Depositional Record

Abstract Thin tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation are laterally widespread in the central part of the West Siberian Basin ( ca 0.5 million km 2 ). However, the source of the tuff beds remains unclear. The stratigraphy, geochemistry and geochronology of the tuff beds were investigated to reveal their magmatic origin and potential source region. Most of the tuff beds are recorded in member 4 and can be correlated through the Bazhenovo sequence. Thin‐section petrography and X‐ray diffraction indicate that the tuffs mostly comprise clay minerals and K‐feldspars. Less common minerals are plagioclase, quartz and pyrite. The geochemical composition of the Bazhenovo tuff beds suggests a parental magma origin of andesite/basalt, which came from volcanic arc‐related settings. Considering the results of geochemical studies along with LA‐ICP‐MS zircon U–Pb dating (141.3 ± 0.3/2.8 Ma), the palaeovolcanoes of the Caucasus region or south‐east Mongolia–North‐East China are one of the potential source regions of the tuffs. The record of these tuffs indicates the intensive volcanic eruption during the Volgian–Ryazanian, accompanied by a very low‐sedimentation rate and preservation in a reducing environment. The tuff beds have broad implications as an isochronous marker horizon and constraints for the numerical age of the Jurassic–Cretaceous boundary in the Boreal Realm.

Timur Bulatov

Yakov Yermakov

Anna Kulikova

Bulat Gareev

Mikhail Spasennykh

The Depositional Record

Provenance and the <scp>U–Pb</scp> age constraints on the tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation, West Siberian Basin

西西伯利亚盆地巴热诺沃组晚侏罗世-早白垩世凝灰岩层的成因及其<scp>U–Pb</scp>年龄约束

Abstract Lake margin deposits are the subject of increased study, but this is often focussed on either clastic or carbonate/microbial dominated end members. This study examines the interaction of clastic and carbonate systems. The Upper Triassic Edderfugledal Formation in East Greenland provides superb exposures through a carbonate dominated lacustrine succession. Fluctuations in lake level, interpreted as a response to cyclic, orbitally forced, climatic variance resulted in a highly mobile lake shore zone. The response of the shore zone environment to these fluctuations in lake level, and the interaction of both clastic and carbonate components, are documented in this study. A general trend from more arid to more humid conditions is recognised through the Edderfugledal Formation. This trend is reflected in a transition from more ephemeral lacustrine conditions with low sediment input to conditions where lacustrine episodes were more prolonged and clastic input was increased. Deposits reflecting more ephemeral conditions are dominated by extensive post‐depositional disruption including desiccation, pedogenic processes and evaporite precipitation. These effects increase towards the lake margins where exposure was most common and most prolonged. Increasingly humid conditions and the associated longer‐lived lacustrine developments and increased clastic sediment input resulted in a very different form of lake margin. During transgressive phases sediment input was pushed back to the lake margin allowing extensive microbialite development. Ooidal shoals developed in shallow water beyond the extent of clastic input. The lakeward migration of the ooidal shoals and the progradation of clastic systems eventually stifled the microbialites prior to the next transgressive event. In a mixed clastic‐carbonate lacustrine setting the interaction of sediment supply and production are key factors in governing facies development and these are in turn predominantly controlled by lake‐level change and lake margin bathymetry.

Steven D. Andrews

Li Guo

Mixed clastic‐carbonate lake margin systems: An example from the Triassic of East Greenland

混合碎屑-碳酸盐湖泊边缘系统：以东格陵兰三叠纪为例

Abstract The Stockton Formation of the Newark Basin represents an exciting time in Earth history during the early stages of rifting of the North Atlantic, with rapid subsidence and sediment deposition. Much of the previous work on this formation has been done using drill cores, with development limiting surface exposure. While this allows us to build a full stratigraphic sequence of deposition, it has the potential to miss smaller‐scale variability and sedimentary structures. It is also difficult to understand the three‐dimensional geometries, architecture and relationships between the depositional elements from drill core alone. An outcrop in North Bergen, NJ that was recently exposed during construction provided an opportunity to study the primary and secondary sedimentary structures of a previously hidden part of the Stockton Formation. These sediments and structures were investigated in the field and laboratory, with geochemical data assisting in the interpretation of their origin and history. Despite its small size, this outcrop provides strong evidence for varying rates of basin subsidence, with rocks deposited during more rapid subsidence also showing secondary structures associated with major earthquakes. Rapid subsidence during fluvial deposition resulted in the preservation of more fine‐grained, lower‐porosity sediments. Recently the Newark Basin has been identified as having characteristics that are favourable for CO 2 storage, however, a detailed understanding of sedimentary lithologies is essential to assessing that potential. If these periods of rapid subsidence have similar lithological consequences basin‐wide, this could potentially impact the capacity for carbon sequestration, by reducing porosity and permeability in many areas, and potentially creating barriers to flow.

Jane L. Alexander

Sean T. Thatcher

Jay Tobon

Victoria Rivelli

Evidence for subsidence rate variation in the Newark Basin and its influence on the deposition of fluvial sediments of the Stockton Formation

纽瓦克盆地沉降速率变化的证据及其对斯托克顿组河流沉积物沉积的影响

Abstract The Smithian–Spathian boundary interval is characterised by a positive carbon isotopic excursion in both δ 13 C carb and δ 13 C org , concurrent with a major marine ecosystem reorganisation and the resurgence of microbialite facies. While these δ 13 C records have been traditionally interpreted as capturing global carbon cycle behaviour, recent studies have suggested that at least some excursions in early Triassic δ 13 C values may incorporate influences from authigenic or early diagenetic processes. To examine the mechanistic drivers of Smithian–Spathian boundary geochemistry, the carbonate geochemistry of a core from Georgetown, Idaho (USA), was analysed using a coupled δ 44/40 Ca, δ 26 Mg and trace‐metal framework. While the δ 13 C record in the Georgetown core is broadly similar to other Smithian–Spathian boundary sections, portions of the record coincide with substantial shifts in δ 44/40 Ca, δ 26 Mg and trace‐metal compositions that cannot feasibly be interpreted as primary. Furthermore, these geochemical variations correspond with lithology: The δ 13 C record is modulated by variations in the extent of dolomitisation, and the diagenetic styles recognised here coincide with individual lithostratigraphic units. A primary shift in local sea water δ 13 C values is inferred from the most geochemically unaltered strata, from ca 3‰ in the middle Smithian to ca 5‰ in the early Spathian, although the timing and pathway through which this occurs cannot be readily identified nor extrapolated globally. Therefore, the Georgetown core may not directly record exogenic carbon cycle evolution, showing that there is a need for the careful reconsideration of the Smithian–Spathian boundary—and more broadly, Early Triassic—geochemical records to examine potential local and diagenetic influences on sedimentary geochemistry.

Jordan P. Todes

Franziska R. Blattmann

Torsten Vennemann

Elke Schneebeli‐Hermann

Hugo Bucher

Dan P. Razionale

Clara L. Blättler

Smithian–Spathian carbonate geochemistry in the northern Thaynes Group influenced by multiple styles of diagenesis

北塞尼斯组中史密斯阶-斯帕西阶碳酸盐岩地球化学受多种成岩作用样式影响

Abstract Coral reefs are hard calcified structures, mainly found in warm tropical water. These ecosystems serve important roles as, for example, a source of food, shelter and nursery for different organisms, and in coastal protection. Reef‐building organisms have evolved to inhabit a narrow ecological niche and thus are particularly susceptible to rapid changes in their environment, for example, under predicted climate‐change scenarios. Anthropogenic climate change is widely accepted as the leading cause of rising ocean temperatures, sea water acidity and sedimentation rate, which all affect a coral's productivity, health and, to some extent, skeletal strength. High‐energy weather events, such as storms and hurricanes, can erode reefs, thereby increasing the amount of suspended sediment and consequently the turbidity of the water. The removal of suspended sediment from the reef is vital for the health of reef producers, and a natural process that removes suspended sediment from reefs are sediment gravity flows. A key factor that controls the ability of sediment gravity flows to transport sediment is cohesion, as cohesion determines the run‐out distance of a flow through changes in its rheological properties. This study examines the cohesive nature of sediment gravity flows laden with fine‐grained CaCO 3 . These gravity flows laden with mud‐grade calcite are compared with flows carrying non‐cohesive, silt‐sized, silica flour, weakly cohesive kaolinite clay and strongly cohesive bentonite clay, by means of laboratory experiments. The results of these experiments show that the mud‐grade calcite flows behave more akin to the silica‐flour flows by reaching maximum mobility at considerably higher volumetric suspended sediment concentrations (47% for silica flour and 53% for CaCO 3 ) than the kaolinite and bentonite flows (22% for kaolinite and 16% for bentonite). Fine CaCO 3 gravity flows can therefore be regarded as physically non‐cohesive, and their high mobility may constitute an effective mechanism for removing suspended sediment from coral reefs, especially at locations where a slope gradient is present, such as at the reef front and forereef. However, biological cohesion, caused by ‘sticky’ extracellular polymer substances produced by micro‐organisms, can render mud‐grade calcite cohesive and sediment gravity flows less mobile. The present study should therefore be seen as a first step towards a more comprehensive analysis of the efficiency of removal of suspended sediment from coral reefs.

Jaco H. Baas

William Hewitt

Stephen Lokier

James Hendry

Coming to light: How effective are sediment gravity flows in removing fine suspended carbonate from reefs?

显露真相：沉积重力流在清除礁石中细悬浮碳酸盐方面的效果如何？

Abstract Feedback processes that drove Earth's second major increase in ocean–atmosphere oxygen levels during the Neoproterozoic are poorly constrained. Variability in seawater redox over geological timescales is commonly linked to changes in the biogeochemical cycling of P and thus the rate of primary production and generation of photosynthetic oxygen. In the modern surface ocean, an important source of bioessential P and micronutrients (Fe, Cu, Co, Zn, Mo, Cr and Ni) is aeolian dust derived from deserts and arid, post‐glacial landscapes. It is interpreted herein that glacial retreat following the Sturtian ( ca 717 to 660 Ma) and Marinoan ( ca 650 to 635 Ma) snowball glaciations provided copious dust to the global ocean. Correlation of interglacial siltstone successions in palaeogeographical context suggests that such dust accumulation was diachronous and concentrated in the palaeo‐horse latitudes (30° N and 30° S). Delivery of this dust from continents is likely reflected in the steep increase in global radiogenic Sr isotope values ( 87 Sr/ 86 Sr) in post‐Sturtian carbonates, and changes in the δ 18 O signatures of Cryogenian zircons derived from subducted marine sediments. Accumulation of sedimentary organic matter also peaked during interglacial periods, suggesting a causal link between glaciation, aeolian dust and primary production. This relationship implies windblown dust was an important source of P and micronutrients for an evolving biological pump that stimulated primary production, enhanced burial of organic carbon and increased ocean–atmosphere oxygen concentrations. Thus, delivery of aeolian dust to the global ocean was likely critical for sustaining Earth's second major increase in oxygen. Sequestration of atmospheric CO 2 in organic‐rich siltstones and shales is also interpreted to have been an important negative feedback process, which together with silicate weathering, prevented runaway greenhouse conditions during interglacial periods. The oxygen produced by this aeolian marine biological pump may have helped pave the way for the evolution of multicellular animals in the Ediacaran.

Abbreviation	Depositional Rec
Journal Impact	1.86
Quartiles(Global)	GEOLOGY(Q1)

ISSN	2055-4877
h-index	18

Publication Information	Publisher: John Wiley & Sons Inc.，Publishing cycle: ，Journal Type: journal，Open Access Journals: Yes
Basic data	Year of publication: 2015，Proportion of original research papers: 92.11%，Self Citation Rate:5.30%， Gold OA Rate: 86.55%
Journal Fees	$2400Details
Average review cycle	网友分享经验：16 Weeks

Depositional Record

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Provenance and the U–Pb age constraints on the tuff beds of the Late Jurassic–Early Cretaceous Bazhenovo Formation, West Siberian Basin

Mixed clastic‐carbonate lake margin systems: An example from the Triassic of East Greenland

Evidence for subsidence rate variation in the Newark Basin and its influence on the deposition of fluvial sediments of the Stockton Formation

Smithian–Spathian carbonate geochemistry in the northern Thaynes Group influenced by multiple styles of diagenesis

Coming to light: How effective are sediment gravity flows in removing fine suspended carbonate from reefs?

Mixed clastic‐carbonate lake margin systems: An example from the Triassic of East Greenland

Interglacial dust, ocean fertilisation and Neoproterozoic earth oxygenation

Evidence for subsidence rate variation in the Newark Basin and its influence on the deposition of fluvial sediments of the Stockton Formation

Smithian–Spathian carbonate geochemistry in the northern Thaynes Group influenced by multiple styles of diagenesis

Coming to light: How effective are sediment gravity flows in removing fine suspended carbonate from reefs?