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To date, discussion of changes in alluvial style and in the character of palaeosols in relation to changes in accommodation and sediment supply on oodplains has primarily been from a conceptual standpoint: few case studies are available against which to test ideas. One hundred and thirty metres of nonmarine strata of the Dunvegan Formation were examined in 14 closely spaced sections in the canyon of the Kiskatinaw River, NE British Columbia, Canada. This site was located about 120 km inland from the transgressive limit of the contemporary marine shoreline and represents almost exclusively freshwater environments. Fluvial channels in the Kiskatinaw River section are of two types. Small, single-storey, very ®ne-to ®ne-grained sandstone ribbons with W/T ratios <30, encased in ®ne-grained¯oodplain sediments are interpreted as anastomosed channels. Fine-to medium-grained, laterally accreted point-bar deposits forming multistorey sand bodies with individual W/T ratios >30 are interpreted as the deposits of meandering rivers ®lling incised valleys. Interchannel facies include the deposits of crevasse channels and splays, lakes, oodplains and palaeosols. Floodplain palaeosols consist of laterally heterogeneous, simple palaeosol pro®les and pedocomplexes similar to modern Entisols, Inceptisols and hydromorphic soils. Inter¯uve, sequencebounding palaeosols adjacent to incised valleys are laterally continuous, up to 3 m thick and can be reliably identi®ed using a combination of (1) stratigraphic position; (2) ®eld observations, such as thickness, structure, colour, degree of rooting; and (3) micromorphological features, such as evidence of bioturbation, clay coatings, ferruginous features and sphaerosiderite. Inter¯uve palaeosols are similar to modern Al®sols and Ultisols. Correlation of the local stratigraphic succession with the regional sequence stratigraphic framework, based on 2340 well logs and 60 outcrop sections, shows that the vertical changes in coastal plain character (more coals and lakes vs. more pedogenesis) can be related to relatively high-frequency base level cycles (eustatic?) that are expressed as transgressive±regressive marine cycles in downdip areas. Regional isopach maps show that these cycles were progressively overprinted and modi®ed by an increasing rate of tectonic subsidence in the north and west. The character of palaeosols developed on aggrading¯oodplains primarily Present addresses: Sedimentology (1999) 46, 861±891 Ó 1999 International Association of Sedimentologists 861re¯ects local sediment supply and drainage. In contrast, well-developed inter¯uve palaeosols record pedogenesis during periods of reduced or negative accommodation (base level fall). Vertical changes in¯oodplain palaeoenvironments and palaeosol types re¯ect changes in accommodation rate. The detailed micromorphological analysis of inter¯uve palaeosols represents a powerful application of an under-used technique for the recognition of key surfaces in the geological record. This has broad implications for non-marine sequence stra...

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ABSTRACT:Turbidites have captioned the attention of sedimentologists during the last decades due their importance as hydrocarbon reservoirs. However, their relationship to delta systems still deserves further studies. This paper presents examples from a late deglacial to early post-glacial deltaic and turbidite strata exposed in the surroundings of Vidal Ramos (Santa Catarina State, Brazil), southern portion of the Paraná Basin. There, the uppermost part of the Mafra Formation and the Rio do Sul Formation onlap the Proterozoic basement and comprises an up to 360 m thick package. It includes (base to top) black shales, mass transport deposits (MTD) and sandy turbidites (Mafra Formation) as well as thin bedded turbidites (tbt), including one interval of black shales and sandy turbidites, overlain by proximal delta front sandstones (Rio do Sul Formation). The analysis of the succession shows two more than 150 m thick coarsening-upwards deltaic successions composed of turbidite sand sheets at their base (prodelta), followed by partially collapsed thin bedded turbidites (delta slope wedge) and delta front sandstones. Both turbidite sand-sheets abruptly overlay black shale intervals related to maximum flooding surfaces and therefore record correlative conformities. A detailed stratigraphic section elaborated from the correlation of four logs (1/100) suggests that distal delta front sands includes both thin bedded turbidites and wave reworked sands whereas the proximal delta front was dominated by long-lived underflows (hyperpycnal flows). The succession suggests that the most expressive turbidite beds (base of the delta systems) have resulted from relative sea-level falls (early lowstand) whereas the thin-bedded turbidites were related to the development of the late lowstand wedge. Black shales represent the transgressive systems tract and HST were not deposited or preserved in the area. High sediment supply associated with lowstand tracts could explain the occasional (Vidal Ramos) to common occurrence of slope failures (slumps and diamictites) involving thin bedded turbidites and delta front sandstones. This situation is quite logical in terms of deglacial periods, and resulting high sediment supply, within a long-term icehouse context, with prevalence of lowstand to transgressive settings.

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Gondwana I (Carbonífero-Eotrih.ico), Gondwana 11 (Meso a Neotriássico), G<.Indwana III (Neojurássico-Eocred.ceo) e Bauru (Neocret:Í.ceo). As três primeiras correspondem a grandes dclos transgressivos paleozóicos, enquanto as dem";s ~ão representadas por pacotes de sedimemitos continent";s e rochas ígneas associadas. Estas superseqüências constituem o registro preservado de suce:llõivas fases de :lCUmulação sedimentar que se intercalaram. a per;odo. de erosio em ampla escalo.. A C"oluçio de cad.:l unidade foi condicionada por contextos panicularesem ~rmos de dima e condições tenÔnicas. A Supen:eq~ncia Rio Ivaí relaciona-.., à implantação da Bacia do Paraná, e a grom~ri:!. de: iS\l:!. área de: ocorrência, com depocentros alongados de orientação geral SW•NE, sugere ter c1asido controlada por algum mtcanismo de ritteamento. A Superseqüência Pun:Í.:lCumulou•.., durante uma épocade amplo afogamem.omarinho tksireascutÔnicasdoGondwana. Condi~dc:b.ri..imracr.aô~ implic..ndo um efetivo isolamento no interior continental, começam a predominar durante a deposição da