Photointerpretation of Tertiary structures in platform cover strata of interior Oscar II Land, Spitsbergen

A structural map of Oscar II Land compiled using black and white, stereo-pair air photos and other available information sources suggests the existence of three structural zones within the deformed platform cover strata. The western zone consists of basement involved overthrusts of complex geometry in the north large-scale folds of platform cover strata with a stepped, down to the east profile in the south. The central zone consists primarily of folds within Kapp Starostin Fm. and overlying Triassic strata that likely formed above a subhorizontal décollement within Gipshuken Fm. strata. Farther to the east thrusts emplace Permian Kapp Starostin Fm. strata over Triassic strata. This zone probably represents stratigraphic climb of the basal decollement. Conservative estimates of shortening for the central and eastern zones are in the 15-25% range. The contribution of the western zone structures to overall Tertiary shortening depends on the geometry of faults underlying the stepped folds and is uncertain at present.
Changes along strike are in part due to differential levels of erosion and changes in transport direction, but also probably important was variable thickness of the platform cover strata involved (less to the north) and the availability of incompetent horizons along which thrust-fiats could form. Two areas with anomalous structural trends may represent oblique ramps.     

A storm-related origin for the Jurassic Brentskardhaugen Bed of Spitsbergen, Norway

The laterally persistent but thin, Jurassic age (Bathonian-Callovian) Brentskardhaugen bed is poorly sorted (often with mud to cobble size), and is crudely normally and/or reversely graded without internal discontinuities. These traits may indicate a short-lived depositional event, and are inconsistent with an origin as a basal, transgressive gravel lag formed in a terrestrial or shoreline setting. Mega-storm events on a shallow marine shelf with an underlying condensed section may account for the poor sorting, grading, stratigraphic position and remanie character of the bed.     

Sediment provenance in a tropical fluvial and marine context by magnetic 'fingerprinting' of transportable sand fractions

The sources and fluxes of sediment to the Great Barrier Reef lagoon from north‐eastern Australian rivers have been the subject of much concern and study, with the large catchments of the Burdekin and Fitzroy Rivers thought to be the key sources at present. Here, the utility of newly developed magnetic ‘fingerprinting’ methods for identifying sediment provenance, both onshore and offshore, and in association with individual large flood events, is investigated. Within the Burdekin catchment, sediments are mobilized from different subcatchments by runoff generated by intense, localized rainfall events. Magnetic measurements were made on untreated and acid‐treated samples of river channel sediments within the Burdekin River subcatchments and from the estuarine and inner shelf depocentres of Burdekin River sediments. The acid treatment removes all discrete magnetic particles and coatings, and leaves magnetic inclusions (protected within host silicate grains) as the basis of the measured magnetic signature of a sample. The magnetic properties of the acid‐treated samples display statistically distinct sediment provenance groupings. Sand samples from the Upper Burdekin River appear magnetically distinct from samples from tributaries of the Burdekin (e.g. Hann Creek, Fanning River) and also from nearby coastal rivers, including the Haughton. Suspended sand samples from a Burdekin flood event in 2000 appear to have a different source compared with those from floods in 1998 and 1999. Comparisons of the terrestrial, acid‐treated sand fractions with the same, acid‐treated, sand‐size fractions from transects taken offshore suggest that the surface sediments in Upstart Bay and Bowling Green Bay have different sources. Some of these sources are as yet unidentified but may represent the unsampled, lower‐discharge south‐western Burdekin subcatchments, and/or along‐shore drift of sand from the south, perhaps even from the Fitzroy River, over millennial timescales of cyclone pumping. The magnetic inclusion method precludes any obfuscation or confounding of sediment source, which might arise from hydraulic sorting and/or post‐depositional magnetic diagenesis or authigenesis.     

Decoupling as an alternate model for transpression during the initial opening of the Norwegian-Greenland Sea

Transpressive plate motions during the opening of the Norwegian-Greenland Sea were in some manner responsible for the development of Spitsbergen's Tertiary fold-and-thrust belt. A flower model has been proposed for the large-scale structural architecture of Tertiary deformation (Lowell 1972). An alternate model of decoupling, where convergent and transcurrent motions were accommodated in totally or partially separated, subparallel belts is suggested.     

Tertiary structures in the platform cover strata of Nordenskiold Land, Svalbard

Air photo interpretation along with limited field work is the basis of a compilation map of Tertiary structures in the Upper Paleozoic through Mesozoic platform cover strata of Nordenskiold Land. Permian Kapp Starostin Formation strata form a continuous marker horizon delineating both a large NE-verging fold complex, which involves the basement (Hecla Hoek sequence) through basal Tertiary strata, and somewhat smaller scale folds, some of which may have formed in association with detachments and thrusts within the platform cover sequence. The map pattern is both a function of local structural plunge and changes in fold geometry along strike. Regional considerations suggest that subsurface basement-involved thrusts exist. In S Nordenskiold Land, to the E of folded Kapp Starostin Formation strata, a 3.5 km wide zone of folding and thrusting in Triassic and Jurassic strata above a subhorizontal decollement is inferred to occur. Further E is the W limb of the central Tertiary basin syncline.     

Late quaternary sea level changes of Gabes coastal plain and shelf: Identification of the MIS 5c and MIS 5a onshore highstands,southern Mediterranean

The continental shelf of the Gulf of Gabes is outlined, during the MIS 5c and MIS 5a onshore highstands, by the genesis of forced regressive beach ridges situated respectively at –19 m b.s.l/100 ka and –8 m b.s.l/80 ka. This area, considered as a stable domain since at least the last 130 ka (Bouaziz et al.2003), is a particular zone for the reconstruction of the late quaternary sea-level changes in the region. Shuttle Radar Topography Mission (SRTM) data and field observations are highlighted to deduce interaction between hydrodynamic factors and antecedent topography. Variations in geomorphology were attributed to geological inheritance. Petrography and sedimentary facies of the submerged coastal ridges reveal that the palaeocoastal morphology was more agitated than today and the fluvial discharges are consistent. Actual morphologic trend deduced from different environment coasts (sandy coasts, sea cliffs and tidal flat) is marked by accumulation of marine sands and progradation.     

The Supanberget area – basement imbrication and detached foreland thrusting in the Tertiary fold-and-thrust belt, Svalbard

The Supanberget area, situated in the southern part of the Tertiary Spitsbergen fold-and-thrust belt, occupies a position mainly within the central zone of the belt, characterized by basement-involved thrusting, but includes part of an eastern foreland zone of detached, thin-skinned thrust tectonics. The peculiar feature of Supanberget is the thrust- 'sliced' tectonic style that deforms a previously tightly folded basement-cover contact. Foreland structures indicate the additional presence of a subsurface detachment at a deeper structural level. Contrasts in magnitude and orientation of basement anisotropics may control lateral changes in tectonic style.