The Influence of Element Diffusion at the Sediment—Water Interface on the Basic Chemical Composition of Overlying Water Mass in Lake Lugu,China

Little work has been done on the influence of seiments on the basic chemical composition of overlying water mass.This paper deals with the vertical profile of the basic constituents such as Ca^ ,K^ ,Na^ ,and HCO3^-,as well as of pH in the overlying water mass and sediment porewater of Lake Lugu-a semi-closed,deep lake in Yunnan Province.The reand sediment porewater of Lake Lugu- a semi-closed,deep lake in Yunnan Province.The results revealed that those basic constituents may diffuse and transport from bottom sediments to overlying water mass through porewater.In the paper are also quantitatively evaluated the diffusive fluxes and the extent of their influence on overlying water mass,indicating that the lake sediment-water interface diffusion plays an important role in controlling the basic chemical composition of water in the whole lake.     

Sm／Nd Evolution of Upper Mantle and Continental Crust：Constraints on Gowth Rates of the Continental Crust

A new approach to the investigation of the Sm/Nd evolution of the upper mantle directly from the data on lherzolite xenoliths is described in this paper.It is demonstrated that the model age TCHUR of an unmetasomatic iherzolite zenolith ca represent the mean depletion age of its mantle source, thus presenting a correlation trend between f^Sm/Nd and the mean depletion age of the upper mantle from the data on xenoliths.This correlation trend can also be derived from the data on river suspended loads as well as from granitoids.Based on the correlation trend mentioned above and mean depletion ages of the upper mantle at various geological times, an evolution curve for the mean f^Sm/Nd value of the upper mantle through geological time has been established.It is suggested that the upwilling of lower mantle material into the upper mantle and the recycling of continental crust material during the Archean were more active ,thus maintaining fairly constantf^Sm/Nd and εNd values during this time period. Similarly ,an evolution curve for the mean f^Sm/Nd value of the continental crust through geological time has also been established from the data of continental crust material.In the light of both evolution curves for the upper mantle and continental crust ,a growth curve for the continental crust has been worked out ,suggesting that :(1)about 30%(in volume )of the present crust was present as the continental crust at 3.8 Ga ago ;(2)the growth rate was much lower during the Archean ;and (3)the Proterozoic is another major period of time during which the continental crust wsa built up .     

Environmental Evolution of the Water Body of Qinghai Lake since the Postglacial Age

Based on the data developed from various s natural waters in the Qinghai Lake area and ostracode shells present in drill core QH-16A of recent lake-floor sediments ,this paper discusses the distribution of stable isotopes in the modern water body of Qinghai Lake,and the initial isotopic composition of the lake water has been deduced ,Studies of δ^18O,δ^13C,Mg/Ca and Sr/Ca in ostracode shells provide the basis for the establishment of the model of climatic fluctuation in the Qinghai Lake area since the postaglacial age,as well as for the elucidation of the environmental evolution of the water body of Qinghai Lake since the postglacial age.     

Jurassic Brachiopods and Paleogeography of North Qinghai-Tibetan Plateau

This paper deals with Jurassic brachiopods from North Tibet and SouthQinghai and the stratigraphical subdivision there.Based on faunas andstrata,a general outline of the palaeogeographical evolution has been traced outalong the line of plate-tectonic movements.In this paper,10 species of 8 gen-era are described,among which the species Lacunosella rhombica,Pentithyrisvulgaris,Tanyothyris appositus,Apatecosia navicularis and Flabellothyris sp.nov.have been recognized as new.     

Age and Thermal History of the East Ore Section,Bayan,Obo Deposit—A Fission Track Study

Considerable attention has been paid in recent years to the study of geothermal history by using spontaneous fission tracks of 238U recorded in minerals.Apatite and zircon were used for fission track study in this paper because apatitie has been widely used as a natural geothermometer(Wang Shicheng et al., 1994) to reveal the thermal evolution of sedimentary rocks based on its low annealing temperature of fission tracks and zircon is characterized by a closing temperature above 700℃,The samples were collected from ferruginous,siliceous slate wall rock at the upper levels of the orebody and Nb-REE-Fe ores from deep tunnels.The age and thermal evolution of the orebody were discussed in terms of fission track characters and their length variations observed in the coexisting apatite and zircon in the same specimen.     

Water Resource Development in the Quaternary Ryukyu Limestone Regions of Japan:Application of the GIS to the Site Selection of Underground Dams

Based on the natural and social conditions as well as hydrogeological characteristics of the Ryukyu limestone, a major aquifer in the Ryukyu Islands, a conception of underground dam, was proposed in the early 1970s in order to develop ground water resources in the Quaternary Ryukyu limestone regions of Japan. The practice of nearly thirty years has shown that the underground dam is an environment-friendly and effective way for developing ground water in these regions.To further improve the technology associated with underground dam, the authors introduced related analytic methods. The application of the geographical information system technology to site selection of the underground dam is reported in this paper.     

There is no such thing as the ‘Ediacara Biota'

The term‘Ediacara Biota’(or many variants thereof)is commonly used to refer to certain megascopic fossils of Precambrian and early Palaeozoic age e but what does the term actually mean?What differentiates a non-Ediacaran‘Ediacaran’and an Ediacaran‘Ediacaran’from an Ediacaran non-‘Ediacaran’?Historically,the term has been used in either a geographic,stratigraphic,taphonomic,or biologic sense.More recent research and new discoveries,however,mean that the term cannot actually be defned on any of these bases,or any combination thereof.Indeed,the term is now used and understood in a manner which is internally inconsistent,and unintentionally implies that these fossils are somehow distinct from other fossil assemblages,which is simply not the case.Continued use of the term is a historical relic,which has led in part to incorrect assumptions that the‘Ediacara Biota’can be treated as a single coherent group,has obscured our understanding of the biological change over the PrecambrianeCambrian boundary,and has confused research on the early evolution of the Metazoa.In the future,the term‘Ediacaran’should be restricted to purely stratigraphic usage,regardless of affnity,geography,or taphonomy;suffcient terminology also exists where reference to specimens on a geographic,taphonomic,or biologic basis is required.It is therefore time to abandon the term‘Ediacara Biota’and to instead treat equally all of the fossils of the Ediacaran System.     

The Uplift of the Longmenshan Thrust Belt and Subsidence of the West Sichuan Foreland Basin

Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e     

The Association of Geoscientists for International Development （AGID） ： Adapting to a changing world

It is just two years since a profile of AGID appeared in Episodes ( Vol 25, No 3, p. 218).At that time we recounted the many achievements of the organization, first established in 1974, but also noted that ‘an awareness of the relevance of geoscience to many aid projects, and the proliferation of NGO‘s, both large and small, working in the environmental and resource sectors has radically changed the world in which AGID seeks to operate‘. We also noted that the change has happened to such an extent that AG1D has ‘to address the question as to whether the time has come either for it to wind up its operations and retire gracefully from the international scene or to continue‘.     

Chemical characterization of aquifers with the same geological origin

In the coastal aquifers of Kaluvelly （Bengal coast, India）, the over exploitation of the main aquifer （the Vanur sandstone） has created a piezometric depression. Water flows from the sea towards inland. A salinization problem is questioned. The geochemical study was dedicated to major, minor and trace elements as well as isotope ratios （δ^18O, δD, δ^37Cl and ^87Sr/^86Sr）. The catchment comprises a crystalline bedrock hinterland （chamockites） overlaid by sediment. The Vanur and Cuddalore sandstones, the two main layers, are issued from the decay of chamockites upland. The geochemical feature of a water body is linked both to the composition of the hosted rock and the interaction time between water and rock. In the deeper parts of the Vanur aquifer, a mixture with long-residence time groundwaters has been evidenced. These waters can originate from a pocket of water entrapped in the Vanur or from the charnockites downward. No seawater intrusion could be assessed. Piezometric data suggest a possible hydraulic connection between the Cuddalore and the Vanur aquifers. Major, minor element data and isotope ratios do not allow to distinguish between old waters from the different aquifers. Data evidence the heterogeneity of the charnokite formation which is characterized by high Ba contents. On the whole, the two sandstones are depleted compared to charnockites in alkaline and earth-alkaline elements, and enriched in less soluble element such as Th or Zr. Trace elements in groundwaters waters from the chamockite aquifer exhibit a high concentration of Ba as compared to Vanur and Cuddalore waters. As Ba is a soluble element, the concentration of Ba in waters is related to the concentration in the hosted rocks. The Li concentration, slightly higher in Vanur rocks, allows to distinguish waters from the deeper parts of the Vanur aquifer. For insoluble elements such as Ti, the hosted rock signature cannot be seen. The Ti concentration in water samples seems to rely on the reaction progress rather than on the available amount. Trace element data show that waters recovered from chamockites and sandstone aquifers present different geochemical features. The host rock signature can be seen in the chamockite and Vanur aquifers for some alkaline and alkaline-earth elements （mainly Ba and Li）.     

Errors Involved in the Taylor‘s Model for the Crustal Composition and Evolution—An Analysis of Their Causers

It is suggested in this paper that the famous Taylor‘s model for the composition and evolution of the continental crust consists of three closely related key links.These links include an assumption that the surfical environment has no effect on the sedimentary REE patterns and the REE patterns in sdhales can reflect the composition of their provenance,a discovery about the discrepancy of sedimentary REE patterns between Archean and Proteroxoic,and a deduction that there was a global scale K-granitoid event at the end of the Archean.Based on a detailed discussion,this paper substantially negates the rationality of the Taylor‘s model and argues that its three critical links be three great errors indeed.Moreover,some other deficiencies or problems it confronts are described in this paper.The authors suggest that what led to the errors invoved in the Taylor‘s model is its wrongly neglecting the effect of the sedimentary envronment on the chemical composition of sediments.and that the environment should be an important factor affecting the distribution patterns of trace elements in the sediments.     

Geochemical Characteristics of Oilfield Waters from the Turpan Depression,Xinjiang and Their Petroleum Geological Significance

This paper,based on the fundamental inorganic chemical and organic geochemical characteristics of oilfield waters from the Turpan Depression,presents the contents of organic matter,the distribution of low-carbon fatty acids and the contents of aromatic hydrocarbons as well as their principal ultraviolet absorption spectral and fluorescence spectral characteristics in oilfield waters from different oil/gas-bearing areas.The oil/gas reservoirs in this depression are classified in terms of their conserving conditions.In additon,the paper also discusses the chemical characteristics of oilfield waters from different types of oil/gas reservoirs with an emphasis on the characteristics of their localization in the γNa/γCa-γN a/γCl correction diagram.On this basis it is attempted to expound the fundamental geochemical characteristics of oilfield waters from the Turpan Depression and their geological significance.     

Acclimatization and screening of a chloramphenicol-degrading strain

Chloramphenicol （CAP） is an antibiotic commonly used in aquaculture as a prophylactic or disinfectant to prevent diseases, or as a chemotherapeutic agent to control diseases. This antibiotic is either spread directly in the aquatic environment or administered through medicated feeds. It may be directly exposed to or enter the environment by leaching from uneaten feeds or from the aquatic animals＇ excrements. The antibiotic also directly enters the environment through pharmaceutical wastewater. Toxicity of CAP to human bone marrow has been linked to fatal aplastic anemia. Antimicrobial residues enter the environment, which may also establish a selective pressure in favour of antimicrobial-resistant bacteria. The residues of antibiotics may pose potential risk to public health or increase the occurrence of antibiotic-resistant bacteria in the aquatic environment. Due to these perceived risk, treatment of CAP in farm animals intended for human consumption has been restricted. However, residue of CAP in the environment is still a concern. There have been some reports on the residual effects of CAP on aquaculture and on microbial resistance to CAP in certain environments. The biotransformation of CAP in aquaculture pond sediments has been reported, which indicated that salinity is one of the many environmental factors that affect the degradation of CAP. However, acclimatization and screening of dominant bacteria for biodegrading CAP have been rarely studied. This paper studied the microbial degradation of CAP. In order to screen the dominant bacteria for degrading, the source of bacteria was sampled from the aquaculture pond sediments of Baiyun Borough, Guangzhou, China. 60 mg/L CAP was used as a sole carbon source to screen CAP-degrading bacteria and the dominant bacteria were acclimated after 2 months.     

Geochemical Styudy of Gold and Arsenic Mineralization of the Carlin-Type Gold Deposits,Qinling Region,China

Element geochemistry of gold arsenic and mineralogical features of their sulfides in the Carlin-type gold depostis of the Qinling region are discussed in this paper.The initial contents of ore-forming elements such as glod and arsenic are high the ore-bearing rock series in the Qinling region.Furthermore,both the metals are concentrated mainly in the diagenetic pyrite.Study on the mineralogy of arsenic-bearing sulfide minerals in the ores demonstrated that there is a poistive correlation between gold and arsenic in the sulfide minerals.Available evidence suggests that gold in the As-bearing sulfide minerals in likely to be presented as a charge species(Au ),and it is most possible for it to replace the exxcess arsenic at the site of iron and war probably deposited together with arsenic as solid in the sulfide minerals. Pyrite is composed of(Aux^3 ,Fe1-2^2 )([AsS]x^3-[S2]1-x^2-),and arenopyrite of (Aux^3 ,Fe1-x^3 )([AsS]x^3-[AsS2]1-x^3-).The occurrence of glod in the As-sulfied minerals from the Carlin-type gold depostis in the Qinling region has been confirmed by electron probe and transmission electron microscopic studies.The results show that gold was probably depostied together with arsenicas coupled solid solutions in sulfide minerals in the early stage of mineralization.Metallogenic chemical reactions concerning gold deposition in the Carlin-type As-rich gold deposits would involve oxidation of glod and concurrent reduction of arsenic.Later,the deposited gold as solid was remobilized and redistributed as exsolutions,as a result of increasing hydrothermal alteration and crystallization,and decreasing resistance to refractoriness of the host minerals.Gold occurs as sub-microscopic grains(ranging from 0.04tp 0.16μm in diameter)of native gold along micro factures in and crystalline grains of the sulfiedes.     

Biomarkers in the Molar Tooth （MT）-Bearing Limestones in the Jilin-Liaoning Area of China

The origin of Molar Tooth (MT) carbonates has been argued for more than 100 years, which are a kind of Proterozoic carbonates especially composed of microsparite with ptygmatically folded and sheet-like structures. Biomarkers detected in the microcalcsparite from the Wanlong and Xingmincun formations in the Jilin-Liaoning area showed there are abundant normal alkanes, isoprenoids, hopanes, steranes, alkylmethylcyclohexanes, and alkyleyclohexanes, indicating a diversity of biological source: long-chain isoprenoids, the major components of chlorophyll, such as C19, C20, a kind of major biomarkers synthesized early by isoprenoid monomers; hopanes a type of characteristic biomarkers from prokaryote, such as archaebacteria and cyanobacteria; sterane a biomarker for eukaryote; and two kinds of alkanes with C17, C18 as the main peaks representing aquatic bacteria and with C23, C24 as the main peaks representing fungi, respectively. Biomarker analysis showed that MT is the result of bacterial and algal activities, which is a kind of organisms between aerobic and anaerobic bacteria, reproducing well in normal or slightly saline sea water under weak oxidation-reduction conditions, resulting in rapid deposition of calcite as microsparite clue to some mechanisms.     

Biogeochemical Model and Simulation of the Effect of Precambrian Algae on the Formation Process of Certain Laminated Cherts

The source of silica in the formation of the Precambrian laminated cherts has long remained a problem to be solved. Through experiments on cherts and living blue-green algae, the authors found that the collected chert samples probably come from primary deposits, and there is a great biomass of fossil algae in chert, among which the filamentous algae can be compared with the living blue-green algae Oscillatoria, that a higher Pco_2 of the gas would be favourable for the increase of the biomass of living blue-green algae and consequently raises the pH value of the water body; and that lack of free oxygen and a higher concentration of SiO_2 in the water have no apparent influence on the biomass of blue-green algae. Based on the evidence above, a biogeochemical model concerning the origin of Precambrian laminated chert has been set up, in which the. photosynthesis of algae under the presumed atmospheric conditions of the Precambrian might raise the pH value of the water body and promote the dissolution of silicate minerals, thus providing a source of colloid SiO_2 for the formation of Precambrian laminated chert.Furthermore, a simulation experiment device has been designed successfully, which can control the temperature(30 ± 0.5°), Pco_2(50662.5 Pa) and Po_2(about zero Pa) of the gas, the rate of photosynthesis of algae and the movement of the water carrying opal. In the simulation experiments, separate measurements have been made on the rate of photosynthesis of algae, pH value and concentration of SiO_2 of the water body, with the results indicating that under the conditions similar to the presumed Precambrian atmosphere, the photosynthesis of algae can make the pH value of the water body go up steadily to over 9.7, leading to the dissolution of the silicate minerals, with the concentration of SiO_2 measured reaching as high as 84 mg/l. Finally, through the vaporation of water, a phenomenon of colloid floccilation has been observed.The simulation experiment has verified the proposed biogeochemical model illustrating the origin of Precambrian laminated chert. Moreover, the device and method of its kind may also be applied to the research on the relationship of the Precambrian algae with the formation of some other mineral deposits such as of Fe, Mn, U and carbonates.     

A New Diverse Macrofossil Lagerst?tte from the Uppermost Ediacaran of Southwestern China

A new macrofossil Lagerstatte was discovered from the uppermost Ediacaran Jiucheng Member at Jinning and Jiangchuan of the eastern Yunnan, yielding numerous diverse well-preserved thallophyte macrofossils. These include the previously-known representatives of vendobionts, Vendotaenia and Tyrasotaenia, and the biggish multicellular benthos such as Chuaria-like and Tawuia- like fossiis, as well as Longfengshaniaceaens with diverse holdfast structures. There are still some other problematic macrofossils with peculiar configurations as well as uncertain relatives. The distinct dominance of the giant, unbranching thallophytes occasionally with holdfast structures distinguishes this assemblage from the other Ediacaran macrofossil Lagerstattes in the Doushantuo Formation at Miaohe, Wenghui and Lantian, and the contemporary assemblage in the Shibantan Member of Dengying Formation, Yangtze Gorges area. This paper outlines the characteristics of some of the multicellular macrofossils from the Jiucheng Member at Jiangchuan. They include some macrofossils with different types of holdfast structure, larger Chuaria-like and Tawuia-like morphology and questionable affinities as well. The discovery of greater diverse macrofossil assemblages from the Jiucheng Member of eastern Yunnan has further indicated that an important diversification and evolutionary radiation of metaphytes took place in the latest Ediacaran time. This radiation of largescale, benthic metaphyte along with phytoplankton was likely important contributors to the early Cambrian explosion of metazoans.     

Biological hydrogen production from organic wastewater with a novel strain B49 isolated from anaerobic sewage sludge

Water pollution of river basin has increased with increasing discharge of sewage and the water quality has deteriorated due to the discharge of organic wastewater. Pretreatment of organic wastewater before discharging is of significance for the protection of water resources. The anaerobic digestion of organic substrates has been a well-developed biological treatment method for wastewater and wastes. Especially, the biohydrogen production using organic wastewater can produce an energy product and simultaneously reduce the pollution intensity of the wastes. Microorganisms with high hydrogen-producing capacity perform an important function in biohydrogen production. In this paper, we investigated the zymolytic characteristics of a novel strain of bacteria B49 isolated from anaerobic activated sludge using waste liquid from a sugarhouse as substrate. The effect of yeast extract on microbial conversion of waste liquid from the sugarhouse was investigated. Different carbohydrates （such as glucose, sucrose, trisaccharide, molasses, etc.） in the waste liquid serve as major energy sources for B49＇s cell growth. The hydrogen yield of 2410 mL-H2/L-culture was obtained using glucose as substrate. When the waste liquid from the sugarhouse （molasses） was used as substrate, maximum hydrogen yield of 2460 mL-H2/L-culture was obtained at 2% of molasses.     

Metamorphism and exhumation of basement gneiss domes in the Quadrilátero Ferrífero:Two stage dome-and-keel evolution?

The presence of dome-and-keel provinces in Archean cratons has been connected with the initiation of plate tectonics on Earth as these features are most commonly observed in Archean rocks.The Quadrilátero Ferrífero in Brazil has been identified as a Paleoproterozoic dome-and-keel province for more than three decades.The prevailing model suggests that it formed during the Rhyacian Transamazonian orogeny,making it unique among dome-and-keel provinces.However,a lack of appropriate lithologies,datable minerals and the metamorphic overprint of later orogenesis has resulted in a cryptic metamorphic record for the formation of this dome-and-keel province.A clinopyroxene-bearing migmatite from the core of the Ba??o dome has peak P-T conditions of 5-7 kbar and 700-750 ℃ and a published age of ca.2730 Ma based on U-Pb ages of zircon from leucosomes,suggesting that this age represents the migmatisation event.A fine-grained epidote-albite-titanite assemblage overprints the coarse-grained clinopyroxene and amphibole,giving P-7 conditions of 8-9 kbar and 550 ℃ with an associated titanite age of ca.2050 Ma.A garnet-bearing amphibolite sample also from the core of the dome has peak P-T conditions of 7-8 kbar and 650-700 ℃,and texturally late titanite from this sample produces an age of ca.2060 Ma.Three additional samples were collected from the edges of the dome.A garnet-gedrite bearing felsic schist produces peak P-T conditions of 8-9 kbar and 650-700℃ on a clockwise P-T evolution.This sample has a U-Pb zircon age of ca.2775 Ma,which could date metamorphism or be the age of its volcaniclastic protolith.Texturally unconstrained titanite from the sample gives an age of ca.2040 Ma.A garnet-bearing amphibolite that occurs as a boudin within the felsic schist gives both zircon and titanite ages of ca.2050 Ma and has peak P-T conditions of 5-6 kbar and 650-700 ℃ on a near isobaric P-T path.An amphibolite dike,observed to cross-cut the felsic schist produces a zircon U-Pb age of ca.2760 Ma.Altogether this data suggests that the samples were metamorphosed in the Archean(ca.2775-2730 Ma)and again during the Transamazonian event.The most plausible explanation for this data is that dome-and-keel formation occurred in the Archean with migmatisation and high-temperature metamorphism occurring at this time.The Paleoproterozoic event is interpreted as a reactivation of the dome-and-keel formation structures,with Paleoproterozoic keels crosscutting Archean keels and producing metamorphic aureoles.The high radiogenic heat production and the presence of dense sedimentary successions in Archean terranes make dome-and-keel provinces a uniquely Archean feature,but they are susceptible to reworking,resulting in an enigmatic record of formation.     

A New Diverse Macrofossil Lagersttte from the Uppermost Ediacaran of Southwestern China

A new macrofossil Lagersttte was discovered from the uppermost Ediacaran Jiucheng Member at Jinning and Jiangchuan of the eastern Yunnan,yielding numerous diverse well-preserved thallophyte macrofossils.These include the previously-known representatives of vendobionts, Vendotaenia and Tyrasotaenia,and the biggish multicellular benthos such as Chuaria-like and Tawuia- like fossils,as well as Longfengshaniaceaens with diverse holdfast structures.There are still some other problematic macrofossils with peculiar configurations as well as uncertain relatives.The distinct dominance of the giant,unbranching thallophytes occasionally with hoidfast structures distinguishes this assemblage from the other Ediacaran macrofossil Lagerstttes in the Doushantuo Formation at Miaohe,Wenghni and Lantian,and the contemporary assemblage in the Shibantan Member of Dengying Formation,Yangtze Gorges area.This paper outlines the characteristics of some of the multicellular macrofossils from the Jiucheng Member at Jiangchuan.They include some macrofossils with different types of holdfast structure,larger Chuaria-like and Tawuia-like morphology and questionable affinities as well.The discovery of greater diverse macrofossil assemblages from the Jiucheng Member of eastern Yunnan has further indicated that an important diversification and evolutionary radiation of metaphytes took place in the latest Ediacaran time.This radiation of large- scale,benthic metaphyte along with phytoplankton was likely important contributors to the early Cambrian explosion of metazoans.