ABSTRACT Upper Triassic and Lower to Middle Jurassic strata in the Plomosas uplift of central Chihuahua accumulated in backarc and rift settings, respectively. The succession, as much as ~3250 m thick, consists of four stratigraphic units. The Cerro El Carrizalillo Formation (Carnian–Norian), a volcanic-lithic shallow-marine succession deposited in the (newly named) El Carrizalillo backarc basin, is characterized by predominantly Triassic detrital zircon ages. The overlying Plomosas Formation consists of three members: (1) the Cerro de Enmedio Member (Hettangian–Toarcian), a succession of conglomerate, siltstone, and shallow-marine carbonate strata deposited during the onset of extension in Chihuahua; (2) the Cerro Nevado Ignimbrite Member (176 ± 1 Ma; late Toarcian), a widespread ash-flow tuff; and (3) La Sofía Member (Aalenian–Callovian?), consisting of alluvial-fan conglomerate, fluvial sandstone, tidal sandstone and siltstone, and delta-plain red beds characterized by rapid facies changes, lithic compositions, and diverse Proterozoic, Paleozoic, and Triassic detrital zircon ages characteristic of a rift-basin setting. The extensional basin in which the Cerro de Enmedio and La Sofía members accumulated is termed the Plomosas basin. Improved age control provided by U-Pb maximum depositional ages from detrital zircon and U-Pb zircon analyses of the ignimbrite indicates that the Cerro El Carrizalillo Formation is partly correlative with the Chinle Formation of the Colorado Plateau, and the Plomosas Formation is equivalent to eolianites of the Glen Canyon and San Rafael Groups of the Colorado Plateau. Detrital zircon ages and sandstone textures are consistent with both proximal and distal sediment sources along the Laurentia-Gondwana suture and adjoining Grenville basement of Laurentia, including sources in northern Mexico and the composite Appalachian orogen. Although the depositional setting of the Cerro El Carrizalillo Formation was not connected to fluvial systems of the Chinle Formation, subsequent eolian transport of voluminous sediment to the overlying Cerro de Enmedio and La Sofía members from the Colorado Plateau ergs is suggested by the composition and texture of some sandstone, thick siltstone accumulations, and detrital zircon characteristics that broadly resemble those of the Colorado Plateau eolianites. Thick siltstone in the upper part of La Sofía Member is interpreted as deflated fine-grained sediment that was transported downwind from a time-equivalent erg to accumulate in shallow-marine and coastal-plain settings of the Plomosas basin.

Abstract The Triassic Fundy rift basin in Nova Scotia is a large (>70 km wide) half-graben filled with alluvial, lacustrine and aeolian deposits. A major lithospheric lineament, the Cobequid–Chedabucto Fault Zone (CCFZ), which forms the tip of the Newfoundland–Gibraltar Fault Zone, occurs within the Fundy Basin. The timing of early movement on this important fault zone is poorly constrained. We present data from the alluvial and aeolian units that crop out adjacent to the CCFZ in the Minas sub-basin to determine the initiation of fault movement. We use the onset of alluvial fan deposition to infer when the fault became sufficiently active to create the intrabasinal topography and document the influence of fault activity on the intrabasinal drainage. The occurrence and preservation of aeolian deposits immediately adjacent to the CCFZ and concomitant with alluvial fan development suggests a wind shadow effect associated with the fault-generated topography. The onset of alluvial fan deposition associated directly with the fault occurred during Norian times, following an earlier phase of sedimentation in the Fundy Basin, and records a potentially important phase of plate reorganization during early Atlantic rifting.

Abstract The Ørsted Dal Member of the Upper Triassic Fleming Fjord Formation in East Greenland is well known for its rich vertebrate fauna, represented by numerous specimens of both body and ichnofossils. In particular, the footprints of theropod dinosaurs have been described. Recently, an international expedition discovered several slabs with 100 small chirotheriid pes and manus imprints (pes length 4–4.5 cm) in siliciclastic deposits of this unit. They show strong similarities with Brachychirotherium , a characteristic Upper Triassic ichnogenus with a global distribution. A peculiar feature in the Fleming Fjord specimens is the lack of a fifth digit, even in more deeply impressed imprints. Therefore, the specimens are assigned here tentatively to cf. Brachychirotherium . Possibly, this characteristic is related to the extremely small size and early ontogenetic stage of the trackmaker. The record from Greenland is the first evidence of this morphotype from the Fleming Fjord Formation. Candidate trackmakers are crocodylian stem group archosaurs; however, a distinct correlation with known osteological taxa from this unit is not currently possible. While the occurrence of sauropodomorph plateosaurs in the bone record links the Greenland assemblage more closer to that from the Germanic Basin of central Europe, here the described footprints suggest a Pangaea-wide exchange. Supplementary material: Three-dimensional model of cf. Brachychirotherium pes–manus set (from MGUH 31233b) from the Upper Triassic Fleming Fjord Formation (Norian–Rhaetian) of East Greenland as pdf, ply and jpg files (3D model created by Oliver Wings; photographs taken by Jesper Milàn) is available at https://doi.org/10.6084/m9.figshare.c.2133546