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1.
Two species of burrowing shrimp occur in high densities in US West Coast estuaries, the ghost shrimp, Neotrypaea californiensis, and the blue mud shrimp, Upogebia pugettensis. Both species of shrimp are considered ecosystem engineers as they bioturbate and irrigate extensive galleries within the sediment. While their burrows comprise a dominant habitat type in west coast estuaries, little is known about these shrimps’ diet and their role in estuarine food webs. The primary goals of this study were to identify major components of burrowing shrimp diets and detect variation in these diets along an estuarine gradient using combined fatty acid (FA) and stable isotope (SI) analyses. Shrimp and potential food sources including eelgrass blades, epiphytes, Ulva, sedimentary particulate organic matter (SPOM), burrow walls, and particulate organic material (POM) were sampled at different locations within Yaquina Bay, Oregon in August 2012. Both SI and FA analyses indicated differences in food resources assimilated by shrimp along the estuarine gradient. SI values showed that diets for U. pugettensis consisted of carbon sources derived primarily from POM and SPOM, while POM and epiphytes were primary carbon sources for N. californiensis. Shrimp from lower estuarine sites had high levels of 16:1ω7 and 20:5ω3 FAs suggesting their diet is enriched with marine diatoms. Shrimp from upriver showed greater proportion of FA associated with dinoflagellates and terrestrial sources as indicated by a high percentage of C18 polyunsaturated FAs (PUFAs). This is the first study to evaluate diets of these two shrimp species using complimentary FA and SI approaches.  相似文献   

2.
Tidal wetlands are affected by sea level rise. In the tidal freshwater stretches of estuaries in the temperate zone, willows (Salix spp.) form tidal freshwater forests above the mean high water level. Willows tolerance to prolonged periodic flooding in riverine systems is well documented, whereas effects of tidal flooding on willows are largely unknown. Flooding stress may play a major role in regeneration failure of willows in tidal forest stands along estuarine shores, and juvenile willows might be specifically affected by partial or total submergence. To assess the tolerance of juvenile willows to tidal flooding, we conducted a mesocosm experiment with cuttings from Salix alba and Salix viminalis, which are both characteristic species for tidal freshwater forests in Europe. Cuttings originating from either fresh or brackish tidal forest stands were grown under four tidal treatments with up to a tidal flooding of 60 cm. A general tolerance to a tidal flooding of 60 cm was observed in chlorophyll fluorescence, growth rates, and biomass production in both willow species. Overall, S. alba showed higher leaf and shoot growth, whereas S. viminalis produced more biomass. S. alba with brackish origin performed worst with increasing tidal flooding, suggesting a possible pre-weakening due to stressful site conditions in tidal wetlands at the estuarine brackish stretch. This study demonstrates that juvenile willows of S. alba and S. viminalis tolerate tidal flooding of up to 60 cm. It is concluded that tidal inundation acts as a stress by causing submergence and soil anaerobiosis, but may also act as a subsidy by reestablishing aerobic conditions and thus maintaining willows performance. Therefore, we suggest investigations on Salix tidal flooding tolerance and possible effects of willows on tidal wetland accretion under estuarine field conditions.  相似文献   

3.
Diatoms and marine palynomorphs from several sections of the Kamyshin Formation (Sengilei-1, Sengilei-2, Balasheika, Kuz’kino, boreholes 38 and 50) are jointly studied for the first time in the Volga middle reaches. According to results, the formation lower part corresponds here to Viborg Zone 4-Viborg Zone 5 (Heilmann-Clausen, 1985)/Alisocysta margarita (part)-Apectodinium hyperacanthum (Powell, 1992) diatom zones of Northern Europe. Higher levels of the formation are correlative with Trinacria ventriculosa and Hemiaulus proteus dinocyst zones (Strelnikova, 1992). Thus, the Kamyshin sedimentary cycle in the Volga middle reaches corresponds to the interval of NP8 (part) and NP9 zones of the general scale. As is established, different terrigenous to siliceous facies of that cycle (sands, diatomites, opokas and clay) are mostly confined to eastern and southeastern areas of the study region. Judging from taxonomic composition, assemblages of diatoms and marine palynomorphs originated in coastal paleosettings with active hydrodynamics and high productivity of water mass. Diatom assemblages from different facies are dissimilar. Three phases of Thanetian transgression are distinguished based on quantitative proportions of different ecologic groups (Paralia/Pyxidicula ratio variations). Within transition from the Trinacria ventriculosa to Hemiaulus proteus Zone, there are recorded considerable changes in composition of diatom assemblages: the appearance of new genera with considerable morphologic innovations (Podosira, Craspedodiscus, Fenestrella, Moisseevia, Solium, Gyrocylindrus) and compositional renewals of genera Pyxidicula, Trinacria, and Hemiaulus. These changes are indicative of a global biotic crisis in the Paleocene-Eocene transition related with thermal maximum and negative C-isotope excursion and extinction of benthic fauna groups.  相似文献   

4.
On the basis of distinct lithologic features such as composition, grain size, bedding characteristics and sedimentary structures, six facies were identified in Callovian to Oxfordian rocks exposed southwest of Bhuj, Kachchh. They are interbedded calcareous shale-siltstone (ICSSF), limestone (LF), ferruginous sandstone (FerSF), felspathic sandstone (FelSF), grey shale (GSF) and oolitic limestone (OLF) facies. The rich and highly diversified trace fossils reveal a wide range of animal behaviours represented by dwelling, feeding, crawling and resting structures. Horizontal feeding structures are found abundantly in all lithofacies indicating low wave and current energy and deposition of poorly sorted muddy to sandy sediments. A few coarse layers containing Arenicolites, Ophiomorpha and Skolithos indicate the presence of opportunistic animals (due to their first appearance under harsh conditions) under -intermittently moderate wave and current energy or storm wave conditions (due to coarse grain size and dominance/presence of only vertical trace fossils) in the shoreface zone. Taenidium occurs mainly in the lower shoreface to transitional zone suggesting low to moderate energy conditions. Thalassinoides occurs in middle to lower shoreface settings under relatively low-energy conditions. Zoophycos represents offshore environment, where it occupies the deepest bioturbation levels.The characteristic lithofacies and assemblages of trace fossils in the rocks of the Chari/Jumara Formation indicate a depositional environment fluctuating from the upper shoreface to offshore zone.  相似文献   

5.
Sundarban is a largest mangrove forest delta developed along the NE-SW direction covering parts of India and Bangladesh. Little work has been done on Indian part of Sundarban in respect of heterogeneity in channel morphology which could be mostly due to the effect of tilting and basin subsidence. These changes might have played a major role on development of high marshes, which offers a congenial environment for survival of Haplophragmoides wilberti, Jadammina macrescens, Trochammina inflata, and Miliammina fusca. These marsh benthonic foraminiferal assemblages provide a direct evidence of recent past sea level changes. To establish the depositional pattern and their effects rendered by merciless changing environment, 11 pit sections have been excavated along three E-W transects from Indian Sundarban. Depth of these pit sections varies from 2 to 3 m. Generally, top 20 cm sediment (in pit section W-1 to W-11) deposited under the intertidal environment, as indicated by the presence of Ammonia tepida. However, sediment below 20 cm in some of the pit sections (W-3 and W-5) exhibits fresh water signatures as indicated by the presence of Charophytes algae. In other pit sections (W-1, W-2, W-6, W-7, W-8, W-9 and W-11), the intertidal assemblage is noticed just above the upper marshes assemblage and vice versa, signifying that depositional environment is in proximity to the mangrove dominated area as indicated by the presence of marsh benthonic foraminiferal assemblage containing T. inflata, H. wilberti, Haplophragmoides sp., J. macrescens and M. fusca. Bottom sediment in most of the pit sections from south to north have different depositional environment with alternate presence of intertidal to subtidal faunal assemblages. The peculiar presence of intertidal assemblage above the upper marshes assemblages in recent sediment points towards the theory of submergence due to relative rise in the sea level. But the effect of relative sea level rise is not uniform throughout the area because of differential subsidence due to varied rate of sediment supply (0.5 to 3.3 cm/year) and eastward tilting of the basin. Based on the upper marshes benthonic foraminiferal assemblage and radiocarbon age (in W-1 at 100 cm ~?150 years age), the average subsidence rate as recorded is approximately 0.3 to 0.5 cm/year. Hence, such depositional sequence conjectures that the Indian part of Sundarban is undergoing a phase of submergence concomitant to basin subsidence.  相似文献   

6.
Continental (fluvial) strata of the Pinjor Formation (Siwalik Group), northwestern Himalayas, India, contain an invertebrate trace fossil assemblage containing Planolites beverleyensis, Palaeophycus isp., Scoyenia gracilis, Taenidium barretti and other undifferentiated traces. The traces are found in an \(\sim \)26 m thick interval of alternating pinkish red siltstone, which is intercalated with mudstone, and thickly-bedded buff and greenish coloured sandstone. These sediments are interpreted as the deposits of floodplains and channel-bars of fluvial environments and low-energy overbank floodplain deposits. The trace fossils studied here are the first well documented ichnofossil assemblage from the vast, late Cenozoic Siwalik depositional system. They are not only of palaeoenvironmental significance, but they add to the growing ichnofossil database in facies of fluvial origin and should be an impetus to further ichnological studies of the Siwalik Group.  相似文献   

7.
The External Tanger Unit represents one of the most complete Cretaceous-Miocene successions in the central areas of the Internal Intrarif sub-Domain (External Rif Zones, Morocco). An interdisciplinary study has been carried out to propose a new characterization of this unit which would allow a better comprehension of the confused and complex relationships among different units of the same sub-domain. The results achieved can be summarized as follows: (1) redefinition of the stratigraphic (litho-, bio-, and chrono-) record and introduction of a new, informal lithostratigraphic terminology; (2) recognition of two main depositional sequences (lower-middle Eocene p.p. and lower Oligocene p.p.-lower Miocene p.p.) separated by extended gaps (latest Cretaceous-early Eocene p.p. and middle Eocene p.p.-early Oligocene p.p.); (3) reconstruction of the evolution of the sedimentary realm, and of the relationships between tectonics and sedimentation; and (4) comparison between the upper Cretaceous-Miocene stratigraphic record and tectonic events of the Intrarif, which is located in the western external portion of the Maghrebian Flysch Basin, and the equivalent sedimentary record of the eastern portion of this basin in the Tunisian Tell. More in general, our results allowed (i) a first reconstruction of the Cretaceous-Miocene main tectono-sedimentary events; (ii) a more detailed location of the sedimentary suite in the external African Margin in the context of a wider palaeogeographic framework; and (iii) the definition of the main stages of the geological evolution of the area.  相似文献   

8.
Benthic microalgae are key contributors to near-shore food webs and sediment stabilization. Temporal variability in microalgal biomass and production throughout the tidal cycle has been well documented; however, due to limitations of traditional methods of analysis patterns of community composition and diversity over such time scales have not been revealed. To explore the latter and better understand how short-term changes throughout the tidal cycle may affect community functioning, we compared benthic diatom composition and diversity over tidal stage shifts. We employed two disparate molecular techniques (denaturing gel gradient electrophoresis with Sanger DNA sequencing of excised bands and high-throughput community metagenome sequencing) to characterize diatom assemblages in representative muddy and sandy intertidal sites in Charleston Harbor, SC, USA. In support of prior studies, we found higher diatom diversity in sandbar as compared to mudflat sediments. Spatial differences were stronger relative to tidal temporal differences, although diversity metrics generally were highest after prolonged tidal immersion as compared to low-tide emersion or just after immersion at flood tide. Composition of the diatom assemblage differed markedly between sites, with species in genera Halamphora, Amphora, and Navicula dominating the sandbar, whereas Cyclotella, Skeletonema, and Thalassiosira were the most prevalent genera on the mudflat. Diatom composition differed by tidal stage, with assemblages during low-tide exposure distinct from samples taken after immersion. Both sandbar and mudflat sediments exhibited increases in relative proportion of epipelic diatoms and decreases in planktonic taxa during low-tide exposure. Our findings of short-term changes in species composition and dominance could inform primary productivity models to better estimate understudied diatom contributions in heterogeneous and highly variable tidal systems.  相似文献   

9.
The Maastrichtian Patti Formation, which consists of shale - claystone and sandstone members, constitutes one of the three Upper Cretaceous lithostratigraphic units of the intracratonic southeastern Bida Basin, in central Nigeria. Well exposed outcrops of this formation were investigated at various locations around the confluence of the Niger and Benue Rivers. The lithostratigraphic sections were measured and their peculiar sedimentological features such as textures, physical and biogenic sedimentary structures, facies variations and associations were documented and used to interpret the depositional environments and develop a paleogeographic model. Some selected representative samples of the sedimentary depositional facies were also subjected to grain size analysis.Three shoreline sedimentary depositional facies composed of shoreface, tidal channel, and tidal marsh to coastal swamp facies were recognized in the study area. Continental sedimentary depositional facies such as fluvial channel, swamp, and overbank were also documented. The sandstones of the shoreface and tidal channel facies are medium- to coarse-grained, moderately sorted (standard deviation ranges from 0.45–1.28 averaging 0.72), and quartzarenitic. The fluvial channel sandstone facies are coarse- to very coarse-grained, mostly poorly sorted (standard deviation ranges from 0.6–1.56 averaging 1.17), and subarkosic. Typical sedimentary structures displayed by the shoreface and tidal channel facies include burrows, clay drapes, hummocky and herringbone cross stratifications, whereas the fluvial channel sandstone facies are dominated by massive and planar cross beddings. The tidal marsh to coastal swamp shales and ferruginised siltstone facies are fossiliferous and bioturbated, whereas the nonmarine swamp siltstones contain vegetal imprints and lignite interbeds. The overbank claystone facies are massive and kaolinitic.In the study area, a regressive to transgressive model is proposed for the Patti Formation. This model correlates with stratigraphically equivalent sediments of the Ajali and Mamu Formations in the adjacent Anambra Basin to a great extent.  相似文献   

10.
Eighteen coastal-plain depositional sequences that can be correlated to shallow- to deep-water clinoforms in the Eocene Central Basin of Spitsbergen were studied in 1 × 15 km scale mountainside exposures. The overall mud-prone (>300 m thick) coastal-plain succession is divided by prominent fluvial erosion surfaces into vertically stacked depositional sequences, 7–44 m thick. The erosion surfaces are overlain by fluvial conglomerates and coarse-grained sandstones. The fluvial deposits show tidal influence at their seaward ends. The fluvial deposits pass upwards into macrotidal tide-dominated estuarine deposits, with coarse-grained river-dominated facies followed further seawards by high- and low-sinuosity tidal channels, upper-flow-regime tidal flats, and tidal sand bar facies associations. Laterally, marginal sandy to muddy tidal flat and marsh deposits occur. The fluvial/estuarine sequences are interpreted as having accumulated as a series of incised valley fills because: (i) the basal fluvial erosion surfaces, with at least 16 m of local erosional relief, are regional incisions; (ii) the basal fluvial deposits exhibit a significant basinward facies shift; (iii) the regional erosion surfaces can be correlated with rooted horizons in the interfluve areas; and (iv) the estuarine deposits onlap the valley walls in a landward direction. The coastal-plain deposits represent the topset to clinoforms that formed during progradational infilling of the Eocene Central Basin. Despite large-scale progradation, the sequences are volumetrically dominated by lowstand fluvial deposits and especially by transgressive estuarine deposits. The transgressive deposits are overlain by highstand units in only about 30% of the sequences. The depositional system remained an estuary even during highstand conditions, as evidenced by the continued bedload convergence in the inner-estuarine tidal channels.  相似文献   

11.
The Jahrum Formation (Upper Paleocene to Middle Eocene) is composed of carbonate and dolomitic carbonate rocks in the Zagros Basin. The Zagros is located at the boundary between the Arabian and Eurasian lithosphere plates and represent the orogenic response to a collision between Eurasia and advancing Arabia during the Cenozoic. The study area is located in the northern part of Kuh-E-Tudej, ~175 km southeast of Shiraz in the Folded Zagros Zone. The Jahrum Formation at Kuh-E-Tudej, with a thickness of 190 m, consists of medium to massive bedded limestone. The following foraminiferal index species are identified in the studied section: Fallotella alavensis, Kathina sp., Miscellanea sp., Lockhartia sp.,Orbitolites shirazeinsis, Nummulites sp., Opertorbitolites sp., Dictyoconus cf. egyptiensis, Orbitolites cf. complanatus, Dictyoconus sp., Coskinolina sp., Somalina stefaninii, Discocyclina sp., Praerhapydionina sp., Coskinolina cf. liburnica, Nummulites cf. globulus, Nummulites cf. aturicus, and Alveolina sp. The age of the studied sediments ranges from Upper Paleocene to Middle Eocene. The microbiostratigraphic studies revealed four biozones based on the foraminifers identified in the studied section.  相似文献   

12.
The echinoid fauna from the Miocene sedimentary succession cropping out south Wadi Tweirig, and Wadi Hommath, south Gebel Ataqa, NW Gulf of Suez, has been examined with the aim to known their stratigraphic and paleogeographic distribution. The Miocene succession includes two formations: Sadat Formation, unconformably overlying the middle/upper Eocene rocks at the base and Hommath Formation at the top. Twenty-eight echinoid species (8 regular and 20 irregular) belonging to 18 genera, 13 families, and 7 orders have been identified, systematically described, and illustrated in this work. Eleven species are recorded for the first time from Egypt: ten of these came from the Hommath Formation (Schizechinus cf. serresii Desor (1856), Schizechinus pentagonus Kier 1972, Clypeaster cf. martini des Moulins 1837, Scutella checchiae occidentalis Desio 1934, Scutella melitensis Airaghi 1902, Echinodiscus desori Duncan and Sladen 1883, Echinolampas cf. zeitensis Fourtau 1920, Schizaster lovisatoi Cotteau 1895, Agassizia (Agassizia) powersi Kier 1972, and Hemipatagus ocellatus Defrance (1827)), and one from the Sadat Formation (Clypeaster campanulatus Schlotheim (1820)). The identified fauna shows a strong affinity with the Mediterranean bio-province.  相似文献   

13.
Salpingoporella species from algal bearing of Barremian-Aptian limestones in the Kopet Dagh basin (NE of Iran) are described. Different species (S. cemi, S. hasi, S. heraldica, S. hispanica, S. milovanovici, S. muehlmbergi, S. parapiriniae, S. piriniae, S. cf. biokovensis, S. steinhauseri, S. polygonalis) are investigated from different biometrical aspects such as depositional environments and biogeographical distribution as well as their systematic palaeontology from two formations (the Tirgan and Sarcheshmeh formations) in nine stratigraphic sections.  相似文献   

14.
The Bir Dakhl section which is located in the southern Galala plateau, north eastern desert was sampled for microfacies analysis of the upper Cretaceous–lower Paleogene succession. Microfacies analysis led to the recognition of eight mixed clastic-carbonate facies types (black shale lithofacies MF-1, pure shale lithofacies MF-2, sandy shale lithofacies MF-3, marly shale lithofacies MF-4, mudstone microfacies MF-5, foraminiferal wackestone microfacies MF-6, bioclastic wackestone microfacies MF-7, and bioclastic packstone microfacies MF-8) of the studied interval. These microfacies can be grouped into three depositional environments: inner, middle and outer ramp. The interpreted depositional environments have been suggested to range from neritic to middle bathyal (~ 700 m). Based on cyclostratigraphy, five deepening upward cycles and three shallowing upward cycles have been differentiated in Bir Dakhl section.  相似文献   

15.
Five successive ammonite assemblages are distinguished in the basal part (Riasanites rjasanensis Zone s. l.) of the Ryazanian Stage of the East European platform. These are (from the base upward) (1) Hectoroceras tolijense; (2) Hectoroceras kochi; (3) Riasanites swistowianus; (4) Riasanites rjasanensis; and (5) Transcaspiites transfigurabilis assemblages. Two lower assemblages consist entirely of boreal taxa, which occur in association with diverse ammonites of the Tethyan origin higher in the section. The data obtained show that three upper assemblages are correlative with the Berriasian Dalmasiceras tauricum, Riasanites rjasanensis-Spiticeras cautleyi, and Euthymiceras euthymi subzones of the northern Caucasus. The succession of five–six ammonite assemblages established in the East European platform above the top of the Craspedites nodiger Zone may correspond to the same number of ammonite assemblages characterizing lower subzones of the standard Berriasian. Berriasella rulevae Mitta, sp. nov. from the upper part of the Riasanites rjasanensis Zone (transfigurabilis biohorizon) is described.  相似文献   

16.
Paleogene sediments of the inner fold belt, Naga hills, have very well preserved ichnofossils. 16 ichnospecies have been documented among 13 ichnogenera such as Arenicolites isp., Chondrites targionii, Cylindrichnus isp., Diplocraterion parallelum, Gyrochorte isp., Ophiomorpha annulata, O. irregulaire, O. nodosa, O. rudis, Palaeophycus tubularis, Planolites beverleyensis, Scolicia palaeobullia, Skolithos linearis, Trypinites weisei, Thalassinoides horizontalis and Zoophycos isp. The ichnofossil assemblages comprise mostly domichnia and fodinichnia benthos of the Skolithos and Cruziana ichnofacies. A shallow marine nearshore to offshore marine environment with fluctuating energy condition has been envisaged.  相似文献   

17.
The analysis of nannoplankton, planktonic and benthic foraminifer assemblages provided detailed biostratigraphic characteristics of the upper part of sedimentary cover in the Markova Depression, rift valley of the Mid-Atlantic Ridge. The Gephyrocapsa oceanica and Emiliania huxleyi nannofossil zones, (LO) Helicosphaera inversa biohorizon, Emiliania huxleyi Acme Zone, and planktonic foraminiferal Globigerina calida calida, Globigerina bermudezi and Globorotalia fimbriata subzones were recognized. The compiled paleotemperature curve is correlated with the upper 10 oxygen isotope stages. The recovered deposits were accumulated during 400 ka. Changes in abundance and species composition of benthic foraminifer assemblages are suggested to be correlative with hydrothermal activity outbreaks in the rift zone.  相似文献   

18.
Smaller foraminifers from Upper Yakhtashian and Bolorian deposits of the stratotype area (Pamir, Darvaz, Tajikistan) are investigated. Four assemblages are defined. The first assemblage is from Chalaroschwagerina vulgaris-Pamirina darvasica Zone. The second assemblage found in the transitional Yakhtashian-Bolorian beds includes Globivalvulina, Palaeotextulariidae, Hemigordiidae, and Glomospira, associated with the first Pachyphloia and Langella forms. Characteristic taxa of third assemblage from the Misellina (Brevaxina) dyhrenfurthi Zone are Geinitzinidae, Globivalvulina, Palaeotextulariidae, Glomospira, and rare Pachyphloia. The forth assemblage of Hemigordiidae, Pachyphloia, Palaeotextulariidae, Geinitzinidae, Pseudoagathammina is identified in the M. (Misellina) parvicostata Zone. The assemblages were compared with concurrent analogs from China, Japan, and Russia. New species and subspecies Glomospira paleograndis sp. nov., G. darvasica sp. nov., Agathammina darvasica sp. nov., Pachyphloia darvasica sp. nov., Nodosinelloides cubanicus elongatus subsp. nov., and Hemigordius saranensis darvasicus subsp. nov. are described.  相似文献   

19.
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20.
Shallow water habitats within estuarine systems are believed to be important areas for small fish. While a wide variety of shallow habitats have been studied, the land that becomes inundated by the damming effect after the closure of intermittently open mouths has previously been overlooked. Fish were sampled monthly from both the main channel and flood zone of an intermittently open estuary between July 2004 and June 2005 using minifyke nets during the day and at night. A total of 7,787 fish were collected during the study representing 13 species and 11 families. Philypnodon grandiceps was the most abundant species and, together with Atherinosoma microstoma, Pseudogobius olorum, and Galaxias maculatus, made up 94% of the total catch. Inundation of the flood zone occurred in two discrete forms associated with mouth condition, which consisted of sporadic flooding while the mouth was open, to long-term flooding for 6 months after its closure. Large numbers of fish were captured on the flood zone, which included nine species; however, A. microstoma dominated the catch. A distinct shift in the flood zone fish assemblage occurred between the two mouth conditions, which is likely associated with changes in hydro-period and food availability of the flood zone and physico-chemical parameters in the main channel. There was no longitudinal variation in the fish assemblage in both the main channel and flood zone; similarly, the diel period was found to have little effect on the fish assemblage. The total catch per unit effort did not vary across seasons and suggests that fish abundance within the estuary is stable throughout the year. Unlike other estuarine systems where shallow water fish assemblages may be structured by variations in tide and elevation within the Surrey, freshwater inflow and, more importantly, mouth condition appear to have the greatest influence in composition of the shallow water flood zone fish assemblage of intermittently open estuaries.  相似文献   

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