Ru Wang, Wonsuck Kim, Luca Colombera, Nigel P. Mountney, Yunhyeong Lee, Jaehyung Lee
Nearshore incised valleys are important conduits for the transport of sediment, nutrients, pollutants and organic carbon from the continents to the sea. Therefore, it is essential to understand the autogenic evolution of deltas confined within incised valleys and how such evolution is affected by relative sea-level rise. To date, limited research has focused on how deltas constrained by incised valleys or other forms of antecedent topography respond to rising sea level. An existing theory of autostratigraphy envisages scenarios in which two-dimensional or unconfined three-dimensional fan deltas can experience three evolutionary stages under constant rates of relative sea-level rise and sediment supply: progradation, autoretreat and post-autobreak transgression. In this work, an integrated study of geometric numerical models and physical experiments is undertaken to investigate autostratigraphic delta evolution for a variety of incised-valley geometries, under conditions of constant rates of relative sea-level rise and sediment supply. Results indicate that interplays of antecedent topography (valley geometries) and sediment mass balance expressed in resultant deltaic geometries can result in autogenic changes in shoreline dynamics and river avulsion frequency on deltas. The following primary findings arise. (i) Compared to valleys with rectangular and trapezoidal cross-sectional profiles, valleys with triangular cross-sections tend to contain deltas that experience faster rates of progradation, autoretreat and post-autobreak transgression under rising sea level, and exhibit a more prominent convex-seaward shoreline trajectory. (ii) The shoreline trajectory is also related to delta topset geometry, becoming more convex-seaward under decreasing topset slopes. (iii) River avulsion frequency on deltas with rising sea level varies markedly across valleys with different geometries, even under the same rate of relative sea-level rise; this is attributed to the difference in temporal evolution of shoreline migration for different valley geometries and the resultant difference in the delta topset aggradation. This study highlights complexities in responses of sedimentary systems under the confinement of different topographic configurations that have hitherto largely been overlooked in sequence-stratigraphic models. The findings provide insight into future shoreline behaviour and river avulsion hazard on confined deltas, and for decoding the stratigraphic record.
{"title":"Autogenic evolution of valley-confined deltas during sea-level rise: Insights from numerical and physical modelling","authors":"Ru Wang, Wonsuck Kim, Luca Colombera, Nigel P. Mountney, Yunhyeong Lee, Jaehyung Lee","doi":"10.1111/sed.13178","DOIUrl":"https://doi.org/10.1111/sed.13178","url":null,"abstract":"Nearshore incised valleys are important conduits for the transport of sediment, nutrients, pollutants and organic carbon from the continents to the sea. Therefore, it is essential to understand the autogenic evolution of deltas confined within incised valleys and how such evolution is affected by relative sea-level rise. To date, limited research has focused on how deltas constrained by incised valleys or other forms of antecedent topography respond to rising sea level. An existing theory of autostratigraphy envisages scenarios in which two-dimensional or unconfined three-dimensional fan deltas can experience three evolutionary stages under constant rates of relative sea-level rise and sediment supply: progradation, autoretreat and post-autobreak transgression. In this work, an integrated study of geometric numerical models and physical experiments is undertaken to investigate autostratigraphic delta evolution for a variety of incised-valley geometries, under conditions of constant rates of relative sea-level rise and sediment supply. Results indicate that interplays of antecedent topography (valley geometries) and sediment mass balance expressed in resultant deltaic geometries can result in autogenic changes in shoreline dynamics and river avulsion frequency on deltas. The following primary findings arise. (i) Compared to valleys with rectangular and trapezoidal cross-sectional profiles, valleys with triangular cross-sections tend to contain deltas that experience faster rates of progradation, autoretreat and post-autobreak transgression under rising sea level, and exhibit a more prominent convex-seaward shoreline trajectory. (ii) The shoreline trajectory is also related to delta topset geometry, becoming more convex-seaward under decreasing topset slopes. (iii) River avulsion frequency on deltas with rising sea level varies markedly across valleys with different geometries, even under the same rate of relative sea-level rise; this is attributed to the difference in temporal evolution of shoreline migration for different valley geometries and the resultant difference in the delta topset aggradation. This study highlights complexities in responses of sedimentary systems under the confinement of different topographic configurations that have hitherto largely been overlooked in sequence-stratigraphic models. The findings provide insight into future shoreline behaviour and river avulsion hazard on confined deltas, and for decoding the stratigraphic record.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139917593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tang, W., Pe Piper, G., Piper, D.J.W., Chen, A., Hou, M., Guo, Z. and Zhang, Y. (2024) Architecture of lacustrine deposits in response to early Carboniferous rifting and Gondwanan glaciation, Nova Scotia, south-east Canada. Sedimentology, 71, 457–485.
The published version of Fig. 5 is incorrect. The correct version, with its caption, is provided below.
Fig. 5
Open in figure viewerPowerPoint
Soft-sediment deformation structures in sandstones and siltstones. (A) Brittle thrust fold (a) and bedding-parallel shear plane (b) in deformed siltstone bed. (B) Brittle boudinage of otherwise undeformed sandstone bed. (C) Detail of sandstone dyke in Fig. 4D; (a) shale parting in dyke; (b) bedding-parallel injection of sand from dyke. (D) Detail of boudins in (B) showing abrupt and undeformed lateral terminations of sandstone bed; (a) load structure at base of bed. (E; right) Detail of ‘breccia’ in Fig. 4D showing loading relationship of sandstone to envelopingblack shale; (left) complex dyke, (a) bedding parallel sandstone; (b) upward injected dyke; (c) downward injecteddyke. The locations of the photographs are shown in Fig. 2.
Tang, W., Pe Piper, G., Piper, D.J.W., Chen, A., Hou, M., Guo, Z. and Zhang, Y. (2024) Architecture of lacustrine deposits in response to early Carboniferous rifting and Gondwanan glaciation, Nova Scotia, south-east Canada.Sedimentology, 71, 457-485.The published version of Fig.图 5在图形浏览器中打开PowerPoint砂岩和粉砂岩中的软沉积变形结构。(A) 变形粉砂岩岩床中的脆性推力褶皱（a）和与层理平行的剪切面（b）。 (B) 原未变形的砂岩岩床中的脆性包岩。 (C) 图 4D 中砂岩堤坝的细节；（a）堤坝中的页岩分块；（b）堤坝中与层理平行的注砂。(D) (B)中 "砾岩 "的细部，显示砂岩岩床的突然和未变形的横向终端；(a) 岩床底部的荷载结构。 (E; 右) 图 4D 中 "砾岩 "的细部，显示砂岩与包裹的黑色页岩的荷载关系；（左）复合堤坝，(a) 与层理平行的砂岩；(b) 向上注入的堤坝；(c) 向下注入的堤坝。照片位置见图 2。
{"title":"Corrigendum to: Architecture of lacustrine deposits in response to early Carboniferous rifting and Gondwanan glaciation, Nova Scotia, south-east Canada","authors":"","doi":"10.1111/sed.13186","DOIUrl":"https://doi.org/10.1111/sed.13186","url":null,"abstract":"<p>Tang, W., Pe Piper, G., Piper, D.J.W., Chen, A., Hou, M., Guo, Z. and Zhang, Y. (2024) Architecture of lacustrine deposits in response to early Carboniferous rifting and Gondwanan glaciation, Nova Scotia, south-east Canada. <i>Sedimentology</i>, 71, 457–485.</p>\u0000<p>The published version of Fig. 5 is incorrect. The correct version, with its caption, is provided below.</p>\u0000<figure><picture>\u0000<source media=\"(min-width: 1650px)\" srcset=\"/cms/asset/79cb53e4-9dfc-4b75-803f-f7f7030f8b90/sed13186-fig-0001-m.jpg\"/><img alt=\"Details are in the caption following the image\" data-lg-src=\"/cms/asset/79cb53e4-9dfc-4b75-803f-f7f7030f8b90/sed13186-fig-0001-m.jpg\" loading=\"lazy\" src=\"/cms/asset/765647f1-3f2f-4e12-a045-ddc9366a5799/sed13186-fig-0001-m.png\" title=\"Details are in the caption following the image\"/></picture><figcaption>\u0000<div><strong>Fig. 5<span style=\"font-weight:normal\"></span></strong><div>Open in figure viewer<i aria-hidden=\"true\"></i><span>PowerPoint</span></div>\u0000</div>\u0000<div>Soft-sediment deformation structures in sandstones and siltstones. (A) Brittle thrust fold (a) and bedding-parallel shear plane (b) in deformed siltstone bed. (B) Brittle boudinage of otherwise undeformed sandstone bed. (C) Detail of sandstone dyke in Fig. 4D; (a) shale parting in dyke; (b) bedding-parallel injection of sand from dyke. (D) Detail of boudins in (B) showing abrupt and undeformed lateral terminations of sandstone bed; (a) load structure at base of bed. (E; right) Detail of ‘breccia’ in Fig. 4D showing loading relationship of sandstone to envelopingblack shale; (left) complex dyke, (a) bedding parallel sandstone; (b) upward injected dyke; (c) downward injecteddyke. The locations of the photographs are shown in Fig. 2.</div>\u0000</figcaption>\u0000</figure>","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139760046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soraia Romão, J. Cascalho, Caroline C. Ferreira, Eric Font, Rui Taborda, Paulo A. Silva, João F. Duarte, Franziska Staudt
The in situ measurement of sediment transport in wave‐dominated environments presents significant challenges and currently often relies upon the use of fluorescent sediment tracers. However, this method is constrained by challenges in conducting unbiased and representative sampling, as well as facing overall logistical complexities and labour‐intensive procedures. Whilst other tracer techniques are available, such as using magnetic tracers, their performance in tracking sediment transport has not been quantified. The objective of this study is to assess the effectiveness of magnetic tracers in evaluating net transport rates and tracer dispersal patterns. Conducted in a controlled large wave flume, the experiments simultaneously employed fluorescent and magnetic tracers, allowing a comprehensive comparison of the tracers' dispersion patterns and the net transport rates. Results show that the dispersal of magnetic and fluorescent tracers displays a high degree of spatial coherence in both horizontal and vertical dimensions. Similarly, net transport rates are comparable (<16% difference), both showing net transport in the direction of the wave propagation (towards onshore) driven by non‐linear and streaming effects. Magnetic tracer recovery rate (49%) was lower than for fluorescent tracers (73%) and is attributed to the loss of magnetic ink from particles; an aspect of the magnetic technique that requires improvement. This study therefore indicates that the use of magnetic tracers to quantify sediment transport is an effective method with the advantages of being significantly less labour‐intensive than using the commonly applied fluorescent sediment tracer method.
{"title":"Testing magnetic tracers as indicators of sediment transport in a wave flume experiment","authors":"Soraia Romão, J. Cascalho, Caroline C. Ferreira, Eric Font, Rui Taborda, Paulo A. Silva, João F. Duarte, Franziska Staudt","doi":"10.1111/sed.13183","DOIUrl":"https://doi.org/10.1111/sed.13183","url":null,"abstract":"The in situ measurement of sediment transport in wave‐dominated environments presents significant challenges and currently often relies upon the use of fluorescent sediment tracers. However, this method is constrained by challenges in conducting unbiased and representative sampling, as well as facing overall logistical complexities and labour‐intensive procedures. Whilst other tracer techniques are available, such as using magnetic tracers, their performance in tracking sediment transport has not been quantified. The objective of this study is to assess the effectiveness of magnetic tracers in evaluating net transport rates and tracer dispersal patterns. Conducted in a controlled large wave flume, the experiments simultaneously employed fluorescent and magnetic tracers, allowing a comprehensive comparison of the tracers' dispersion patterns and the net transport rates. Results show that the dispersal of magnetic and fluorescent tracers displays a high degree of spatial coherence in both horizontal and vertical dimensions. Similarly, net transport rates are comparable (<16% difference), both showing net transport in the direction of the wave propagation (towards onshore) driven by non‐linear and streaming effects. Magnetic tracer recovery rate (49%) was lower than for fluorescent tracers (73%) and is attributed to the loss of magnetic ink from particles; an aspect of the magnetic technique that requires improvement. This study therefore indicates that the use of magnetic tracers to quantify sediment transport is an effective method with the advantages of being significantly less labour‐intensive than using the commonly applied fluorescent sediment tracer method.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139798258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soraia Romão, J. Cascalho, Caroline C. Ferreira, Eric Font, Rui Taborda, Paulo A. Silva, João F. Duarte, Franziska Staudt
The in situ measurement of sediment transport in wave‐dominated environments presents significant challenges and currently often relies upon the use of fluorescent sediment tracers. However, this method is constrained by challenges in conducting unbiased and representative sampling, as well as facing overall logistical complexities and labour‐intensive procedures. Whilst other tracer techniques are available, such as using magnetic tracers, their performance in tracking sediment transport has not been quantified. The objective of this study is to assess the effectiveness of magnetic tracers in evaluating net transport rates and tracer dispersal patterns. Conducted in a controlled large wave flume, the experiments simultaneously employed fluorescent and magnetic tracers, allowing a comprehensive comparison of the tracers' dispersion patterns and the net transport rates. Results show that the dispersal of magnetic and fluorescent tracers displays a high degree of spatial coherence in both horizontal and vertical dimensions. Similarly, net transport rates are comparable (<16% difference), both showing net transport in the direction of the wave propagation (towards onshore) driven by non‐linear and streaming effects. Magnetic tracer recovery rate (49%) was lower than for fluorescent tracers (73%) and is attributed to the loss of magnetic ink from particles; an aspect of the magnetic technique that requires improvement. This study therefore indicates that the use of magnetic tracers to quantify sediment transport is an effective method with the advantages of being significantly less labour‐intensive than using the commonly applied fluorescent sediment tracer method.
{"title":"Testing magnetic tracers as indicators of sediment transport in a wave flume experiment","authors":"Soraia Romão, J. Cascalho, Caroline C. Ferreira, Eric Font, Rui Taborda, Paulo A. Silva, João F. Duarte, Franziska Staudt","doi":"10.1111/sed.13183","DOIUrl":"https://doi.org/10.1111/sed.13183","url":null,"abstract":"The in situ measurement of sediment transport in wave‐dominated environments presents significant challenges and currently often relies upon the use of fluorescent sediment tracers. However, this method is constrained by challenges in conducting unbiased and representative sampling, as well as facing overall logistical complexities and labour‐intensive procedures. Whilst other tracer techniques are available, such as using magnetic tracers, their performance in tracking sediment transport has not been quantified. The objective of this study is to assess the effectiveness of magnetic tracers in evaluating net transport rates and tracer dispersal patterns. Conducted in a controlled large wave flume, the experiments simultaneously employed fluorescent and magnetic tracers, allowing a comprehensive comparison of the tracers' dispersion patterns and the net transport rates. Results show that the dispersal of magnetic and fluorescent tracers displays a high degree of spatial coherence in both horizontal and vertical dimensions. Similarly, net transport rates are comparable (<16% difference), both showing net transport in the direction of the wave propagation (towards onshore) driven by non‐linear and streaming effects. Magnetic tracer recovery rate (49%) was lower than for fluorescent tracers (73%) and is attributed to the loss of magnetic ink from particles; an aspect of the magnetic technique that requires improvement. This study therefore indicates that the use of magnetic tracers to quantify sediment transport is an effective method with the advantages of being significantly less labour‐intensive than using the commonly applied fluorescent sediment tracer method.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139857926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
William J. Taylor, David M. Hodgson, Jeff Peakall, Ian A. Kane, Emma A. Morris, Stephen S. Flint
Mixed grain-size bedforms comprise alternating sand-rich and poorly sorted mud-rich laminae and bands. These bedforms have been identified in distal submarine settings formed underneath unidirectional flows. This study documents mixed grain-size bedforms in a proximal submarine slope setting formed beneath both unidirectional and combined flows. Core and outcrop data with well-constrained palaeogeographical context are used to describe two types of mixed grain-size bedform. Type A bedforms comprise mud-rich current ripples and low-amplitude bed-waves with alternating concave and planar sandstone–mudstone foresets that pass into mud-rich troughs, and aggradational sinusoidal laminasets. Type B bedforms consist of sandstone–mudstone laminasets that comprise rounded, biconvex ripples with sigmoidal-shaped foresets and swale and hummock-like laminasets and banded sets. These bedforms occur in channel-margin, internal-levée and external-levée, intraslope and disconnected lobe environments, and represent 27 to 63% by stratigraphic thickness of the studied successions. They are interpreted as deposits of clay-rich transitional flows, whose depositional style is governed by the balance of cohesive and turbulent forces, and the rate of flow deceleration. Type B bedforms are further interpreted as combined transitional flow deposits, resulting from flow deflection and ponding processes by seabed topography. Upward and lateral transitions between different bedforms create distinct bedform sequences, demonstrating progressive spatio-temporal transformations in flow properties and their topographic interactions. By using a well-constrained palaeogeographical setting, mixed grain-size bedforms are shown to be situated close to sites of erosion into muddy substrates, abrupt losses in confinement, and/or changes in slope gradient. These bedforms demonstrate that flow transformation and transitional flow behaviour are not restricted to distal submarine settings. Furthermore, mixed grain-size bedforms are not a diagnostic criterion for bottom currents, because such flows cannot account for the high mud content in laminasets, or the interlamination of sand and mud.
{"title":"Unidirectional and combined transitional flow bedforms: Controls on process and distribution in submarine slope settings","authors":"William J. Taylor, David M. Hodgson, Jeff Peakall, Ian A. Kane, Emma A. Morris, Stephen S. Flint","doi":"10.1111/sed.13177","DOIUrl":"https://doi.org/10.1111/sed.13177","url":null,"abstract":"Mixed grain-size bedforms comprise alternating sand-rich and poorly sorted mud-rich laminae and bands. These bedforms have been identified in distal submarine settings formed underneath unidirectional flows. This study documents mixed grain-size bedforms in a proximal submarine slope setting formed beneath both unidirectional and combined flows. Core and outcrop data with well-constrained palaeogeographical context are used to describe two types of mixed grain-size bedform. Type A bedforms comprise mud-rich current ripples and low-amplitude bed-waves with alternating concave and planar sandstone–mudstone foresets that pass into mud-rich troughs, and aggradational sinusoidal laminasets. Type B bedforms consist of sandstone–mudstone laminasets that comprise rounded, biconvex ripples with sigmoidal-shaped foresets and swale and hummock-like laminasets and banded sets. These bedforms occur in channel-margin, internal-levée and external-levée, intraslope and disconnected lobe environments, and represent 27 to 63% by stratigraphic thickness of the studied successions. They are interpreted as deposits of clay-rich transitional flows, whose depositional style is governed by the balance of cohesive and turbulent forces, and the rate of flow deceleration. Type B bedforms are further interpreted as combined transitional flow deposits, resulting from flow deflection and ponding processes by seabed topography. Upward and lateral transitions between different bedforms create distinct bedform sequences, demonstrating progressive spatio-temporal transformations in flow properties and their topographic interactions. By using a well-constrained palaeogeographical setting, mixed grain-size bedforms are shown to be situated close to sites of erosion into muddy substrates, abrupt losses in confinement, and/or changes in slope gradient. These bedforms demonstrate that flow transformation and transitional flow behaviour are not restricted to distal submarine settings. Furthermore, mixed grain-size bedforms are not a diagnostic criterion for bottom currents, because such flows cannot account for the high mud content in laminasets, or the interlamination of sand and mud.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139760148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Franklin W. C. Hobbs, Yihang Fang, Noah Lebrun, Yiping Yang, Huifang Xu
In contrast to the prevalence of dolomite [CaMg(CO3)2] in the geological record, there are few instances of recent formation. This discrepancy occurs despite supersaturation with respect to dolomite in many modern marine and lacustrine environments. Additionally, laboratory experiments have struggled to precipitate dolomite at ambient temperatures (<40°C) even under highly saturated conditions. However, recent work has found dissolved silica to be an effective catalyst for the direct precipitation of dolomite. To test this hypothesis, the hydrology and mineralogy of Deep Springs Lake, a playa setting with primary dolomite precipitation has been explored. In this study, the central playa sites with the highest sedimentation rates were found to have dissolved silica concentrations close to saturation. Rietveld refinement showed that bulk mineral assemblages of core samples contain 20 to 40% fine-grained, partially ordered dolomite along with a 10 to 20% poorly crystalline clay fraction, while transmission electron microscopy imaging found a co-precipitation relationship between the fine-grained dolomite and Mg-rich smectite clays, where the Mg-rich smectite clays act as a sink for the excess dissolved silica during evaporation. Transmission electron microscopy results indicate that the nanodolomite crystals formed through surface-induced nucleation and growth processes in the presence of dissolved silica as a catalyst. The broad coincidence of conditions for the direct precipitation of dolomite and Mg-rich smectite clays provides evidence that silica may be a key to the dolomite problem, as well as constraining palaeoenvironments such as the Pre-salt Barra Velha Formation.
{"title":"Co-precipitation of primary dolomite and Mg-rich clays in Deep Springs Lake, California","authors":"Franklin W. C. Hobbs, Yihang Fang, Noah Lebrun, Yiping Yang, Huifang Xu","doi":"10.1111/sed.13176","DOIUrl":"https://doi.org/10.1111/sed.13176","url":null,"abstract":"In contrast to the prevalence of dolomite [CaMg(CO<sub>3</sub>)<sub>2</sub>] in the geological record, there are few instances of recent formation. This discrepancy occurs despite supersaturation with respect to dolomite in many modern marine and lacustrine environments. Additionally, laboratory experiments have struggled to precipitate dolomite at ambient temperatures (<40°C) even under highly saturated conditions. However, recent work has found dissolved silica to be an effective catalyst for the direct precipitation of dolomite. To test this hypothesis, the hydrology and mineralogy of Deep Springs Lake, a playa setting with primary dolomite precipitation has been explored. In this study, the central playa sites with the highest sedimentation rates were found to have dissolved silica concentrations close to saturation. Rietveld refinement showed that bulk mineral assemblages of core samples contain 20 to 40% fine-grained, partially ordered dolomite along with a 10 to 20% poorly crystalline clay fraction, while transmission electron microscopy imaging found a co-precipitation relationship between the fine-grained dolomite and Mg-rich smectite clays, where the Mg-rich smectite clays act as a sink for the excess dissolved silica during evaporation. Transmission electron microscopy results indicate that the nanodolomite crystals formed through surface-induced nucleation and growth processes in the presence of dissolved silica as a catalyst. The broad coincidence of conditions for the direct precipitation of dolomite and Mg-rich smectite clays provides evidence that silica may be a key to the dolomite problem, as well as constraining palaeoenvironments such as the Pre-salt Barra Velha Formation.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139648805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
East Asia experienced complex climatic changes during the Eocene. Due to the lack of a high‐precision time framework covering the Eocene, the characteristics of sedimentary and climate evolution in this period remain unclear. The Jianghan Basin (Central China) developed an Eocene continental succession, which is composed of lower red beds and upper salt‐lake deposits exhibiting clear sedimentary rhythms, making these strata an ideal target for astronomical cycle analysis. Based on the established floating astronomical timescale, the lower red beds in the basin formed during the early–middle Eocene and were dominated by eccentricity cycles. The upper salt‐lake deposits formed during the middle–late Eocene and recorded obliquity cycles. The change in facies indicates that the climate transitioned from continuously arid to less arid with periodic relative wetness, which was forced by orbital cycles. Significant obliquity signals recorded by salt rhythmites responded to Eocene global temperature changes and Tibetan region uplift, which can be important markers of a monsoon‐like climate. Comparing the sedimentary and climatic characteristics of other Eocene lake basins in East Asia, the extension of the Eocene East Asian monsoon may have initiated during ca 43.6 to 40.0 Ma. This study provides a new perspective for understanding the early evolution of the East Asian monsoon.
{"title":"Eocene monsoon climate expansion in East Asia: Evidence from orbital‐cycle driven terrestrial successions in the Jianghan Basin, Central China","authors":"Yuan Cai, Xiangxin Kong","doi":"10.1111/sed.13181","DOIUrl":"https://doi.org/10.1111/sed.13181","url":null,"abstract":"East Asia experienced complex climatic changes during the Eocene. Due to the lack of a high‐precision time framework covering the Eocene, the characteristics of sedimentary and climate evolution in this period remain unclear. The Jianghan Basin (Central China) developed an Eocene continental succession, which is composed of lower red beds and upper salt‐lake deposits exhibiting clear sedimentary rhythms, making these strata an ideal target for astronomical cycle analysis. Based on the established floating astronomical timescale, the lower red beds in the basin formed during the early–middle Eocene and were dominated by eccentricity cycles. The upper salt‐lake deposits formed during the middle–late Eocene and recorded obliquity cycles. The change in facies indicates that the climate transitioned from continuously arid to less arid with periodic relative wetness, which was forced by orbital cycles. Significant obliquity signals recorded by salt rhythmites responded to Eocene global temperature changes and Tibetan region uplift, which can be important markers of a monsoon‐like climate. Comparing the sedimentary and climatic characteristics of other Eocene lake basins in East Asia, the extension of the Eocene East Asian monsoon may have initiated during ca 43.6 to 40.0 Ma. This study provides a new perspective for understanding the early evolution of the East Asian monsoon.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140472909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rui Wang, Kefu Yu, Brian Jones, Wei Jiang, Tianlai Fan, Yang Yang, Songye Wu
Strontium isotopes (87Sr/86Sr) are commonly used to assess the age of Cenozoic dolostones found on many isolated oceanic islands. The possible influence of Rubidium (Rb) content on the 87Sr/86Sr ratios, however, has generally been ignored. This critical issue is assessed by examining the 87Sr/86Sr ratios and elements (Rb, Sr, Al, Ti and K) of seventy-one samples that came from a ca 339 m thick cored interval of Cenozoic dolomite on the Xisha Islands, South China Sea. For the dolomite from the upper Pliocene Yinggehai Formation (180.5 to 308.5 m; average 23% dolomite) there is a positive correlation between the 87Sr/86Sr ratios and Rb concentrations, whereas for the dolomite from the lower late Miocene Huangliu Formation (308.5 to 519 m; average >98% dolomite) such a correlation is not evident. Combined with high-temperature experiments, correlation between Al, Ti, K, Rb and 87Sr/86Sr indicates that Rb containing old 87Rb from terrestrial materials modified the 87Sr/86Sr ratios of the Yinggehai dolomite, but not those from the Huangliu dolomite. This is mainly attributed to the different sources of terrestrial dust carried by different East Asian monsoon systems between the late Miocene and Pliocene, and probably also influenced by the dolomitization process to some extent. To test for 87Rb contamination, extrapolation of results from the Yinggehai dolomite and Huangliu dolomite indicate that concentrations of Rb < 1 ppm, Al < 1000 ppm, Ti < 15 ppm and K < 250 ppm in the dolomite indicates that terrestrial inputs are minimal and that the measured 87Sr/86Sr ratios can be used for determining the dolomitization age. Potentially, these concentration thresholds may serve as a screening criterion for assessing the reliability of Sr isotope chronostratigraphy of other island dolostones throughout the world.
{"title":"Strontium isotope dating influenced by Rubidium contamination from terrestrial material: A case study from the Cenozoic dolomite in the Xisha Islands, South China Sea","authors":"Rui Wang, Kefu Yu, Brian Jones, Wei Jiang, Tianlai Fan, Yang Yang, Songye Wu","doi":"10.1111/sed.13175","DOIUrl":"https://doi.org/10.1111/sed.13175","url":null,"abstract":"Strontium isotopes (<sup>87</sup>Sr/<sup>86</sup>Sr) are commonly used to assess the age of Cenozoic dolostones found on many isolated oceanic islands. The possible influence of Rubidium (Rb) content on the <sup>87</sup>Sr/<sup>86</sup>Sr ratios, however, has generally been ignored. This critical issue is assessed by examining the <sup>87</sup>Sr/<sup>86</sup>Sr ratios and elements (Rb, Sr, Al, Ti and K) of seventy-one samples that came from a <i>ca</i> 339 m thick cored interval of Cenozoic dolomite on the Xisha Islands, South China Sea. For the dolomite from the upper Pliocene Yinggehai Formation (180.5 to 308.5 m; average 23% dolomite) there is a positive correlation between the <sup>87</sup>Sr/<sup>86</sup>Sr ratios and Rb concentrations, whereas for the dolomite from the lower late Miocene Huangliu Formation (308.5 to 519 m; average >98% dolomite) such a correlation is not evident. Combined with high-temperature experiments, correlation between Al, Ti, K, Rb and <sup>87</sup>Sr/<sup>86</sup>Sr indicates that Rb containing old <sup>87</sup>Rb from terrestrial materials modified the <sup>87</sup>Sr/<sup>86</sup>Sr ratios of the Yinggehai dolomite, but not those from the Huangliu dolomite. This is mainly attributed to the different sources of terrestrial dust carried by different East Asian monsoon systems between the late Miocene and Pliocene, and probably also influenced by the dolomitization process to some extent. To test for <sup>87</sup>Rb contamination, extrapolation of results from the Yinggehai dolomite and Huangliu dolomite indicate that concentrations of Rb < 1 ppm, Al < 1000 ppm, Ti < 15 ppm and K < 250 ppm in the dolomite indicates that terrestrial inputs are minimal and that the measured <sup>87</sup>Sr/<sup>86</sup>Sr ratios can be used for determining the dolomitization age. Potentially, these concentration thresholds may serve as a screening criterion for assessing the reliability of Sr isotope chronostratigraphy of other island dolostones throughout the world.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139578534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The grain-size distributions of sediments can yield important information about sediment provenance and sedimentary processes; however, grain-size distributions are frequently polymodal, rendering analyses difficult. To improve analyses of polymodal grain-size data, the present study decomposed the grain-size distributions of bottom surface sediments from Lake Kitaura, a shallow lake in Japan, into lognormal distributions and performed logratio analysis of their mixing proportions. The polymodal grain-size distributions of the studied samples were separated into four common components at most sites. This logratio analysis revealed clear differences in the characteristics of the spatial distributions of the separated grain-size components. The logratio values indicated that the three finer components were uniformly deposited within the lake, whereas the coarsest component was spatially diverse, reflecting differences in their sources and sedimentary processes. These results demonstrate the effectiveness of decomposition and logratio analysis of polymodal grain-size distributions for estimating sedimentary processes. This method can be applied to modern sediments and for palaeoenvironmental reconstructions using sediment cores.
{"title":"Logratio analysis of components separated from grain-size distributions and implications for sedimentary processes: An example of bottom surface sediments in a shallow lake","authors":"Naofumi Yamaguchi, Tsuyoshi Ando, Hirotaka Enokida, Natsumi Nakada, Syota Yamaki, Tohru Ohta","doi":"10.1111/sed.13174","DOIUrl":"https://doi.org/10.1111/sed.13174","url":null,"abstract":"The grain-size distributions of sediments can yield important information about sediment provenance and sedimentary processes; however, grain-size distributions are frequently polymodal, rendering analyses difficult. To improve analyses of polymodal grain-size data, the present study decomposed the grain-size distributions of bottom surface sediments from Lake Kitaura, a shallow lake in Japan, into lognormal distributions and performed logratio analysis of their mixing proportions. The polymodal grain-size distributions of the studied samples were separated into four common components at most sites. This logratio analysis revealed clear differences in the characteristics of the spatial distributions of the separated grain-size components. The logratio values indicated that the three finer components were uniformly deposited within the lake, whereas the coarsest component was spatially diverse, reflecting differences in their sources and sedimentary processes. These results demonstrate the effectiveness of decomposition and logratio analysis of polymodal grain-size distributions for estimating sedimentary processes. This method can be applied to modern sediments and for palaeoenvironmental reconstructions using sediment cores.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138826238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Haein Shin, Wonsuck Kim, Hyojae Lee, Joel P. L. Johnson, Chris Paola
Autogenic feedbacks can produce large-scale, organized stratigraphic patterns in alluvial fans, but autogenic depositional signatures of specific upstream boundary conditions remain challenging to interpret. Here, a combination of theory, experiment and field application is used to explore how autogenic lithofacies changes can be interpreted as stratigraphic indicators of upstream boundary conditions. Six experiments were conducted to test the effects of sediment supply and water discharge rates on autogenic advance and retreat of the lithofacies boundary (grain-size transition) in an alluvial fan with two dominant grain sizes. Migration of the grain-size transition caused a short-term zigzag pattern in the grain-size transition position in the dip-directional deposit section. For each experiment, time-lapse images and laser topographic scans of the fan surface and stratigraphic cross-sections of the final deposits were used to quantify characteristic timescales of autogenic processes. Timescales for fan-margin migration, surface wet-fraction change and grain-size transition migration generally shorten as sediment supply rate increases and water discharge rate decreases. Increasing the sediment supply rate shortens the duration of the fluvial sediment storage and release cycle, producing higher frequency zigzags in the grain-size transition trajectory. Increasing the water discharge tends to widen channels and lengthens the duration of the fluvial sediment storage and release cycle, constructing lower frequency zigzags in the grain-size transition trajectory. Increasing the water discharge also enables more sediment to transport further downstream during release events, leading to higher magnitude zigzags in the grain-size transition trajectory. These relationships between upstream boundary conditions and the grain-size transition trajectory demonstrate how autogenic stratigraphic signals could be used as a tool to infer relative changes in boundary conditions.
{"title":"Fossilized autogenic responses of grain-size transition to sediment supply and water discharge: Alluvial fan experiments","authors":"Haein Shin, Wonsuck Kim, Hyojae Lee, Joel P. L. Johnson, Chris Paola","doi":"10.1111/sed.13173","DOIUrl":"https://doi.org/10.1111/sed.13173","url":null,"abstract":"Autogenic feedbacks can produce large-scale, organized stratigraphic patterns in alluvial fans, but autogenic depositional signatures of specific upstream boundary conditions remain challenging to interpret. Here, a combination of theory, experiment and field application is used to explore how autogenic lithofacies changes can be interpreted as stratigraphic indicators of upstream boundary conditions. Six experiments were conducted to test the effects of sediment supply and water discharge rates on autogenic advance and retreat of the lithofacies boundary (grain-size transition) in an alluvial fan with two dominant grain sizes. Migration of the grain-size transition caused a short-term zigzag pattern in the grain-size transition position in the dip-directional deposit section. For each experiment, time-lapse images and laser topographic scans of the fan surface and stratigraphic cross-sections of the final deposits were used to quantify characteristic timescales of autogenic processes. Timescales for fan-margin migration, surface wet-fraction change and grain-size transition migration generally shorten as sediment supply rate increases and water discharge rate decreases. Increasing the sediment supply rate shortens the duration of the fluvial sediment storage and release cycle, producing higher frequency zigzags in the grain-size transition trajectory. Increasing the water discharge tends to widen channels and lengthens the duration of the fluvial sediment storage and release cycle, constructing lower frequency zigzags in the grain-size transition trajectory. Increasing the water discharge also enables more sediment to transport further downstream during release events, leading to higher magnitude zigzags in the grain-size transition trajectory. These relationships between upstream boundary conditions and the grain-size transition trajectory demonstrate how autogenic stratigraphic signals could be used as a tool to infer relative changes in boundary conditions.","PeriodicalId":21838,"journal":{"name":"Sedimentology","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138826293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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