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.

The eastern Laurentian margin in northeastern North America is marked by promontories and embayments that are defined by northeast-striking rift zones offset by northwest-striking transform faults. The complete history of the northeastern margin, from the initiation of continental rifting to the onset of passive-margin thermal subsidence, is preserved in a dynamic stratigraphic succession and in anorogenic magmatic suites. Late Neoproterozoic–Early Cambrian clastic and volcanic deposits overlie ca. 1.0 Ga and older Laurentian basement and define multiphase continental extension that rifted Laurentia out of Rodinia, opening the Iapetus Ocean as well as the more marginal Humber Seaway. Continental extension is also expressed in a set of basement fault systems that extend into the craton perpendicular to the northeastern Laurentian margin. Lower Cambrian sandstones at the base of a transgressive passive-margin succession overlie synrift rocks and basement, defining the time of transition for the eastern Laurentian margin from an active rift to a passive-margin environment. The passive margin is expressed as a broad late Early Cambrian through early Middle Ordovician carbonate bank and associated offshelf facies. Synthesis of the available data reveals significant along-strike variations in the thickness, composition, age, and facies of important synrift and postrift stratigraphic successions between the northern Appalachian rift zones. These variations are consistent with models for low-angle detachment rift systems and allow for the resolution of the underlying basement architecture of the eastern Laurentian margin specific to low-angle detachments, including upper-plate margins, lower-plate margins, and transform faults that bound zones of oppositely dipping low-angle detachments.

Meguma, the most outboard northern Appalachian terrane, is characterized by Upper Neoproterozoic to Lower Ordovician turbiditic rocks that have an exposed thickness of more than 11 km. As a result of geological mapping, combined with petrological studies, the stratigraphy of these rocks has been redefined. The traditional twofold division into the meta-sandstone–dominated Goldenville Group and the overlying slate-dominated Halifax Group is retained, but the Chebogue Point shear zone divides these groups into western and southern stratigraphic packages containing different formations. In both packages, psammitic rocks are dominantly feldspathic wacke, and they have mineralogical compositions indicative of deposition in an active margin from a source dominated by quartz and plagioclase; rare conglomeratic units contain mainly psammitic clasts with some mafic through felsic volcanic clasts, and rare tonalite clasts. In the southern area, psammitic units tend to contain more quartz and grade to arenite. Although fine material increases in relative abundance, little change in provenance up section is indicated by petrography of psammitic rocks. Chemical compositions of 116 psammitic and pelitic samples from the western area and 471 from the larger southern area are consistent with the petrographic data. Their compositions are indicative of derivation from felsic to intermediate igneous material, and the depositional environment was probably in a rift along the Gond wanan margin. It is likely that Pan-African orogenic belts containing recycled sediments from older cratons were major contributors to the sediments, rather than sediments being derived directly from large ancient cratonic areas.

The Horton Group (late Famennian to Tournaisian) of Atlantic Canada provides an unusually complete record of Early Mississippian wetland biota. Best known for tetrapod fossils from “Romer's Gap,” this unit also contains numerous horizons with standing vegetation. The taphonomy and taxonomy of Horton Group fossil forests have remained enigmatic because of poor preservation, curious stump cast morphology, and failure to recognize the unusual sedimentary structures formed around standing plants. Four forested horizons within the Horton Group are preserved as cryptic casts and vegetation-induced sedimentary structures formed by the interaction of detrital sediment with in situ plants. Protostigmaria , the lobed base of the arborescent lycopsid Lepidodendropsis , occur as sandstone-filled casts attached to dense root masses. Mudstone-filled hollows formed when a partially entombed plant decayed, leaving a void that was later infilled by muddy sediment. A scratch semi-circle formed where a current bent a small plant, causing it to inscribe concentric grooves into the adjacent muddy substrate. Obstacle marks developed where flood waters excavated erosional scours into sandy sediment surrounding juvenile Lepidodendropsis . These cryptic lycopsid forests had considerably higher densities than their Pennsylvanian counterparts. Vegetation-induced sedimentary structures are abundant in Horton Group strata and could easily be misidentified as purely hydrodynamic or soft-sediment deformation structures without careful analysis. Recognition of these structures in early Paleozoic strata has great potential to expand our knowledge about the distribution of early land plants.