大连湾赤潮生物──赤潮异弯藻   总被引：29，自引：6，他引：29  

郭玉洁 《海洋与湖沼》1994,25(2):211-215,T001

于１９８５，１９８６和１９８７三年的夏季在辽宁大连湾采集赤潮生物──赤潮异弯藻，以相差显微镜和扫描电镜进行了形态观察和分类研究；同时述及其分类沿革及至今仍存在的争议，结合本种在大连湾的生态特点简要地综述了其在世界上的分布，生理宗，昼夜垂直移动，营养摄取以及细胞分裂周期和种群繁殖等。结果表明，在温带近海夏，秋季潮异弯藻的生长率最高，冬季休眠于海底；温度是限制其复苏的主要因子。本种昼夜都能摄取营养，生  相似文献   

Magnetostratigraphy of the Plio‐Pleistocene carbonate section of the Great Australian Bight     

M. Fuller  R. Molina-Garza  M. Antretter  F. Lichowski 《Australian Journal of Earth Sciences》2013,60(3):447-466

ODP Leg 182 drilled two north‐south transects in the western Great Australian Bight close to longitude 128°E. These transects penetrated a remarkably thick section of uppermost Pliocene and Pleistocene carbonate sediments, which are separated from Miocene sections by a major hiatus. In the eastern transect, at sites 1129, 1131 and 1127, the Brunhes‐Matuyama boundary (onset of C1n) was found at 343 m, between 280 and 300 m, and at 343 m below the sea floor, respectively. In the western transect, at sites 1132 and 1130, it was found between 170 and 181 m, and at 200 m, respectively. Within the Brunhes chron, inclination and intensity fluctuations and correlations between susceptibility and standard δ¹⁸O records were used to give age‐depth relations. These age relations from the palaeomagnetics are broadly consistent with the biostratigraphy and the δ¹⁸O results from Leg 182, but do not provide an entirely independent dataset. Rock magnetism stratigraphy at site 1131 revealed the principal bryozoan buildup to be at the time of the last glacial lowstand, as suggested by previous workers. At all sites the sedimentation rate increases from the basal unconformity up into the thick Upper Pleistocene section. In the western transect there appears to be a partial record of most of the Late Pliocene and Early Pleistocene chron boundaries (C1r1n to C2An3n) in a condensed section, but in the eastern transect only the Jaramillo (C1r1n) is observed.  相似文献   

Environmental influence on phytoplankton production during summer on the KwaZulu-Natal shelf of the Agulhas ecosystem     

T Lamont  RG Barlow 《African Journal of Marine Science》2015,37(4):485-501

During February 2010, studies of primary production (PP) and physiology were conducted at five selected sites in the KwaZulu-Natal (KZN) Bight of the Agulhas ecosystem as part of a programme to elucidate the influence of major physical driving forces and nutrient inputs on the structure and functioning of biological communities. These sites were located in the vicinity of the Durban lee eddy, in the midshelf region of the central part of the bight, off the Thukela Mouth, and to the north and south of Richards Bay. At four of the sites, chlorophyll a ranged from 0.10 to 1.44?mg m–3 and integrated PP ranged between 0.35 and 2.58?g C m–² d–1. The highest biomass and PP, which were comparable to those observed in a wind-driven upwelling system, were associated with a diatom community observed at the midshelf site, and varied between 0.26 and 4.27?mg m–³ and 7.22 and 9.89?g C m–² d–1, respectively. Environmental conditions at each of the sites differed substantially and appeared to be influential in initiating and controlling the development and distribution of phytoplankton biomass and production. Phytoplankton adaptation to variable environmental conditions was characterised by a decreased light-limited slope (αB) and increased rate of photosynthesis (P_m ) and light saturation (Ek) with elevated temperatures. The converse (increased α^B and decreased P_m and Ek) was observed as irradiance levels declined. Generalised additive models indicated that irradiance, temperature and biomass were important variables influencing photosynthetic parameters and photosynthetic rates.  相似文献   

NIZUSE: a deep seismic reflection line in north-eastern Germany     

Wolfgang Horst  Michael Börngen  Ernst R. flueh 《International Journal of Earth Sciences》1994,83(1):161-169

Out of a dense network of seismic reflection lines for hydrocarbon exploration in the North-east German Basin, several lines were recorded to 12 s TWT to obtain information about the structure of the crust and the crust-mantle transition. One of these profiles is presented here. This stretches for 110 km in a NNE direction between Neustrelitz and the island of Usedom. It reaches from the External Variscides in the south across the North German Massif into the Rügen-Pomorze Terrane in the Baltic Sea. Below Cenozoic-Mesozoic-Paleozoic cover with clear reflections down to base Zechstein, the reflectivity varies considerably with depth and also laterally. The Paleozoic and Precambrian sediments and basement are generally void of reflections, but the lower crust and the Moho show strong reflections. To the north the reflectivity decreases, and the Moho depth increases to beyond the bottom of the record section at 12 s. There are no direct indications for deep-reaching faults such as the Trans-European Fault in the north. The North German Massif acted as a ramp towards the Variscan Orogeny, similar to the London-Brabant Massif further west.  相似文献   

The thermal regime of the Northeastern-German Basin from 2-D inversion   总被引：2，自引：0，他引：2  

Hans-Dieter Vosteen  Volker Rath  Andreas Schmidt-Mumm  Christoph Clauser   《Tectonophysics》2004,386(1-2):81-95

The thermal regime and the distribution of heat flow at the base of sedimentary basins is fundamental to the understanding of the process of basin evolution and the associated mobilization and migration of hydrocarbon and other fluids. For the Northeastern-German sedimentary basin, available information on structure, temperature, and thermal properties along a seismic DEKORP reflection profile allow high resolution 2-D forward and inverse simulations. This approach is attractive in situations where much information is available, if only with considerable uncertainty. In particular, this allows to introduce “soft” information into the analysis. In our case, forward simulations yield initial a priori estimates of the parameters while inversion calculations yield a posteriori estimates of the parameters and their uncertainty. The a priori parameters as well as their assumed uncertainty are input for a Bayesian parameter estimation scheme. In respect to the Northeastern-German sedimentary basin, the inverse analysis postulates a significant and characteristic a posteriori variation of thermal conductivity of the Zechstein unit along the entire profile as well as a generally large a posteriori thermal conductivity of the (pre-Permian) basement in the northern part of the basin. For inverse calculations, we used two alternative scenarios: One assumes the thermal conductivity of the Zechstein unit to be homogeneous along the profile while the other allows a lateral variation. A posteriori heat flow across the base of the model varies from 40 to 60 and 50 to 65 mW m⁻² for models in which values for thermal conductivity and radiogenic heat generation rate were either based on literature values or direct measurements, respectively.  相似文献   

The Mesozoic–Cenozoic structural framework of the Bay of Kiel area, western Baltic Sea     

Martin Bak Hansen  Holger Lykke-Andersen  Ali Dehghani  Dirk Gajewski  Christian Hübscher  Morten Olesen  Klaus Reicherter 《International Journal of Earth Sciences》2005,94(5-6):1070-1082

A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic, E–W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence. Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned faulting.  相似文献   

River plume patterns and dynamics within the Southern California Bight     

J.A. Warrick  P.M. DiGiacomo  S.B. Weisberg  N.P. Nezlin  M. Mengel  B.H. Jones  J.C. Ohlmann  L. Washburn  E.J. Terrill  K.L. Farnsworth 《Continental Shelf Research》2007

Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r²=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r²=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes.  相似文献   

Tasman Geosyncline greenstones and ophiolites   总被引：1，自引：1，他引：0  

K. A. W. Crook  E. Anne Felton 《Australian Journal of Earth Sciences》2013,60(1):117-131

Palaeozoic greenstones lying at the base of stratigraphic sequences or in fault blocks in the Tasman Geosyncline are compared with the Penrose Conference definnition of an ophiolite by using tabulated petrological, structural, and metallogenic data. Of 45 occurrences, only 9 are recognizably ophiolites: 4 are in rift zones adjoining Precambrian continental crust at the ends of the geosyncline; and away from the margins, in that part of the geosyncline most typically of West Pacific‐type, only 5 of the 33 greenstone occurrences are recognizably ophiolites. Ophiolites are rare in the Tasman Geosyncline, in contrast to several Atlantic‐type geosynclines. This may be a characteristic of West Pacific‐type geosynclines in general.

Alpine‐type serpentinites are rather common in the Tasman Geosyncline. The metallogeny of some shows affinities with ophiolites, suggesting a common origin as oceanic crust. Their relative abundance suggests that West Pacific‐type geosynclines, such as the Tasman Geosyncline, may have developed on oceanic crust of unusual composition. Alternatively, it may reflect differences of deformation style between Atlantic‐ and West Pacific‐type geosynclines.

The term ophiolite has been used uncritically in plate tectonic analyses of the Tasman Geosyncline, calling in question the objectivity of these analyses. If objectivity is to be maintained, some indication should be given of the quality of the data used in plate tectonic analyses.  相似文献   

Plate-driven extension and convergence along the East Gondwana active margin: Late Silurian–Middle Devonian tectonics of the Lachlan Fold Belt,southeastern Australia     

A. G. Rossiter  C. M. Gray 《Australian Journal of Earth Sciences》2013,60(1):109-110

The Werner deconvolution technique for automatic analysis of magnetic data is a powerful tool for the interpretation of magnetic profiles. In particular, the technique is a valuable aid to the interpretation of deep crustal structures beneath the continental margin which frequently lie below the penetration of all but the most high-powered seismic reflection tools. Inverse modelling of selected simple geological structures (buried scarp, graben, half-graben) confirms that the interface model is valuable in delineating the tops of magnetic bodies, while the thin sheet model gives an indication of the depth extent of the bodies. In the case of horizontal sheets in contact (simulating oceanic spreading anomalies), the thin sheet model delineates the boundary, while the interface model gives estimates which are too shallow.

As an illustration of the value of the Werner deconvolution method in regional marine studies, the magnetic basement in the Great Australian Bight (GAB) has been mapped using a set of magnetic profiles; seismic data in the GAB is of limited use in this mapping. Interpretation of the profiles confirms earlier assessments that there is a minimum of 10 km of sediment beneath the Ceduna Terrace (Great Australian Bight Basin), 3 km beneath the Eyre Terrace (Eyre Sub-basin), 6 km in the Duntroon Embayment, 3 km in the Polda Trough, and 4 km beneath the continental rise. The most prominent basement structure in the GAB is the east-west-trending scarp which delineates the northern flank of the Eyre Sub-basin, GAB Basin, and Polda Trough. The gross linearity of this escarpment for 1000 km and the fact that it appears to mark a northern boundary to the extensional basins of the margin suggests that continental extension in the pre-Middle Jurassic took place preferentially south of an old (Precambrian) lineament in the Gawler Block. Polda Trough sediments are probably included in fault-blocks underlying the northern part of the GAB Basin. The interpretation supports the concept of northwest-southeast extension prior to Late Cretaceous breakup.  相似文献   

Shelf currents,lee-trapped and transient eddies on the inshore boundary of the Agulhas Current,South Africa: their relevance to the KwaZulu-Natal sardine run     

《African Journal of Marine Science》2013,35(2):423-447

The existence and strength of the annual KwaZulu-Natal (KZN) sardine run has long been a conundrum to fishers and scientists alike ― particularly that the sardine Sardinops sagax migrate along the narrow Transkei shelf against the powerful, warm Agulhas Current. However, examination of ship-borne acoustic Doppler current profiler (S–ADCP) data collected during two research surveys in 2005 indicated that northward-flowing coastal countercurrents exist at times between the Agulhas Bank and the KZN Bight, near Port Alfred, East London, Port St Johns and Durban. The countercurrent near Port Alfred extended as far east as the Keiskamma River, within an upwelling zone known to exist there. An ADCP mooring at a depth of 32 m off Port Alfred indicated that the countercurrent typically lasted a few days, but at times remained in the same direction for as long as 10 days. Velocities ranged between 20 and 60 cm s^?1 with maximum values of ～80 cm s^?1. The S–ADCP data also highlighted the existence of cyclonic flow in the Port St Johns–Waterfall Bluff coastal inset, with a northward coastal current similarly ranging in velocity between 20 and 60 cm s^?1. CTD data indicated that this was associated with shelf-edge upwelling, with surface temperatures 2–4 °C cooler than the adjacent core temperature (24–26 °C) of the Agulhas Current. Vertical profiles of the S–ADCP data showed that the countercurrent, about 7 km wide, extends down the slope to at least 600 m, where it appeared to link with the deep Agulhas Undercurrent at 800 m. S–ADCP and sea surface temperature (SST) satellite data confirmed the existence of the semi-permanent, lee-trapped, cyclonic eddy off Durban, associated with a well-defined northward coastal current between Park Rynie and Balito Bay. Analysis of three months (May–July 2005) of satellite SST and ocean colour data showed the shoreward core-boundary of the Agulhas Current (24 °C isotherm) to commonly be close to the coast along the KZN south coast, as well as between the Kei and Mbhashe rivers on the Transkei shelf. The Port St Johns–Waterfall Bluff cyclonic eddy was also frequently visible in these satellite data. Transient cyclonic eddies, which spanned 150–200 km of shelf, appeared to move downstream in the shoreward boundary of the Agulhas Current at a frequency of about once a month. These seemed to be break-away Durban eddies. Data collected by ADCP moorings deployed off Port Edward in 2005 showed that these break-away eddies and the well-known Natal Pulse are associated with temporary northward countercurrents on the shelf, which can last up to six days. It is proposed that these countercurrents off Port Alfred, East London and Port St Johns assist sardine to swim northwards along the Transkei shelf against the Agulhas Current, but that their progress north of Waterfall Bluff is dependent on the arrival of a transient, southward-moving, break-away Durban cyclonic eddy, which apparently sheds every 4–6 weeks, or on the generation of a Natal Pulse. This passage control mechanism has been coined the ‘Waterfall Bluff gateway’ hypothesis. The sardine run survey in June–July 2005 was undertaken in the absence of a cyclonic eddy on the KZN south coast, i.e. when the ‘gate’ was closed.  相似文献