Glaciation and ~ 770 Ma Ediacara (?) Fossils from the Lesser Karatau Microcontinent,Kazakhstan

The Cambrian explosion, c. 530–515 Ma heralded the arrival of a diverse assembly of multicellular life including the first hard-shelled organisms. Fossils found in Cambrian strata represent the ancestors of most modern animal phyla. In contrast to the apparent explosiveness seen in the Cambrian fossil record, studies of molecular biology hint that the diversification observed in Cambrian strata was rooted in ancestry extending back into the Ediacaran (635–542 Ma). Fossil evidence for this mostly cryptic phase of evolution is derived from the soft-bodied fossils of the Ediacaran biota found throughout the world and bilaterian embryos found in the Doushantuo lagerstätte in South China. The first appearance of Ediacara fauna is thought to have followed the last of the ~ 750–635 Ma Neoproterozoic glacial episodes by 20–30 million years. In this paper, we present evidence for the oldest discovery of the ‘Ediacara’ discoidal fossils Nimbia occlusa and Aspidella terranovica (?) that predate the early Cryogenian glaciations by more than fifty million years. There is considerable disagreement over the significance of discoidal Ediacaran fossils, but our findings may support earlier suggestions that metazoan life has roots extending deeper into the Proterozoic Eon. We also confirm the presence of a Late Cryogenian (e.g. “Marinoan”) glaciation on the Lesser Karatau microcontinent including dropstones and striated clasts within the glacial strata.     

Deep marine trace fossil assemblages from the Lower Carboniferous of Menorca,Balearic Islands,western Mediterranean

Sediments of Lower Carboniferous age in eastern Menorca, Balearic Islands contain a diverse and exceptionally well preserved ichnofauna, including Neonereites biserialis, Nereites isp., Arthrophycus isp., Dictyodora liebeana, two ichnospecies of Chondrites, several ichnospecies of Lophoctenium, two ichnospecies of Phycosiphon, Syncoprulus pharmaceus, annulated burrows and a vertical burrow. The host lithologies are conglomerates, sandstones, siltstones and mudstones; most are the product of debris flows, and of high concentration [Ta(bc) intervals] to relatively dilute (Tcd/Tde intervals) turbidity currents. The rocks are interpreted as deposits of an inner- to mid-fan palaeoenvironment. Channelized deposits, sequences of overbank deposition and interchannel deposits interspersed with the deposits of unconfined debris flows and high concentration turbidity currents are present. The ichnofauna is most frequently, and best, preserved within the Td interval of turbidities, which are interpreted as interchannel deposits, produced by low concentration turbidity flows. The distribution of the ichnofauna is partly controlled by the lithologies in which they are preserved. The rarity and poor preservation of trace fossils in the coarser grained facies contrasts with the detailed preservation of very delicate traces in the finer grained lithologies. However, the ichnofauna is also partitioned between different subenvironments of the mid-fan to produce a series of palaeoichnocoenoses. Thin intervals of interchannel deposits, separated by deposits of high concentration turbidity currents, repeatedly contain only Phycosiphon incertum and small (?juvenile)Dictyodora liebeana. These traces are interpreted as the products of opportunistic colonization of near-channel environments during episodes of quiescent deposition. Thicker intervals of interchannel deposits contain diverse assemblages of trace fossils characteristic of more stable environments, in which widespread colonization occurred. Overbank deposits at Cabo de Favaritz are medium- to thick-bedded, fine-grained beds. In these, the ichnofauna occurs in a simple, two-tier profile. The upper tier is dominated by Nereites isp.; this is underlain by a partially bioturbated layer characterized by large Dictyodora liebeana and Arthrophycus isp.     

A Fresh Look at Dickinsonia： Removing It from Vendobionta

The Ediacaran Dickinsonia is well-known for being the only fossil to be assigned to many phyla, ranging from lichens, Cnidaria, Piatyheiminthes, Annelida, and a phylum of its own to a nonmetazoan kingdom. A new specimen from the Ediacaran fine-grained sandstone on the Winter Coast of the White Sea in northern Russia, which has an age of -555 million years ago, preserved convincing internal anatomies of definite animals, comparable with meridionai canals of extant ctenophores （comb jellies）. Additionally, we reconsidered Dickinsonia as a biradiaily symmetrical animal rather than a bilateral one as previously thought. The animal nature of Dickinsonia is, thus, well established and its affinities are most probably allied to ctenophores. This research is not only removing Dickinsonia from Vendobionta, but also bringing the fossil record of ctenophores forward to 20 million years before the Cambrian ＂explosion＂.     

Accumulation of muds and metals in the Hudson River estuary turbidity maximum

 In the Hudson River estuary, fine mud and toxic metals are enriched in the upstream turbidity maximum. The mechanisms causing the enrichment were assessed through the analysis of suspended-sediment concentration (SSC) (bottom and surface), particle size, and trace metal distributions. Bottom SSCs varied across the study area by a factor of ten, and the turbidity maximum activity was observed in between kilometers 45 and 80. The particle-size analysis defined two accumulation modes: <4.65 and >22.1 μm. The ratio of the fine-to-coarse mode increased from 1.75 to 2.75 in the turbidity maximum. The fine mud concentration (55–60%) in the turbidity maximum was found to have a high correlation (r=0.98;p<0.005) with the concentration of <2-μm particles. A conceptual model was derived in order to understand the possible mechanisms by which fine mud (and specifically <2-μm particles) is concentrated. The two dominant size modes were analyzed for toxic metals. The upstream tributaries are major sources of metals compared to point sources at downstream locations. In the turbidity maximum, Cd, Cu, Zn, and Pb are significantly enriched compared to average shale metal values and ERM toxicity guidelines by 580, 42, 10, 16 and 12, 7, 2.4, 1.4 times, respectively. Decreasing metal concentrations downstream of the turbidity maximum imply that Haverstraw Bay acts as temporary storage for fine particles and enriched metals. It is demonstrated in this study that toxic metals are enriched in Haverstraw Bay due to the mud accumulation. The high levels of toxic metals in the sediments of the Hudson River estuary are a major concern because human activities (dredging and river traffic) cause resuspension of sediments and can change the mobility patterns of bioavailable contaminants. Received: 4 June 1997 · Accepted: 9 September 1997     

<Emphasis Type="Italic">Trachyhystrichosphaera</Emphasis>: An age-marker acanthomorph from the Bhander group,upper Vindhyan,Rajasthan

A highly diversified, advanced and exceptionally well preserved microfossil assemblage, dominated by a planktic community, has been recorded from petrographic thin sections of chert belonging to the Sirbu Shale Formation, Bhander group, upper Vindhyans, Rajasthan. Recently, it was noticed that the assemblage also contains well preserved, large-sized acanthomorphic acritarchs, Trachyhystrichosphaera considered to be an age-marker microfossil of the Cryogenian (850-630 Ma). It is reported for the first time from any Indian microfossil assemblage of Proterozoic succession. The other microfossils of the Sirbu Shale Formation are: well preserved simple, small and large-sized sphaeromorphs; complex acanthomorphs, cyanobacterial community; especially a very small-sized but exceptionally well preserved Obruchevella, a form resembling Volvox colonies; cf. vase-shaped microfossils and morphologies, possibly inclining towards fungal affinity, or lichenlike symbiotic associations of algae and fungi. Till date, Trachyhystrichosphaera has so far not been reported from successions older than the Tonian (1000850 Ma). It is believed that acanthomorphs attained maximum size in Ediacaran (630-542 Ma), and further decreased in size in the Cambrian. The global paleontological literature indicates that Trachyhystrichosphaera ranges in age from Tonian-Ediacaran (1000-542 Ma). The present record of Trachyhystrichosphaera as well as the earlier studies of micro and megascopic life of the Bhander Group in general and the Sirbu Shale in particular (aided by the absence of any Cambrian fossil record) indicate that in all possibilities, age of the Sirbu Shale should lie near Cryogenian (850-630 Ma) and the uppermost Bhander group, may incline towards the Ediacaran (630-542 Ma).     

Exceptional fidelity of preservation in a reworked fossil,Chalk drift,South London,England

Reworking of fossils commonly leads to loss of morphological detail and inferior preservation; the main contributions of such specimens to geology are in sedimentology, regional geology and neoichnology. A reworked specimen of the Late Cretaceous (chalk) sponge boring Entobia cretacea Portlock is unusually well preserved. This specimen is from superficial deposits and is well enough preserved that delicate apertural and intercameral canals are apparent. Two factors are recognized as important in maintaining the fine features of this trace fossil: preservation in flint and, presumably, minimal fluvial transport. Copyright © 2013 John Wiley & Sons, Ltd.     

A middle–late Ediacaran volcano‐sedimentary record from the eastern Arabian‐Nubian shield

The Ediacaran Jibalah Group comprises volcano‐sedimentary successions that filled small fault‐bound basins along the NW–SE‐trending Najd fault system in the eastern Arabian‐Nubian Shield. Like several other Jibalah basins, the Antaq basin contains exquisitely preserved sedimentary structures and felsic tuffs, and hence is an excellent candidate for calibrating late Ediacaran Earth history. Shallow‐marine strata from the upper Jibalah Group (Muraykhah Formation) contain a diversity of load structures and intimately related textured organic (microbial) surfaces, along with a fragment of a structure closely resembling an Ediacaran frond fossil and a possible specimen of Aspidella. Interspersed carbonate beds through the Muraykhah Formation record a positive δ¹³C shift from ?6 to 0‰. U‐Pb zircon geochronology indicates a maximum depositional age of ~570 Ma for the upper Jibalah Group, consistent with previous age estimates. Although this age overlaps with that of the upper Huqf Supergroup in nearby Oman, these sequences were deposited in contrasting tectonic settings on opposite sides of the final suture of the East African Orogen.     

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.     

Possible animal body fossils from the Late Neoproterozoic interglacial successions in the Kimberley region, northwestern Australia

New specimens of the enigmatic Ediacara-type fossil Palaeopascichnus have been identified from the upper part of the Neoproterozoic Ranford Formation in the Kimberley region, northwest Australia. New material is morphologically similar to Palaeopascichnus and represents the largest species of this genus. They resemble the present-day xenophyophore protists in chamber morphology and growth patterns, supporting the interpretation that Palaeopascichnus is possibly a xenophyophore body fossil rather than a trace fossil. Stratigraphic correlation reveals that the new Palaeopascichnus specimens are preserved in the interglacial successions between the Landrigan/Marinoan and Egan/Ediacaran glaciations. If correlation with the early Ediacaran formations of South Australia is accepted, this represents the earliest known identifiable member of the Ediacara biota. New fossil record fills the evolutionary gap between the Cryogenian and Ediacaran animal assemblages and well-known Ediacaran biota. The new Palaeopascichnus specimens represent the first record of Ediacara-type fossils in Kimberley, and suggest the probability that additional Ediacaran fossils may be found in northwestern Australia.     

Ediacaran fossils in Meso- and Paleoproterozoic rocks in peninsular India extend Darwin

Typically or arguably Ediacaran fossils (635 Ma to 543 Ma) are reported by several research groups from one unit of the Chhattisgarh and two units of the Vindhyan Supergroups in peninsular India. Depositional ages of the host sediments, however, are inferred to be ∼1000 Ma and ∼ 1630 Ma as determined by U-Pb dating of magmatic and detrital zircons in rhyolitic tuff (∼ porcellanite) and sandstones, provenance considerations and paleopole positions. The contradiction of absolute ages results from inferring the Ediacaran age strictly on the basis of fossils. I argue that the fossils reported from the Chhattisgarh and Vindhyan Supergroups should be considered mostly Mesoproterozoic and late Proterozoic in age. I also argue that although the Ediacaran Period records explosive diversity of preserved fossils, many forms very likely appeared much earlier with variable degrees of preservation or none at all at times, and, that their age-ranges extend to the Paleoproterozoic. I hypothesize that the rate of increase of biological diversity was lower than the rate of preservation in certain geological intervals, especially immediately after extinction events.     

New Data of Macrofossils in the Ediacaran Wenghui Biota from Guizhou, South China

The abundance and diversity of macrofossils in the Ediacaran have attracted much attention. The upper Doushantuo macrobiotas in South China, including the Miaohe biota from Hubei and the Wenghui biota from Guizhou, are mainly preserved as the carbonaceous compressions and dominated by macroscopic algae and metazoans. Here, we describe 10 genera and 10 species (including 6 new genera and species) of macrofossils from the Wenghui biota. At present, the Wenghui biota yields macrofossils in more than 31 genera and 33 species, excluding those given no image and established on a few unascertained specimens. Based on the occurrence and distribution of macrofossils in both Miaohe and Wenghui areas, the middle-late Ediacaran (back shales of the upper Doushantuo Formation) in South China can be subdivided into two assemblage biozones in biostratigraphy: (i) the Protoconites–Linbotulitaenia–Eoandromeda–Anomalophton assemblage biozone characterized by abundant and diverse macrofossils and by the ranges of Protoconites, Linbotulitaenia and Anomalophton; and (ii) the Baculiphyca–Gesinella–Cucullus–Beltanelliformis assemblage biozone characterized by the acme of the longer macrofossils Baculiphyca and Gesinella, and by few shorter and discoidal macrofossils.     

The light transmission and seiche depth of Izmir Bay,western Turkey

Izmir Bay is one of the most polluted estuaries in the whole Mediterranean Sea. The inner part of the Bay (Inner Bay) is heavily affected by domestic and industrial discharge. As a result of these loads, strong eutrophication occurs in the Inner Bay, which is temporally anaerobic. The ecologically sensitive approach of the local authorities during the last decade has given rise to a wide variety of monitoring and research studies on this bay. On the other hand, the municipality of Izmir started to operate wastewater treatment facilities since January 2000. The Institute of Marine Sciences and Technology — Izmir (IMST) with its research vessel R/V K Piri Reis has been conducting an intensive monitoring program since 1988 and especially during the recent few years. These investigations provide an opportunity for the evaluation of the performance of the wastewater treatment plant in terms of the change in the optical properties of Izmir Bay water in a positive manner. The turbidity values measured in these monitoring studies indicate that the values have changed drastically after January 2000. Their spatial variation indicates that the values decrease from the Inner Bay towards the Aegean Sea. The turbidity (light transmission) values are measured with an automatic CTD (conductivity, temperature and depth) system during each cruise. The seiche disc depth measurement is carried out only occasionally. The accuracy of the seiche disc depth is dependent on certain daylight conditions and depends on the operator. The seiche disc depth (D _s) is an important parameter to estimate primary production of organic matter (hereafter called production). A relation between light transmission (turbidity) value and seiche disc depth (D _s) is found with very good agreement. The correlations are very high (approximately 0.94) with slight seasonal variation.     

Remarkable preservation of microbial mats in Neoproterozoic siliciclastic settings: Implications for Ediacaran taphonomic models

It is beyond doubt that the appearance of infaunal bioturbation and metazoan biomineralization across the Ediacaran–Cambrian transition irreversibly affected the nature of marine sediment architecture and biogeochemistry. Here we review those changes in relation to their likely effect upon the processes of fossil preservation, especially within siliciclastic sediments. Processes of soft-tissue preservation in siliciclastic settings from the Ediacaran Period, including microbes and microbial mats as well as Ediacaran macrofossils, are here reviewed within this context. Highlighted examples include the exceptional preservation of microbes found in association with wrinkle structures and Ediacaran macrofossils in England and Newfoundland (replicated by silicate minerals) and in the White Sea region of Russia (replicated by iron sulphide). These occurrences show that soft-tissue preservation in siliciclastic settings went well beyond that typical for Ediacaran macrofossils alone and also extended to similar modes of preservation in associated microbes. Using these new observations it can be argued that several existing explanations for Ediacaran fossil preservation can be united within a biogeochemical model that involves evolution of the sediment mixed layer across this transition.     

Seasonal and long-term trends in the water quality of Florida Bay (1989–1997)

Analysis of 6 yr of monthly water quality data was performed on three distinct zones of Florida Bay: the eastern bay, central bay, and western bay. Each zone was analyzed for trends at intra-annual (seasonal), interannual (oscillation), and long-term (monotonic) scales. the variables TON, TOC, temperature, and TN∶TP ratio had seasonal maxima in the summer rainy season; APA and Chla, indicators of the size and activity of the microplankton tended to have maxima in the fall. In contrast, NO₃ ⁻, NO₂ ⁻, NH₄ ⁺, turbidity, and DO_sat, were highest in the winter dry season. There were large changes in some of the water quality variables of Florida Bay over the study period. Salinity and TP concentrations declined baywide while turbidity increased dramatically. Salinity declined in the eastern, central, and western Florida Bay by 13.6‰, 11.6‰, and 5.6‰, respectively. Some of the decrease in the eastern bay could be accounted for by increased freshwater flows from the Everglades. In contrast to most other estuarine systems, increased runoff may have been partially responsible for the decrease in TP concentrations as input concentrations were 0.3–0.5 μM. Turbidity in the eastern bay increased twofold from 1991 to 1996, while in the central and western bays it increased by factors of 20 and 4, respectively. Chla concentrations were particularly dynamic and spatially heterogeneous. In the eastern bay, which makes up roughly half of the surface area of Florida Bay, Chla declined by 0.9 μg l⁻¹ (63%). The hydrographically isolated central bay zone underwent a fivefold increase in phytoplankton biomass from 1989 to 1994, then rapidly declined to previous levels by 1996. In western Florida Bay there was a significant increase in Chla, yet median concentrations of Chla in the water column remained modest (∼2 μg l⁻¹) by most estuarine standards. Only in the central bay did the DIN pool increase substantially (threefold to sixfold). Notably, these changes in turbidity and phytoplankton biomass occurred after the poorly-understood seagrass die-off in 1987. It is likely the death and decomposition of large amounts of seagrass biomass can at least partially explain some of the changes in water quality of Florida Bay, but the connections are temporally disjoint and the process indirect and not well understood.     

华南伊迪卡拉纪类水母化石新发现

An abundant and diversified assemblage of benthic fossils from the Ediacaran Doushantuo black shales in the Wenghui section of Guizhou Province contains two discoidal carbonaceous forms, Kullingia rotadiscopsis sp. nov. and Eoaequorea xingi gen. & sp. nov. The fossils have well-preserved concentric rings and radiating lines, and resemble many circular casts and moulds in Ediacaran clastic and carbonate rocks in the world, such as Aspidella, Ediacaria, Cyclomedusa, Eoporpita, Ovatoscutum, Spriggia and Kullingia. The Doushantuo carbonaceous macrofossils help us to inquire into the current functional identifications of circular disks as the holdfasts of unknown organism or scratch circles. Although there is not sufficient correspondence in morphology to warrant reinterpreting all previously described Kullingia and Aspidella form-genus-type structures, these carbonaceous compressions are prone to be the ancestor of pelagic jellyfish-like organisms with medusoid hydrozoan affinity.     

An Ordovician age for the Muggort's Bay Lower Palaeozoic inlier,County Waterford,Ireland—the southernmost exposure of the Irish Caledonides

The most southerly exposed Lower Palaeozoic strata in Ireland occur on the southwest coast of County Waterford along a 2.5 km long coastal section at Muggort's Bay where they are surrounded by Devonian rocks. Five formations can be distinguished which, in ascending order, are: the Ballycurreen, Carrickbrean, Rathnameenagh, Moanbrack and Killinoorin formations. The total thickness of the succession is over 1800 m. No macrofossils are present, but the lithologies are largely fine‐grained turbidites and subordinate volcanic rocks which closely resemble the Ribband Group seen elsewhere in southeast Ireland and have previously therefore been classified with it. Palynological analysis was undertaken on 25 samples collected from Muggort's Bay, of which eight were productive. Diagnostic microfossils, comprising acritarchs, chitinozoans and scolecodonts, indicate an Early to Middle Ordovician age for both the Rathnameenagh and the Moanbrack formations. These ages confirm that the strata are part of the Ribband Group which elsewhere has been biostratigraphically dated as ranging from Mid‐Cambrian to Mid‐Ordovician. Reworked mid‐Middle Cambrian acritarchs occur in the Moanbrack Formation and reworked late Middle to early Late Cambrian acritarchs in the Rathnameenagh Formation. Despite generally poor preservation of the organic matter, some 20 acritarch species have been distinguished. Among these, three species belong to the herein revised genus Retisphaeridium for which an emended diagnosis is proposed together with two new combinations, Retisphaeridium capsulatum (Jankauskas, 1976 ) Vanguestaine nov. comb. and Retisphaeridium pusillum (Moczydlowska, 1998 ) Vanguestaine nov. comb. Copyright © 2005 John Wiley & Sons, Ltd.     

The oldest record of Ediacaran macrofossils in Gondwana (~563 Ma,Itajaí Basin,Brazil)

The Avalon biota (Ediacaran Period, 570–559 Ma) marks the first appearance of macroscopic and complex benthic communities in the fossil record. This assemblage is known from a few localities worldwide, mainly in Canada and England. Here, we report for the first time the presence of Ediacaran macrofossils in deposits of similar age from Gondwana (Itajaí Basin, southern Brazil). Our new radiometric date (~563 Ma) indicates that the Itajaí Basin can be chronocorrelated with the classic Avalonian deposits and thus represents one of the oldest records of the Ediacaran biota in Gondwana. We describe the presence of the Ediacaran genus Palaeopascichnus, as well as discs (Aspidella and Nimbia), and other problematic forms. Contrary to the deep-marine macroorganisms of the Avalon Assemblage, the Itajaí fossils are associated with abundant and exceptionally preserved three-dimensional microbial mats and microbially induced sedimentary structures (MISS) in relatively shallow settings (upper slope and distal delta front deposits). In this sense, the Itajaí biota could represent early adaptations of benthic macrobiota to the shallower and more photic environments that characterize the later White Sea Assemblage.     

The unconformity-related palaeokarst in the uppermost Ediacaran carbonate rocks in the northwestern Tarim Block,NW China: implication for sedimentary evolution during the Ediacaran–Cambrian transition

ABSTRACT

The unconformity between the Ediacaran and Cambrian and its associated palaeokarst was well preserved within the Aksu area of the northwestern margin of the Tarim Block and provides new insights into the sedimentary evolution of the Tarim Basin during the Ediacaran–Cambrian transition. In this contribution, the typical palaeokarst features in the uppermost Ediacaran dolostones at nine outcrops in the Aksu area were documented, including palaeocaves, cave-sediment infills, solution vugs, and pores. Large-scale collapsed breccia assemblages in palaeocaves indicate that strong karstification had occurred in the south belt from the Xiaoerburak to Kule sections. Karst characterized by small-scale caves and solution vugs at the Chigebrak and Kakebashi sections suggests that the karstification in the north belt was not stronger than that in the south belt. Whereas sparse solution pores and small vugs can only be observed at the Sugetbrak and Yuermeinak sections, demonstrating that the karstification was weak in the middle belt. Combined with the thickness of sediments in the base of the Cambrian which subsequently overlay on the Ediacaran–Cambrian unconformity, it is speculated that the palaeo-upland was probably located in the middle belt from the Sugetbrak to Yuermeinak sections and the slope was developed in the south and north belts during the Ediacaran–Cambrian transition. The palaeokarst documented in the uppermost Ediacaran dolostones in the Aksu area illustrates an important sedimentary hiatus of the Tarim Block during the Ediacaran–Cambrian transition, which might be due to the sea-level fall at the end of the Ediacaran.