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Tectonic forcing of stratigraphic architecture is likely in foreland basins. Tectonic driving forces are increasingly being invoked to explain stratigraphic patterns in the Cretaceous Western Interior Seaway Basin of North America, yet the evidence is largely circumstantial, and the details of driving forces remain elusive. In this paper I show direct stratigraphic evidence for syndepositional growth of a structural arch with at least 50 m of relief during accumulation of the upper Turonian Ferron Sandstone in south-central Utah, United States. Progressive growth of the arch was superimposed on several high-frequency stratal cycles that were driven by a more regionally extensive process (geodynamic or eustatic) and that produced laterally amalgamated sandstone bodies in a depositional strike-parallel orientation (north-south). All of this stratigraphy was then truncated by a more or less planar erosion surface (sequence boundary) that can be traced physically over at least 67 km north-south. This surface was later tilted northward, such that the upper member of the Ferron Sandstone thins progressively southward from 50 to 10 m over 67 km. The facies juxtapositions revealed by the Ferron Sandstone could, if seen in exposure of limited lateral extent, be wrongly interpreted as recording regionally extensive relative sea-level drops and potentially used in error as evidence for substantial eustatic sea-level falls during the Turonian. The folding and tilting documented in this study can be clearly attributed to geodynamic and/or tectonic driving forces, likely related to migration of a forebulge. [ABSTRACT FROM AUTHOR]

Inconsistencies between regional seismicity and block tectonic models, the recent recognition of the Bering plate, and the availability of global positioning system data motivated a large-scale kinematic analysis of Alaska and western Canada. We provide a synoptic view of the neotectonics of the region through kinematic modeling of the longterm strain rate and velocity field constrained by geologic and geophysical observations. Our results provide evidence that a wide zone of diffuse deformation defines the boundaries between the North America, Pacific, and Bering plates, and that the relative motion between these plates may be the source for much of the modern deformation. [ABSTRACT FROM AUTHOR]

A combination of biostratigraphic markers (ammonites, inoceramid bivalves) and carbon isotope excursions is employed to establish a high-resolution correlation between the middle to late Cenomanian successions of the Western Interior Basin (USA) and the Anglo-Paris Basin (southern UK). Sequences identified from sedimentologic criteria in the Pueblo succession and elsewhere in the Western Interior Basin are shown to coincide precisely with globally recognized sea-level events and were therefore under eustatic control. This evidence refutes arguments that Cenomanian sequences in the Western Interior Basin were formed by local tectonic events. The interaction of longer-term tectonic movements and more rapid eustatic change may have simply enhanced the amount of erosion associated with sequence boundaries. A crossplot of radiometric ages derived from North American bentonites against an orbitally tuned time scale developed in the Anglo-Paris Basin provides support for the argument that the sequences were controlled by the 405-k.y.-long eccentricity cycle. [ABSTRACT FROM AUTHOR]

The North Pacific Rim is a tectonically active plate boundary zone, parts of which may be characterized as a laterally moving orogenic stream. Crustal blocks are transported along large-magnitude strike-slip faults in western Canada and central Alaska toward the Aleutian-Bering Sea subduction zones. Throughout much of the Cenozoic, at and west of its Alaskan nexus, the North Pacific Rim orogenic Stream (NPRS) has undergone tectonic escape. During transport, relatively rigid blocks acquired paleomagnetic rotations and fault-juxtaposed boundaries while flowing differentially through the system, from their original point of accretion and entrainment toward the free face defined by the Aleutian-Bering Sea subduction zones. Built upon classical terrane tectonics, the NPRS model provides a new framework with which to view the mobilistic nature of the western North American plate boundary zone. [ABSTRACT FROM AUTHOR]

New 40Ar/39Ar analyses from a transect across the major tectonic units of the southwest Amazon craton document the heterogeneous effects of the late Mesoproterozoic collision with the Grenville margin of North America. Basement rocks of the Amazon and adjacent Paragua cratons mostly preserve pre-Grenvillian ages (older than 1.3 Ga). Localized isotopic age resetting at 1.18–1.12 Ga is caused by Grenvillian activation of widespread, sinistral strike-slip shear zones in the Amazon basement. In the Nova Brasilândia belt between these two cratons, new 40Ar/39Ar data record cooling through 920 Ma after the granulite facies deformation of this suture zone. Regional cooling rates calculated from compiled U/Pb, 40Ar/39Ar, and Rb/Sr thermochronologic data are used to establish post-Grenvillian exhumation patterns for the southwest Amazon and the North American belt. Paleodepths calculated for 1.0 Ga along a transect of the restored 1300-km-wide belt vary from uniformly deep levels (15–30 km) exposed in North America to shallower levels (5–15 km) observed in the southwest Amazon. We interpret this difference as reflective of a change in tectonic architecture, i.e., thrust-dominated deformation in Laurentia versus strike-slip dominated deformation in the Amazon, with a commensurate variation in crustal thickness. This interpretation explains the widespread preservation of both pre-Grenvillian ages and collisional ages from the Amazon craton, in contrast with the more homogeneous array of cooling ages from the North American Grenville Province marking the postorogenic extensional collapse of an overthickened crust. The asymmetrical orogenic architecture from the reconstructed Grenville belt mirrors cross sections proposed for modern orogenic belts where deep-crustal rocks are not yet exposed. [ABSTRACT FROM AUTHOR]

This paper addresses one part of an outstanding tectonic problem regarding the nature of the plate boundary between Eurasia and North America in northeastern Russia. In this region, the northwestern corner of the Pacific plate interacts either simply with the North American plate, or more complexly with one or more blocks independent of North America. North of this corner, evidence of uplift, tilting, and convergence contradicts the prevailing, simpler model. On the Ozernoi Peninsula, ∼150 km north of the subducting Pacific plate, marine terraces indicate uplift rates of 0.1 to 0.3 mm/yr, with faster rates to the east. Historic and paleoseismic records provide evidence for recurring tsunamigenic, thrust earthquakes offshore of the Ozernoi Peninsula, the most recent a Mw 7.7 earthquake in 1969. A multiplate model where an eastward-moving Okhotsk block, including most of Kamchatka, is converging with a clockwise-rotating Bering block better explains these observations than does the unbroken North American plate model. [ABSTRACT FROM AUTHOR]

Summer monsoonal rains (the southwest monsoon) are an important source of moisture for parts of the southwestern United States and northern Mexico. Improved documentation of the variability in the southwest monsoon is needed because changes in the amount and seasonal distribution of precipitation in this semiarid region of North America influence overall water supply and fire severity. Comparison of abundance variations in the planktic foraminifer Globigerinoides sacculifer in marine cores from the western and northern Gulf of Mexico with terrestrial proxy records of precipitation (tree-ring width and packrat-midden occurrences) from the southwestern United States indicate that G. sacculifer abundance is a proxy for the southwest monsoon on millennial and submillennial time scales. The marine record confirms the presence of a severe multicentury drought centered ca. 1600 calendar (cal.) yr B.P. as well as several multidecadal droughts that have been identified in a long tree-ring record spanning the past 2000 cal. yr from west-central New Mexico. The marine record further suggests that monsoon circulation, and thus summer rainfall, was enhanced in the middle Holocene (ca. 6500–4500 14C yr B.P.; ca. 6980–4710 cal. yr B.P.). The marine proxy provides the potential for constructing a highly resolved, well-dated, and continuous history of the southwest monsoon for the entire Holocene. [ABSTRACT FROM AUTHOR]

Investigates the veracity of the Baja British Columbia hypothesis which holds that a large segment of northern North America used to be alongside California during the middle Cretaceous period. Provenance of zircons in Cretaceous sedimentary basins of Baja; Changes in the detrital-zircon provenance in the Nanaimo Group; Northward tectonic transport of the Baja B.C. terranes.

Tests a method that enables dispersed ensialic terranes to be more precisely positioned along their original continental margins. Presentation of a case sample, Neoprotozoic Avalonian-Cadomian orogenic belt of North America and Western Europe; Tectonic setting; Comparison between the detrital age distribution and cratonic provinces.