Stratigraphic and palaeoenvironmental significance of a Pennsylvanian (Upper Carboniferous) palynoflora from the PiauFormation, Parnaba Basin, northeastern Brazil

A well-preserved palynoflora is reported from within a cored interval of a coal-exploratory borehole (1-UN-23-PI of the Geological Survey of Brazil) in the southern part of the Parnaiba Basin, northeastern Brazil. The sample studied is from the lower portion of the Piaui Formation. Its palynoflora is characterized by particular abundance of the trilete cavate/pseudosaccate miospores Spelaeotriletes triangulus Neves and Owens, 1966 and S. arenaceus Neves and Owens, 1966, together with cingulizonate forms mainly attributable to Vallatisporites Hacquebard, 1957 and Cristatisporites R. Potonie and Kremp emend. Butterworth et al., 1964. Radially and bilaterally symmetrical monosaccate pollen grains are also well-represented, chiefly by Plicatipollenites Lele, 1964 and Potonieisporites Bhardwaj, 1954, respectively. Taeniate grains (i.e., monosaccates and bisaccates) are relatively minor constituents of the palynoflora; no marine microplankton were encountered. Several species are described in detail : the trilete apiculate spores Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 and Horriditriletes uruguaiensis (Marques-Toigo) Archangelsky and Gamerro, 1979; and the taeniate pollen grains Meristocorpus ostentus sp. nov. and Lahirites segmentatus sp. nov. A Pennsylvanian (Late Carboniferous : late Westphalian) age is adduced for the palynoflora via its correlation with part of the Tapajos Group (specifically, the upper Itaituba Formation) of the Amazonas Basin in northern Brazil. The entirely land-derived palynomorphs, associated with abundant plant debris, corroborate previous suggestions that the lower part of the Piaui Formation accumulated in a nonmarine setting under conditions of aridity.

Permian Palynofloral Assemblages of the Chaco-Paraná Basin (Argentina): Systematics and Stratigraphic Significance

Core samples from an upper Palaeozoic, partly glaciogene borehole section (Ordóñez: YPF Cd O es-1) in the southern Chaco-Paraná Basin (Córdoba Province, northeastern Argentina) have produced variable palynological results. Samples from the lower part of the section (i.e., from the diamictite-bearing upper Ordóñez Formation) proved non-palyniferous. Those from the overlying, essentially post-glacial Victoriano Rodríguez Formation yielded spore-pollen assemblages in varying concentrations and in good to excellent states of preservation, thus providing the material basis for the present account. The palynomorph taxa represented in the assemblages comprise 20 species of spores (distributed among 14 genera) and 25 species of pollen grains (14 genera). The majority of the species are described in systematic detail. One trilete spore species -Convolutispora archangelskyi- is newly proposed. Several other, possibly new species (three of trilete spores, one of monosaccate pollen) are represented insufficiently for other than informal naming. The following new combinations, also of trilete spore species, are instituted: Converrucosisporites confluens (Archangelsky & Gamerro, 1979), C. micronodosus (Balme & Hennelly, 1956), and Anapiculatisporites tereteangulatus (Balme & Hennelly, 1956). Sculptural intergradation (granulate through verrucate) among three species -Granulatisporites austroamericanus Archangelsky & Gamerro, 1979, C. confluens, and C. micronodosus- prompts their informal grouping, proposed herein, as the Converrucosisporites confluens Morphon, which is also recognizable elsewhere in the Gondwanan Permian. The possibility, if not the likelihood, that G. austroamericanus is conspecific with Microbaculispora tentula Tiwari, 1965 is canvassed. The palynologically productive borehole section of the Victoriano Rodríguez Formation studied here is assignable to the middle to upper Cristatisporites Zone and to the succeeding Striatites Zone, thus signifying an Early Permian age for this section and facilitating correlation with strata of the Paraná and Paganzo Basins. From this and prior work, the Ordóñez well sequence embracing the Ordóñez and Victoriano Rodríguez Formations includes, in addition to the latter two zones, the preceding (late Pennsylvanian) Potonieisporites-Lundbladispora Zone which is known from the lower to mid-upper part of the Ordóñez Formation. Thus, the Carboniferous-Permian boundary can be inferred to lie within the upper part of the latter formation

Analysis of the wind field and heat budget in an alpine lake basin during summertime fair weather conditions

Observational data collected in the Lake Tekapo hydro catchment of the Southern Alps in New Zealand are used to analyse the wind and temperature fields in the alpine lake basin during summertime fair weather conditions. Measurements from surface stations, pilot balloon and tethersonde soundings, Doppler sodar and an instrumented light aircraft provide evidence of multi-scale interacting wind systems, ranging from microscale slope winds to mesoscale coast-to-basin flows. Thermal forcing of the winds occurred due to differential heating as a consequence of orography and heterogeneous surface features, which is quantified by heat budget and pressure field analysis. The daytime vertical temperature structure was characterised by distinct layering. Features of particular interest are the formation of thermal internal boundary layers due to the lake-land discontinuity and the development of elevated mixed layers. The latter were generated by advective heating from the basin and valley sidewalls by slope winds and by a superimposed valley wind blowing from the basin over Lake Tekapo and up the tributary Godley Valley. Daytime heating in the basin and its tributary valleys caused the development of a strong horizontal temperature gradient between the basin atmosphere and that over the surrounding landscape, and hence the development of a mesoscale heat low over the basin. After noon, air from outside the basin started flowing over mountain saddles into the basin causing cooling in the lowest layers, whereas at ridge top height the horizontal air temperature gradient between inside and outside the basin continued to increase. In the early evening, a more massive intrusion of cold air caused rapid cooling and a transition to a rather uniform slightly stable stratification up to about 2000 m agl. The onset time of this rapid cooling varied about 1-2 h between observation sites and was probably triggered by the decay of up-slope winds inside the basin, which previously countered the intrusion of air over the surrounding ridges. The intrusion of air from outside the basin continued until about mid-night, when a northerly mountain wind from the Godley Valley became dominant. The results illustrate the extreme complexity that can be caused by the operation of thermal forcing processes at a wide range of spatial scales.

Numerical simulations of wind and temperature structure within an Alpine lake basin, Lake Tekapo, New Zealand

High-resolution numerical model simulations have been used to study the local and mesoscale thermal circulations in an Alpine lake basin. The lake (87 km(2)) is situated in the Southern Alps, New Zealand and is located in a glacially excavated rock basin surrounded by mountain ranges that reach 3000 m in height. The mesoscale model used (RAMS) is a three-dimensional non-hydrostatic model with a level 2.5 turbulence closure scheme. The model demonstrates that thermal forcing at local (within the basin) and regional (coast-to-basin inflow) scales drive the observed boundary-layer airflow in the lake basin during clear anticyclonic summertime conditions. The results show that the lake can modify (perturb) both the local and regional wind systems. Following sunrise, local thermal circulations dominate, including a lake breeze component that becomes embedded within the background valley wind system. This results in a more divergent flow in the basin extending across the lake shoreline. However, a closed lake breeze circulation is neither observed nor modelled. Modelling results indicate that in the latter part of the day when the mesoscale (coast-to-basin) inflow occurs, the relatively cold pool of lake air in the basin can cause the intrusion to decouple from the surface. Measured data provide qualitative and quantitative support for the model results.

Contributions à la paleontology du Miocène moyen continental du basin du tage

This study on middle Miocene Charophytes from the Tagus'basin indicates the presence of two species. hitherto undescribed from these strata in Portugal, Correlation diagrams of height and width of gyrogonite demonstrate that the populations of Nitellopsis (Tectochara) etrusca from the localities Póvoa de Santarém and Pêro Filho are identical to that from La Grenatière (Hérault, France), The population of Lychnothamnus duplicicarinatus from Tremês is identical to that already known from Anwill (Switzerland). The age of this flora is therefore suggested as being the upper part of the middle Miocene. The results of Charophyte studies are in accordance with stratigraphical conclusions from previously conducted mammalian studies (Antunes and Mein), A table showing the distribution of species in the three portuguese localities is given.

Contributions à la paleontology du Miocène moyen continental du basin du tage

The lignite-clays of Póvoa de Santarém dated as Upper «Vindobonian» (mammalian zone MN6), fielded abundant remains of animals and plants (spores, pollens, seeds, etc.). The forms identified are indicative of several environments. Plants, either aquatic or belonging to swampy areas are predominant (Nuphar sp., Sparganium sp., Stratiotes kaltennordheimensis, cf. Ranunculus sp.). There are also remains of plants characteristiques of a humid rather than a swampy soil such as Polypodiaceae, Myrica ceriferiformis, Toddalia maii, Spirematospermum wetzeleri. The genera Vitis and Ephedra, although rare, point fowards the existence of drier regions in the neighbourhood. The presence of polens such as Picea indicate the presence at some distance less warm upland forest areas.

A reconnaissance study of Upper Jurassic sediments of the Lusitanian Basin

The Upper Jurassic evolution of the Lusitanian Basin is shown to be linked to the rifting phase which preceded the separation of Iberia and the Grand Banks. Structural controls on sedimentation include both NNE-SSW trending faults in the Hercynian basement, and contemporaneous movement of salt diapirs. At the beginning of Upper Oxfordian times, the entire basin had been levelled to within a few metres of sea level, so that the freshwater algal marsh and marginal marine facies of the Cabaços and Vale Verde Beds rest on Triassic to Callovian strata. In the latter part of the Upper Oxfordian. carbonate sedimentation continued, with fluctuating salinity lagoons in the north (Pholodomya protei Beds) separated from shallow open marine carbonates in the south (Montejunto Beds) by the Caldas da Rainha diapir-barrier island complex. The commencement of rifting is recorded in the Kimmeridgian by the sudden influx of terrigenous clastics (developed in both fluviatile and deltaic/submarine fan environments) and accelerated depositional rates in excess of 10cm/10 k.yrs in association with contemporaneous faulting along the SE margin of the Arruda sub-basin. The Caldas-Santa Cruz chain of diapiric structures continued to influence the distribution of carbonate and clastic sediments. In the Portlandian, a simpler facies pattern occurs, with fluviatile clastics interfingering to the south with shallow low energy carbonates.

Contributions à la paleontology du Miocène moyen continental du basin du Tage; (IV) Charophytes - Póvoa de Santarém, Pero Filho et Tremês

This study on middle Miocene Charophytes from the Tagus' basin indicates the presence of two species, hitherto undescribed from these strata in Portugal. Correlation diagrams of height and width of gyrogonite demonstrate that the populations of Nitellopsis (Tectochara) etrusca from the localities Póvoa de Santarém and Pêro Filho are identical to that from La Grenatière (Hérault, France), The population of Lychnothamnus duplicicarinatus from Tremês is identical to that already known from Anwill (Switzerland). The age of this flora is therefore suggested as being the upper part of the middle Miocene. The results of Charophyte studies are in accordance with stratigraphical conclusions from previously conducted mammalian studies (Antunes and Mein). A table showing the distribution of species in the three portuguese localities is given.