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Grenville-age (1.3–0.9 Ga) zircons represent one of the most ubiquitous detrital zircon (DZ) age modes on Earth. In North America, given the widespread occurrence of Grenville basement, Grenville DZs are commonly viewed as nondiagnostic with regard to source region in provenance studies. Systematic recovery of DZ core-rim U-Pb ages makes it possible to identify and differentiate previously indistinguishable basement source terranes by leveraging their multistage tectono-magmatic evolution. Our analysis demonstrates that Grenville DZs exhibit distinct rim ages in different parts of the North American Paleozoic Appalachian-Ouachita-Marathon foreland. Whereas Grenville DZ grains in the eastern foreland, sourced from the southern Appalachian orogen in the eastern United States, exhibit Taconian and Acadian (490–350 Ma) rims, grains in the western foreland, derived from Mexico, mainly show Neoproterozoic (750–500 Ma) rim ages. This difference permits differentiation of nondiagnostic core ages by their distinctive rim ages. Furthermore, core-rim paired ages can illuminate potential genetic relationships among coexisting age components in DZ spectra, thereby indicating whether the DZs are derived from separate sources or from a single source with multistage tectono-magmatic histories. Thus, DZ rim-core ages can provide critical insights into reconstructing global source-to-sink systems and elucidating genetic linkages within multistage orogenic systems.

[Late Palaeozoic continental‐continental collision and related sediment routing changes and evolution of sedimentary basins in southwestern Laurentia. , Abstract Sea level is thought to be the primary driver of alternating deposition of carbonate and siliciclastic sediment in shelf settings, with carbonates dominating during transgressive/highstands and siliciclastics during lowstands. Although sediment supply is critically important for shelf‐margin growth in siliciclastic systems, few studies demonstrate its impact on mixed carbonate‐siliciclastic systems. The Permian Basin in Texas, United States, provides an opportunity to investigate the basin evolution regarding the source, sediment routing and particularly shelf/slope growth from syn‐ to postorogenic phases during alternating carbonate and siliciclastic sedimentation. Published detrital zircon data show that the proportion of orogen‐related sources decreased significantly from an earliest Permian synorogenic phase (ca. 298 Ma) to a Leonardian (ca. 280–271 Ma) postorogenic phase, in concert with a grain‐size change from fine‐ to medium‐grained sand to silt. Although along‐strike lateral variabilities exist on the shelf margin, the shelf‐margin evolution characteristics show a significant difference among the Northern Shelf, Eastern Shelf and Central Basin Platform. The synorogenic Eastern Shelf exhibits a significant higher progradation rate than does the postorogenic Northern Shelf. The progradation and aggradation ratio of siliciclastic‐rich intervals in the Eastern Shelf is significantly higher than those of carbonate‐rich intervals in the Eastern Shelf and carbonate‐ or siliciclastic‐rich intervals in the Northern Shelf. In contrast, the Central Basin Platform, with no siliciclastic sediment supply, records almost no progradation regardless of orogenic phases. There is an increase in slope gradient with decreasing sediment supply during this second‐order sequence from the Permian Cisuralian Series to the end of the Guadalupian Series. This study demonstrates that tectonically driven siliciclastic sediment supply was the main mechanism controlling the shelf and slope evolution in alternating siliciclastic and carbonate deposition.]

Subsidence history and sandstone provenance of the Bisbee basin of southwestern New Mexico, southern Arizona, and northern Sonora, Mexico, demonstrate basin evolution from an array of Late Jurassic–Early Cretaceous rift basins to a partitioned middle Cretaceous retroarc foreland basin. The foreland basin contained persistent depocenters that were inherited from the rift basin array and determined patterns of Albian–early Cenomanian sediment routing. Upper Jurassic and Valanginian–Aptian strata were deposited in three narrow extensional basins, termed the Altar-Cucurpe, Huachuca, and Bootheel basins. Initially rapid Late Jurassic subsidence in the basins slowed in the Early Cretaceous, then increased again from mid-Albian through middle Cenomanian time, marking an episode of foreland subsidence. Sandstone composition and detrital zircon provenance indicate different sediment sources in the three basins and demonstrate their continued persistence as depocenters during Albian foreland basin development. Late Jurassic basins received sediment from a nearby magmatic arc that migrated westward with time. Following a 10–15 m.y. depositional hiatus, an Early Cretaceous continental margin arc supplied sediment to the Altar-Cucurpe basin in Sonora as early as ca. 136 Ma, but local sedimentary and basement sources dominated the Huachuca basin of southern Arizona until catchment extension tapped the arc source at ca. 123 Ma. The Bootheel basin of southwestern New Mexico received sediment only from local basement and recycled sedimentary sources with no contemporary arc source evident. During renewed Albian–Cenomanian subsidence, the arc continued to supply volcanic-lithic sand to the Altar-Cucurpe basin, which by then was the foredeep of the foreland basin. Sandstone of the Bootheel basin is more quartzose than the Altar-Cucurpe basin, but uncommon sandstone beds contain neovolcanic lithic fragments and young zircon grains that were transported to the basin as airborne ash. Latest Albian–early Cenomanian U-Pb tuff ages, detrital zircon maximum depositional ages ranging from ca. 102 Ma to 98 Ma, and ammonite fossils all demonstrate equivalence of middle Cretaceous proximal foreland strata of the U.S.-Mexico border region with distal back-bulge strata of the Cordilleran foreland basin. Marine strata buried a former rift shoulder in southwestern New Mexico during late Albian to earliest Cenomanian time (ca. 105–100 Ma), prior to widespread transgression in central New Mexico (ca. 98 Ma). Lateral stratigraphic continuity across the former rift shoulder likely resulted from regional dynamic subsidence following late Albian collision of the Guerrero composite volcanic terrane with Mexico and emplacement of the Farallon slab beneath the U.S.–Mexico border region. Inferred dynamic subsidence in the foreland of southern Arizona and southwestern New Mexico was likely augmented in Sonora by flexural subsidence adjacent to an incipient thrust load driven by collision of the Guerrero superterrane.

A comprehensive correlation chart of Pennsylvanian–Eocene stratigraphic units in Mexico, adjoining parts of Arizona, New Mexico, south Texas, and Utah, as well as Guatemala, Belize, Honduras, and Colombia, summarizes existing published data regarding ages of sedimentary strata and some igneous rocks. These data incorporate new age interpretations derived from U-Pb detrital zircon maximum depositional ages and igneous dates that were not available as recently as 2000, and the chart complements previous compilations. Although the tectonic and sedimentary history of Mexico and Central America remains debated, we summarize the tectonosedimentary history in 10 genetic phases, developed primarily on the basis of stratigraphic evidence presented here from Mexico and summarized from published literature. These phases include: (1) Gondwanan continental-margin arc and closure of Rheic Ocean, ca. 344–280 Ma; (2) Permian–Triassic arc magmatism, ca. 273–245 Ma; (3) prerift thermal doming of Pangea and development of Pacific margin submarine fans, ca. 245–202 Ma; (4) Gulf of Mexico rifting and extensional Pacific margin continental arc, ca. 200–167 Ma; (5) salt deposition in the Gulf of Mexico basin, ca. 169–166? Ma; (6) widespread onshore extension and rifting, ca. 160–145 Ma; (7) arc and back-arc extension, and carbonate platform and basin development (ca. 145–116 Ma); (8) carbonate platform and basin development and oceanic-arc collision in Mexico, ca. 116–100 Ma; (9) early development of the Mexican orogen in Mexico and Sevier orogen in the western United States, ca. 100–78 Ma; and (10) late development of the Mexican orogen in Mexico and Laramide orogeny in the southwestern United States, ca. 77–48 Ma.

Jurassic northward migration of Mexico, which lay on the southern part of the North America plate, resulted in temporal evolution of climate-sensitive depositional environments. Lower–Middle Jurassic rocks in central Mexico contain a record of warm-humid conditions, indicated by coal, plant fossils, and compositionally mature sandstone deposited in continental environments. Paleomagnetic data for central Oaxaca and other regions of central and eastern Mexico indicate that Lower and Middle Jurassic rocks were deposited at near-equatorial paleolatitudes. In the Late Jurassic, the Gulf of Mexico formed as a subsidiary basin of the Atlantic Ocean when the Pangea supercontinent ruptured. Upper Jurassic strata across Mexico, including eolianite and widespread evaporite deposits, indicate dry-arid conditions. Available paleomagnetic data (compaction-corrected) from southern and northeast Mexico for Upper Jurassic strata indicate deposition at ~15°N–20°N. As North America moved northward during Jurassic opening of the Atlantic Ocean, different latitudinal regions experienced coeval Middle–Late Jurassic climatic shifts. Climate transitions have been widely recognized in the Colorado Plateau region. The plateau left the horse latitudes in the late Middle Jurassic to reach temperate humid climates at ~40°N in the latest Jurassic. Affected by the same northward drift, the southern end of the North America plate represented by central Mexico gradually reached the arid horse latitudes in the late Middle Jurassic as the Colorado Plateau was leaving them. As a result, Late Jurassic epeiric platforms developed in the circum–Gulf of Mexico region after a long period of margin extension and were surrounded by arid land masses. We propose that hydrocarbon source-rock deposition was facilitated by arid conditions and wind-induced coastal upwelling.

Sandstone petrography, detrital zircon geochronology, and sedimentology of Lower Cretaceous to Paleocene strata in the Cuicateco terrane of southern Mexico indicate an evolution from extensional basin formation to foreland basin development. The Early Cretaceous extensional basin is characterized by deposition of deep-marine fans and channels, which were mainly sourced from Mesoproterozoic and Permian crystalline rocks of the western shoulder of the rift basin. Some submarine fans, especially in the northern Cuicateco terrane, record an additional source in the Early Cretaceous (ca. 130 Ma) continental arc. The fans were fed by fluvial systems in updip parts of the extensional basin system. The transition from middle Cretaceous tectonic quiescence to Late Cretaceous shortening is recorded by the Turonian–Coniacian Tecamalucan Formation. The Tecamalucan Formation is interpreted as pre-orogenic deposits that represent submarine-fan deposits sourced from Aptian–Albian carbonate platform and pre-Mesozoic basement. The foreland basin in the Cuicateco terrane was established by the Maastrichtian, when foredeep strata of the Méndez Formation were deposited in the Cuicateco terrane, Veracruz basin, and across the western Gulf of Mexico, from Tampico to Tabasco. In the Zongolica region, these strata were derived from a contemporaneous volcanic arc (100–65 Ma) located to the west of the basin, the accreted Guerrero terrane (145–120 Ma), and the fold belt itself. By the Paleocene, sediments were transported to the foreland basin by drainages sourced in southwestern Mexico, such as the Late Cretaceous magmatic rocks of the Sierra Madre del Sur, and the Chortis block.

The Gulf of Mexico is best understood as a subsidiary basin to the Atlantic, resulting from breakup of Pangea. The rifting process and stratigraphy preceding opening of the gulf are, however, not fully understood. We present new stratigraphic, sedimentologic, and provenance data for the Todos Santos Formation (now Todos Santos Group) in southern Mexico. The new data support a two-stage model for rifting in the Gulf of Mexico. Field and analytical evidence demonstrate that strata assigned to the Todos Santos Group in Mexico belong to two unrelated successions that were juxtaposed after rotation of the Yucatán block. An Upper Triassic fluvial siliciclastic succession in the western Veracruz basin is intruded by the San Juan del Río pluton (194 Ma, U-Pb) along the Valle Nacional fault. We refer to this succession as the Valle Nacional formation (informal) of the Todos Santos Group, and correlate it with El Alamar Formation of northeast Mexico and the Eagle Mills Formation of the northern Gulf of Mexico. Triassic red beds register an early rifting phase in western equatorial Pangea. Sandstone composition indicates that the Valle Nacional formation is mostly arkoses derived from multiple sources. Paleocurrent indicators in fluvial strata of the Valle Nacional formation are S-SW directed, but restoration of paleomagnetically determined counterclockwise rotation indicates a W-SW–flowing fluvial system. Triassic rifting in the Valle Nacional formation and the Central Cordillera of Colombia Triassic extensional event, the record of which is preserved in mid-crustal levels, may represent conjugate margins. The Early–Middle Jurassic Nazas continental volcanic arc predated the Jurassic rifting phase that led to opening of the gulf. A record of arc magmatism is present in eastern Mexico underlying Middle Jurassic synrift successions, and it is present in La Boca and Cahuasas formations in the Sierra Madre Oriental and La Silla Formation north of the Chiapas Massif. These units have a similar age range between ca. 195 and 170 Ma. Arc magmatism in eastern Mexico is correlated with the Jurassic Cordilleran arc of Sonora, California, and Arizona, as well as the Jurassic arc of the Central Cordillera of Colombia. La Boca and La Silla units record intra-arc extension driven by slab rollback. The Jurassic rifting phase is recorded in the Jiquipilas formation of the Todos Santos Group and is younger than ca. 170 Ma, based on young zircon ages at multiple locations. The informal El Diamante member of the Jiquipilas formation records the maximum displacement rift stage (rift climax). Coarse-grained, pebbly, arkosic sandstones with thin siltstone intercalations and thick conglomerate packages of the Jericó member of the Jiquipilas formation are interpreted as deposits of a high-gradient, axial rift fluvial system fed by transverse alluvial fans. These rivers flowed north to northeast (restored for ~35° rotation of Yucatán). The Concordia member of the Jiquipilas formation records the postrift stage. Thick synrift successions are preserved in the subsurface in the Tampico-Misantla basin, but they cannot be easily assigned to the Triassic or the Jurassic rifting stages because of insufficient study. The Todos Santos Group at its type locality in Guatemala marks the base of the Lower Cretaceous transgression. Overall, three regional extensional events are recognized in the western Gulf of Mexico Mesozoic margin. These include Upper Triassic early rifting, an extensional continental arc, and Middle Jurassic main rifting events that culminated with rotation of Yucatán and formation of oceanic crust in the gulf.

The sedimentary fill of peripheral foreland basins has the potential to preserve a record of the processes of ocean closure and continental collision, as well as the long-term (i.e., 107–108 yr) sediment-routing evolution associated with these processes; however, the detrital record of these deep-time tectonic processes and the sedimentary response have rarely been documented during the final stages of supercontinent assembly. The stratigraphy within the southern margin of the Delaware Basin and Marathon fold and thrust belt preserves a record of the Carboniferous–Permian Pangean continental assembly, culminating in the formation of the Delaware and Midland foreland basins of North America. Here, we use 1721 new detrital zircon (DZ) U-Pb ages from 13 stratigraphic samples within the Marathon fold and thrust belt and Glass Mountains of West Texas in order to evaluate the provenance and sediment-routing evolution of the southern, orogen-proximal region of this foreland basin system. Among these new DZ data, 85 core-rim age relationships record multi-stage crystallization related to magmatic or metamorphic events in sediment source areas, further constraining source terranes and sediment routing. Within samples, a lack of Neoproterozoic–Cambrian zircon grains in the pre-orogenic Mississippian Tesnus Formation and subsequent appearance of this zircon age group in the syn-orogenic Pennsylvanian Haymond Formation point toward initial basin inversion and the uplift and exhumation of volcanic units related to Rodinian rifting. Moreover, an upsection decrease in Grenvillian (ca. 1300–920 Ma) and an increase in Paleozoic zircons denote a progressive provenance shift from that of dominantly orogenic highland sources to that of sediment sources deeper in the Gondwanan hinterland during tectonic stabilization. Detrital zircon core-rim age relationships of ca. 1770 Ma cores with ca. 600–300 Ma rims indicate Amazonian cores with peri-Gondwanan or Pan-African rims, Grenvillian cores with ca. 580 Ma rims are correlative with Pan-African volcanism or the ca. 780–560 Ma volcanics along the rifted Laurentian margin, and Paleozoic core-rim age relationships are likely indicative of volcanic arc activity within peri-Gondwana, Coahuila, or Oaxaquia. Our results suggest dominant sediment delivery to the Marathon region from the nearby southern orogenic highland; less sediment was delivered from the axial portion of the Ouachita or Appalachian regions suggesting that this area of the basin was not affected by a transcontinental drainage. The provenance evolution of sediment provides insights into how continental collision directs the dispersal and deposition of sediment in the Permian Basin and analogous foreland basins.

New analyses of U-Pb ages along with previously published analyses of detrital zircons from sandstones in the foreland of the Marathon orogen in west Texas have significant implications regarding provenance. The most prominent concentrations of U-Pb ages are at 1200–1000, 700–500, and 500–290 Ma. The accreted Coahuila terrane in the Marathon hinterland and nearby terranes with Gondwanan (Amazonia) affinity include Paleozoic volcanic and plutonic rocks, as well as Precambrian basement rocks. Late Paleozoic Las Delicias arc rocks have ages of 331–270 Ma. Detrital zircons from Upper Jurassic and Lower Cretaceous sandstones, which were deposited in local basins around the Coahuila terrane, provide a record of detritus available from proximal sources within Coahuila, including important peaks at 1040, 562, 422, 414, 373, and 282 Ma. Components of the detrital-zircon populations in the Marathon foreland have unique matches with primary and/or detrital sources in the Coahuila terrane. Although some components of the Marathon populations also have age matches in Laurentia (Appalachians), others do not; however, all components of the Marathon populations have potential sources in Coahuila. Analyses of εHft show generally more negative values in Amazonia than in Laurentia, and εHft values for Marathon sandstones have distributions similar to those in Amazonia. Therefore, the Coahuila terrane provides a provenance for all of the detrital-zircon ages in the Marathon foreland, requiring no mixing from other sources.

The Late Cretaceous-Paleogene Mexican foreland basin (MFB), defined herein, represents the southern continuation of the late Mesozoic Cordilleran foreland basin. Sandstone petrography, new detrital...

The Flinders and Willouran ranges of South Australia contain over 20 examples of exposed allochthonous salt sheets and canopies comprising the Callanna Group megabreccias. The identification of a g...

The excursion route is shown in Fig. 3.1. The itinerary provides a detailed look at La Popa weld to observe the structural and stratigraphic variability of that feature. La Popa salt weld was the first weld described in detail from outcrop exposures (Giles and Lawton 1999).

The excursion for each day is shown in Fig. 3.1. Excursion 1 consists of a visit to El Papalote diapir in La Popa basin and return via Potrero Chico near Hidalgo to compare diapiric and detachment structures. Excursion 2 is a tour of La Popa weld to observe the structural and stratigraphic variability of that feature. Both excursions, especially Excursion 2, contain ambitious itineraries polished during many trips by the authors; a newcomer to these itineraries might consider allotting additional time to visit all of the stops described here.

The Mexican orogen is the expression in Mexico of the Cordilleran orogenic system. The orogen extends the length of Mexico, a distance of 2000 km from the state of Sonora in the northwest to the state of Oaxaca in the south. The Mexican orogen consists of (1) a western hinterland of accreted oceanic basinal rocks and magmatic arc rocks generally known as the Guerrero volcanic superterrane, (2) a foreland orogenic wedge , commonly termed the Mexican fold and thrust belt (MFTB), composed of imbricated and folded Upper Jurassic-Lower Cretaceous carbonate rocks and Upper Cretaceous foreland-basin strata, and (3) an assemblage of variably folded and inverted Late Cretaceous to Eocene foreland basins that lie northeast and east of the MFTB. The Mexican orogen encompasses the entire country, spanning several physiographic provinces and deformational domains that display both thin-skinned and thick-skinned structural styles determined by inherited crustal structure and contrasting pre-kinematic sedimentary sections. The orogen contains kinematic characteristics of both the Sevier and Laramide orogens in the United States (U.S.), and deformation in the Mexican orogen spanned the deformational history of those U.S. orogens. The overall trend of the Mexican orogen is NW-SE, although it displays local trend variations. At presently exposed levels, the orogen consists of folded and reverse-faulted Mesozoic-Eocene strata. Lower Cretaceous strata of the deformed foreland are dominated by carbonate rocks, whereas time-equivalent strata in the hinterland consist of deformed plutons belonging to one or more magmatic arcs, as well as turbidites, pillow lavas and altered mafic rocks deposited in an offshore basin prior to consolidation of fringing arc systems to mainland Mexico. Upper Cretaceous syntectonic strata of the foreland orogenic wedge constitute siliciclastic turbidite successions that grade eastward to carbonate pelagites of the distal foreland basin, which was starved of siliciclastic sediment input. Uppermost Cretaceous and Paleogene strata of the foreland basin constitute a shelfal, deltaic and coastal plain fluvial succession in northeastern Mexico and a succession of turbidites in the Tampico-Misantla basin east of the MFTB. Structural geometry of the orogen was controlled by the spatial distribution of pre-Cretaceous crustal elements, such as Jurassic extensional basins and basement blocks, and detachment horizons at varying stratigraphic levels, as well as the direction of structural vergence, which is dominated by NE-directed tectonic transport throughout the belt. Jurassic evaporite horizons and Upper Jurassic carbonaceous shale units provide detachment surfaces in some parts of the orogen. The structural style of the MFTB is generally thin-skinned, although high-angle faults are present at several localities, where the steep faults cut thin-skinned, shallowly-dipping faults, detachment horizons and associated folds. Strain magnitude decreases toward the foreland and generally satisfies critical wedge predictions. Values of shortening > 70% are present in the hinterland of central Mexico; these decrease systematically to values Shortening history in the Mexican orogen approximately spanned Late Cretaceous-Eocene time. Deformation timing has been constrained using Ar-Ar systematics on illite generated by layer-parallel slip in the limbs of chevron folds. Estimates of deformation timing are in good agreement with the age of synorogenic sedimentary successions, and with ages of syn-tectonic plutons. Published data from central Mexico suggest episodic pulses of deformation between 93–80 Ma, 75–64 Ma and 55–43 Ma, which postdate the closure of the Arperos basin. Each of these shortening events affects rock units lying progressively farther to the east to yield a temporal eastward advance of deformation and sedimentation. Effects of successively younger shortening were superimposed on the westernmost exposures of the thrust belt and are evidenced on a map scale by abrupt trend variations in orogen-interior folds, compared to generally linear or broadly arcuate axial traces of frontal folds. Although potential tectonic mechanisms for shortening in the Mexican orogen remain debated, our analysis indicates that orogenic wedge development took place in a retroarc setting that postdated consolidation of the hinterland oceanic assemblages, which lay offshore western Mexico during Albian time. Orogen development followed a protracted period of early Mesozoic extension that affected most of the Mexico due to the combined effects of Laurentia-Gondwana separation and long-term Triassic-Jurassic rollback of a paleo-Farallon plate. Slab rollback ultimately resulted in the development of a marginal basin, the Arperos basin, between a rifted Late Jurassic magmatic arc and mainland Mexico. Initial shortening in the Mexican orogen, which followed Arperos basin closure and Guerrero superterrane accretion by ~ 5–10 Ma, was coeval with voluminous magmatism on the Pacific margin of Mexico, drowning of the western carbonate platforms and onset of foreland-basin sedimentation in Cenomanian time. Subduction of the Farallon slab from early Late Cretaceous to Eocene time was thus the primary driving mechanism of shortening in the Mexican orogen.

Exposures of salt diapirs and flanking strata in La Popa basin, in the Mexican states of Nuevo Leon and Coahuila, contain world-class examples of salt–sediment interaction that provided the basis for the concept of halokinetic sequences. The basin also contains one of the first secondary salt welds described in outcrop. The two-day field trip described here provides an easily accessible overview of salt–sediment relations within a short distance of Monterrey, the capital city of Nuevo Leon. The first day constitutes an introduction to basin stratigraphy, a traverse through halokinetic sequences at El Papalote diapir, and visits to the Cretaceous–Paleogene boundary bed and a salt-cored detachment fold near the town of Hidalgo, north of Monterrey. The second day is a visit to La Popa salt weld, where stops at several parts of the weld permit comparison of different structural styles developed along the weld. The trip begins and ends at the Marriott Courtyard Hotel, near the Monterrey airport.

Late Mississippian to middle Permian sediment-dispersal networks of regional to continental scale in western equatorial Pangea, depicted here in a series of paleogeographic maps, developed in response to temporally and spatially changing influences of climate, eustasy, and a continent-wide late Paleozoic orogenic system. The orogenic system included linked Alleghanian, Ouachita-Marathon-Sonora collisional belts and associated foreland basin systems on Laurentia and magmatic arcs on Gondwana, intracratonic basement uplifts and basins of the Ancestral Rocky Mountains, flexural arches and intracratonic basins of the US midcontinent region, and basins and uplifts of the southwestern Laurentian transcurrent continental margin. Consideration of new and published U-Pb detrital-zircon datasets permits delineation of Laurentian sediment-dispersal networks of the developing supercontinent. The Transcontinental Arch deflected Late Mississippian transcontinental rivers with Alleghanian headwaters toward the southern midcontinent and nascent, deep-marine foreland basins along the Ouachita collision orogen. Pennsylvanian rivers likewise headed in the Alleghanian Orogen, transporting sediment southwest across the midcontinent and along the Alleghanian foreland basin to empty into the Arkoma Basin and Fort Worth Basin, which also received voluminous sediment from Gondwana and the Ouachita Orogen. Concomitantly, major growth of Ancestral Rocky Mountains uplifts yielded basement-derived sediment, much of which was retained in local flexural basins. Increased aridity drove ascendant eolian transport in early Permian (Artinskian) time, just as lowstand desiccation of a midcontinent seaway exposed unconsolidated silt and sand derived from eastern, western, and southern sources in an extensive interior desert sink. Eolian transport within the interior desert further mixed and deflated the already-cosmopolitan sediment, pushing it southwest toward the Permian Basin and westward beyond the Ancestral Rocky Mountains. Intercepted by newly developed monsoonal circulation, the deflated sediment came to reside in erg systems along the western marine margin of Pangea. Subtropical Pennsylvanian transcontinental fluvial networks were similar to those of modern big river systems of the eastern and midcontinent United States that drain toward the Gulf of Mexico. In contrast, Permian drainage networks yielding sediment to a continental desert more resembled Pleistocene sediment routes of the Arabian Plate; there, intermittent wadis draining western rift highlands and big rivers of the Mesopotamian foreland contribute sediment to Arabian eolian sands via zonal and monsoonal surface winds to create widespread sand seas of mixed Eurasian and Arabian provenance.

The Laramide orogeny had a spatially variable lifespan, which we explain using a geodynamic model that incorporates onset and demise of flat-slab subduction. Laramide shortening and attendant uplift began in southeast California (USA) at ca. 90 Ma, swept to the northeast to arrive in the Black Hills of South Dakota (USA) at ca. 60 Ma, and concluded in South Dakotawithin ∼10 m.y. During subsequent slab rollback, the areal extent of Laramide deformation decreased as the eastern edge of active deformation retreated to the southwest rapidly from ca. 55 to 45 Ma and more slowly from ca. 45 to 40 Ma, with deformation ultimately ceasing in the southwestern part of the orogen at ca. 30 Ma. Geodynamic modeling of this process suggests that changes in the strength of the North America plate and densifcation of the Farallon plate played important roles in controlling the areal extent of the Laramide orogen and hence the lifespan of the orogenic event at any particular location in western North America.

Lower Cretaceous depositional systems of southwestern Oaxaquia, in south-central Mexico, were influenced by initiation of a continental arc on mainland Mexico and subsequent accretion of the Guerrero composite arc terrane to mainland Mexico. The Atzompa Formation, defined herein, which crops out in the Sierra de Tentzo, constitutes a succession of conglomerate, sandstone, siltstone, and limestone with Early Cretaceous fauna and detrital zircon maximum depositional ages that range 126–123 Ma (late Barremian to early Aptian). The lower part of the Atzompa records a transition from alluvial to deep lacustrine depositional environments, suggesting the early stages of an extensional basin; overlying deposits of anabranching axial fluvial systems that flowed to the NE–SE accumulated after a period of rapid subsidence in the Tentzo basin, also formerly undescribed. Fluvial facies grade up-section to tidal deposits overlain in turn by a carbonate ramp succession that contains late Barremian to early Aptian fossils. The ramp deposits of the uppermost Atzompa Formation are overlain on a sharp contact by basinal carbonates of early Albian age.The Tentzo basin, formed due to crustal extension of the overriding plate in a backarc setting, was characterized by very high rates of sedimentation (3.6 mm/yr) during the early stages of basin formation (rift initiation and rift climax), and slower rates during the development of tidal systems and the carbonate ramp (post-rift stage). Regional and local subsidence took place in the backarc region of the Zicapa magmatic arc, which was established in the western margin of Mexico by Hauterivian time. Abrupt deepening following Atzompa Formation deposition is attributed to flexural subsidence related to collision of the Guerrero composite volcanic terrane with the western margin of Mexico. Following late Aptian accretion of the Guerrero terrane to Oaxaquia, the carbonate basin eventually shallowed to become a carbonate platform that faced the Gulf of Mexico.

The source-to-sink (S2S) concept is focused on quantification of the various components of siliciclastic sedimentary systems from initial source sediment production areas, through the dispersal system, to deposition within a number of potential ultimate sedimentary sinks, and has more recently been applied to deep-time stratigraphic systems. Sequence-stratigraphic analysis is a key first step that allows depositional systems to be correlated and mapped, within a time-stratigraphic framework, such that fluvial transport systems can be linked to down-dip shorelines, shelf and deep-water deposits and interpreted in the context of allogenic processes. More recently, attempts have been made to quantify catchment areas for ancient depositional systems, using scaling relationships of modern systems. This also helps predict the size of linked depositional systems, such as rivers, deltas and submarine fans, along the S2S tract. The maximum size of any given depositional system, such as a river, delta, or submarine fan, is significantly controlled by the area, relief, and climate regime of the source area, which in turn may link to the plate tectonic and paleogeographic setting. Classic provenance studies, and more recent use of detrital geochronology, including zircons, provide critical information about source areas, and place limits on catchment area. Provenance studies, especially when linked to thermochronometry also provide key information about rates of exhumation of source areas and the link to the tectonic setting. In this paper the techniques for estimation of water and sediment paleodischarge and paleo-drainage area are outlined, and sediment budgets are calculated for a number of Mesozoic systems, primarily from western North America. The relevance for hydrocarbon exploration and production is discussed for each example. In Mesozoic Western Interior basins of North America, extensive outcrop and subsurface data allow the largest trunk rivers to be identified, typically within incised valleys. Thickness, grain size, and sedimentary structures can be used to infer slope and flow velocities, and using width estimations, water and sediment paleodischarge can be calculated. River paleoslope can also be independently measured from stratigraphic-geometric considerations and used to assess paleo-river flow. Paleodischarge in turn is used to estimate the size of the catchment source area. Paleodischarge of rivers can also be estimated independently by integrating estimates of catchment source area, for example by using detrital zircons integrated with paleoclimate. The catchment areas of North America evolved significantly during the late Mesozoic. During the Jurassic–Early Cretaceous, fluvial systems consisted of continental-scale low slope (S = 10− 4), axially drained rivers, forming the 40-m-deep channels in the Mannville Group in Canada, which now host the supergiant heavy-oil-sands reserves. During the times of maximum transgression of the Cretaceous Seaway, such as the Turonian and Campanian, the western North American foreland basin was characterized by smaller-scale (typically 10-m deep), steeper gradient (S = 10− 3) sand and gravel bedload rivers, dominated by transverse drainages in the rising Cordillera. This created a number of smaller river-delta S2S systems along the coast. As the Laramide Orogeny progressed, the Western Interior Seaway receded, and by the Paleocene the modern continental-scale drainage of North America was largely established with a major continental division separating south-flowing Mississippi drainages from north-flowing systems. The integration of paleodischarge estimates with provenance analysis enables the improved use of the sedimentary record to make estimates about the entire S2S system, as opposed to primarily the depositional component. Clinothem stacking relationships and isopach mapping of stratigraphic volumes have also been integrated with chronostratigraphic data to analyze long-term S2S sediment budgets. A more quantitative approach to estimating the scale of erosional, transport and depositional components of sedimentary systems, especially in the context of linked source and depositional areas, also puts constraints on the size and scale of potential hydrocarbon reservoirs and thus has significant economic value.

Intermontane basins developed adjacent to and between broken-foreland uplifts of the Laramide orogen in western North America during the time interval 76–38 Ma. The basin array consists of perimeter basins around the edge of the orogen, ponded basins in the interior of the orogen, and narrow, thick axial basins that lie along the eastern edge of the stable Colorado Plateau in a fairway of great structural relief, the front ranges, between the ponded and perimeter basins. The basins filled with continental strata that consist of, in order of proximity to active uplift margins, deposits of alluvial fans, braided and meandering rivers, and lakes. Lakes were largely restricted to the ponded basins, but some southern perimeter basins contained lakes during development of maximum structural relief. Lacustrine environments ranged from freshwater fluctuating profundal conditions, when lakes likely had outlets to exterior parts of the orogen, to evaporative conditions when basins lacked high-volume fluvial inflow and did not drain externally. Although climate may have influenced fluvial style, emerging data sets suggest that tectonic factors played important roles in facies tracts of ponded basins by instigating drainage capture, thereby altering fluvial routes, and creating barriers to basin outflow. Provenance data from sandstone petrology and U Pb detrital-zircon analysis indicate the presence of intra-orogen and extra-orogen sediment routing systems. Intra-orogen drainages contributed sediment from local uplifts to adjacent basins; some of this sediment bypassed perimeter basins to exterior sinks, principally in northeastern Mexico and the Gulf of Mexico. Extra-orogen river systems transferred sediment from active and quiescent segments of the continental-margin arc to ponded basins, which tended to trap the sediment, and to exterior sinks. Subduction of a flat slab, rendered buoyant by a thick oceanic plateau that constitutes a conjugate to the Shatsky Rise of the present northwestern Pacific Ocean, drove crustal shortening in the Laramide orogen. Dynamic topography of the subducted plateau modulated orogenic uplift and enhanced traction coupling between the subducted plateau and continental lithosphere of North America to produce diachronous deformation and an evolving drainage network within the Laramide orogen.

Consideration of petrographic and U-Pb provenance data and paleocurrent analysis of Kungurian (upper Leonardian) Cutler Group strata in the salt anticline province of the Paradox Basin of Utah demonstrates striking contrasts in composition and inferred sources of stratigraphically adjacent eolian and fluvial facies. Eolian strata, termed here the Castle Valley Sandstone, exposed in the Castle Valley northeast of Moab, Utah, and long correlated with the White Rim Sandstone, were deposited on the southwestern flank of a NW-trending diapiric salt wall. The eolian strata, which overlie red fluvial sandstone and conglomerate of the undifferentiated Cutler Formation, are as much as 183 m thick in outcrop and consist of two eolianite members separated by a thin sheet-flood deposit that contains pebbles derived from the salt wall and upturned conglomeratic strata adjacent to it. Both eolian and underlying fluvial deposits thin and onlap eastward onto the now-collapsed salt wall. Fluvial strata at Castle Valley and in exposures to the northeast were transported northwestward, parallel to the salt wall. Large-scale foresets in the lower eolianite member indicate dominant northeasterly wind directions (present coordinates) and transport directly away from the contemporary Uncompahgre uplift, whereas foresets in the upper member indicate variable northeasterly and northwesterly paleowinds. The eolian strata thus accumulated on the lee side of the salt wall, but sandstone composition and northwesterly wind components indicate net transport from the northwest, comparable with dominant southeastward sand transport, away from the Pangean shoreline, documented for the greater White Rim erg to the west and northwest. The NW and NE winds are both predicted by late Paleozoic atmospheric circulation models for western Pangea. Cutler fluvial sandstones are compositional arkoses (mean Qt 56 F 42 L 2 ) containing basement-derived detrital components that include potassium feldspar, plagioclase, biotite, and zircons with a restricted, bimodal age distribution of ∼1790–1689 Ma and ∼1466–1406 Ma. These grain ages exactly match known basement ages in the nearby Uncompahgre uplift. In contrast, the Castle Valley Sandstone ranges from quartz-rich arkose to subarkose and exhibits a consistent upsection decrease in feldspar content, from Qt 71 F 27 L 2 in the lower eolianite member to Qt 90 F 10 L 0 in the upper member. Like the underlying fluvial arkose, the lower eolianite member contains potassium feldspar, plagioclase, and mica derived from the Uncompahgre uplift, but the locally derived zircon age groups constitute only 23%–37% and 13% of the zircon grain ages in the lower and upper eolianite members, respectively; whereas older Archean and Paleoproterozoic grains, including ca. 1.5 Ga grains uncommon in the Laurentian detrital-zircon record, and Grenville, Neoproterozoic, and early Paleozoic grains constitute the bulk of the zircons. Quartzarenite of the greater White Rim erg contains detrital-zircon populations similar to those of the upper eolianite member. The Grenville and younger grains are interpreted as having an eastern Laurentian (Appalachian) source, whereas the ca. 1.5 Ga grains probably had an ultimate source in Baltica. Sediment-transport directions indicate that zircon grains not directly attributable to local basement of the Ancestral Rocky Mountains, including grains with a likely Baltica source, were transported to the western shoreline of Laurentia by transcontinental fluvial systems and then southeastward to their depositional site at the erg margin in salt-withdrawal minibasins.

The northern Flinders Ranges and eastern Willouran Ranges, South Australia, expose Neoproterozoic salt diapirs, salt sheets, and associated growth strata that provide a natural laboratory for testing and refining models of allochthonous salt initiation and emplacement. The diapiric Callanna Group (∼850–800 Ma) comprises a lithologically diverse assemblage of brecciated rocks that were originally interbedded with evaporites that are now absent. Using stereonet analysis to derive three-dimensional information from two-dimensional outcrops of stratal geometries flanking salt diapirs and beneath salt sheets, we evaluate 10 examples of the transition from steep diapirs to salt sheets, 3 of ramp-to-flat geometries, and 2 of flat-to-ramp transitions. Stratal geometries adjacent to feeder diapirs range from a minibasin-scale megaflap to halokinetic drape folds to high-angle truncations and appear to have no relationship to subsequent allochthonous salt development. In all cases, the transition from steep diapirs to salt sheets is abrupt and involved piston-like breakthrough of thin roof strata, which permitted salt to flow laterally. We suggest two models to explain the transition from steep diapirs to subhorizontal salt: (1) salt-top breakout, where salt rise occurs inboard of the salt flank, thereby preserving part of the roof strata beneath the sheet; and (2) salt-edge breakout, where rise occurs at the edge of the diapir with no roof preservation. Lateral emplacement of salt sheets is dependent on the interplay between the rate of salt supply to the front of the sheet and the sediment-accumulation rate. When the ratio of salt-supply rate to sediment-accumulation rate is high to moderate, thrust advance produces base-salt flats and truncation ramps, respectively. Halokinetic folds are absent because the thrust emerges at the base of the sea-floor scarp and mass-transport complexes are rare as a result of relatively low scarp relief. If the ratio is low, pinned inflation leads to drape folding of the top salt and cover into a fold ramp, with occasional slumping of the sheet and its roof and further breakout on thrust or reverse faults. In the shallow-water depositional environments of South Australia, lateral emplacement of salt sheets occurred through some combination of thrust advance, extrusive advance, and open-toed advance, with no evidence for subsalt thrust imbricates, shear zones, or continuous rubble zones. In deep-water environments, such as the northern Gulf of Mexico, thrust imbricates and rubble zones, which represent slumped carapace, are more common. The presence of slumped carapace is caused primarily by higher topographic relief related to thicker hemipelagic roofs, a lack of dissolution, and gravity-driven transport of overburden strata to the toes of large canopies.

Laser ablation-multi collector-inductively coupled mass spectrometry U-Pb geochronology, detailed field mapping and stratigraphic data offer improved insights into the timing and style of Laramide deformation and basin development in the Little Hatchet Mountains, southwestern New Mexico, USA, a key locality in the ‘southern Laramide province.’ The Laramide synorogenic section in the northern Little Hatchet Mountains comprises upper Campanian to Maastrichtian strata consisting of the Ringbone and Skunk Ranch formations, with a preserved maximum thickness of >2400 m, and the correlative Hidalgo Formation with a total thickness >1700 m. The Ringbone Formation and superjacent Skunk Ranch Formation are each generally composed of (1) a basal conglomerate member; (2) a middle member consisting of lacustrine shale, limestone, sandstone, and interbedded ash-fall tuffs; and (3) an upper sandstone and conglomerate member. Basaltic andesite flows are intercalated with the upper member of the Ringbone Formation and the middle member of the Skunk Ranch Formation. The Hidalgo Formation, which crops out in the northern part of the range, is dominantly composed of basaltic andesite breccias and flows equivalent to those of the Ringbone and Skunk Ranch formations. The Laramide section was deposited in an intermontane basin partitioned across intrabasinal thrust structures, which controlled growth-stratal development. U-Pb zircon ages from five tuffs indicate that the age range of the Laramide sedimentary succession is ca. 75– 70 Ma. U-Pb detrital-zircon age data (n = 356 analyses) from the Ringbone Formation and a Lower Cretaceous unit indicate sediment contribution from uplifted Lower and Upper Cretaceous rocks adjacent to the basin and the contemporary Tarahumara magmatic arc in nearby northern Sonora, Mexico. The new ages, combined with published data, indicate that uplift, basin development, and magmatism in the region proceeded diachronously northeastwards as the subducting Farallon slab flattened under northern Mexico and southern New Mexico from Campanian to Palaeogene time.

The Upper Cretaceous (lower Campanian) Drip Tank Member of the Straight Cliffs Formation in the Grand Staircase region of southern Utah is an upward-coarsening, sandstone-rich, low-sinuosity fluvial deposit in the Cordilleran foreland basin. The Drip Tank Member thins from 75 m to 30 m eastward across the basin foredeep, approximately parallel to its dominant eastward sediment-dispersal direction, and thins southward along the foredeep to as little as 17 m near its southern outcrop extent along modern cliff lines. It overlies and underlies mudstone-rich fluvial strata of the John Henry Member of the Straight Cliffs Formation and lower member of the Wahweap Formation, respectively, both of which were deposited by northeast-flowing rivers. The John Henry–Drip Tank contact lies in an interfingering, progradational stratigraphic transition from medium-grained lenticular sandstone bodies to tabular coarse-grained amalgamated sandstone bodies. The contact with the overlying Wahweap Formation is locally a prominent surface of erosion or sediment reworking. Sandstone petrography and detrital-zircon age populations of the strata indicate detrital sources in basement south of the foreland basin, thrust sheets to the west, and magmatic arc rocks to the southwest. The uppermost part of the John Henry Member contains as much as 10% feldspar and abundant ∼ 1.84–1.60 Ga detrital zircons derived from Yavapai–Mazatzal basement rocks in the Mogollon Highlands. The Drip Tank Member ranges from quartzarenite to chert-bearing sublitharenite with Grenville (∼ 1.2–1.1 Ga), Neoproterozoic and early Paleozoic detrital zircons derived from Proterozoic through Jurassic strata exposed in the Sevier orogenic belt. Lower member Wahweap litharenites contain abundant thrust-belt-derived detrital carbonate grains absent from compositionally mature Drip Tank sandstones, as well as a broad range of zircon ages. The Drip Tank Member constitutes deposits of a sand-rich, fluvial megafan, or distributive fluvial system, that displaced a subjacent, but partly time-equivalent axial-fluvial system eastward as the megafan, driven in part by seasonally high discharge fed by monsoonal precipitation, prograded across the basin foredeep. A thick, amalgamated fan-axis succession present in northern exposures contrasts with a thinner fan-flank succession in southern localities. Tabular sixth–order lithosomes, each containing channels on the order of 7 m deep, define three individual fluvial fans or fan lobes in the megafan system. Younger Wahweap fluvial channels eroded uppermost Drip Tank deposits of the fan axis and fan flank. Transverse fan progradation across the foredeep recorded falling accommodation/sediment supply in an aggradational to progradational systems tract. Erosion and reworking of the upper fan surface record decreased accommodation, sediment bypass, and erosion prior to reoccupation of the foredeep by the Wahweap axial-fluvial system. The upper contact of the Drip Tank Member is thus the primary sequence boundary in this multi-component fluvial system, and the lower Wahweap represents transitional systems-tract deposits accumulated as accommodation/sediment supply increased.

Allochthonous salt structures and associated primary and secondary minibasins are exposed in Neoproterozoic strata of the eastern Willouran Ranges, South Australia. Detailed geologic mapping using high-quality airborne hyperspectral remote-sensing data and satellite imagery, combined with a qualitative structural restoration, are used to elucidate the evolution of this complex, long-lived (>250 Myr) salt system. Field observations and interpretations at a resolution unobtainable from seismic or well data provide a means to test published models of allochthonous salt emplacement and associated salt-sediment interaction derived from subsurface data in the northern Gulf of Mexico. Salt diapirs and sheets are represented by megabreccias of nonevaporite lithologies that were originally interbedded with evaporites that have been dissolved and/or altered. Passive diapirism began shortly after deposition of the Callanna Group layered evaporite sequence. A primary basin containing an expulsion-rollover structure and megaflap is flanked by two vertical diapirs. Salt flowed laterally from the diapirs to form a complex, multi-level canopy, now partly welded, containing an encapsulated minibasin and capped by suprasalt basins. Salt and minibasin geometries were modified during the Late Cambrian–Ordovician Delamerian Orogeny (ca. 500 Ma). Small-scale structures such as subsalt shear zones, fractured or mixed ‘rubble zones’ and thrust imbricates are absent beneath allochthonous salt and welds in the eastern Willouran Ranges. Instead, either undeformed strata or halokinetic drape folds that include preserved diapir roof strata are found directly below the transition from steep diapirs to salt sheets. Allochthonous salt first broke through the diapir roofs and then flowed laterally, resulting in variable preservation of the subsalt drape folds. Lateral salt emplacement was presumably on roof-edge thrusts or, because of the shallow depositional environment, via open-toed advance or extrusive advance, but without associated subsalt deformation.

U-Pb ages of ignimbrites and detrital-zircon analyses from Middle Jurassic through lowermost Cretaceous strata in northeastern Durango, Mexico, indicate the age of local volcanism and the age range, respectively, of the Jurassic continental-margin arc in north-central Mexico, where it is termed the Nazas arc. The type Nazas Formation along the Rio Nazas consists of red continental sandstone and siltstone, ignimbrites, and intermediate flows that provide an important record of the extensional Jurassic Nazas magmatic arc. Overlying shallow-marine sandstone and shale of Late Jurassic to earliest Cretaceous age represent deposits of younger extensional basins that are part of the Border rift system, which extended from southern Arizona to the Gulf of Mexico. The younger strata constitute volcanic litharenite and lithic arkose derived from the Jurassic volcanic rocks and from basement rocks of the Coahuila block to the north. Two ignimbrites in the upper part of the Nazas Formation have statistically indistinguishable ages of 170 ± 2 and 169 ± 2 Ma. The ages are consistent with their stratigraphic order and position above volcanic-lithic sandstone with a maximum depositional age of ca. 180–178 Ma calculated from detrital zircons. Six detrital-zircon age populations were defined from four sandstone samples ( n = 377 zircon grains) of the Nazas Formation and overlying La Casita and Carbonera Formations. The most prominent age clusters (≥10% of the entire grain population) have ranges ca. 1277–890 Ma (Grenville, 22% of total), ca. 486–310 Ma (early Paleozoic, 11%), and ca. 202–159 Ma (Jurassic, two populations constituting 54% of total grains). The Jurassic age cluster indicates that Nazas arc magmatism in the region took place during the Early and Middle Jurassic and ended by early Late Jurassic time. The Nazas Formation correlates with arc-related Middle Jurassic strata in Sonora, southern Arizona, and southeastern California that contain interbedded eolian sandstone derived from the Jurassic ergs of the Colorado Plateau; absence of interbedded eolianite in the Nazas Formation thus indicates that the outcrops of north-central Mexico were likely not translated to their present locations along a regional, Late Jurassic transcurrent fault system, as postulated by some workers. Detrital-zircon data from the Upper Jurassic and lowermost Cretaceous strata indicate that Jurassic volcanic rocks covered the Coahuila block, directly north of the study area, at the end of Middle Jurassic time. Sandstone composition and detrital-zircon ages record erosional unroofing of the Coahuila block, whereby removal of Lower and Middle Jurassic volcanic and volcaniclastic strata exposed Grenville, Pan-African, and peri-Gondwanan basement of the block during Late Jurassic time.

Combined U-Pb and (U-Th)/He ages on a small sample set of Cretaceous foreland-basin sandstone from a transect of the fold-thrust belt in east-central Mexico reveal correspondence between episodes of thrust-belt exhumation with previously postulated deformational events and with at least one wedge of synorogenic sediment in the adjacent Tampico-Misantla basin. Detrital zircon U-Pb ages, sandstone petrography and multidimensional scaling analysis of the Cenomanian-Turonian Mineral de Pozos sandstone, the Coniacian Soyatal and Campanian San Felipe formations, and the Paleocene Chicontepec Formation indicate sediment sources in the Mexican Cordilleran magmatic arc of western Mexico, the accreted Guerrero arc terrane, and Mesozoic sedimentary rocks of central and western Mexico. (U-Th)/He cooling ages define into three age clusters: (1) ~136-120 Ma, (2) ~99-80 Ma, and (3) ~66-56 Ma. Cooling ages are younger toward the transect's western part, which represents the interior part of the fold-thrust belt. Dominant Early Cretaceous cooling ages in the San Felipe Formation indicate lack of, or partial, resetting of the He system. Late Cretaceous cooling ages are dominant in the Soyatal Formation and are partially equivalent to their maximum depositional age (88 ± 1 Ma), suggesting derivation of grains from adjacent rapidly exhumed thrust sheets. Alternatively, these grains were partial reset. Youngest cooling ages dominate the Mineral de Pozos sandstone samples, indicating Paleocene exhumation and erosion of interior thrust sheets. The Paleocene exhumation event is equivalent to stratal ages of the lower part of the Chicontepec Formation, and sandstone composition of that unit indicates dominant sediment sources in carbonate rocks of the frontal part of the fold-thrust belt. Combined cooling ages and sandstone petrography thus indicate coeval exhumation of the entire width of the orogen in the Paleogene, rather than out-of-sequence thrust-sheet uplift and exhumation of only the interior part of the thrust wedge. Orogen-wide exhumation is corroborated by a previously published early Paleocene illite 40Ar/39Ar age of 64 ± 2 Ma for thrust deformation at the eastern flank of the Valles-San Luis Potosi carbonate platform, which formed the latest Cretaceous-Paleocene boundary between the fold-thrust belt and foreland basin in which the Chicontepec Formation was deposited.

New stratigraphic and petrographic data and zircon U–Pb geochronology from sandstones and volcanic rocks in the states of Queretaro and Guanajuato in central Mexico indicate an important provenance change between Late Triassic and latest Jurassic–Early Cretaceous time. The Upper Triassic El Chilar Complex consists of pervasively deformed, deep-marine olistostromes, and debris-flow deposits of arkosic and subarkosic composition. Detrital-zircon populations range from latest Palaeoproterozoic (1.65 Ga) to Middle Triassic (240 Ma), all predating the depositional age of the strata. The detrital-zircon populations are similar to those previously reported from turbidites of the Potosi fan complex of north-central Mexico and interpreted as derived from Grenville and Pan-African (Maya block) basement and Permo-Triassic arc of continental Mexico directly to the east of the basin. A single sample with a dominant Proterozoic population at ∼1.65–1.30 Ga was likely derived either from the Rio Negro-Juruena province of...

LA-ICPMS U–Pb ages of individual zircon crystals from reworked ash-fall tuff beds in lacustrine strata of the Skunk Ranch Formation, a synorogenic unit deposited in a Laramide intermontane basin in the Little Hatchet Mountains, southwestern New Mexico, indicate an early Maastrichtian depositional age of 71–70 Ma. The dated beds are equivalent to nearby growth strata that are partially cut by, and folded over, a Laramide reverse fault. The strata thus record final displacement on the reverse fault and indicate an early Maastrichtian age for fault offset. The Skunk Ranch Formation was previously interpreted as Eocene in age and inferred to record the second event in a two-stage Laramide deformational history in the mountain range. In addition to significantly condensing the age range of the Laramide section and clarifying stratigraphic correlation in the Little Hatchet Mountains, the new ages of the formation also indicate that Laramide deformation in the range was likely restricted to a single Late Cretaceous episode.

International audience; Paleoaltimetric studies have characterized in detail the relationship between carbonate oxygen isotope ratios (d18Oc) and elevation in orogens with simple, single-moisture-source hydrological systems, and applied this relationship to ancient continental carbonates to provide constraints on their past elevation. However, mixing of different atmospheric moisture sources in low-elevation orogens should affect d18Oc values, but this effect has not yet been confirmed unequivocally. In the American Southwest, summer monsoonal moisture, sourced in the Equatorial Pacific and the Gulf of Mexico, and winter moisture, sourced in the East Pacific, both contribute to annual rainfall. We present stable isotope results from Quaternary carbonates within the American Southwest to characterize the regional d18Oc-elevation relationship. We then provide stable isotope results from local Eocene carbonates to reconstruct late Laramide paleoelevations. The Quaternary d18Oc-elevation relationship in the American Southwest is not as straightforward as in more simple hydrological systems. d18Oc changes with altitude are non-linear, scattered, and display an apparent isotopic lapse rate inversion above 1200 m of elevation. We speculate that decreasing surface temperatures at high altitudes limit the duration of carbonate growth to the summer months, biasing d18Oc values toward higher values typical of the summer monsoon and leading to lapse rate inversion. d18Oc-elevation relationships based on modern water isotope data or distillation models predict paleoelevations that range up to as much as 2 km higher than the modern elevations of 2000 to 2400 m for our late Eocene sites located at the southern edge of the Colorado Plateau. By contrast, our d18Oc-elevation relationship for the American Southwest yields lower paleoelevation estimates. These alternate estimates nonetheless suggest that significant elevation (at least ϳ1 km) had already been attained by the Eocene, but are also compatible with < 1 km of uplift by post-Laramide mechanisms. Our results show the limitations of standard d18Oc-elevation models in complex hydrological systems and suggest that similar mechanisms may have led to summer-biased paleoaltimetry estimates for the initial stages of other orogenies -in the American Southwest and elsewhere.