ABSTRACT Coastal mud belts, which lie parallel to the coast just seaward of the shoreface, are one of the most important settings where shallow‐marine muddy deposits accumulate. However, sedimentary processes and facies distributions of coastal mud belts remain largely uninvestigated. This study uses process‐oriented sedimentology, coupled with provenance analysis and organic geochemistry of sedimentary records at the northern entrance to the Taiwan Strait, to investigate one of the largest such systems in the world, the Changjiang coastal mud belt. Carbon‐14 dates indicate that deposition has been intermittent throughout Marine Isotope Stages 1, 2 and 3, with several cryptic gaps in the muddy succession as a result of exposure or transgressive erosion during periods of lower or rising sea level, respectively. The palaeowater depth of each depositional unit was roughly estimated based on a global sea‐level curve and the elevation and age of the depositional units. Integrated provenance and sedimentology studies suggest that an incised valley most likely cut by the Minjiang, a nearby river draining the Chinese mainland, probably during Marine Isotope Stage 6, was filled with shelf mud during Marine Isotope Stage 3. These results demonstrate that deposition of mud on the Changjiang coastal mud belt was influenced by sea‐level changes that controlled water depth and flow patterns through Taiwan Strait. The Changjiang coastal mud belt migrates landward when sea level rises and moves seaward when sea level drops. In addition, changes in oceanic circulation associated with opening and closing of Taiwan Strait due to sea‐level changes causes significant changes in the source of the mud, with an alternation between sediment contributions from the Changjiang in the north, the nearby Minjiang, and the island of Taiwan to the south‐east. This study also reveals that the Changjiang coastal mud belt deposits are composed of both shallower‐water and deeper‐water facies. The shallower‐water facies predominantly comprises abundant fluid‐mud beds generated by waves and tidal currents. The deeper‐water facies contains shell‐rich mud and bioturbated mud, which were likely deposited by the Chinese coastal current and Taiwan Warm current. The bed types and interpretation of sedimentary processes of the Changjiang coastal mud belt are useful for recognition of ancient deposits of coastal mud belts elsewhere.

Xin Shan

Robert W. Dalrymple

Xuefa Shi

Lina Jin

Shengfa Liu

Chenguang Liu

Shihao Liu

Shuqing Qiao

Qingjie Zhou

Xisheng Fang

Sedimentology

Changjiang coastal mud‐belt deposits in Taiwan Strait: Controls on its distribution and facies

ABSTRACT Contourites (contour‐current deposits) are commonly associated with deep‐water environments, but this study documents a shallow‐water, muddy contourite drift in the centre of Taiwan Strait. The drift body (water depths of 30 to 70 m, 220 km long, 50 to 70 km wide, 0 to 30 m thick), with its long axis approximately colinear with the Taiwan Strait Current, is flanked on both sides by moats. Compositional data show that the drift is composed of sediment carried northward by the Taiwan Strait Current from the Choshui River draining Taiwan. The coast‐normal Changyun Ridge directly offshore of the Choshui River splits the Taiwan Strait Current into two branches that occupy the moats. Oblique cross‐drift flow from west to east contributes to drift growth. The dispersal system shows a down‐current fining from sands on the Changyun Ridge ( ca 100 km long, 25 to 45 km wide) to the fine‐grained elongate drift; these together represent the asymmetrical subaqueous portion of the Choshui delta. Cores show that the drift is &lt;8 kyr old, with sedimentation rates up to 7.8 m/ka. It coarsens upward during the initial phase of drift growth, perhaps due to an increase in current strength, with smaller‐scale textural bedding attributed to fluctuating current strengths or variations in wave energy depending on the location. Seismic data show that the southern end of the drift is migrating westward, due to elongation of the Changyun Ridge, whereas the middle and distal end are migrating eastward because of cross‐drift flow. Erosion by the eastern branch of the Taiwan Strait Current detached the drift from the coeval coastal mud belt. The influence of tidal currents is small because of the destructive interference of tidal waves entering from the two ends, creating weak rotary tidal currents over the drift. Wave energy is small within the Strait but larger waves arriving from the East China Sea are thought to be responsible for upward coarsening of the more exposed northern end. Taiwan Strait serves as a starting point for developing a facies model for ocean‐current‐dominated straits and seaways.

Zhengquan Yao

Qingfeng Hua

Han Feng

Shan Liu

Char‐Shine Liu

Paul Liu

Taiwan Strait: An ocean‐current‐dominated shallow‐water setting with a river‐fed detached muddy contourite deposit

台湾海峡：受洋流主导的浅水环境与河流补给的离散泥质等深流沉积

The Cretaceous sandstone reservoir in the Kuche Depression, Tarim Basin, western China, was investigated with reference to its reservoir property evolution during diagenesis. Six general diagenetic stages were recognized through petrographic, mineralogical and geochemical analyses. Fluid–rock interaction experiments were conducted under these six continuous diagenetic conditions, that is with a simulation sequence of compaction → early diagenesis → organic acid incursion I → elevated temperature/pressure → organic acid incursion II → late diagenesis. Corresponding to these six experimental stages, a total of six models were constructed. Finally, an extended model of fluid–rock interaction during diagenesis at a geological timescale (from 30 Ma to present) was constructed after various parameters had been validated. Results demonstrate that the diagenetic stages from both the experimental and numerical simulations generally matched findings obtained from the petrographic and geochemical analyses: (i) With compaction becoming weakened, cementation by various minerals was gradually increased. (ii) Quartz overgrowth occurred because the contemporaneous sedimentary water was alkaline. (iii) Most minerals (for example, calcite and feldspar minerals) displayed dissolution owing to the first organic acid incursion, resulting in the visual porosity increasing to 29·26%. (iv) Increases in temperature and pressure caused a minor fluctuation of the porosity change. (v) The cement that formed during earlier stages largely dissolved with the second organic acid incursion. (vi) During the last stage, the reservoir fluid was diluted by sedimentary alkaline water and most minerals precipitated under an alkalic environment. The present porosity simulated is about 11·4%, comparable with the actually measured data. This study demonstrates that the combination of petrographic observations, laboratory experiments and numerical simulations can not only reconstruct the diagenetic process, but also provide a quantitative evaluation and prediction of reservoir petrophysical properties.

Leilei Yang

Tianfu Xu

Keyu Liu

Bo Peng

Zhichao Yu

Xiaomeng Xu

Fluid-rock interactions during continuous diagenesis of sandstone reservoirs and their effects on reservoir porosity

砂岩储层连续成岩过程中的流体-岩石相互作用及其对储层孔隙度的影响

Abstract The lower Eocene Willwood Formation of the Bighorn Basin, Wyoming, USA, is an alluvial succession with a sand content varying around 25%. It has been studied intensively for palaeontology, palaeoenvironments and palaeoclimates, as well as sedimentological and stratigraphic analysis. Channel dynamics were studied at a relatively low resolution throughout the basin over the geological time from late Palaeocene to early Eocene. Here, a high‐resolution study is reported to complement previous research at the basin scale. Efforts are made to document the characteristics and river planform styles of most sandstone bodies encountered through ca 300 m of alluvial stratigraphy in a 10 km 2 area of the Deer Creek part of the McCullough Peaks area situated in the basin axis of northern Bighorn Basin. Four channel facies associations are recognized and ascribed to four river planform styles: crevasse channel, trunk channel, braided‐like channel and sinuous‐like channel, with the latter two types dominant. Braided‐like and sinuous‐like channel sandstone bodies differ significantly in thicknesses, being on average 6.1 m versus 9.0 m, but they have similar palaeoflow–perpendicular widths of on average 231 m and palaeoflow directions of on average N 003°. Braided‐like and sinuous‐like river planform styles show no spatial dependency in the 10 km 2 study area. Results of this study are in line with existing basin‐scale depositional models that are composed of a single axial system fed by several transverse systems dominantly from the west. The feeding of these systems could be influenced by palaeoclimate changes possibly controlling their contribution over time, thereby impacting river planform styles. At the same time, changing water discharge hydrograph, sediment load and overbank cohesiveness may have equally driven the observed river planform style changes within the basin without a major role of catchments.

Youwei Wang

Timothy F. Baars

Hiranya Sahoo

Joep E. A. Storms

Allard W. Martinius

Philip Gingerich

Hemmo A. Abels

Sandstone body character and river planform styles of the lower Eocene Willwood Formation, Bighorn Basin, Wyoming, USA

美国怀俄明州大角盆地始新统下部威尔伍德组砂岩体特征与河流平面形态样式

ABSTRACT Continental red beds are coloured by secondary Fe(III)‐oxy‐hydroxides (mainly hematite) which makes them excellent archives of ancient near‐surface redox conditions. However, colour is often treated as a subjective physical property, and opinions differ widely as to the environment and timing of colouration of the red beds. This study utilizes diffuse spectral reflectance to address the degree of reddening (hematitization) of the Siluro‐Devonian Old Red Sandstone representing a dryland fluvial system with abundant palaeo‐Vertisols, coinciding with the period of land colonization by vascular plants. The hematitization was studied along with the stratigraphy, facies, pedogenic features, petrology, element and Molybdenum isotope geochemistry. The mudstones and palaeosols are typically red while sandstones are often grey. The red colouration corresponds to approximately 30 to 36% of red band (625 to 700 nm) reflectance and high hematite to goethite ratios. The red sediments contain hematitized biotite, submicronic hematite in mudstone and sandstone matrix, and hematite cement in calcretes. The hematitization was synchronous with formation of pedogenic mudcracks, Vertic slickensides, calcretes, reduction spots, sometimes hydrodynamic reworking, and accompanied by local (grain‐scale) depletion in Fe(II), enrichment in Fe(III), and mobilization of U, V, As, Cu, Zn and Mo. It is estimated that the hematite growth was rapid (several hundred to thousand years) but the average sedimentation rates were low (approximately 3 to 10 cm/kyr). Erosion led to development of reactivation surfaces separating layers with contrasting hematite content and geochemistry. It is suggested that high rates of pedogenesis and low sedimentation rates favour the reddening and may represent an important control on the formation of continental red beds. Limited levels of soil waterlogging, and the published δ 13 C values (−9 to −12‰ Vienna Pee Dee Belemnite) of the pedogenic carbonate, might reflect the changes in the nature of the soil biomantle during the early Devonian land colonization by vascular plants.

Ondřej Bábek

Lukáš Ackerman

Daniel Šimíček

V. Paul Wright

Susan Marriott

Tomáš Pluháček

Salahaddin Shahrokhi

Hedvika Weinerová

Pedogenic continental red beds: How, why and when red? Redox geochemistry and quantitative colour analysis of the Old Red Sandstone, South Wales, UK

成土大陆红层：如何、为何及何时变红？英国南威尔士老红砂岩的氧化还原地球化学与定量颜色分析

ABSTRACT Middle Ordovician iron ooids in the Upper Yangtze region of South China are composed mainly of hematite and/or chamosite, found in mixed siliciclastic and carbonate successions, with hematitic ooids occurring in the west, and predominantly chamositic ooids in the east of the study area. In the three iron ooid‐bearing Middle–Upper Ordovician successions, 19 microfacies are recognized and grouped into eight facies associations, representing a shallow‐water mosaic comprising restricted and semi‐restricted lagoons, and open marine subtidal deposits interfingering with tidal flat and shoal facies. Hematitic ooids with well‐sorted and well‐rounded quartz grains formed in the transgressive shoal setting when the depositional environments changed from restricted lagoon to bioclast–quartz shoal and open marine subtidal. Episodic stasis and erosional intervals during transgression controlled the formation of hematite‐rich and mixed hematite–chamosite laminae within the cortices of hematitic ooids. In contrast, chamositic ooids formed in a semi‐restricted lagoonal environment, under long‐term transgressive condensation. Alternating episodes of relatively oxic conditions with thriving organisms and eutrophication‐driven anoxia resulted in the alternation of porous and dense laminae consisting mainly of chamosite in chamositic ooids. The stromatolite‐like cauliflower structures associated with chamositic ooids suggest microbial activity that promoted iron concentration, similar to the origin of approximately coeval iron‐rich oncoids in South China. Various iron ooid types demonstrate that these coated grains could form in a range of depositional setting and palaeooceanographic conditions on a generally shallow‐marine platform during the Ordovician.

Xiaocong Luan

Colin D. Sproat

Jisuo Jin

Renbin Zhan

Depositional environments, hematite–chamosite differentiation and origins of Middle Ordovician iron ooids in the Upper Yangtze region, South China

沉积环境、赤铁矿-鲕绿泥石分异及华南上扬子地区中奥陶世铁鲕石的起源

Abstract Carbonates formed by anaerobic oxidation of methane at localized seeps have been recognized in the rock record based on a list of criteria, including anomalous deposition within detrital facies, complex petrofabrics, seep‐endemic macrofauna and 13 C‐depleted isotopic signatures. While much emphasis has been placed on the latter, it is only one of several tools used for identification. This study reports on two different and rare limestone units in the forearc deposits of the Jurassic Bedford Canyon Formation in the Santa Ana Mountains, California (USA). Isolated, metre‐scale limestone pods were found to host abundant endemic Anarhynchia dimerelloid brachiopods and display diverse petrofabrics, including multiple generations of cements. However, the δ 13 C values of the petrofabrics ranged from −14.5 to 4.52‰ Vienna PeeDee Belemnite. These values are only slightly 13 C‐depleted relative to contemporaneous seawater, thus likely recording a stronger component of oceanic dissolved inorganic carbon than hydrocarbons. Additionally, although the petrofabrics are common for seeps (primary micrite, microbialite, pelsparite, intraclastic micrite; early isopachous and botryoidal cements and yellow calcite; late‐stage void‐filling spar), the isotopic values did not follow a predicted trend of increasing δ 13 C with paragenetic sequence. Pelsparite δ 13 C values ranged from −10.65 to −7.09‰ Vienna PeeDee Belemnite while coarse spar and vein cements ranged from −11.42 to −2.44‰ Vienna PeeDee Belemnite. Olistostromes composed of brecciated pelmicrite sourced from shallow fringing‐arc environments are typical of forearc settings. Olistostromes in the Bedford Canyon Formation contain much lower δ 13 C values than the more classically characterized seep deposits, ranging from −21.77 to −10.78‰ Vienna PeeDee Belemnite. While the original shallow‐water source may not have a been a confined seep, the low δ 13 C values require the incorporation of carbon sourced from the oxidation of localized hydrocarbons. Together, these findings recommend a reconsideration of the weight placed on δ 13 C values as the key criterion for distinguishing seeps in the rock record.

Russell S. Shapiro

Miquela Ingalls

Challenges to the ancient methane seep search strategy: The Bedford Canyon Formation (Middle Jurassic, Santa Ana Mountains, California)

古代甲烷渗漏搜索策略的挑战：贝德福德峡谷组（中侏罗世，圣安娜山脉，加利福尼亚）

Abstract Research on the ichnology of brackish‐water environments began in the 1930s and has led to the identification of predictable infaunal patterns. Brackish‐water deposits characteristically display low‐diversity tracefossil assemblages consisting of both vertical and horizontal structures. These salinity‐reduced ecosystems are dominated by opportunistic euryhaline‐tolerant species. Osmoregulation‐related selective pressures lead to decreased diversity and an abundance of infaunal organisms. In environments with fluctuating or low salinity, fauna adopt r‐selected strategies and are characterized by rapid colonization dynamics, high population densities, elevated mortality rates and low‐diversity assemblages. Tides in brackish‐water settings contribute a plentiful food supply with tidal currents transporting marine‐sourced and terrestrially sourced organic matter that settles on the sediment–water interface during slack‐water periods. This increased food availability favours trophic generalists using various feeding strategies to exploit both intrastratal and surficial food resources. The ichnological characteristics of modern and ancient brackish‐water strata are used to propose the Teichichnus Ichnofacies; they are temporally and spatially recurrent and reflect the biology of brackish‐water settings. The Teichichnus Ichnofacies is recognized by reduced trace‐fossil diversity, smaller trace sizes, dominance of structures reflecting trophic generalist behaviours, sporadic distributions of ichnofossils, locally high bioturbation intensities and opportunistic colonization. This ichnofacies is characterized by trace fossils interpreted to be associated with surface deposit feeding, intrastratal deposit feeding and subordinate filter feeding.

Murray K. Gingras

James A. MacEachern

Shahin E. Dashtgard

Kerrie L. Bann

The <i>Teichichnus</i> Ichnofacies: Its neoichnological basis and identification in the rock record

《Teichichnus》遗迹相：其现代遗迹学基础与岩石记录中的识别

ABSTRACT The Yukon–Koyukuk Basin is a wide, triangular depression in northern Alaska that initiated as the consequence of the collision between an intraoceanic arc and the Arctic Alaska margin. It is bordered by the metamorphic terranes of the Seaward Peninsula, the Brooks Range and the Ruby Terrane. The Yukon–Koyukuk Basin is divided into two sub‐basins separated by remnants of the volcanic arc. Two different models have been suggested for its formation. One model interprets the Yukon–Koyukuk Basin to have formed during collision in a forearc–backarc setting, while the other favours an extensional regime that was active after the cessation of collision. To test the two models, ten sedimentary samples from the two stratigraphically lowest units cropping out along the middle reaches of the Koyukuk River were analysed. Point counting and Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMSCAN ® ) are used to evaluate sedimentary provenance. This study also presents zircon U–Pb ages from three interbedded tuffaceous layers to better constrain the age of the units. The base of the succession indicates a volcanic source (enriched in clinopyroxene) deposited at ca 138.3 ± 0.8 Ma (2σ), while younger overlying strata are dominated by metamorphic input (enriched in garnet and epidote) reflecting the erosion of the surrounding metamorphic terranes at ca 112.6 ± 1.1 Ma (2σ). The application of a multi‐method provenance approach has been essential in constraining the formation and evolution of the northern Yukon–Koyukuk Basin. This is of significant importance for advancing the understanding of Alaskan geology and for providing insights into modern basins within analogous tectonic settings, such as the Banda Arc in Southeast Asia.

Simone Seminara

Victoria Pease

Jaime Toro

Jenny Omma

Provenance studies and basin evolution: Insight from the Yukon–Koyukuk Basin, Alaska

原产地研究与盆地演化：来自阿拉斯加育空-科尤库克盆地的启示

Abstract The Upper Ordovician (Katian) Neda Formation, a phosphatic ironstone, records a widespread but short‐lived shift to ferruginous waters across a vast epicontinental area. Lithofacies and stratigraphic reappraisal indicate that Neda ironstone deposition occurred on a storm‐dominated ramp when coastal upwelling emplaced eutrophic ferruginous waters that mixed with oxygenated surface water. This stimulated primary productivity and precipitated Fe‐(oxyhydr)oxides in the water column that formed phosphorous and iron‐rich mud. Remobilization of iron beneath the seafloor led to the syndepositional authigenic precipitation of P and Fe minerals in the sediment, preferentially coating grains and forming granular ironstone in the top few decimetres of the sediment. The top of the Neda Formation is a pronounced unconformity punctuated by laterite that formed as sea level fell during the Hirnantian Glaciation. The transition from oxygenated to ferruginous conditions that led to ironstone deposition is interpreted to have been caused by an increase in the equator‐to‐pole temperature gradient and concomitant reorganization of thermohaline circulation during the Katian. This intensified upwelling off the Laurentian margin with upwelled waters transported into the midcontinent where ironstone accumulated through the Sebree Trough. The Neda ironstone's deposition coincident with, and potentially caused by, the same drivers as global oceanographic and biotic change during the Late Ordovician both adds greater insight into the major changes in the oceans preceding the Late Ordovician Mass Extinction and Hirnantian Glaciation, and also furthers an emerging model tying ironstone deposition throughout the Phanerozoic to major Earth system events.

Edward J. Matheson

Jackson D. Malone

Peir K. Pufahl

Eric E. Hiatt

Late Ordovician ironstone and its relation to ocean redox instability, climate and glaciation

晚奥陶纪铁矿石及其与海洋氧化还原不稳定性、气候和冰川作用的关系

作为该领域的国际领导者，SEDIMENTOLOGY 发表了跨越沉积学、沉积地质学和沉积地球化学的开创性研究。涵盖的领域包括：实验和理论谷物运输；沉积物通量；现代和古代沉积环境；层序地层沉积物-生物相互作用；古土壤；成岩作用；稳定同位素地球化学；环境沉积学

As a leading international journal in the field of sedimentology, Sedimentology publishes pioneering research that spans sedimentology, sedimentary geology, and sedimentary geochemistry. The covered areas include experimental and theoretical grain transport, sediment flux, modern and ancient sedimentary environments, sediment-biota interactions in sequence stratigraphy, paleosols, diagenesis, stable isotope geochemistry, and environmental sedimentology.

作为沉积学领域的国际领导者，Sedimentology 发表了跨越沉积学、沉积地质学和沉积地球化学的开创性研究。涵盖的领域包括实验和理论的颗粒运输、沉积物通量、现代和古代沉积环境、层序地层中的沉积物与生物相互作用、古土壤、成岩作用、稳定同位素地球化学以及环境沉积学。

Journals	Sedimentology
ISSN	0037-0746, 1365-3091
h-index	126
Journal Impact	2.69
Quartiles(Global)	GEOLOGY(Q1)
Quartiles(China)	地球科学(2区)地球科学地质学(1区)