Abstract The wide continental shelves of Atlantic Canada are characterized by a series of banks separated by transverse troughs. These shelves have been imprinted by repeated Quaternary glaciations, so that fluvial valleys have been deepened into fjords and shelf-crossing troughs, and a suite of glacigenic sediments has been deposited. In shallow areas the seafloor is shaped by waves and currents, including the strong tidal currents of the macrotidal Bay of Fundy. Glacigenic sediments have been reworked by modern processes to yield thick muds in basins, and thinner deposits of sand and gravel on wave-dominated banks and the littoral zone. As a result of a cold climate and the Labrador Current, seasonal sea ice occurs to varying degrees across the region, and iceberg impact continues on much of the Newfoundland and Labrador shelves. For the purpose of description, we divide Atlantic continental shelves into four regions and focus on advances in understanding over the past several decades relating to: (1) processes on upper continental slopes; (2) glacial history in the last glacial cycle; (3) glacial land systems; (4) geographical changes caused by glacio-isostasy; and (5) sediment mobility on the offshore banks. We conclude with a brief overview of the biota.

Abstract The Jiao-Liao massif is located in the hanging wall of the north-dipping Dabie–Sulu suture zone and is an important part of the Eastern Block of the North China Craton. Several important tectonic models for the tectonic evolution of Eastern Asia rely on critical information from the Jiao-Liao massif. This paper combines new sensitive high-resolution ion microprobe (SHRIMP) U–Pb zircon ages of the Dandong Granite in the southern Liaoning Province, China, with extensive field data for the eastern North China Craton, including the Bohai Bay Basin. Combined with other recent SHRIMP dating, we use this information to summarize the Mesozoic tectonic reactivation and evolutionary processes of the Jiao-Liao massif of the Eastern Block of the North China Craton. In this study we identify a c . 160 Ma episode of partial melting of Palaeoproterozoic plutons in the Jiao-Liao massif. Cathode luminescence and backscatter electron imagery reveal c . 167–157 Ma magmatic euhedral single zircons and magmatic zircon rims surrounding c . 2100 Ma cores in the Dandong Granites near the Liaonan Neoarchaean terrane. This partial melting is probably related to in situ remelting of ancient lower continental material, mostly the North China Craton. The Dandong plutons are aligned in a NE–SW direction and are extensively deformed by subhorizontal ductile thrust-related shearing and subsequent NNE–SSW trending folds. Here, we show that for the Dandong area the first deformation occurred between 195 and 193 Ma, based on K–Ar and 40 Ar/ 39 Ar ages of muscovites from east–west-trending shear zones on the Liaodong Peninsula. Based on the field relationships between the plutons and structural fabrics, a range from 153 to 145 Ma is defined as the duration of the second deformation in the Dandong Granites. The third deformation is marked by the formation of NNE–SSW strike-slip faults between 135 and 95 Ma. This deduced age range is similar to an 40 Ar/ 39 Ar age range of 128–132 Ma of initial sinistral strike-slip faulting of the Tan-Lu fault in Anhui Province and to a biotite cooling age of 100±2.3 Ma of the Yilan–Yitong segment of the Tan-Lu fault in the Jilin Province. These faults are transtensive and controlled the formation of pull-apart basins. However, during the third deformation, some metamorphic core complexes in Eastern China formed in the overlapping area between the large-scale sinistral faults. Our SHRIMP data also indicate that the Liaodong basement and its Early Mesozoic magmatism are similar to the Jiaodong basement and its Mesozoic magmatism. Therefore, the Early Mesozoic evolution of the Liaodong area, similar to that of the Jiaodong area, was also closely related to the Sulu orogen in the Early Mesozoic and to the Pacific subduction throughout the Mesozoic.

Abstract To better understand Mesozoic tectonic transition processes in Eastern China, this paper offers a comparison of Mesozoic basin-fill records around the eastern North China Craton. These Mesozoic basins have similar evolutionary features: inception since the Early Jurassic; basin-fills recording a tectonic evolution from compression and lithospheric thickening before Late Jurassic and/or Early Cretaceous time to intracontinental stretching and lithospheric thinning from Early Cretaceous time; tectonic transition during the late Jurassic with a time lag in shallow crust relative to deep lithosphere. However, basin-fill records reflect two distinct basin systems occurring in the southern and northern margins of the eastern North China Craton. First, varied volcanic rocks including mafic, intermediate–mafic and intermediate–felsic assemblages occur in the Yanshan–Liaoxi basins on the northern margin of the eastern North China Craton from the Early Jurassic to Cretaceous; in contrast, limited calc-alkaline volcanic rocks filled the Hefei basin system on the southern margin of the eastern North China Craton during the Late Jurassic–Early Cretaceous. Second, late Mesozoic lithospheric thinning began at about 163 Ma and 149 Ma in the northern and southern margins, respectively, culminating in basin-scale extensional events at about 145 Ma and 132 Ma, respectively. Third, coarse clastic sediments developed in the northern and southern basins during the tectonic transition phase reflect fluvial and alluvial systems, respectively, indicating greater topographic relief in the southern area than in the northern area. Fourth, Mesozoic depocentre migration was complicated in the Yanshan–Liaoxi basin but should a south to north trend in the Hefei basin system. Mesozoic basin-fill depositional and volcanic records in the southern margin of the eastern North China Craton were dominantly controlled by early Mesozoic deep subduction of the Yangtze block and subsequent post-orogenic extension of the Dabie Mountains. On the other hand, basin-fill evolution along the northern margin of the North China Craton was principally controlled by intensive crust–mantle and/or asthenosphere–lithosphere interactions, with regional transition from contractile to extensional strain during Mesozoic time. This study suggests that the late Mesozoic tectonic transition was first induced by crust–mantle interactions in the northern North China Craton and then it extended southwards. Late Mesozoic lithospheric thinning and subsequent tectonic transition are a linked systematic geodynamic process that has no direct relation to the Triassic plate convergence events around the North China Craton.

The Main Seam in the Greymouth coalfield (Upper Cretaceous Paparoa Coal Measures) is exceptionally thick (>25m) and occurs in three locally thick pods, termed north, middle, and south. These pods are separated by areas of thin or absent (“barren”) coal. The barren zone between the north and middle coal pods is characterized by a sequence that is 60 m thick comprising relatively thin (1–2.5 m thick) but laterally extensive (up to 500 m) sandstone units. The orientation of both the thin and the barren coal zones is approximately east to west. This is coincident with basement fault systems that occur in the region. Therefore, the stacked nature of the sandstones within this narrow zone may be a result of differential subsidence across basement fault blocks. The Main Seam, like the sandstone units in the “barren” zone, is inferred to represent a stacked sequence. Two zones of thin partings (<20 cm in thickness) occur in the coal, and even where these zones do not occur, an interval of abundant vitrain bands is present. As has been suggested for other coal beds, intervals with high vitrain content may represent a demarcation between different paleomire systems, or, as in the case of the Main Seam, periods where the paleomire was rejuvenated with plant nutrients, allowing continued aggradation of the mire. The low ash yield (<5% dry basis) indicates that the Main Seam was rarely affected by flood incursions. This may have been the result of both doming of the peat surface as well as restriction of the dominant sediment flow by syn-sedimentary faulting. Palynological analyses indicate that the Main Seam mire throughout most of its time was dominated by gymnosperms, particularly a relative of the Huron pine ( Lagarostrobus franklinii ). However, a distinct floral change to a Gleichenia -dominated mire occurs in the upper few meters of the Main Seam. This vegetation change may have resulted from basinwide environmental or climatic change. Gleichenia does not produce much biomass, and if it was the dominant mire plant it may not have been able to keep peat accumulation rates higher than subsidence. Whether the cause was a decrease in peat accumulation or a drying of mire, the result would have been lowering of the surface to a degree that flooding and final termination would be likely.