deep water facies processes and models a review and classification scheme for modern and ancient sediments abstract a review of previous work on modern and ancient deep water facies processes and models is presented with a new classification scheme involving 40 distinct facies related to 15 conceptually distinct facies groups these facies are fixed points in a spectrum of facies generated in a process continuum from resedimentation processes through semi permanent bottom currents to pelagic settling in essence the scheme is descriptive of the sedimentary attributes of sediments although it is designed to aid interpretation of possible sediment transport deposition processes the classification scheme is three tier with facies classes groups and constituent facies and is hierarchical to allow flexibility in its use there are seven facies classes with classes a e defined largely on the basis of grain size differences class f on the basis of internal organization and class g on composition the facies classes are class a gravels muddy gravels gravelly muds and pebbly sands with 5 gravel grade class b sands with 80 sand grade and 80 mud 40 silt and 0 20 sand class e muds and clays with 95 mud grade for the purpose of large scale mapping or reconnaissance fieldwork either the level of facies classes or groups may be appropriate whereas for more detailed sedimentology the more detailed facies level will be necessary

well preserved late precambrian paleosols from northwest scotland abstract two paleosol profiles were developed side by side on gneiss sheigra clay paleosol and amphibolite staca clay paleosol along the same unconformable contact of lewisian metamorphic rocks 2 7 1 7 ga overlain by torridonian sandstones 0 8 ga in northwestern scotland although altered during burial by compaction and illitization these profiles are well preserved compared with most other precambrian paleosols that are metamorphosed to at least greenschist facies in addition deformation of pegmatite veins in a manner similar to soil creep can be taken as an indication that upper horizons of these paleosols have been preserved soil development in both profiles was characterized by the oxidation of iron in biotite and magnetite and by hydrolysis of plagioclase orthoclase and hornblende clay skins soil like microfabrics and pedogenic smectite have been preserved in the profiles alteration of silicate grains other than quartz microcline and biotite has been intense but chemical analyses failed to show dramatic removal of alkalis and alkaline earths from the profiles microscopic concretions similar to pedogenic carbonate were found in subsurface horizons of the staca clay rare earth elements are more abundant within the paleosols than in their parent materials these paleosols developed on a well drained landscape that was buried by torridonian alluvial fans atmospheric oxidation was greater than revealed by studies of archean paleosols but probably still short of modern levels paleoclimate was subhumid and probably seasonal organic carbon and its light isotopic composition in the paleosol is evidence for photosynthetic microbial crusts paleosols of such great antiquity do not fit comfortably within modern soil taxonomies and are for the moment assigned to the informal category of green clays

alternating coarse and fine grained sedimentation in precambrian deep water ramp apiuna formation se of brazil tectonic and climate control or sea level variations abstract are the depositional processes and architecture of precambrian deep water deposits the same of the phanerozoic time few examples of precambrian deep water deposits exist in the literature this paper describes the apiuna formation a neoproterozoic deep water succession c 4500 m thick located in se brazil detailed facies analysis six large logs 2000 3150 m thick and a geological map have been applied to define types and geometrical distribution of three fine grained and four coarse grained architectural elements fine grained elements mudstone and fine grained sandstone constitute more than 70 of the thickness of the apiuna formation these enclose coarse grained elements constituted of lenticular sandstone or pebbly sandstone bodies isolated coarse grained elements display parallel palaeoflow directions suggesting multi point source of the sediment due to this last aspect and the mud dominance the apiuna formation is interpreted as fine grained ramp depositional system characterised by episodes of coarse grained sedimentation nevertheless this unit diverges from the phanerozoic models for having 1 a wide range of grain size 2 small channel levee systems 3 immature clastic material and 4 irregular distribution of the architectural elements in apiuna sedimentary succession five phases of coarse grained sedimentation alternate to six phases of fine grained sedimentation in unvegetated earth different rates of chemical weathering and mechanical erosion of the soils controlled by climate and tectonic activity can explain these variations of the clastic input in rainy and warm climate conditions precambrian soils on silicate rocks formed thick clayey profiles during quiescent or low tectonic activity a dynamic equilibrium between weathering and erosion by runoffs on unprotected by rooted vegetation soils produced high quantity of fine grained material during high tectonic activity and drier climate conditions clayey soils did not form or were very reduced and mechanical erosion of the silicate rocks produced coarse grained sediment thereby high input of fine grained deposits can be considered a peculiar characteristic of precambrian deep water systems

heat flow distribution and thermal structure of the nankai subduction zone off the kii peninsula detailed heat flow surveys were carried out in the central part of the nankai trough southeast of the kii peninsula off kumano for investigation of the thermal structure of the subducting plate interface at stations in the kumano trough forearc basin and its vicinity long term monitoring of temperature profiles in surface sediments was conducted because bottom water temperature variations btv significantly disturb subbottom sediment temperatures heat flow values were successfully determined at seven stations by removing the influence of btv from temperature records for 300 to 400 days the surface heat flow data were combined with estimates from depths of methane hydrate bottom simulating reflectors to construct a heat flow profile across the subduction zone heat flow decreases from 90 110 mw m2 on the floor of the nankai trough to 50 60 mw m2 at around 30 km from the deformation front while it is rather uniform 40 60 mw m2 in the kumano trough the values measured on the nankai trough floor are concordant with the value estimated from the age of the subducting philippine sea plate about 20 m y taking into account the effect of sedimentation the obtained heat flow profile was used to constrain thermal models of the subduction zone the subsurface thermal structure was calculated using a two dimensional steady state model in which the frictional heating along the plate interface and the radioactive heat production are treated as unknown parameters comparison of the calculated surface heat flow in the kumano trough with the observed data indicates that the effective coefficient of friction is small about 0 1 or less and thus the shear stress on the plate interface is very low in this subduction zone

two types of outer fan lobe sequence from the late precambrian kongsfjord formation submarine fan finnmark north norway abstract a comparison of outer fan sections from different parts of the kongsfjord formation submarine fan has revealed two types of outer fan lobe sequence designated type i and type ii both types of lobe sequence contain lobes including lobe fringe deposits that are between 2 m and 15 m thick although type i lobes are generally less than 10 m thick there are no obvious differences in bed thickness grain size or other sedimentary attributes the distinction between type i and type ii lobes is based primarily upon their vertical frequency within fan fringe deposits type i lobes are separated by lobe fringe plus fan fringe deposits of similar thickness therefore in vertical sections the lobes are regularly spaced type ii lobes occur sporadically within sections where lobe fringe plu fan fringe deposits vary from tens of centimeters to 70 m in the two representative sections that illustrate the typological differences type i lobes plus lobe fringe deposits comprise 60 percent of the section compared to 22 percent for the type ii lobe sequences type i lobe sequences are interpreted as the result of regular lobe switching immediately downfan from the middle fan channels within a relatively proximal outer fan environment type ii lobe sequences are interpreted as a consequence of sporadic progradation of lobes in a relatively distal fan environment that usually received fan fringe sedimentation type i lobes represent regular and stable deposition controlled by intrafan intrabasinal processes whereas type ii lobes developed because of relatively catastrophic intrafan e g major channel relocation or extrafan source control processes this distinction may serve as a proximality indicator in outer fan successions

depositional models for fine grained sediment in the western hellenic trench eastern mediterranean sediment in tectonically active topographically restricted settings of the western hellenic arc eastern mediterranean consists primarily of clayey silt and silty clay failure of metastable sediment temporarily stored on relatively steep slopes is triggered by earthquake tremors and eustatic oscillations redeposition of these materials by gravitative transport has resulted in markedly different lithofacies from site to site most piston cores include three late quaternary stratigraphic units that can be correlated with sections in other parts of the eastern mediterranean numerous radiocarbon age determinations enhance the correlation seven fine grained sediment types are identified in cores from eight distinct depositional environments some muds are closely related to specific environments slump and debris flow deposits on slope and high relief environments or to time well laminated mud during the latest pleistocene mid holocene or to both uniform and faintly laminated muds restricted to trench basins turbiditic and hemipelagic muds are common throughout the study area mud distribution patterns correlate closely with calculated sedimentation rates we propose two depositional models for these sediments the first emphasizes downslope transformations resulting in progressively reduced flow concentration during transport from slump and debris flow turbidity current low density turbidity current or turbid layer mechanisms the distal end member deposits settling from low concentration flows are thick rapidly emplaced fine grained uniform muds closely associated with faintly laminated muds these were ponded in flat trench basin plains planktonic and terrigenous fractions in the turbiditic finely laminated and uniform muds record mixing of materials of gravitative and suspension origin during redeposition this sequence prevails under conditions of minimal stratification of water masses as characterized by the present mediterranean in the second model developed for conditions of well developed water mass stratification well laminated rather than uniform mud prevails as the end product of low concentration flows these very finely laminated and graded muds record particle by particle settling from detached turbid layers concentrated along density interfaces they include material from turbid layers complemented by the normal rain of pelagic material stratification barriers resulted in region wide distribution of such deposits in both slope and trench environments

depositional mechanisms and architecture of a pre early cambrian mixed sand mud deepwater ramp apiuna unit south brazil abstract the apiuna unit is located in the south of brazil in the state of santa catarina it is a deepwater depositional system which is part of the sedimentary fill of the itajai basin pre early cambrian in age interpreted as a foredeep basin we have described and interpreted the depositional mechanisms according to the terminology proposed by mulder and alexander mulder t alexander j 2001 the physical character of subaqueous sedimentary density flows and their deposits sedimentology 48 2 269 299 and have recognized seven architectural elements the apiuna unit is interpreted as a mixed sand mud deepwater ramp system the slope deposits are characterized by laminated argillite with slumped beds the proximal and medial ramp is characterized by channel levee systems the distal ramp shows sandstone sheet which pass distally into interlayered sandstone pelite the sequence development of this ramp unit differs from other known ancient ramp systems the apiuna unit shows at least five phases of sandy input recording times of progradation or retrogradation of the ramp interstratified with muddy deposits related to sand starved phases in the upper part of the succession the ramp building was interrupted and the sandy deposits are replaced by pelitic slope deposits the depositional mechanisms have a direct relationship to the architectural elements and the regions of the depositional system settling very low density turbidity currents and slumps formed the slope deposits channel deposits are formed by debris flows hyperconcentrated density flows and concentrated density flows in that vertical sequence order levee deposits were made of surge like turbidity flows proximal sandstone sheet deposits were formed by concentrated density flows distal sandstone sheet deposits are formed by concentrated density flows and surge like turbidity flows surge like turbidity flows and quasi steady turbidity flows formed the interchannel deposits

sequence stratigraphy of the precambrian rooihoogte timeball hill rift succession transvaal basin south africa third order sequence stratigraphic analysis is performed on the rooihoogte timeball hill second order rift succession of the paleoproterozoic transvaal basin south africa this provides a case study for systems tract and sequence development during a time of glacio eustatic fall when accommodation was generated by subsidence related to syn rift and post rift tectonic processes two third order depositional sequences have been identified separated by a basin wide subaerial unconformity the lower third order sequence includes the complete succession of lowstand transgressive and highstand systems tracts lst tst and hst whereas the upper third order sequence only preserves lowstand and transgressive systems tracts this indicates that the fall in base level associated with the upper second order boundary of the rooihoogte timeball hill sequence was of higher magnitude relative to the third order subaerial unconformity which is in agreement with the principles of boundary hierarchy based on the magnitude of base level changes the position of the lower boundary of the rooihoogte timeball hill second order sequence has been revised from the base of the chert breccias to the contact between the breccias and the overlying chert conglomerates this is because a major tilting event occurred between the deposition of the two facies which are genetically unrelated and which are separated by a subaerial unconformity the lithostratigraphic contact between the rooihoogte and timeball hill formations is interpreted as a diachronous transgressive surface of erosion in this interpretation the polo ground member of the rooihoogte formation may be coeval with the basal black shales of the timeball hill formation the two facies fluvial and marine respectively forming together a transgressive systems tract d 2002 elsevier science b v all rights reserved

the precambrian turbidite tempestite transition as displayed by the amphibolite facies puolankajarvi formation finland abstract the puolankajarvi formation pjf forms the lowermost unit of the progradational central puolanka group it is at least 2200 ma old metamorphosed to amphibolite facies displays polyphase deformation and is commonly near vertical or overturned the pjf is about 1500 2000 m thick and 30 km in strike length but grades into gneisses both below and at its northern extension thus the original sediments could have been much thicker and perhaps hundreds of kilometres long in strike length the lower part of the pjf consists of graded bedded mica schists and associated massive or graded arkosites at least 500 1000 m thick which represent metamorphosed turbidites deposited by low concentration and high concentration turbidite currents respectively the turbiditic unit is overlain and partly interfingers with semipelitic mica schists containing combined flow origin hummocky cross stratification and related structures indicating that these rocks about 100 200 m thick were originally fine sands and silty muds deposited by storm waves and other shelf processes large scale cross bedded quartzite interbeds at the top of the pjf indicate a progradational change into the overlying akanvaara formation of shallower water origin the pjf shows a change of relatively thin bedded turbidites to tempestites which is interpreted as representing either the distal and middle parts of a relatively steep shelf or the upper slope and the distal middle part of a narrow shelf

marine to fluvial transition proterozoic upper rewa sandstone maihar india abstract the proterozoic upper rewa sandstone in central india is generally interpreted as entirely marine a detailed study in maihar madhya pradesh however reveals upward transition from marine to fluvial through a mixed facies association also bearing eolian imprints facies associations differ in stratal geometry and arrangement palaeocurrent direction and pattern as well as in grain size and sorting the fine grained marine association is dominated by tidal sheet deposits with characteristic rhythmic changes in thickness and style of cross stratification and their packages as well as local evidence of current reversals subordinate beach deposits are also present the major palaeocurrent direction is highly consistent and westward the coarse grained often granule rich sandstones of the fluvial association are embodied by four facies correlatable with flow stages and relative bed shear these braided stream deposits are preserved in vertical stacks of tabular sandbodies in response mainly to basin subsidence the palaeocurrent pattern is unimodal and northwestward but its dispersion covers 180 the rocks are poorly sorted and at places incorporate sand clasts although they are virtually mud free and mineralogically mature as in two other associations the medium to fine grained sandstones at the intermediate interval between the marine and fluvial associations are of distinct lensoid geometry they incorporate representatives from the previous two associations as well as translatent strata interdune erg deposits and possibly aeolian cross strata consequently the palaeocurrent pattern is polymodal with a spread over 270 an overall coarsening up trend in the fluvial part and thinning up trend in the tidal part imply progradation in spite of evidence of basin subsidence a high rate of sediment discharge from a perennial river system in a humid climate is suggested

origin of a crustal splay fault and its relation to the seismogenic zone and underplating at the erosional north ecuador south colombia oceanic margin 1 splay faults within accretionary complexes are commonly associated with the updip limit of the seismogenic zone prestack depth migration of a multichannel seismic line across the north ecuador south colombia oceanic margin images a crustal splay fault that correlates with the seaward limit of the rupture zone of the 1958 mw 7 7 tsunamogenic subduction earthquake the splay fault separates 5 6 6 km s velocity inner wedge basement rocks which belong to the accreted gorgona oceanic terrane from 4 to 5 km s velocity outer wedge rocks the outer wedge is dominated by basal tectonic erosion despite a 3 km thick trench fill subduction of 2 km high seamount prevented tectonic accretion and promotes basal tectonic erosion the low velocity and poorly reflective subduction channel that underlies the outer wedge is associated with the aseismic decollement thrust subduction channel fluids are expected to migrate upward along splay faults and alter outer wedge rocks conversely duplexes are interpreted to form from and above subducting sediment at 14 to 15 km depths between the overlapping seismogenic part of the splay fault and the underlying aseismic decollement coeval basal erosion of the outer wedge and underplating beneath the apex of inner wedge control the margin mass budget which comes out negative intraoceanic basement fossil listric normal faults and a rift zone inverted in a flower structure reflect the evolution of the gorgona terrane from cretaceous extension to likely eocene oblique compression the splay faults could have resulted from tectonic inversion of listric normal faults thus showing how inherited structures may promote fluid flow across margin basement and control seismogenesis

submarine fan systems i characterization and stratigraphic prediction submarine fan and related deep marine clastic systems such as submarine ramps and slope aprons are important hydrocarbon reservoirs in many parts of the world the origin and character of these systems reflect a complex interplay between a range of autocyclic and allocyclic controls including sea level fluctuations basinal tectonics and the rate type and nature of sediment supply these controls are commonly interdependent this paper reviews the characteristics which distinguish different submarine fans and their subsurface prediction then proposes a classification framework for fans which discriminates between different systems on the basis of their fundamental controls the proposed classification is discussed in terms of its value as a predictive tool in hydrocarbon exploration development and production a modus operandi is developed which uses the classification for reservoir description and prediction and involves three stages of investigation basin screening fan delineation and fan characterization each stage demands the integration of a range of tools and techniques including sequence stratigraphy seismic facies analysis seismic redisplay and geophysical modeling these stages of analysis are linked in turn with core and wireline log data to constrain the range of possible fan types within a basin fill and assess the implications for reservoir seal and trap development this structured approach to stratigraphic analysis is also valuable in constraining the range of reservoir architectural options in appraisal development and production

the molecular structure of melts along the carbonatite kimberlite basalt compositional joint co2and polymerisation transitional melts intermediate in composition between silicate and carbonate melts form by low degree partial melting of mantle peridotite and might be the most abundant type of melt in the asthenosphere their role in the transport of volatile elements and in metasomatic processes at the planetary scale might be significant yet they have remained largely unstudied their molecular structure has remained elusive in part because these melts are difficult to quench to glass here we use ftir raman 13c and 29si nmr spectroscopy together with first principle molecular dynamic fpmd simulations to investigate the molecular structure of transitional melts and in particular to assess the effect of co2on their structure we found that carbon in these glasses forms free ionic carbonate groups attracting cations away from their usual depolymerising role in breaking up the covalent silicate network solution of co2in these melts strongly modifies their structure resulting in a significant polymerisation of the aluminosilicate network with a decrease in nbo si of about 0 2 for every 5 mol co2dissolved this polymerisation effect is expected to influence the physical and transport properties of transitional melts an increase in viscosity is expected with increasing co2content potentially leading to melt ponding at certain levels in the mantle such as at the lithosphere asthenosphere boundary conversely an ascending and degassing transitional melt such as a kimberlite would become increasingly fluid during ascent hence potentially accelerate carbon rich transitional melts are effectively composed of two sub networks a carbonate and a silicate one leading to peculiar physical and transport properties

formation and diagenesis of a sub huronian saprolith comparison with a modern weathering profile an early proterozoic paleosol that preserves archean granite protolith textures occurs beneath the lorrain formation in the early proterozoic huronian supergroup near ville marie quebec textural mineralogical and geochemical comparisons between this saprolith and a modern weathering profile developed on the devonian toorongo granodiorite in eastern australia indicate similarities that can be attributed to the effects of primary weathering reactions the comparison also reveals anomalous features at ville marie that are caused by diagenetic reactions between the weathered granite and meteoric waters k metasomatism in the form of sericite replacement of kandites is ubiquitous in the ville marie saprolith zone and is ascribed to reaction of low na k meteoric waters with the weathered profile as they moved along a relatively permeable unconformity surface earlier diagenetic reactions may have produced calcite alteration occurring in a thin zone at the base of the profile thought to represent the po

significance of late precambrian turbidite sequences bordering the east antarctic shield a late precambrian turbidite succession is described from north victoria land antarctica in its sedimentological biological and tectonic aspects similar sequences occurring across the whole continent along the present transantarctic mountains are discussed the geotectonic significance of this flysch belt is analysed in its relation to the east antarctic shield the gondwana craton and a proto pacific

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

frontal wedge deformation near the source region of the 2011 tohoku oki earthquake 1 we report an uplift of 5 m with a horizontal displacement of more than 60 m due to the 2011 tohoku oki earthquake the uplift was measured by an ocean bottom pressure gauge installed before the earthquake on a frontal wedge which formed an uplift system near the japan trench horizontal displacements of the frontal wedge were measured using local benchmark displacements obtained by acoustic ranging before and after the earthquake the average displacements at the frontal wedge were 58 m east and 74 m east southeast these results strongly suggest a huge coseismic slip beneath the frontal wedge on the plate boundary the estimated magnitude of the slip along the main fault was 80 m near the trench our results suggest that the horizontal and vertical deformations of the frontal wedge due to the slip generated the tremendous tsunami that struck the coastal area of northeastern japan

present day principal horizontal stress orientations in the kumano forearc basin of the southwest japan subduction zone determined from iodp nantroseize drilling site c0009 a 1 6 km riser borehole was drilled at site c0009 of the nantroseize in the center of the kumano forearc basin as a landward extension of previous drilling in the southwest japan nankai subduction zone we determined principal horizontal stress orientations from analyses of borehole breakouts and drilling induced tensile fractures by using wireline logging formation microresistivity images and caliper data the maximum horizontal stress orientation at c0009 is approximately parallel to the convergence vector between the philippine sea plate and japan showing a slight difference with the stress orientation which is perpendicular to the plate boundary at previous nantroseize sites c0001 c0004 and c0006 but orthogonal to the stress orientation at site c0002 which is also in the kumano forearc basin these data show that horizontal stress orientations are not uniform in the forearc basin within the surveyed depth range and suggest that oblique plate motion is being partitioned into strike slip and thrusting in addition the stress orientations at site c0009 rotate clockwise from basin sediments into the underlying accretionary prism

possible strain partitioning structure between the kumano fore arc basin and the slope of the nankai trough accretionary prism 1 a 12 km wide 56 km long three dimensional 3 d seismic volume acquired over the nankai trough offshore the kii peninsula japan images the accretionary prism fore arc basin and subducting philippine sea plate we have analyzed an unusual trench parallel depression a notch along the seaward edge of the fore arc kumano basin just landward of the megasplay fault system this bathymetric feature varies along strike from a single steep walled 3 5 km wide notch in the northeast to a broader 5 km wide zone with several shallower linear depressions in the southwest below the notch we found both vertical faults and faults which dip toward the central axis of the depression dipping faults appear to have normal offset consistent with the extension required to form a bathymetric low some of these dipping faults may join the central vertical fault s at depth creating apparent flower structures offset on the vertical faults is difficult to determine but the along strike geometry of these faults makes predominantly normal or thrust motion unlikely we conclude therefore that the notch feature is the bathymetric expression of a transtensional fault system by considering only the along strike variability of the megasplay fault we could not explain a transform feature at the scale of the notch strike slip faulting at the seaward edge of fore arc basins is also observed in sumatra and is there attributed to strain partitioning due to oblique convergence the wedge and decollement strength variations which control the location of the fore arc basins may therefore play a role in the position where an along strike component of strain is localized while the obliquity of convergence in the nankai trough is comparatively small 15 we believe it generated the kumano basin edge fault zone which has implications for interpreting local measured stress orientations and suggests potential locations for strain partitioning related deformation in other subduction zones

splay fault slip in a subduction margin a new model of evolution in subduction zones major thrusts called splay faults are thought to slip coseismically during large earthquakes affecting the main plate interface we propose an analytical condition for the activation of a splay fault based on force balance calculations and suggest thrusting along the splay fault is generally conditioned by the growth of the accretionary wedge or by the erosion of the hanging wall in theory normal slip on the splay fault may occur when the decollement has a very low friction coefficient seaward such a low friction also implies an unstable extensional state within the outer wedge finite element elasto plastic calculations with a geometry based on the nankai kumano section were performed and confirm that this analytical condition is a valid approximation furthermore localized extension at a shallow level in the splay hanging wall is observed in models for a wide range of friction coefficients from 0 to the value of internal friction coefficient of the rock here equals to 0 4 the timing of slip established for the splay fault branch drilled on nankai kumano transect suggests a phase of concurrent splay and accretionary wedge growth 2 ma to 1 5 ma followed by a locking of the splay 1 3 ma active extension is observed in the hanging wall this evolution can be explained by the activation of a deeper and weaker decollement followed by an interruption of accretion activation of a splay as a normal fault as hypothesized in the case of the tohoku 2011 earthquake can be achieved only if the friction coefficient on the decollement drops to near zero we conclude that the tectonic stress state largely determines long term variations of tightly related splay fault and outer decollement activity and thus influences where and how coseismic rupture ends but that occurrence of normal slip on a splay fault requires coseismic friction reduction

depositional age and provenance of the itajai basin santa catarina state brazil implications for sw gondwana correlation abstract the itajai basin is a fault bounded late to post orogenic basin deposited adjacent to the dom feliciano belt in the state of santa catarina brazil the basin is composed of alluvial deltaic and platformal successions followed by a turbiditic complex and fan delta deposits u pb zircon dating of a tuff and five sandstone samples indicates a maximum depositional age of 563 3 ma for the intermediate and upper sections of the itajai basin and zircon dating of a rhyolite stock indicates a minimum depositional age of 549 4 ma these dates are compatible with the previous assignment of an ediacaran age to the sediments based on the discovery of ediacara type fossils such as parvancorina charniodiscus cyclomedusa and aspidella the u pb detrital zircon ages show a change in the sedimentary input from the base to the top at the base zircon grains from the transamazonian and brasiliano pan african orogenic cycles occur as major sources with some archean contribution the upper section is dominated by brasiliano pan african zircon grains most of which range in age from 824 to 770 ma and 656 to 563 ma pb and sm nd whole rock isotope data suggest that the main source area for the basin infill was a reworked crust such as the dom feliciano belt we also present the regional correlation of the itajai basin with the basins formed during the late stages of the sw gondwana