Sedimentary Geology最新文献_第2页

A best-practices guide to X-ray diffraction studies of sedimentary carbonates 沉积碳酸盐x射线衍射研究的最佳实践指南

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2026-01-07 DOI: 10.1016/j.sedgeo.2026.107028

Georgina Lukoczki , David L. Bish , Jay M. Gregg

The accurate identification of sedimentary dolomites and related Ca-Mg carbonates is critical for understanding their formation and, by extension, the evolution of Earth's oceans and climate. However, the literature contains numerous examples of misapplication and misinterpretation of X-ray diffraction (XRD) data. For instance, experimental studies claiming successful low-temperature dolomite synthesis have frequently misidentified very high-Mg calcite (VHMC) or other phases as dolomite due to incorrect evaluation of XRD data. Rigorous analytical standards are needed to avoid misinterpretations and to advance the understanding of sedimentary dolomite formation. This paper provides a best-practices guide for powder XRD analysis of trigonal carbonate minerals, with particular emphasis on Rietveld refinement methods for evaluating cation ordering, unit-cell parameters, crystallite size, strain, and stoichiometry. Recommendations are presented for sample preparation, data collection, and analysis, aimed at improving the reliability of carbonate mineral identification and characterization, with particular emphasis on dolomite. Additionally, the nomenclature and classification challenges in distinguishing calcite, high-Mg calcite, VHMC, protodolomite, dolomite, ferroan dolomite, and ankerite are addressed. Finally, the implications of dolomite mineralogy for interpreting past environmental conditions are critically assessed, highlighting the pervasive effects of recrystallization over geological timescales.

沉积白云岩和相关钙镁碳酸盐的准确鉴定对于了解它们的形成，进而了解地球海洋和气候的演化至关重要。然而，文献中包含了大量x射线衍射（XRD）数据误用和误读的例子。例如，声称成功合成低温白云石的实验研究，由于对XRD数据的错误评价，经常将very high-Mg方解石（VHMC）或其他相误认为白云石。需要严格的分析标准来避免误解，并促进对沉积白云岩形成的理解。本文提供了三角碳酸盐矿物粉末XRD分析的最佳实践指南，特别强调Rietveld细化方法，用于评估阳离子有序，单元参数，晶体尺寸，应变和化学计量学。提出了关于样品制备、数据收集和分析的建议，目的是提高碳酸盐矿物鉴定和特征的可靠性，特别强调白云岩。此外，还讨论了方解石、高镁方解石、VHMC、原白云石、白云石、铁白云石和铁白云石的命名和分类问题。最后，对白云岩矿物学对解释过去环境条件的影响进行了批判性评估，强调了在地质时间尺度上再结晶的普遍影响。

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引用次数: 0

Steep nested clinoforms in the mixed siliciclastic‐carbonate Eocene Sobrarbe Deltaic Complex, Aínsa Basin, Spain 西班牙Aínsa盆地始新世Sobrarbe三角洲杂岩中陡峭的嵌套斜形岩

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2026-01-04 DOI: 10.1016/j.sedgeo.2025.107019

Leticia Rodriguez-Blanco , Miquel Poyatos-Moré , Ivar Midtkandal , Ingrid Anell

This study investigates and discusses the processes controlling the development of nested clinoforms in outcrops of the Eocene Sobrarbe Deltaic Complex of the Aínsa Basin, and demonstrates that early cementation in fine-grained sediments can help preserving steep deltaic foresets. Small-scale clinoforms (few 10s of m thick, few 100s of m long) record the higher-frequency cycles of delta progradation and the coetaneous development of a carbonate factory, while large-scale clinoforms (several 10s of m thick, few km long) record longer-term high-energy processes on the shelf and slope, including the reworking of previous deltaic/shelf deposits. Detailed lithological analysis across three of the high-frequency cycles reveals a downdip transition along the small-scale clinothems from subaqueous channels to distal delta front and shelf settings. The coarsest grain sizes are restricted to the proximal delta plain deposits evidencing some periods of limited coarse sediment transfer to deeper waters, enabling the development of coeval carbonate production on the delta front/shelf. Early cementation of carbonate-rich horizons preserved the relatively steep, yet fine-grained clinoform slopes and prevented their collapse. Observation of steep cemented foresets in fine-grained lithologies challenges a univocal relation between delta slope and grain size. In addition, we propose that early cementation is linked to in-situ carbonate production, which implies faunal adaptation probably favored by hiatuses in sedimentation between successive stages of delta progradation. The study also emphasizes the importance of recognizing heterogeneity in such mixed siliciclastic‑carbonate environments, and contributes to the understanding of depositional processes and sedimentary architecture in shallow-marine prograding systems.

本研究探讨了Aínsa盆地始新统Sobrarbe三角洲杂岩露头中巢状斜形发育的控制过程，并证明了细粒沉积物的早期胶结作用有助于保存陡峭的三角洲森林。小尺度的斜形（几米厚，几米长）记录了三角洲进积的高频旋回和同期碳酸盐工厂的发育，而大尺度的斜形（几米厚，几公里长）记录了陆架和斜坡上较长期的高能过程，包括以前的三角洲/陆架沉积的改造。对三个高频旋回的详细岩性分析表明，从水下河道到远端三角洲前缘和陆架环境，沿小范围的斜向构造发生了下倾转变。最粗粒度限制在三角洲平原的近端沉积，这表明在某些时期，有限的粗沉积物向较深的水域转移，使三角洲前缘/陆架的同世碳酸盐生产得以发展。富含碳酸盐的地层的早期胶结作用保存了相对陡峭但细粒的斜形斜坡，并防止了它们的崩塌。在细粒岩性中观察陡峭胶结预集，挑战了三角洲坡度与粒度之间的单一关系。此外，我们认为早期胶结作用与原位碳酸盐生产有关，这意味着动物适应可能有利于三角洲沉积过程中连续阶段之间的沉积中断。该研究还强调了识别这种混合硅酸-碳酸盐岩环境的非均质性的重要性，有助于理解浅海进积体系的沉积过程和沉积构型。

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引用次数: 0

Effects of particle size distribution and moisture content on the motion and deposit characteristics of debris avalanches 粒径分布和含水率对碎屑雪崩运动和沉积特性的影响

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-12-19 DOI: 10.1016/j.sedgeo.2025.107018

Ming-wei Ma , Jia-wen Zhou , Xing-guo Yang , Yi-hui Liang , Tao-Yang , Hai-mei Liao

Debris avalanches characterized by rapid granular flow pose significant hazards, yet the joint influence of particle size distribution, moisture content, and compound topography on their dynamics remains poorly constrained. To address this, we performed multivariable flume experiments simulating the transformation of landslides into granular flows under varying gradations and moisture levels (0–4 %). Our results reveal a robust linear scaling law between deposit runout and width, establishing a stable geometric proportion governing planform spreading. Kinematic analysis demonstrates that moisture content shortens total motion duration primarily by accelerating the deposition stage, whereas mixed gradations exhibit regime-shifting behaviors due to particle segregation. Crucially, we introduce a planform spreading-angle framework that unifies these observations into a single back-calculated coefficient (η). This parameter quantifies lateral spreading capacity, increasing monotonically with particle size while remaining weakly sensitive to moisture for single-size groups. Furthermore, a volumetric-equivalent scale analysis indicates that moisture drives a three-dimensional redistribution of the deposit mass rather than uniform scaling. These findings offer a simplified, physically based approach to predict the runout and spreading of non-cohesive debris avalanches under complex terrain conditions.

以快速颗粒流动为特征的碎屑雪崩具有显著的危险性，但粒度分布、含水率和复合地形对其动力学的共同影响尚不清楚。为了解决这个问题，我们进行了多变量水槽实验，模拟在不同等级和湿度水平（0 - 4%）下滑坡向颗粒流的转变。我们的研究结果揭示了沉积物跳动与宽度之间存在鲁棒的线性标度规律，建立了稳定的控制平台扩展的几何比例。运动学分析表明，水分含量主要通过加速沉积阶段来缩短总运动时间，而混合级配由于颗粒偏析而表现出状态转移行为。至关重要的是，我们引入了一个平台扩展角框架，将这些观测结果统一为单个反算系数（η）。该参数量化横向扩散能力，随着粒径单调增加，同时对单一粒径组的湿度保持弱敏感。此外，体积等效尺度分析表明，水分驱动沉积物质量的三维再分布，而不是均匀的结垢。这些发现提供了一种简化的、基于物理的方法来预测复杂地形条件下非粘性碎片雪崩的爆发和蔓延。

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引用次数: 0

Migration and timing of an erosional surface of forced regression: A Holocene analogue from the Kanto Plain, Japan 强迫退缩侵蚀面迁移与时间：日本关东平原全新世模拟

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-12-11 DOI: 10.1016/j.sedgeo.2025.107017

Susumu Tanabe, Yoshiki Sato

Erosional surfaces, including sequence boundaries within coastal sedimentary successions formed in response to sea-level fall, are known to propagate either seaward or landward. Verification of these processes requires millennial-scale reconstruction of entire coastal plains based on radiocarbon ages; however, no such systematic studies have been conducted to date. In this paper, we analyzed six sediment cores and 143 radiocarbon ages from the Nakagawa Lowland in the Kanto Plain, Japan, to reconstruct the migration process and timing of an erosional surface of forced regression (ESFR) formed since the mid-Holocene. In the Nakagawa Lowland, the ESFR is recognized between deltaic marine sediments and the overlying fluvial sediments. The ESFR formed between 6.2 and 1.2 cal kyr BP and truncates the underlying marine sediments in a diachronous manner. Excluding the influence of local topography, the ESFR developed on a tidal flat as a tidal ravinement generated in response to a sea-level fall of approximately 5 m around 4–3 ka. Because marsh-derived peaty silt directly overlies this surface without any time gap, erosion and subsequent deposition are inferred to have occurred nearly simultaneously. Furthermore, the downlapping isochrons of the fluvial sediments onto the ESFR indicate that the formation of the erosional surface did not propagate landward. The peaty silt overlying the surface, which is not eroded by upstream incision, therefore serves as a key marker for identifying the ESFR in the stratigraphic record.

众所周知，侵蚀面，包括因海平面下降而形成的海岸沉积序列中的层序边界，要么向海方向扩展，要么向陆方向扩展。验证这些过程需要基于放射性碳年龄对整个沿海平原进行千年尺度的重建；然而，迄今为止还没有进行过这样的系统研究。本文通过对日本关东平原中川低地6个沉积物岩心和143个放射性碳年龄的分析，重建了中全新世以来形成的强迫回归侵蚀面（ESFR）的迁移过程和时间。在中川低地，ESFR在三角洲海相沉积物和上覆河流沉积物之间被识别。ESFR形成于6.2 ~ 1.2 calkyr BP之间，以历时方式截断了下伏的海洋沉积物。排除当地地形的影响，ESFR是在一个潮滩上发展起来的，是在4-3 ka左右海平面下降约5米时形成的潮汐沟。由于沼泽衍生的泥炭质淤泥直接覆盖在这一表面上，没有任何时间间隙，因此推断侵蚀和随后的沉积几乎同时发生。此外，河流沉积物在ESFR上的下冲等时线表明，侵蚀面的形成没有向陆地扩展。因此，覆在地表的泥炭质粉砂没有受到上游切口的侵蚀，可以作为地层记录中识别ESFR的关键标志。

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引用次数: 0

A digital framework for estuarine stratigraphy: an example of a machine learning approach to paleo-environmental classification and coastal evolution 河口地层学的数字框架：古环境分类和海岸演化的机器学习方法的一个例子

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-12-05 DOI: 10.1016/j.sedgeo.2025.107008

N. Simon, R.H. Worden

Estuarine successions are globally significant stratigraphic archives, fundamental to understanding coastal evolution, assessing petroleum and groundwater reservoirs, and evaluating carbon storage potential. Yet, their interpretation remains hindered by facies heterogeneity and interpretive subjectivity. This study establishes a new digital framework for estuarine sedimentology by integrating high-resolution core analysis with a machine learning–based sediment classification system (Automated Prediction of Environments using Grain Size: APEGS). Applied to Holocene successions from the River Esk arm of the Ravenglass Estuary (northwest England) and trained on 482 modern reference samples, the workflow objectively discriminates six depositional sub-environments—salt marsh, mud flat, mixed flat, sand flat, tidal bar, and tidal inlet/north foreshore—with reproducibility beyond the reach of lithostratigraphic approaches. The results resolve vertical and lateral facies variability at unprecedented precision, capturing transgressive and highstand infilling phases and revealing tide-dominated early Holocene conditions when the current inner estuary was directly connected to the sea. The method establishes a transferable analytical protocol with international applicability across marginal-marine successions, offering a step-change in the quantitative reconstruction of coastal evolution. By replacing subjectivity in facies classification with a reproducible, scalable, and globally transferable digital toolset, this research sets a new benchmark for the stratigraphic interpretation of estuaries. Its methodological innovation directly informs depositional modelling, resource evaluation, and climate adaptation strategies.

河口演替是全球重要的地层档案，是了解海岸演化、评估石油和地下水储层以及评估碳储存潜力的基础。然而，它们的解释仍然受到相异质性和解释主观性的阻碍。本研究通过将高分辨率岩心分析与基于机器学习的沉积物分类系统（Automated Prediction of Environments using Grain Size: APEGS）相结合，建立了一个新的河口沉积学数字框架。该工作流程应用于拉文格拉斯河口（英格兰西北部）埃斯克河支流的全新世序列，并对482个现代参考样本进行了训练，客观地区分了6种沉积亚环境——盐沼、泥滩、混合滩、沙滩、潮坝和潮入口/北滨，其重复性超出了岩石地层学方法的范围。研究结果以前所未有的精度解决了垂向和侧向相的变化，捕捉了海侵和高点充填阶段，揭示了当前内河口与海洋直接相连时的全新世早期潮汐主导条件。该方法建立了一个可转移的分析协议，具有国际适用性，适用于边缘海洋演替，为海岸演变的定量重建提供了一个阶梯。通过使用可重复、可扩展和全球可转移的数字工具集取代相分类中的主观性，本研究为河口地层解释设定了新的基准。它的方法创新直接影响了沉积模型、资源评估和气候适应策略。

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引用次数: 0

Short eccentricity controls fluvial depositional architecture of upper reaches in the Middle-Late Pennsylvanian paleotropics (~306–308 Ma, Pilsen Basin) 短偏心控制着宾夕法尼亚中晚期古热带地区上游河流沉积构型（~306 ~ 308 Ma， Pilsen盆地）

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-12-03 DOI: 10.1016/j.sedgeo.2025.107007

Richard Lojka , Jiří Laurin , Stanislav Opluštil

Fluvial deposits often exhibit repetitive changes in depositional architecture, such as the alternation of coarse-grained intervals of highly amalgamated channel deposits and fine-grained intervals of floodplain-dominated strata. These patterns are typically attributed to changes in accommodation related to sea level fluctuations in a downstream fluvial setting, which can affect fluvial deposition hundreds of kilometers inland. However, the control of depositional architecture and repetitive stacking patterns in upstream fluvial systems remains less clear due to the complex interactions between climate, sediment supply, and water discharge. Here, we present a high-precision dated sedimentary record of an ancient fluvial system from a landlocked basin far from the influence of sea level, which was active during the non-glacial phase of the Late Paleozoic Ice Age (LPIA) in the eastern part of the paleotropical region of Pangea. Cyclostratigraphic time series analysis of geophysical borehole data suggests that the alternations observed between braidplain- and floodplain-dominated strata, forming 10–15 m thick sand–mud couplets with nearly basin-wide lateral extent, are most likely related to the “short” cycle of orbital eccentricity (~100 kyr). Larger-scale, 40–70 m thick stacks of these cycles may represent the 405-kyr “long” eccentricity cycle. The observed orbital forcing of the upstream fluvial depositional architecture indicates that climate change played a key role in shaping these systems and their deposits by altering discharge and sediment supply. The results also indicate a persistent seasonal pattern inherent to the tropical climate rather than one caused by glacioeustatic changes. This may suggest limited glacial feedback strength and decoupling of low- and high-latitude climates during the Middle-Late Pennsylvanian phase of LPIA.

河流沉积常表现出沉积结构的反复变化，如高度混合的河道沉积的粗粒度层段与洪泛平原为主的地层的细粒度层段的交替。这些模式通常归因于下游河流环境中与海平面波动相关的调节变化，这可能影响内陆数百公里的河流沉积。然而，由于气候、沉积物供应和水排放之间复杂的相互作用，上游河流系统的沉积构型和重复堆积模式的控制尚不清楚。本文对盘古大陆东部古热带地区晚古生代冰期（LPIA）非冰期活跃的一个远离海平面影响的内陆盆地的古河流系统进行了高精度的沉积年代记录。地球物理钻孔资料的旋回地层时间序列分析表明，辫状平原和洪泛平原为主的地层之间的交替，形成了10-15 m厚的砂泥联，横向范围接近整个盆地，这很可能与轨道偏心率的“短”周期（~100 kyr）有关。这些旋回的更大尺度，40-70米厚的堆积可能代表405 kyr的“长”偏心旋回。观测到的上游河流沉积结构的轨道强迫表明，气候变化通过改变流量和输沙量在形成这些系统及其沉积中发挥了关键作用。结果还表明，热带气候固有的持续季节模式，而不是由冰川变化引起的季节性模式。这可能表明在LPIA的中晚期宾夕法尼亚阶段，有限的冰川反馈强度和低纬度和高纬度气候的解耦。

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引用次数: 0

First record of paleowind-driven wave and storm activities and their controls on reservoir quality of Shahejie Formation, Liaodong Bay Depression, Bohai Bay Basin, China 渤海湾盆地辽东湾坳陷古风浪风暴活动首次记录及其对沙河街组储层质量的控制

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-11-24 DOI: 10.1016/j.sedgeo.2025.107006

Zhikang Wang , Yuanfu Zhang , Jianping Guo , Yuxiu Li , Xiaobo Huang , Wei Xu , Junyang Li , Xiaodong Yuan , Kai Ma

Lacustrine depositional models for wind-driven basins often inadequately represent the significant role of wave and storm processes, despite their recognition in modern analogs. This study utilizes the early Oligocene (E₂s₂) succession of the Liaodong Bay Depression (Bohai Bay Basin, China) as a critical ancient case study to address this gap. Through meticulous core analysis revealing 14 lithofacies and 5 lithofacies associations, we further conclusively identified storm events by correlating with the Paleogene ideal storm sequence in the Bohai Bay Basin. Integrating these data with logging and seismic interpretations, we propose a new depositional model: a wave-dominated clastic littoral system in the west and a fluvial-dominated braided-delta system in the east. Based on the NE-SW trend of beach bars concentrated in the northwestern study area, we infer a prevailing southeasterly wind direction—consistent with the Pacific summer monsoon that transported abundant moist air to the Liaodong Bay Basin, fostering a humid climate. This interpretation is further corroborated by palynological and oxygen isotope evidence. Furthermore, wave-reworked reservoirs are characterized by low matrix and unstable lithic fragment contents, well-sorted and highly rounded grains, and a high proportion of rigid grains. These attributes impart strong resistance to compaction and enhance dissolution, leading to superior reservoir quality. This study underscores that wave-reworked deposits should be prioritized as exploration targets in wind-driven lakes. The depositional model and reservoir formation mechanism established herein hold broad applicability for oil and gas exploration and development in other wind-driven continental lacustrine systems.

风驱动盆地的湖相沉积模式往往不能充分反映波浪和风暴过程的重要作用，尽管它们在现代类似物中得到了承认。本研究利用辽东湾坳陷早渐新世（E2s2）的演替作为解决这一空白的关键古案例研究。通过细致的岩心分析，揭示了14种岩相和5种岩相组合，并与渤海湾盆地古近系理想风暴序列进行了对比，进一步确定了风暴事件。将这些资料与测井和地震解释相结合，我们提出了一种新的沉积模式：西部为波浪主导的碎屑海岸体系，东部为河流主导的辫状三角洲体系。根据集中在西北研究区的滩坝的NE-SW走向，推断其主要风向为东南风向，与太平洋夏季风相一致，向辽东湾盆地输送了丰富的湿润空气，形成湿润气候。孢粉学和氧同位素证据进一步证实了这一解释。波浪改造储层具有基质含量低、岩屑不稳定、颗粒分选好、颗粒圆度高、刚性颗粒比例高的特点。这些特性使储层具有较强的抗压实性和增强的溶蚀性，从而具有较好的储层质量。该研究强调，波浪改造矿床应优先作为风力湖泊的勘探目标。本文建立的沉积模式和成藏机理对其他陆相风驱湖系的油气勘探开发具有广泛的适用性。

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引用次数: 0

Soft-sediment deformation structures in eolian sandstones: Morphology, genesis, and stratigraphical relationships through time 风成砂岩中的软沉积变形结构：形态、成因和地层关系

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-11-08 DOI: 10.1016/j.sedgeo.2025.106996

Gabriel Schäffer Sipp , Claiton Marlon Dos Santos Scherer , Amanda Goulart Rodrigues , Ezequiel Galvão De Souza , Rossano Dalla Lana Michel , Monica Oliveira Manna , César Alejandro Goso Aguilar , Fábio Herbert Jones

Soft-sediment deformation structures (SSDS) are widespread in the eolian sedimentary record, with examples commonly associated with other depositional systems. In such contexts, deformation is typically enhanced by sealing horizons related to interdunes or sabkha deposits. The Late Permian Buena Vista Formation of the Paraná Basin contains extensive intervals with SSDS, but these are restricted to eolian dune deposits lacking dry or wet interdune facies or sealing horizons. The deformed horizons record multiple events, with superimposed structures that allow the reconstruction of deformation episodes at the outcrop scale. These distinctive features make the Buena Vista Formation an exceptional case for understanding SSDS in eolian environments and for evaluating the role of driving forces behind their formation. The active SSDS described in this study include sand diapirs, interpenetrative cusps, sand blows, complex recumbent folds, intra-set convolute folds, massive beds, and pockets. Passively generated structures comprise overturned beds, contorted strata, and intra-set syn-deformational faults. Seismic activity is inferred as the primary trigger for deformation, based on several lines of evidence: (i) similarities with other seismically induced structures, (ii) large areal distribution with zonation in structural complexity, (iii) wide lateral continuity along individual outcrops, (iv) stratigraphic recurrence, and (v) the active geotectonic setting during deposition of the unit. This tectonic activity coincides with the accretion of the Patagonia Terrane to southwestern Gondwana. Under these conditions, rapid water-table rise likely generated overpressure, facilitated by air entrapment in the eolian sediments, ultimately enabling widespread soft-sediment deformation.

软沉积变形构造（SSDS）在风成沉积记录中广泛存在，通常与其他沉积体系相关。在这种情况下，封闭与沙丘间或sabkha矿床有关的层位通常会加强变形。帕拉南盆地晚二叠世Buena Vista组含有广泛的SSDS层段，但这些层段仅限于风成沙丘沉积，缺乏干或湿沙丘间相或封闭层。变形层记录了多个事件，其叠加结构允许在露头尺度上重建变形事件。这些独特的特征使Buena Vista地层成为了解风成环境中SSDS并评估其形成背后驱动力作用的特殊案例。本研究中描述的活动ssd包括砂底辟、穿透尖、吹砂、复杂的平卧褶皱、套内卷曲褶皱、块状层和袋状。被动生成的构造包括翻覆层、扭曲地层和套内同变形断层。基于以下几方面的证据，地震活动被推断为变形的主要触发因素：(i)与其他地震诱发构造的相似性；（ii）构造复杂性具有带状分布的大面积分布；（iii）沿个别露头的横向连续性较宽；（iv）地层复现；(v)单元沉积期间活跃的大地构造背景。这一构造活动与巴塔哥尼亚地体向冈瓦纳西南部的扩张相吻合。在这种情况下，地下水位的快速上升可能会产生超压，风成沉积物中的空气夹持促进了超压，最终导致广泛的软沉积物变形。

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引用次数: 0

‘Reciprocal bioturbation’: A high-frequency low-order sequence-stratigraphic concept over the basin-margin settings within a Miocene mixed-siliciclastic‑carbonate system “互反生物扰动”：中新世混合硅酸-碳酸盐岩体系中盆地边缘环境的高频低阶层序地层概念

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-11-08 DOI: 10.1016/j.sedgeo.2025.106995

Ayush Srivastava , Sudipta Dasgupta , Mohuli Das , Pramod Kumar

High-frequency sequences characterized by carbonate-dominated TST and HST and siliciclastic-dominated FSST and LST within a mixed-siliciclastic‑carbonate system can be elucidated by the ‘reciprocal sedimentation’ concept. This study integrates lithofacies and ichnofacies analyses, leading to a higher-resolution (4th- to 5th-order) sequence-stratigraphic interpretation, whereby the response of sensitive infaunal niches to these high-frequency base-level changes reciprocates itself ichnologically. The concept of ‘reciprocal bioturbation’, i.e., the ichnological expression of reciprocal sedimentation, offers a novel idea through which the low-order cycles within a mixed siliciclastic–carbonate system can be diagnosed. The bioturbation pattern varies distinctly between the proximal and distal parts of the basin margin. The former records an alternating stacking of the contrasting (A) shallow-marine (e.g., Skolithos Ichnofacies developed in the shoreface deposits) and (B) the continental ichnofacies (e.g., Termitichnus Ichnofacies in the supratidal environments) within the transgressive and the pedogenized regressive intervals, respectively, without showing any gradual transformation in both lithofacies and ichnofacies. This abrupt stacking of reciprocal bioturbation suites reflects omission due to stratigraphically punctuated erosion (e.g., subaerial erosion, regressive marine erosion, and transgressive ravinement) vis-à-vis the scarcity of accommodation in the proximal part of the basin margin. The distal part records gradual and subtle stacking of reciprocal suites, although a convergence can be observed through the reciprocation of normal marine and brackish water (Teichichnus Ichnofacies) assemblages. Hence, identification of ‘reciprocal bioturbation’ serves as the clinching evidence – (a) in delineating the reciprocal sedimentation and (b) in understanding the high-frequency base-level cycles while constructing the low-order sequence-stratigraphic model in a basin-margin setting.

以碳酸盐为主的TST和HST，以及以硅塑性为主的FSST和LST为特征的高频层序可以用“反向沉积”的概念来解释。该研究整合了岩相和鱼相分析，从而获得了更高分辨率（4 - 5级）的层序地层解释，从而使敏感的河流生态位对这些高频基准面变化的响应在技术上相互回报。“互反生物扰动”的概念，即互反沉积的技术表达，提供了一种新的思路，通过这种思路，可以诊断混合硅-塑料-碳酸盐系统中的低阶旋回。生物扰动模式在盆地边缘近端和远端有明显差异。前者分别记录了海侵期和成土退期内对比鲜明的(A)浅海相（如滨面沉积中发育的Skolithos鱼相）和(B)陆相（如潮上环境中的Termitichnus鱼相）的交替叠加，而岩相和鱼相均未表现出任何渐变。这种相互生物扰动组合的突然堆积反映了由于地层间断侵蚀（如陆上侵蚀、海侵侵蚀和海侵侵蚀）对-à-vis盆地边缘近端可容纳空间的缺乏而造成的遗漏。远端部分记录了相互套逐渐而微妙的叠加，尽管可以通过正常海相和咸淡水（Teichichnus Ichnofacies）组合的相互作用观察到收敛。因此，“互反生物扰动”的识别是(a)描述互反沉积和(b)在构建盆地边缘低阶层序地层模型时理解高频基准面旋回的决定性证据。

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引用次数: 0

Sedimentary processes of fine-grained sedimentary rocks in lacustrine basins: A case study of the Upper Cretaceous Qingshankou Formation, northern Songliao Basin, China 湖相盆地细粒沉积岩沉积过程——以松辽盆地北部上白垩统青山口组为例

IF 2.9 2区地球科学 Q1 GEOLOGY

Sedimentary Geology

Pub Date : 2025-10-25 DOI: 10.1016/j.sedgeo.2025.106987

NingLiang Sun , Jinyou Zhang , Jianhua Zhong , Jianbo Gao , Pengpeng Sheng , Zhiwei Chen , Zhifeng Cao , Pingshuai Wang

Fine-grained sedimentary rocks (FGSRs) in lacustrine basins are traditionally interpreted as low-energy suspension deposits. However, extensive shale oil exploration has revealed pronounced lithofacies heterogeneity within mudstone successions, necessitating a re-evaluation of their dynamic depositional processes. This study integrates data from eleven cored boreholes, along with petrographic and geochemical analyses, to characterize lithofacies variability, depositional processes, and environmental evolution of the Upper Cretaceous Qingshankou Formation FGSRs in the Songliao Basin. Sedimentological and geochemical proxies indicate that FGSR deposition occurred in brackish-saline waters with moderate stratification and persistent anoxia under warm-humid climatic conditions. A revised depositional framework identifies eight lithofacies and delineates four lacustrine depositional environments that were shaped by intermittent marine incursions: (i) sublittoral proximal deposits, consisting of interlaminated mudstones and siltstones associated with storm-induced tempestites and muddy hyperpycnal flows; (ii) sublittoral distal deposits, dominated by wave-enhanced sediment gravity flows with tripartite microstratigraphy recording turbulent-to-laminar flow transitions; (iii) semi-profundal deposits, comprising hybrid event beds and bottom-current deposits with rhythmically discontinuous silt laminae and mud ripples, the latter formed through bedload transport of clay aggregates under sustained current velocities; (iv) profundal deposits, including laminated varves, organic-rich suspension mudstones, and tuff layers. Their high organic carbon content and minimal bioturbation establish them as important targets for unconventional shale oil exploration. These findings challenge the conventional paradigm of deep-lacustrine quiescence, highlighting the pervasive influence of energetic depositional processes in shaping shale heterogeneity and organic matter preservation. The results have significant implications for the exploration and characterization of lacustrine shale reservoirs on a global scale.

湖盆细粒沉积岩（FGSRs）传统上被解释为低能悬浮沉积。然而，广泛的页岩油勘探揭示了泥岩层序中明显的岩相非均质性，需要对其动态沉积过程进行重新评价。本研究综合了松辽盆地上白垩统青山口组11个取心钻孔资料，结合岩石学和地球化学分析，对松辽盆地上白垩统青山口组的岩相变异性、沉积过程和环境演化进行了研究。沉积学和地球化学指标表明，FGSR沉积发生在温湿气候条件下的中等分层和持续缺氧的微咸海水中。经修订的沉积格架确定了8种岩相，并圈定了4种由间歇性海侵形成的湖泊沉积环境：(1)海下近端沉积，由层间泥岩和粉砂岩组成，与风暴引起的暴风雨和泥质超旋流有关；（ii）以波浪增强沉积物重力流为主的滨海下远端沉积物，其三段式微地层记录了湍流到层流的转变；（iii）半深层沉积，包括混合事件层和底流沉积，具有节律不连续的粉砂纹层和泥纹，后者是在持续水流速度下由粘土集料的层载搬运形成的；（iv）深层沉积，包括层状阀、富有机质悬浮泥岩和凝灰岩层。有机碳含量高，生物扰动小，是非常规页岩油勘探的重要靶区。这些发现挑战了深湖静止的传统范式，强调了高能沉积过程在形成页岩非均质性和有机质保存方面的普遍影响。研究结果对全球范围内湖相页岩储层的勘探和表征具有重要意义。

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引用次数: 0