentary basins, and has been recognized with numerous awards including the Francis J. Pettijohn Medal from the Society for Sedimentary Geology and the Geological Society of America Laurence L. Sloss Award. He holds a B.S. in Geology from the University of Notre Dame and both a Ph.D. and M.S. in Geology from Indiana University, with postdoctoral experience at Stanford University.

Research topics

• Paleontology
• Geology
• Oceanography
• Geography
• Climatology
• Physical geography
• Geochemistry
• Seismology
• Cartography
• Geomorphology

Selected publications

• The Roles of Climate and Tectonics in the Tectonomorphic Evolution of the Sagarmatha (Mt. Everest) Region, Eastern Nepal Himalaya

  Geochemistry Geophysics Geosystems · 2026-05-01

  articleOpen access

  Abstract To understand the interplay of climate and tectonics in driving long‐term erosion and landscape evolution in the Himalayan orogen, this study examines the tectono‐thermal evolution of the Sagarmatha (Mt. Everest)‐Rolwaling‐Okhaldhunga region in eastern Nepal. We present new low‐temperature thermochronological data and thermal history models focused on two transects along the Tama Kosi and Dudh Kosi Rivers up to the Sagarmatha/Mt. Everest region in eastern Nepal. New zircon (U‐Th)/He cooling dates for 10 samples and apatite fission track cooling dates for 16 samples were combined with published muscovite 40 Ar/ 39 Ar and zircon fission track data to investigate regional cooling patterns. We leverage thermochronometric constraints to create sample‐specific inverse thermal history models, which show a northward‐younging trend of Middle‐Late Miocene rapid cooling independent of structural position. In contrast, the kinematic history of the thrust belt in this region shows a southward propagation of thrusting. Thus, tectonic processes alone do not account for the observed cooling and exhumation patterns. Instead, we propose that northward propagating incision and subsequent isostatic uplift, likely triggered by the late Miocene development of the Lesser Himalayan duplex ca. 8–5 Ma, have driven spatially variable exhumation. Preservation of Middle‐Late Miocene dates in the northern High Himalaya and on the Numbur high‐elevation low‐relief surface in the Sagarmatha region indicate that the incisional wave has not extended to the northernmost eastern Nepal Himalaya.

  PublisherDOI

• Sedimentological and paleoslope reconstruction of the Late Triassic Chinle Formation, western USA: Constraints on models for dynamic subsidence

  Geological Society of America Bulletin · 2025-03-11

  article

  Abstract The Shinarump and Gartra Members form the basal part of the Chinle Formation in western USA and are the deposits of a river system that flowed northwestward from the Ouachita Orogen to the Auld Lang Syne basin during the Late Triassic. Previous estimates of paleoslope for this river have been limited by low numbers of data points. This study, therefore, presents a dataset of 1133 cross-set height measurements to form the basis for paleoslope reconstructions, and as part of a facies analysis which additionally includes clast counts identifying a total of 13,584 clasts, grain-size analyses measuring 7400 grains and paleoflow analyses composed of a further 975 trough cross-sets. Lithofacies analyses describe the Shinarump and Gartra Members as the deposits of a braided river system and identify previously unrecognized antidune deposits at the Vermilion Cliffs, northern Arizona. This suggests that the sandy facies at the top of the Shinarump Member may be deposits of flash flood events. Grain-size and cross-set height analysis allow for estimates of paleoslope to be produced, which range from 9.6 × 10−5 to 4.3 × 10−4, with a median value ~2.5 × 10−4, on par with many modern continental scale rivers. These estimates predict that the upper surface of the Chinle basin was ~75–150 m above sea level on the Colorado Plateau at its time of deposition. To reveal the amount of subsidence necessary to accommodate the Chinle Formation, we tied a 2-D backstripping analysis to the calculated paleoslope reconstruction. The resulting basin accommodation distribution describes a low-magnitude (hundreds of meters), long-wavelength (>1000 km) deflection, fully compatible with characteristics of dynamic topography. The combination of subsidence analysis with an independent paleoelevation metric can be applied to other members of the Chinle Formation and may be useful in other similar contexts where dynamic topography is difficult to quantify.

  PublisherDOI

• Miocene Construction of the High Andes Recorded by Exhumation of the Frontal Cordillera, La Ramada Massif of Western Argentina (32°S)

  Tectonics · 2025-01-01 · 3 citations

  articleSenior author

  Abstract The Frontal Cordillera is a first‐order geologic feature of the southern central Andes, hosting the highest hinterland topography above the modern Pampean flat‐slab segment. The timing of Frontal Cordillera exhumation is important for testing models of Andean tectonics, yet large latitudinal gaps exist between structural and thermochronological constraints for the region. We conducted a thermochronometric study using a 4.4 km age‐elevation transect along the northeast ridge of Cerro Mercedario, the highest peak in the La Ramada massif at ∼32°S. Zircon (U‐Th)/He dates indicate partial resetting, supporting a limited magnitude of exhumation in even the most extreme Andean topography. Single grain apatite (U‐Th‐Sm)/He dates range from 8.5 ± 0.9 to 35.8 ± 3.6 Ma, with median dates of ∼10.5 to ∼15.7 Ma with increasing elevation. Integrated with geologic mapping and thermal history modeling, these data suggest Early to Middle Miocene exhumation along the Santa Cruz and Espinacito faults concomitant with uplift of the La Ramada massif. New apatite helium data from the Cordillera del Tigre segment of the Frontal Cordillera are partially reset and preferred modeling interpretations suggest exhumation ca. 11–9 Ma, coeval with shortening in the eastward adjacent Precordillera. These data add to accumulating regional evidence for out‐of‐sequence deformation during the Miocene, consistent with internal (hinterland) growth of a subcritical orogenic wedge contemporaneous with surface uplift and crustal thickening in the south‐central Andes.

  PublisherDOI

• New Geochronological Constraints on the Late Palaeozoic Tarija Basin, Southern Bolivia: Tectonic and Palaeoclimatic Implications

  Terra Nova · 2025-08-01 · 1 citations

  articleOpen access

  ABSTRACT The Carboniferous‐Permian Tarija basin of southern Bolivia evolved under major tectonic and climatic influence. The timing of transition from glacially influenced to arid conditions, after the Gondwanide tectonic event, has been based mainly on palynological correlations. This study presents data from three U–Pb detrital zircon samples (~500 grains each), providing two robust maximum deposition ages (327 ± 4 and 259 ± 3 Ma). These results are integrated with stratigraphic cycles defining the Macharetí, Mandiyutí and Cuevo Groups. Our interpretation, supported by our data and previous studies, constrains a Mississippian to earliest Pennsylvanian age for the Macharetí Group and a Pennsylvanian age for the later Mandiyutí Group, both bounded by the regional Intra‐Carboniferous unconformity (~318 Ma). A major depositional hiatus followed the end of glaciation, with arid sedimentation recorded only after the late Permian (Cuevo Group).

  PublisherOA PDFDOI

• Increased moisture availability in the Central Andes during the Miocene Climatic Optimum

  Palaeogeography Palaeoclimatology Palaeoecology · 2025-01-08 · 2 citations

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  PublisherDOI

• Regional exhumation of the Laramide Province

  Geological Society of America Bulletin · 2025-02-18 · 6 citations

  article

  Abstract Western North America is the archetypical Cordilleran orogenic system that preserves a Mesozoic to Cenozoic record of oceanic Farallon plate subduction-related processes. After prolonged Late Jurassic through mid-Cretaceous normal-angle Farallon plate subduction that produced the western North American batholith belt and retroarc fold-thrust belt, a period of low-angle, flat-slab subduction during Late Cretaceous–Paleogene time caused upper plate deformation to migrate eastward in the form of the Laramide basement-involved uplifts, which partitioned the original regional foreland basin. Major questions persist about the mechanism and timing of flat-slab subduction, the trajectory of the flat-slab, inter-plate coupling mechanism(s), and the upper-plate deformational response to such processes. Critical for testing various flat-slab hypotheses are the timing, rate, and distribution of exhumation experienced by the Laramide uplifts as recorded by low-temperature thermochronology. In this contribution, we address the timing of regional exhumation of the Laramide uplifts by combining apatite fission-track (AFT) and (U-Th-Sm)/He (AHe) data from 29 new samples with 564 previously published AFT, AHe, and zircon (U-Th)/He ages from Laramide structures in Arizona, Utah, Wyoming, Colorado, Montana, and South Dakota, USA. We integrate our results with existing geological constraints and with new regional cross sections to reconstruct the spatial and temporal history of exhumation driven by Laramide deformation from the mid-Cretaceous to Paleogene. Our analysis suggests a two-stage exhumation of the Laramide province, with an early phase of localized exhumation occurring at ca. 100–80 Ma in Wyoming and Montana, followed by a more regional period of exhumation at ca. 70–50 Ma. Generally, the onset of enhanced exhumation occurs earlier in the northern Laramide province (ca. 90 Ma) and later in the southern Laramide province (ca. 80 Ma). Thermal history models of selected samples along regional cross sections through Utah–Arizona–New Mexico and Wyoming–South Dakota show that exhumation occurred contemporaneously with deformation, implying that Laramide basement block exhumation is coupled with regional deformation. These results have implications for testing proposed migration pathway models of Farallon flat-slab and for how upper-plate deformation is expressed in flat-slab subduction zones in general.

  PublisherDOI

• Cordilleran Orogenic Wedge Evolution in a Transitional Segment of the South-Central Andes (34.5°S), Chile and Argentina

  Abstracts with programs - Geological Society of America · 2025-01-01

  articleSenior author
  PublisherDOI

• Sedimentary Provenance Change During Late Triassic in Northwestern South China Block and Its Implications for Sichuan Foreland Basin Evolution and Closure of the Paleo‐Tethys Ocean

  Tectonics · 2025-10-01 · 1 citations

  article

  Abstract The Sichuan basin (SB) in southwestern China is a key region to understand the closure of the Paleo‐Tethys Ocean. Based on sedimentary petrographic, dense mineral, and detrital zircon U‐Pb geochronology data from two outcrop sections located in northwestern SB, a new compositional transition level is documented within the Upper Triassic Xujiahe Formation. Below this level, the strata contain pure quartzose sandstone, ultra‐stable dense minerals, and detrital zircon age populations of 230–290, 430–460, and 850–1,200 Ma. Above this level, the strata contain lithic‐rich recycled‐orogen detritus, abundant unstable dense minerals, and detrital zircon age clusters of 210–290, 440, 650–850, and 1,750–1,950 Ma. The compositional changes signify a change in provenance from the southern South China block (SCB) to the Longmenshan thrust belt (LTB) and Songpan‐Ganzi terrane and probably reflect transition from distal foredeep to proximal foredeep deposits of the foreland basin system associated with the LTB. Combined with the depositional characteristics, regional distribution of stratigraphic intervals, and a major unconformity within the Upper Triassic strata, a simple foreland basin evolution model is constructed. The timing of provenance change along the western margin of the SCB was probably during Late Triassic instead of between Middle and Late Triassic time as commonly believed. Commencement of unroofing of the Songpan‐Ganzi terrane and the LTB may have occurred during Norian time. Models for Paleo‐Tethys Ocean closure should incorporate coeval deformation and erosion of the Songpan‐Ganzi basin and LTB during the Late Triassic.

  PublisherDOI

• Exhumation of the Eastern Cordillera, NW Argentina: a record of competing river incision and fold-and-thrust belt propagation

  Abstracts with programs - Geological Society of America · 2025-01-01

  article
  PublisherDOI

• Slab-mantle interactions and erosional controls on crustal thickening of the Central and Southern Andes: coupling numerical modeling with geophysical and geological observations

  Abstracts with programs - Geological Society of America · 2025-01-01

  articleSenior author
  PublisherDOI

Recent grants

• Are Remnants of the Tibetan Plateau Preserved in the Southern Himalayan Thrust Belt?

  NSF · $521k · 2018–2023

• Collaborative Research: Tectonic Significance of Long Run-Out Coarse-Grained Facies in the Cordilleran Foreland Basin

  NSF · $228k · 2015–2020

• Collaborative Research: Investigation of Syncollisional Extension and Basin Development in the High Himalaya

  NSF · $291k · 2005–2008

• Collaborative Research: Stratigraphic Signatures of Orogeny: Assessing the Timing of Initial Andean Crustal Shortening

  NSF · $111k · 2007–2010

• Erosion and Exhumation History of the Nepalese Frontal Himalaya Since Earliest Miocene Time: Constraints on Kinematic History

  NSF · $513k · 2012–2016

Frequent coauthors

• Bárbara Carrapa

  104 shared

• Paul Kapp

  University of Arizona

  69 shared

• George E. Gehrels

  58 shared

• Jay Quade

  38 shared

• Mihai N. Ducea

  University of Bucharest

  23 shared

• T. P. Ojha

  19 shared

• Lin Ding

  Institute of Tibetan Plateau Research

  18 shared

• Gilby Jepson

  University of Oklahoma

  16 shared

Awards & honors

• Francis J. Pettijohn Medal, Society for Sedimentary Geology-…
• American Geophysical Union Fellow (2017)
• Geosciences Alumni Board Outstanding Faculty Award, Universi…
• Galileo Circle Fellow, University of Arizona (2009)
• Laurence L. Sloss Award, Geological Society of America (2008…