Abstract The Colorado River in the SW of the USA is one of Earth's few continental-scale rivers with an active margin delta. Deformation along this transform margin, as well as associated intra-plate strain, has resulted in significant changes in sediment routing from the continental interior and post-depositional translation of older deltaic units. The oldest candidate deposits, fluvial sandstones of the Eocene Sespe Group, are now exposed in the Santa Monica Mountains, 300 km to the north of the Colorado River. Heavy mineral data from this basin indicate that sediment was sourced by a large river system, with some affinity to the early Pliocene Colorado River, but was unlikely to have been integrated across the Colorado Plateau. Sedimentological and mineralogical evidence from the earliest ( c. 5.3 Ma) unequivocal Colorado River-derived sediments in the Salton Trough provide evidence for a rapid transition from locally derived sedimentation. Lack of evidence for a precursor phase of suspended-load sediment suggests that drainage capture took place in a proximal position, favouring a ‘top-down’ process of lake spillover. Following drainage integration, significant changes in heavy mineral assemblages of fluvio-deltaic sediments, particularly evident from apatite–tourmaline and garnet–zircon indices, as well as U–Pb ages of detrital zircons, document the integration of the fluvial system to its present form and progressive incision of the Colorado Plateau from the Miocene to the present.

Abstract The processes that govern formation and development of cratonic basins are poorly understood, both individually and as a class. The cratonic Silurian–Jurassic Parnaíba Basin in NE Brazil is less well-studied than North American examples such as Williston, Illinois and Michigan but offers an opportunity to study stratal architecture both in outcrop and the subsurface. Published stratigraphic compilations emphasize basin-wide unconformities separating layer-cake, basin-wide packages; analysis of geological maps indicates this interpretation is over-simplified, with at least 12 local unconformities, concentrated along the SW basin margin. Comparison of basin-margin and intrabasinal well-correlation panels shows that unconformities are more common in marginal areas, so the current exposure margins may have some validity as near-original margins. Palaeocurrents suggest a consistent SW–NE transport direction for the Serra Grande and lower Canindé groups. Supporting heavy mineral analysis from Silurian–Carboniferous strata on the SW and NE basin margins show that assemblages are dominated by ultra-stable zircon, tourmaline and rutile with minor amounts of staurolite, especially in the SW and older units. Tourmaline varietal results are remarkably consistent across the basin. U–Pb age spectra from detrital zircons are dominated by Neoproterozoic grains, with subsidiary Meso-Paleoproterozoic provenance. We infer that the source terrane was a medium-grade regionally metamorphosed mica schist, probably the Araguaia Fold Belt. These results are indicative of a large sediment routing system feeding material across an evolving crustal sag, analogous to observations from North American cratonic basins; this suggests that cratonic basins may not have strongly shaped or controlled the routing system. Supplementary material: High-resolution geological map of the Parnaíba Basin as a PDF. This shows all of the basement units and small details of the stratigraphic relationships between different basin-fill formations. This map is derived from the ArcGIS files of CPRM (2004) . Supplementary material available at https://doi.org/10.6084/m9.figshare.c.4183472

Abstract The intracratonic Paleozoic Parnaíba Basin, NE Brazil covers c . 600 000 km 2 . Lithostratigraphic, mineralogical and geochemical approaches were used to deduce the changing environments of deposition of the Parnaíba Basin based on 150, mostly argillite, samples (Silurian–earliest Triassic). The results indicate that brackish conditions and mixed kerogen sources were important and that the palaeowater depth and sources of meteoric water varied from west to east. The chemical index of alteration results, together with other elemental and mineralogical data, indicate that the western margin was humid until the end of the Carboniferous and then became arid, whereas the eastern margin showed the reverse pattern. This supports observations of major stratigraphic differences between the two margins. There were also major variations in the palaeoredox and palaeosalinity conditions (oxic and fresh to brackish water systems in the east v. suboxic to dysoxic and saline water systems in the west). The clay mineral assemblages are characteristically dominated by kaolinite, which is considered to be inherited from weathering horizons developed in silicic granitic terranes. Regional palaeoclimate reconstructions were carried out in the Parnaíba Basin by linking GPlates software with the South America plate motion model (northwards drift during the Paleozoic coupled with a latest Paleozoic rotation phase) and with the regional database of information on the location, formation name and original references for each locality. Supplementary material: Chemical composition data and geographical coordinates from the 177 outcrops investigated as part of this study: a detailed description of the geochemical and mineralogical analyses with calculation of the CIA value and the GPlates Markup Language File (Animation 1). Supplementary material available online at https://doi.org/10.6084/m9.figshare.c.4100348

Abstract This paper uses an extensive dataset from more than 200 samples to provide a comprehensive source-to-sink analysis of the Amur River and its delta in the Russian Far East. The majority of sand-sized sediment in the Amur River and its former delta comes from upstream of the Lesser Khingan Ridge, shown by uniformity of sediment composition in the lower 1700 km of the river. Stable mineral ratios, U–Pb age spectra and garnet geochemistry show little stratigraphic provenance-specific variation in the Neogene delta. This renders Miocene–Pliocene drainage capture models unlikely. The onset of uplift in the delta is marked by a decrease in the apatite–tourmaline index (ATi) in Upper Pliocene offshore well samples, caused by dissolution of apatite as sediments were uplifted and eroded onshore Sakhalin. These wells also show variable ATi and garnet–zircon index (GZi) values in Lower Miocene samples, which could potentially be used for stratigraphic correlation. A positive correlation between GZi values and distance from the river mouth is attributed to hydrodynamic sorting across the delta system. This has negative implications for the use of this stable mineral index and others of a similar hydraulic equivalence as regional correlation tools on a basin scale (>100 km). Supplementary material: Heavy mineral data, petrographic data, geochronometric data, sample locations available at www.geolsoc.org.uk/SUP18643 .

Abstract During the Mesozoic, the present-day Antarctic Peninsula was the site of an active volcanic arc related to the eastwards subduc-tion of proto-Pacific oceanic crust. Alexander Island is the largest of the many islands that lie on the western (forearc) side of the Antarctic Peninsula. The island is comprised of a greenschist facies, accretionary prism complex (LeMay Group), unconformably overlain and faulted against the forearc sedimentary deposits of the Fossil Bluff Group. The Fossil Bluff Group ranges in age from Middle Jurassic to latest Early Cretaceous and has a stratigraphic thickness of 7 km (4.4 mi). Aalonian-Tithonian clastic units are derived from the accretionary complex, recording the transition from trench-slope to forearc basin sedimentation. The upper formations represent a large-scale, shallowing-upwards cycle of Kimmeridgian to Albian age, with a volcanic arc provenance. The Himalia Ridge Formation is a 2.2 km (1.4 mi)-thick sequence of Late Jurassic to Early Cretaceous conglomerates, immature arkosic sandstones, and mudstones, derived from an andesitic volcanic arc, and deposited in a north-south elongate forearc basin. At the type locality (Himalia Ridge on Ganymede Heights), the formation was deposited as a series of migrating, conglomerate-filled, innet-fan channels and associated overbank-crevasse-splay sheet sands, thin-bedded levees, and interchannel mudstones flanking the basin matgin. The basin was inverted within a strike-slip regime in the middle Cretaceous, and the sttata deformed into a broad monocline with associated thrusting. At Himalia Ridge, the formation is exposed as a continuous section dipping southeast at about 30°. The upper part of the formation is repeated

Cretaceous sediments in the Antarctic have yielded diverse fossil floras, and a few occurrences of thin coal have been described. Their presence illustrates that the climate was favorable for plant growth, despite Antarctica’s polar position, and there was good potential for organic matter accumulation. We suggest that there is no a priori reason why Cretaceous coals should not have formed in Antarctica. It is probable that they have not been found because exposed upper Mesozoic sedimentary basins are in the Antarctic Peninsula region of West Antarctica, and were intimately related to a volcanic arc in Cretaceous times. High sedimentation rates in these active-margin basins probably led to clastic dilution of organic material. During the Cretaceous, coals were much more likely to have formed in basins along the East Antarctic passive margin.

Abstract The Antarctic Peninsula is a relatively accessible area of the continent, a fact which has stimulated interest in its hydrocarbon potential. This chapter uses known stratigraphic information to provide general constraints on the hydrocarbon potential of the Mesozoic basins of the Antarctic Peninsula. The peninsula lies on a medium-sized block of continental crust. It is one of a mosaic of crustal blocks forming West Antarctica which underwent a complex tectonic evolution during Gondwana breakup. It was the site of an active volcanic arc above easterly subducting proto-Pacific ocean floor throughout the Mesozoic and part of the Cenozoic. As a result the exposed Mesozoic basins display a complex stratigraphy, reflecting local tectonic and volcanic events. No units can be correlated between any two basins, but there are a few general trends. Almost all basins are post-Oxfordian; their fill is entirely clastic, and largely derived from the Antarctic Peninsula volcanic arc. Most basins were affected by a period of arc expansion in Late Jurassic or Early Cretaceous times, which manifests itself as inputs of lava or coarse volcaniclastic sediment. Berriasian and older mudstones are generally finer-grained and darker than mudstones from post-Berriasian strata. Deformation is variable, but rarely penetrative. This stratigraphic information provides the basis for general constraints on the hydrocarbon potential. Organic geochemistry shows that Berriasian and older mudstones from the backarc region are the best potential oil source rocks; all other mudstones tend to be lean and gas-prone. Reservoir and seal facies tend to be better in deep marine (generally older) strata. Reservoir quality is generally poor due to breakdown of labile volcanic grains, but younger sandstones tend to be more quartz-rich. The only significant prospective basin is the Larsen Basin, east of the Antarctic Peninsula. Geological evidence suggests that the best plays would involve deep strata. The major problem in this basin is the very difficult access, even by Antarctic standards.