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The scenery of Western Amazonia once consisted of fl uvial systems that originated on the Amazonian Craton and were directed towards the sub-Andean zone and the Caribbean. In the course of the Early Miocene these fl uvial systems were largely replaced by lakes, swamps, tidal channels and marginal marine embayments, forming a mega-wetland. In this chapter we will review the characteristics of this mega-wetland and its different phases of development. These aquatic environments hosted a diverse fauna whereas the shores of these systems were fringed by palm swamps, and a diverse rainforest occurred in the peripheral dry lands.

An updated and revised lithostratigraphic scheme is presented for the Cretaceous of North-East Greenland from Traill Ø in the south to Store Koldewey in the north. The Ryazanian to lower Maastrichtian succession is up to several kilometres thick and comprises four groups, 12 formations and 18 members. The groups record the tectonic evolution of the East Greenland depocentre on the western flank of the evolving proto-Atlantic seaway. The Wollaston Forland Group encompasses the uppermost Jurassic – lowermost Cretaceous rift-climax succession and contains the Lindemans Bugt and Palnatokes Bjerg Formations; two new members of the latter formation are erected from Store Koldewey. Post-rift Cretaceous strata are referred to the new Brorson Halvø Group and the Home Forland Group. The Brorson Halvø Group (uppermost Hauterivian – middle Albian) is dominated by slope and basinal mudstones of the new Stratumbjerg Formation but also includes fluvio-deltaic and shallow marine sandstones of the revised Steensby Bjerg Formation on northern Hold with Hope and submarine slope apron breccias and conglomerates of the revised Rold Bjerge Formation on Traill Ø. The Home Forland Group covers the middle Albian – Coniacian succession. The basal unconformity records an important mid-Albian tectonic event involving intrabasinal uplift, tilting and erosion, as exemplified by the middle Albian conglomerates of the new Kontaktravine Formation on Clavering Ø. The Home Forland Group is dominated regionally by mud-dominated slope to basinal deposits of the elevated and revised Fosdalen Formation; it also includes lowstand basin-floor fan sandstones of the new upper Albian Langsiden Member. The new Jackson Ø Group (upper Turonian – lower Maastrichtian), records a phase of basin reorganisation marked by a significant fall in sedimentation rate in North-East Greenland, probably linked to rift events in, and bypass to, the central proto-Atlantic rift system. The base of the group is an erosional unconformity on Traill Ø and Geographical Society Ø overlain by submarine slope-apron conglomerates of the Turonian Månedal Formation. The base is conformable on Hold with Hope but is defined by a condensed interval (the Coniacian Nanok Member) that is succeeded conformably by slope and basin-floor turbidite sandstones of the Coniacian–Santonian Østersletten Formation and slope to basinal mudstones of the Campanian – lower Maastrichtian Knudshoved Formation. The new Leitch Bjerg Formation of Campanian slope-apron conglomerates and sandstones in eastern Geographical Society Ø erosionally overlies the Knudshoved Formation.

Upper Miocene strata in the Acre sub-basin, Brazil, consist dominantly of various types of inclined heterolithic stratification and pedogenic horizons. These strata were sedimentologically and ichnologically described to: (i) study different temporal controls responsible for inclined heterolithic stratification generation and their variation in a distal-proximal trend; and (ii) delineate the depositional setting. For this purpose, nine representative outcrops were sedimentologically and ichnologically studied, and their facies associations described. Thickness variations of the heterolithic strata of various orders (lamina, lamina bundles and beds) were analysed by statistical methods (Fourier transform). The deposits were interpreted as tidally and seasonally influenced estuarine or delta-related and continental strata. The inclined heterolithic stratification deposits represented vastly different settings ranging from tidally dominated, brackish-water ichnofossils-bearing channels to seasonally controlled, articulated Purussaurus (a freshwater alligator) fossilbearing channels. Several time cycles were distinguished in the strata, including semi-diurnal, fortnightly and seasonal. Tidal imprint was best observed in low-energy brackish-water settings, whereas seasonal rhythmicity was distinguishable throughout the depositional system. However, the latter was most apparent in riverine channels proximal to the inferred fluvio-tidal transition. The different temporal controls commonly had distinguishable impact on sedimentological and ichnological properties in the studied sediments. The differing properties included: (i) the degree and nature of lateral variability with respect to lithology and bedforms in inclined heterolithic stratification; (ii) the lateral continuity of inclined heterolithic stratification; (iii) the nature of sedimentary contacts between the inclined heterolithic stratification members; (iv) thickness variation of inclined heterolithic stratification members within a set; (v) the cyclicities observed in inclined heterolithic stratification series; (vi) the degree of bioturbation; (vii) the types of trace fossils observed; and (viii) the distribution of bioturbation in adjacent inclined heterolithic stratification members.

Marine infl uence in Amazonia during the Miocene is a controversial issue, one about which nearly opposite theories (continental vs marine) have been proposed. Increasing multidisciplinary palaeoenvironmental data sets from various Miocene stratigraphic levels and parts of Amazonia have revealed depositional complexities triggered by repeated, high-frequency base-level changes and a very low depositional gradient. As a result, Early-Middle Miocene strata (Pebas phase) are organized into recurring 3-10 m-thick transgressive-regressive bay-margin successions. An array of evidence indicates some sort of marine infl uence in these deposits. This evidence includes mangrove pollen, foraminifers, rare brackish-water mollusc species, barnacles, common brackish-water trace fossil assemblages and tidal sediments. The ongoing debate now focuses on the degree of saltwater infl uence in the Pebas phase strata. The Late Miocene (Acre phase) stratigraphic record comprises mainly channelized deposits, and fossil faunas are dominated by terrestrial and freshwater vertebrates. The evidence for marginal marine infl uence in these strata is mainly confi ned to inclined heterolithic stratifi cation (IHS)-bearing channels and includes tidal sediments, restricted brackish-water ichnofossil assemblages, and locally teeth of euryhaline sharks and mangrove pollen (Nauta and Madre de Dios Formations). In particular, the tidal signature in these deposits is well developed, pointing to local development of deltaic/estuarine settings. There are also suggestions of marine infl uence on other stratigraphic intervals throughout Amazonia, particularly in Pliocene and Quaternary strata. The allegedly marine conditions have been proposed based on purported global sea-level highstands, the low altitude of the Amazon region and supposed coastal geomorphological features such as deltas. We conclude that these suggestions are misconceptions and that geological data to support such marine settings during the Late Neogene are lacking.

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Current depositional models largely promote the perception that all open-coastal distal (sea)-proximal (land) gradients are reflected by upward-coarsening grain-size trends, and that shoreline deposits are represented by prominent sand bodies. Although commonly the case, significant departures from this model may occur when the availability of coarser sediment calibers (sand-sized and larger) is limited. This is especially true where alongshore sediment-transport-influenced depositional systems are associated with rivers that supply abundant suspended sediments. Underestimating the role of grain-size segregation may lead to misinterpretations of energy levels and water depths, especially in some shale-dominated sedimentary units.The Upper Cretaceous Alderson Member (Lea Park Fm) is an up to 180-m-thick, gas-charged shale unit that we interpret as an ancient analogue for modern offshore and mud-dominated deltaic coasts. Sedimentological and ichnological data collected from 27 cores indicate that much of the sediment volume of the Alderson Member was deposited in relatively shallow water under the influence of tidal and wave processes in a deltaic coastal setting. Characteristic features reflecting these depositional affinities include: (1) increased proportions of terrestrially derived organic matter; (2) indications of thixotropic to soupy substrates (e.g., fluid mud) coupled with rapid depositional rates; (3) an impoverished ichnological signal (Planolites-dominated suites); (4) micro-laminated shale; (5) shale-on-shale erosional contacts; (6) scour-and-fill structures; and (7) intervals of lowangle cross-stratification. The interpretation of relatively shallow-water settings is also supported by recurring root-bearing horizons, Glossifungites Ichnofacies-demarcated transgressive surfaces of erosion, and conglomeratic surfaces at particular stratigraphic levels. The deposits are interpreted to include offshore, ''subaqueous deltas,'' muddy shoreface and/or tidal flat, and aggradational muddy coastal plain (chenier plain) sub-environments.The results of this study improve our knowledge of ichnological and sedimentological characteristics of shallow-marine shale units, and are potentially useful for recognition of similar nearshore mud-prone deposits elsewhere. J S R J S R FIG. 7.-Core 12, Southern Saskatchewan, upper Alderson. 812J. HOVIKOSKI ET AL. J S R