OCEANOGRAPHIC OBSERVATIONS IN THE LAGOON OF KAIAFA (W PELOPONNESE)

The Kaifa lagoon is a coastal marine ecosystem located in the Kyparisiakos Bay. The purpose of this study is to: (a) To determine the spatial and temporal changes of the physicochemical parameters in the water column of the Kaifa lagoon and (b). To create a base of information for future use for the restoration of the lagoon. Temperature, salinity, pH and dissolved oxygen were measured insitu in 28 stations. Furthermore, water samples were taken for the determination of NO2, NO3, NH4 and PO4 on seasonal bnsin from November '94 to September '95. The temperature was fluctuating from 15,90 °C in March to 30,41 °C in late August and late September. Further the seasonal variation of the temperature showed the expected two thermal periods. The first period is a hot period showing a continuous increase of temperature from March to September. The second period is a cold period showing a continuous decrease of temperature from the September to March. For each period of sampling the temperature of lagoonal water in all the extent of the lagoon remains practically constant because the fluctuation of temperature is very small each time. The salinity varied between 7,2%o and 9,20%o. The salinity like the temperature presented seasonal fluctuation patterns but the lagoon is brackish all the year round. The spatial changes of salinity were absent for every sampling period. The pH values ranged from 6,70 to 8,40. So, the pH values fluctuated in the normal levels for aquatic animals. Further, these are relatively high in spring (arithmetic mean=7.8) owing probably to higher photosynthesis rate. Dissolved oxygen ranges from 3,30 mg/l to 10,00 mg/l. In the sampling periods of September and November the oxygen values were less than 7,00mg/l for a large part of the lagoon except southern margins. This evidence suggests dangerous conditions for the fish life. Phosphate concentrations were low (0,010 mg/l - 0,07 mg/l), in November. On the contrary the phosphate levels were high (on the average 0,111 mg/l) in the sampling period of September and in particular in the southern part of the lagoon. So, this part indicated photosynthetic activity. Further, In March the phosphate concentrations have an intermediate value for every sampling station in relation to the other sampling periods. Ammonia concentrations were considered high (0,24 mg/l - 2,68 mg/l) all the year round. Nitrate levels fluctuated around normal values (0,018 mg/l -0,11mg/l) during the year. The high amount of the ammonia nitrite and nitrate in November suggests the pollution of lagoon from the fertilizers into lagoon through two drainage canals. Nitrite concentrations were high during the cold period (0,041 mg/l - 0,280 mg/l). The spatial and temporal variability of the abiotic parameters of the lagoonal water must be attributed mainly to the strong influence of fresh water witch is discharged into the lagoon from a adjacent karst with hot springs.

Climate Change Impacts Assessment in Coastal Lagoons Using Available Modelling Tools

Climate change such as sea level rise, change in temperature, precipitation, and storminess are expected to impact significantly coastal lagoons. The nature and magnitude of these impacts are uncertain. The objective of the research is to determine the climate change impacts on mixing and circulation at Songkhla lagoon, Thailand. Songkhla lagoon is the largest lagoonal water resource in Thailand and Southeast Asia. The lagoon is a combined freshwater and estuarine complex of high productivity which represents an extraordinary combination of environmental resources believed to be unique in the region. This work is part of a Climate Change impact assessment framework. It is the validation phase (step 5) of the framework applying a case study. Delft 3D was used to simulate CC scenarios in the climate downscaling models, part of the previous framework steps. These results were compared to the current conditions to determine the main changes in mixing and circulation in the coastal lagoon. Three indicators were applied to quantify the impacts: flushing time, salinity intrusion and stratification. The results suggest an increase in water velocities at the inlet in future scenarios and a decrease of flushing time. Salinity and stratification showed more complex changes in futures scenarios.

Chemical signature of two Permian volcanic ash deposits within a bentonite bed from Melo, Uruguay

A Permian bentonite deposit at Melo, Uruguay is composed of a calcite-cemented sandstone containing clay pseudomorphs of glass shards (0-0.50 m) overlying a pink massive clay deposit (0.50-2.10m). The massive bed is composed of two layers containing quartz and smectite or pure smectite respectively. The smectite is remarkably homogeneous throughout the profile: it is a complex mixed layer composed of three layer types whose expandability with ethylene glycol (2EG 1EG or 0EG sheets in the interlayer zone which correspond to low-, medium- and high-charge layers respectively) varies with the cation saturating the interlayer zone. The smectite homogeneity through the profile is the signature of an early alteration process in a lagoonal water which was over saturated with respect to calcite. Compaction during burial has made the bentonite bed a K-depleted closed system in which diagenetic illitization was inhibited. Variations in major, REE and minor element abundances throughout the massive clay deposit suggest that it originated from two successive ash falls. The incompatible element abundances are consistent with that of a volcanic glass fractionated from a rhyolite magma formed in a subduction/collision geological context.

A PROCESS-RESPONSE MODEL FOR HURRICANE WASHOVERS

The passage of Hurricane Allen over Padre Island in August 1980 presented an excellent opportunity to study the effects and controls of coastal morphology on hurricane deposits. In the Caribbean Sea, Hurricane Allen achieved a central pressure of 899 mb, making it the second strongest Atlantic hurricane ever recorded. Once in the Gulf of Mexico, the storm approached the Texas coast from the east-southeast, building a significant storm surge. Near Brownsville, the storm stalled, spending much of its energy offshore before making landfall early on August 10th near Brazos Santiago Pass at the southern tip of Padre Island. Surge gauges show that peak recorded storm tides of about 3 m occurred at Port Mansfield, some 35 km north of landfall. Analysis of tide data indicates a time lag of some 14 hours on the rising storm tide between the Gulf and south Laguna Madre. This is due both to the limited tidal exchange across Padre Island and to set-down in the lagoon due to southward-directed cyclonic winds. By contrast, measurements taken in Corpus Christi Bay, some 180 km north of landfall, show that at that point Gulf and bay tides were in phase. The cross-barrier water level differential at South Padre Island (up to 1.5 m) greatly facilitated hurricane breaching of the island. Oblique and vertical aerial photography show that Padre Island was breached in many places, with about 40 major hurricane channels still open several days after the storm. Surge heights were sufficient to inundate all of South Padre Island except for isolated "dune islands" resulting in broad and often coalescing washover deposits. The more continuous dune ridge on North Padre Island resulted in smaller, discrete washovers. Intensity, distribution, and morphology of washovers are functions of storm tide elevation, its phase relationships, island topography, and lagoonal water depth. The relationship is complex, yet precise enough to permit prediction of the island's response to the impact of a given storm.

Carbonate–sulphate–redbed facies and cyclic sedimentation of the Windsorian Stage (Middle Carboniferous), Maritime Provinces

After the late Devonian orogeny, thick Carboniferous, mainly continental redbeds, derived from intrabasinal horsts, accumulated in a complex rift-valley system called the Fundy basin. During the mid-Carboniferous Windsorian Stage, generally hypersaline seas flooded repeatedly into the tortuously interconnected, intrabasinal grabens. The resulting carbonate–sulfate blankets intertongue laterally with increasingly coarser redbeds and even basalt adjacent to the horst. Macrofaunal, microfaunal, insoluble residue, heavy-mineral, and trace-element analyses and Irwin-logs have limited success in identifying remnants of each particular blanket. Nevertheless, a Windsorian facies model is constructed from detail microscopy and Recent analogues, including field work in Bermuda.Windsorian carbonates are mainly shallow marine to supratidal; calcium sulfate is mainly diagenetic and supratidal, precipitated within, not on, subaerial salt flats; and redbeds are mainly subaerial and diagenetic, pigmented by post-depositional alteration of iron-rich detrital minerals. Dolomitization was both penecontemporaneous within the salt flat by influxing lagoonal water, and also secondary within buried, permeable, basinward lithosomes by refluxing brine. Gypsum–anhydrite nodules metamorphose on stress from mosaic, through penemosaic structures, and finally to massive, porphyroblastic plutons.Floodings in the Antigonish–Mabou basin were from the north–the present Gulf of St. Lawrence. Cyclic sedimentation was probably due to fluctuating supply of terrigenous detritus into a continually subsiding basin.