Paul Umhoefer

Northern Arizona University | NAU

Detrital-zircon U–Pb geochronology has revolutionized sediment provenance studies over the last two decades, and zircon has been successfully analyzed from nearly all sedimentary lithologies, depositional environments, and sediment grain sizes. However, despite the ubiquity of this method and the far-reaching interpretations supported by detrital-z...

Miocene basins of the Lake Mead region (southwestern United States) contain a well-exposed record of rifting and the evolving paleogeography of the eastern central Basin and Range. The middle Miocene Horse Spring Formation and red sandstone unit allow for detailed stratigraphic, chronostratigraphic, and structural analysis for better understanding...

The persistent debate over the timing of initial Arabia–Eurasia collision has eluded consensus for decades, with most estimates ranging widely from ~50 to 10 Ma along both the Anatolian and Zagros segments of the orogen. Here, we independently evaluate the timing and location of initial collision using a quantitative plate tectonic reconstruction t...

The northern Cascade Mountains in Washington (USA) preserve an exceptional shallow to mid-crustal record of Eocene transtension marked by dextral strike-slip faulting, intrusion of dike swarms and plutons, rapid non-marine sedimentation, and ductile flow and rapid cooling in parts of the North Cascades crystalline core. Transtension occurred during...

Despite long-standing recognition of high-amplitude, high-frequency sea-level variation resulting from repeated glaciations of Gondwanaland, recorded as “cyclothems” in late Paleozoic strata worldwide, major questions remain concerning their precise timing and expression in the stratigraphic record. A deep meandering canyon in southern Utah cut by...

Cyclic strata exposed in the Inyo Mountains of eastern California contain a continuous 6 m.y. record of deep marine deposition that spans the Pennsylvanian−Permian boundary. To better understand the geologic evolution of southwest Laurentia and the role of glacially driven eustasy in upper Paleozoic stratigraphy, we measured two detailed ∼600 m com...

Strike-slip faults form in a wide variety of tectonic settings and are a first-order control on the geometry and sediment accumulation patterns in adjacent sedimentary basins. Although the structural and depositional architecture of strike-slip basins is well documented, few studies of strike-slip basins have integrated depositional age, lithofacie...

NW-striking faults with km-scale displacement cut mountain ranges surrounding the Blythe basin in southeastern California, but the geometry, kinematics, and timing of these faults are poorly known. Fault activity is presently only constrained to postdate Late Cretaceous metamorphism and predate Quaternary alluvium that overlaps fault traces. Some a...

The effects of Arabia-Eurasia collision are recorded in faults, basins, and exhumed metamorphic massifs across eastern and central Anatolia. These faults and basins also preserve evidence of major changes in deformation and associated sedimentary processes along major suture zones including the Inner Tauride suture where it lies along the southern...

The effects of Arabia-Eurasia collision are recorded in faults, basins, and exhumed metamorphic massifs across eastern and central Anatolia. These faults and basins also preserve evidence of major changes in deformation and associated sedimentary processes along major suture zones including the Inner Tauride suture where it lies along the southern...

This poster illustrates the main findings from the fluid part of my thesis. The main findings from this study show the use of novel methods for understanding syn-tectonic paleo-fluid flow directions and model the evolution of paleo-fluids within the East Kaibab monocline, Utah.

[I will gladly send this full-text privately to colleagues, researchers and students if requested]. The Sivas Basin overlaps the northern Neotethys suture zone in central Anatolia (Turkey) and contains a ~12 km‐thick succession of Cenozoic strata that provides an exceptional record of major tectonic transitions from subduction to continental assemb...

This poster highlights the main findings and interpretations of the tectonic and structural part of my master's thesis project. This part of my thesis explored if magnetic fabrics in deformation bands can be used as a proxy for tectonic strain in terms of relative deformation amount, timing and direction.

Detrital zircon U‐Pb data are routinely used to assess provenance in sedimentary systems. However, recent studies have suggested that zircon provenance interpretation may be biased by grain‐size‐dependent selective transport and deposition. In this study, we present zircon grain‐size and U‐Pb data from 11 sandstone and 11 mudstone samples from the...

This research poster was designed before full completion of my master's thesis research, to present at the regional GSA Rocky Mountain Division conference. New developments in this research have been made and will be available as two separate research posters highlighting both the tectonic strain and syn-tectonic fluid flow parts of my thesis. This...

The southern Baja California (Mexico) microplate has been rapidly moving away from the North America plate since ca. 12 Ma. This relative motion toward the northwest developed an oblique-divergent plate boundary that formed the Gulf of California. The rift-drift hypothesis postulates that when a continent ruptures and seafloor spreading commences,...

The Ancestral Rocky Mountains system consists of a series of basement-cored uplifts and associated sedimentary basins that formed in southwestern Laurentia during Early Pennsylvanian–middle Permian time. This system was originally recognized by aprons of coarse, arkosic sandstone and conglomerate within the Paradox, Eagle, and Denver Basins, which...

The architecture, kinematics, and timing of fold-and-thrust belt development provide essential first-order constraints on the structural evolution of continental collision zones. The southern Sivas fold-thrust belt (SSFTB) is a ~300 × 50 km-long, ENE-trending contractional belt located in the Sivas Basin at the western end of the Arabia-Eurasia col...

Continental collisions exert a profound influence on the configuration and evolution of orogenic systems. The effects of Arabia-Eurasia collision on the geodynamics of the eastern Mediterranean are difficult to unravel, however, because the timing of initial collision (i.e., intercontinental contact) remains controversial. We present the first detr...

We compiled geochronology data from 87 published studies within the Anatolia orogen (32.5°E–44°E) to investigate the spatial and temporal patterns of continental magmatism during the final stages of Neotethys Ocean closure. The number and diversity of studies compiled here collectively provide a thorough characterization of magmatism (>700 ages) in...

The geologic record of the formation of marine basins during continental rifting is uncommonly preserved. Using GIS-based paleotectonic maps, we show that marine basin formation in the Gulf of California–Salton trough oblique rift (Mexico and the United States) occurred in a stepwise manner as crustal thinning lowered elevations within the Gulf of...

The paleogeographic evolution of the Lake Mead region of southern Nevada and northwest Arizona is crucial to understanding the geologic history of the U.S. Southwest, including the evolution of the Colorado Plateau and formation of the Grand Canyon. The ca. 25-17 Ma Rainbow Gardens Formation in the Lake Mead region, the informally named, roughly co...

The purpose of this study is to understand the nature and cause of an extensive alluvial fan progradation and its related depositional environments between 15.70-15.35 Ma in the middle Thumb Member of the Horse Spring Formation located in the western Lake Mead domain. The Thumb Basin records extension and the initiation of breakup of the basin into...

The Lake Mead domain of the central Basin and Range province provides an excellent example of large-scale continental extension. There are many proposed models that attempt to explain the magnitude and timing of extension but with no consensus. The Rainbow Gardens Formation of the Lake Mead domain is understood to largely represent deposition durin...

Ophiolitic rocks derived from Tethyan seaways are abundant in Anatolia; many are in arrays that mark sutures between Eurasia, Gondwana, and continental ribbons and island arcs. Ophiolitic fragments also occur dispersed between sutures, indicating tectonic transport of possibly hundreds of kilometers. Scattered fragments of the Central Anatolian Oph...

The tectonic origin of the Pennsylvanian-Permian Ancestral Rocky Mountain system is debated. Most models invoke stress from collision along the Ouachita-Marathon belt as the primary driver for Ancestral Rocky Mountain (ARM) (western USA) tectonism, but no existing model has convincingly explained the timing, northeastsouthwest contractional kinemat...

Despite significant progress toward understanding the kinematics of modern tectonic escape in Anatolia, considerable uncertainty remains regarding the dynamics of the transition from collision to escape. Because of the relatively small size of the Anatolia microplate, regional-scale studies spanning the plate margins and interior are well-suited to...

Because subduction is a destructive process, the surface record of subduction-dominated systems is naturally incomplete. Sedimentary basins may hold the most complete record of processes related to subduction, accretion, collision, and ocean closure, and thus provide key information for understanding the kinematic evolution of oro-gens. In central...

The late Oligocene to mid-Miocene volcanic and volcaniclastic rocks of the Comondú Group are well exposed along the Main Rift Escarpment of Baja California Sur from the Bahía de La Paz region to Bahía Concepción. New mapping and stratigraphic analysis of the Comondú Group from Bahía de La Paz to Loreto reveal facies trends and correlations that for...

The topography of the present-day Washington Cascades impacts atmospheric circulation and precipitation patterns in the Pacific Northwest, introducing a pronounced orographic rain-shadow in the lee of the mountain range. The temporal development of Cascade topography, however, remains largely unconstrained for the Early Cenozoic. Based on coupled c...

The Early Eocene Swauk Formation was deposited in a complex forearc setting during a regional shift from transpression to transtension associated with subduction of a spreading ridge beneath western North America. The basin forming mechanism for the Swauk Fm is not well understood; previous workers have suggested that it was a strike-slip basin, mo...

The Ancestral Rocky Mountains (ARM) represent one of the least understood major tectonic episodes of North American Phanerozoic geologic history. Most tectonic models are based on perceived far field compressional stress transmitted from either the SW, SE, or east with more a recently suggested western component. With previous studies being limited...

The Anatolian plate (Turkey) was formed during the late Miocene-Pliocene transition from contractional strain in central and eastern Anatolia (collision) to localized strike-slip faulting along inherited collisional structures (escape tectonics). Structural inheritance undoubtedly played a role in this major plate boundary reorganization, although...

The presence of early Eocene neartrench magmatism in western Washington and southern British Columbia has led to speculation that this area experienced ridge-trench interaction during that time. However, the effects of this process as they are preserved in other parts of the geologic record are poorly known. We present highprecision U-Pb zircon geo...

Late Oligocene to Miocene sedimentary strata of the Lake Mead, Nevada, region hold evidence that can test models of central Basin and Range extension and tectonic evolution and illuminate paleodrainage systems related to the carving of the Grand Canyon. In this region, Sevier contraction and a period of relative tectonic quiescence predate Miocene...

The southwest margin of the Gulf of California has an array of active normal faults despite this being an oblique-divergent plate boundary with spreading centers that localized deformation along the plate boundary 2-3 million years ago. The Carrizal and Centenario faults form the western border fault of the Gulf of California marginal fault system...

Tectonic reconstructions of the Pacific-North America (PAC-NAM) plate boundary across the Gulf of California and Salton Trough (GCAST) constrain the controversial magnitude of Baja California microplate-North America (BCM-NAM) relative motion since middle Miocene time. We use estimates of total PAC-NAM relative dextral-oblique motion from the updat...

An array of north-striking, left-stepping, active normal faults cuts the southwest margin of the Gulf of California and across the southern tip of the Baja California peninsula. This is the gulf margin fault system of the oblique-divergent plate boundary within the Gulf of California. Detailed geologic and geomorphic mapping along the onshore San J...

It has long been known that a seaway formed during the proto-Gulf of California stage of the oblique–divergent Pacific-North America plate boundary, but the processes that formed the seaway are poorly known. Microfossils and volcanic units date the first marine incursions at ~8 Ma at the mouth of the Gulf, ~7 Ma in the central Gulf, and 6.3 – 6.5 M...

We present GIS-based reconstructions for the Pacific-North America (PAC-NAM) oblique plate boundary. Our maps track PAC-NAM deformation since 12 Ma, at 1-2 Myr intervals, and use existing data to close basins, restore slip on faults, and restore rotated blocks. We use modern-day GPS motion between the Baja California microplate (BCM) and North Amer...

A multichannel seismic (MCS) experiment spanning 600 km across the Alarcon Rise and its conjugate rifted margins in the southern Gulf of California (western North America) provides insight into the spatial and temporal evolution of extension between Baja California and the mainland (Mexico). Stratigraphic analysis of multiple rift basins within the...

Subduction of the Farallon plate beneath northwestern Mexico stalled by ˜12 Ma when the Pacific-Farallon spreading-ridge approached the subduction zone. Coupling between remnant slab and the overriding North American plate played an important role in the capture of the Baja California (BC) microplate by the Pacific Plate. Active-source seismic refl...

Transtensional basins have formed along the Pacific-North America plate boundary in the Gulf of California and Salton Trough region during Late Cenozoic time. Axial basins occupy a 50-60 km wide belt along the main plate boundary, and change from sedimentstarved oceanic spreading centers in the south that are oriented perpendicular to long NW-strik...