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Sedimentologic and stratigraphic criteria to distinguish between basin-floor and slope mudstones: Implications for the delivery of mud to deep-water environments 区分盆地底泥岩和斜坡泥岩的沉积学和地层学标准:泥浆向深水环境输送的意义
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-04-07 DOI: 10.1002/dep2.191
Kévin Boulesteix, Miquel Poyatos-Moré, Stephen S. Flint, David M. Hodgson, Kevin T. Taylor, Rufus L. Brunt

Deep-water mudstones overlying basin-floor and slope sandstone-prone deposits are often interpreted as hemipelagic drapes deposited during sand starvation periods. However, mud transport and depositional processes, and resulting facies and architecture of mudstones in deep-water environments, remain poorly understood. This study documents the sedimentology and stratigraphy of basin-floor and slope mudstones intercalated with sandstone-prone deposits of the Laingsburg depocentre (Karoo Basin, South Africa). Sedimentologic and stratigraphic criteria are presented here to distinguish between slope and basin-floor mudstones, which provide a tool to refine palaeogeographical reconstructions of other deep-water successions. Several mudstone units were mapped at outcrop for 2500 km2 and investigated using macroscopic and microscopic core descriptions from two research boreholes. Basin-floor mudstones exhibit a repeated and predictable alternation of bedsets dominated by low-density turbidites, and massive packages dominated by debrites, with evidence of turbulent-to-laminar flow transformations. Slope mudstones exhibit a similar facies assemblage, but the proportion of low-density turbidites is higher, and no repeated or predictable facies organisation is recognised. The well-ordered and predictable facies organisation of basin-floor mudstones suggest local point sources from active slope conduits, responsible for deposition of compensationally stacked muddy lobes. The lack of predictable facies organisation in slope mudstones suggests deposition took place in a more variable range of sub-environments (i.e. ponded accommodation, minor gully/channel-fills, levees). However, regional mapping of three mudstone units evidence basinward tapering and similar thicknesses across depositional strike. This geometry is consistent with the distal part of basin margin clinothems, and suggests laterally extensive mud delivery across the shelf edge combined with along-margin transport processes. Therefore, the sedimentology and geometry of mudstones suggests that mud can be delivered to deep-water dominantly by sediment gravity flows through point source and distributed regionally, during periods of up-dip sand storage. These findings challenge the common attribution of deep-water mudstones to periods of basin-floor sediment starvation.

覆盖盆地底部和斜坡砂岩沉积的深水泥岩通常被解释为在缺沙期沉积的半水层垂帘。然而,对深水环境中的泥浆输送和沉积过程,以及由此产生的泥岩相和结构,仍知之甚少。本研究记录了Laingsburg沉积中心(南非卡鲁盆地)的盆地底部和斜坡泥岩的沉积学和地层学,这些泥岩夹有砂岩沉积。这里提出了沉积学和地层标准,以区分斜坡和盆地底部泥岩,这为完善其他深水序列的古地理重建提供了工具。在露头处绘制了2500个泥岩单元的地图 km2,并使用两个研究钻孔的宏观和微观岩心描述进行调查。盆地底部泥岩表现出以低密度浊积岩为主的床层和以碎屑岩为主的块状包裹体的重复和可预测的交替,有证据表明湍流向层流转变。斜坡泥岩表现出相似的相组合,但低密度浊积岩的比例更高,并且没有识别出重复或可预测的相组织。盆地底部泥岩的有序和可预测的相组织表明,局部点源于活动斜坡导管,负责补偿堆叠的泥质凸起的沉积。斜坡泥岩中缺乏可预测的相组织,这表明沉积发生在更为多变的亚环境中(即积水区、小冲沟/河道填充物、堤坝)。然而,三个泥岩单元的区域测绘表明,沉积走向上向盆地逐渐变细,厚度相似。这种几何形状与盆地边缘斜坡的远端部分一致,表明陆架边缘的横向广泛泥浆输送与沿边缘的输送过程相结合。因此,泥岩的沉积学和几何学表明,在上倾储沙期,泥浆主要通过点源沉积物重力流输送到深水中,并呈区域分布。这些发现挑战了深水泥岩与盆地底部沉积物匮乏时期的共同归因。
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引用次数: 5
Observed and modelled tidal bar sedimentology reveals preservation bias against mud in estuarine stratigraphy 观测和建模的潮坝沉积学揭示了河口地层学中对泥浆的保存偏见
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-04-07 DOI: 10.1002/dep2.190
Lisanne Braat, Harm Jan Pierik, Wout M. van Dijk, Wietse I. van de Lageweg, Muriel Z. M. Brückner, Bas van der Meulen, Maarten G. Kleinhans
Mud plays a pivotal role in estuarine ecology and morphology. However, field data on the lateral and vertical depositional record of mud are rare. Furthermore, numerical morphodynamic models often ignore mud due to long computational times and simplifications of mixed depositional processes. This study aims to understand the spatial distribution, formative conditions and preservation of mud deposits in the intertidal zone of bars in high‐energy sand‐dominated estuaries, and to elucidate the effects of mud on morphology, ecology and stratigraphic architecture. To meet these objectives, field data (historic bathymetry, bio‐morphological maps and sediment cores of the shoal of Walsoorden, Western Scheldt estuary, the Netherlands) were combined with complementary hydro‐morphodynamic numerical modelling (Delft3D). Based on the field observations, two types of mud deposits were distinguished: (1) mudflat deposits, which are thick (>10 cm) mud beds at the surface associated with high elevations and low accumulation rates; and (2) mud drapes, which are thin (millimetre to centimetre) buried laminae that form and preserve at a wide range of elevations and energy conditions. Model results show that deposition on mudflats occurs just after high‐tide slack water in areas shielded from high flood velocities, suggesting that mud accumulation is mostly controlled by elevation, flow velocity and flow direction. Mud accumulation increases shoal elevation, sometimes to supratidal levels. This reduces flow over the shoal, which in turn reduces chute channel formation, stabilises bar morphology and decreases local tidal prism. These effects further promote mud deposition and vegetation settling. Although observations show that mud cover at the surface is relatively high (20%–40% of the intertidal area), mud constitutes only a small percentage of the total estuary volume (ca 5%) revealing that only a small fraction is preserved in the stratigraphy. Due to this mismatch between surface and subsurface expression of mud, interpretations of estuarine stratigraphy risk underestimating the influence of mud at the surface on morphodynamics and habitats.
淤泥在河口生态和形态中起着举足轻重的作用。然而,关于泥浆横向和垂直沉积记录的现场数据很少。此外,由于计算时间长和混合沉积过程的简化,数值形态动力学模型经常忽略泥浆。本研究旨在了解高能沙占主导地位的河口潮间带沙坝泥沉积物的空间分布、形成条件和保存情况,并阐明泥对形态、生态和地层结构的影响。为了实现这些目标,将现场数据(荷兰西舍尔德河口Walsoorden浅滩的历史测深、生物形态图和沉积物岩心)与补充的水文形态动力学数值建模(Delft3D)相结合。根据现场观测,区分了两种类型的泥浆沉积:(1)泥滩沉积,即与高海拔和低堆积率相关的地表厚(>10cm)泥浆床;以及(2)泥帘,这是一种薄的(毫米到厘米)埋藏薄层,在各种海拔和能量条件下形成并保存。模型结果表明,在高洪速屏蔽区,泥滩上的沉积发生在高潮松弛水之后,这表明泥浆堆积主要受高程、流速和流向控制。淤泥堆积增加了浅滩高程,有时甚至达到潮上水位。这减少了浅滩上的流量,进而减少了斜槽的形成,稳定了沙洲形态,并减少了局部潮汐棱镜。这些效应进一步促进了泥浆沉积和植被沉降。尽管观测结果表明,表层的泥浆覆盖率相对较高(潮间带面积的20%-40%),但泥浆仅占河口总体积的一小部分(约5%),这表明地层中只保留了一小部分。由于地表和地下泥浆表达之间的不匹配,河口地层学的解释可能低估了地表泥浆对形态动力学和栖息地的影响。
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引用次数: 1
Channel trajectories control deep-water stratigraphic architecture 水道轨迹控制深水地层结构
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-04-06 DOI: 10.1002/dep2.189
Paul D. Morris, Zoltán Sylvester, Jacob A. Covault, David Mohrig

Interpretation of deep-water channel deposits is challenging because the spatial arrangement of their constituent lithologies is highly variable. This variability is often thought to be a signature of complex interactions between controlling boundary conditions and processes. A three-dimensional forward stratigraphic model of a sinuous meandering channel is used to explore the production of channelised deep-water stratigraphy. This model highlights three stages of stratigraphic evolution for channel belts: (1) an initial phase of rapid growth in mean belt width and variability in belt width driven by increasing channel sinuosity; (2) a subsequent phase of reduced belt-width growth rate because of cutoff processes; and (3) a mature phase during which repeated bend lifecycles act to produce a statistically stable channel-belt width. When a trajectory defining the vertical movement of a channel over time is added to the model, commonly recognised patterns of deep-water channel-belt stratigraphy are produced. These results demonstrate how forward stratigraphic models provide insights into processes governing the evolution of deep-water stratigraphy that elude interpretations of static outcrops and seismic images of subsurface examples.

深水水道沉积物的解释具有挑战性,因为其组成岩性的空间排列是高度可变的。这种可变性通常被认为是控制边界条件和过程之间复杂相互作用的标志。利用弯曲河道的三维正演地层模型,探讨了河道化深水地层的成因。该模式突出了河道带地层演化的三个阶段:(1)初始阶段,在河道弯曲度增大的驱动下,平均带宽快速增长,带宽变化;(2)由于切断过程导致带宽增长率降低的后续阶段;(3)一个成熟阶段,在此期间,反复的弯曲生命周期产生统计上稳定的沟道带宽度。当在模型中加入一条确定水道随时间垂直运动的轨迹时,就产生了通常公认的深水水道带地层学模式。这些结果表明,正演地层模型如何提供对深水地层演化过程的见解,而这些过程无法解释静态露头和地下例子的地震图像。
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引用次数: 0
Palaeoenvironments and elemental geochemistry across the Permian–Triassic boundary at Ursula Creek, British Columbia, Canada, and a comparison with some other deep-water Permian–Triassic boundary shelf/slope sections in western North America 加拿大不列颠哥伦比亚省Ursula Creek二叠纪-三叠纪边界的古环境和元素地球化学,以及与北美西部其他一些深水二叠纪-三叠纪界线陆架/斜坡剖面的比较
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-03-20 DOI: 10.1002/dep2.187
Michael E. Brookfield, Alan G. Stebbins, Jeremy C. Williams, Robyn E. Hannigan

The Permian–Triassic boundary sediments at Ursula Creek accumulated in a continental shelf basin, or on the continental slope of the western Canadian passive margin, at 30°N palaeolatitude along the eastern Panthalassic Ocean margin. The area lay within the cold northerly ocean currents at the junction of westerly and north-easterly trade wind belts, the latter causing summer coastal upwelling. The shift from uppermost Permian grey radiolarian cherts and grey shales to lowermost Triassic grey and black shales and fine-grained dolomites is typical of deep-water Panthalassic sediments. The palaeogeographical situation and palaeoenvironments are comparable to those of the present Canadian north-western Pacific margin. The Ursula Creek section reveals the progressive decline of seafloor oxygen values in the Changhsingian Stage), followed by the persistent development of euxinic conditions in the latest Changhsingian and throughout the Early Triassic; a transition that coincides with the disappearance of a siliceous sponge fauna and the loss of diverse radiolarian populations. Much of the detrital sediment was supplied by summer north-east Trade winds from the deserts of western North America, although variable amounts may have come across the Panthalassic Ocean as dust from contemporary volcanic eruptions. Relative palaeoproductivity changes show no consistent change in productivity across the Permian–Triassic boundary producing results that are comparable with those from the similar Opal Creek section to the south-east. The Ni/Co, Cu/Zn, U/Al and Th/U ratios indicate variable redox conditions in all sections, but with a tendency for oxic conditions to change to dysoxic across the Permian–Triassic boundary. The lack of consistent element geochemical changes across the boundary accompanied by significant isotopic changes, here and elsewhere, suggests that atmospheric and oceanic chemistry rather than physical changes, like provenance and sea-level changes, drove Permian–Triassic environmental changes and extinctions.

Ursula Creek的二叠纪-三叠纪边界沉积物堆积在大陆架盆地中,或加拿大西部被动边缘的陆坡上,古纬度为30°N,沿潘塔拉西洋东部边缘。该地区位于西风带和东北信风带交界处的寒冷偏北洋流中,后者导致夏季沿海上升流。从最上层的二叠纪灰色放射虫燧石和灰色页岩到最下层的三叠纪灰色和黑色页岩以及细粒白云岩的转变是典型的深水潘他拉质沉积物。古地理位置和古环境与现在的加拿大西北太平洋边缘相当。Ursula Creek剖面揭示了长兴期海底氧值的逐渐下降,随后在长兴期晚期和整个早三叠世,真新世条件持续发展;这一转变与硅质海绵动物群的消失和多种放射虫种群的丧失相吻合。大部分碎屑沉积物是由北美洲西部沙漠的夏季东北信风提供的,尽管不同数量的碎屑沉积物可能是作为当代火山喷发的尘埃穿过潘特拉西海。相对古生产力变化表明,二叠纪-三叠纪边界的生产力没有一致的变化,产生的结果与东南部类似的Opal Creek剖面的结果相当。Ni/Co、Cu/Zn、U/Al和Th/U的比值表明,所有剖面的氧化还原条件都是可变的,但在二叠纪-三叠纪边界,有氧条件有向失氧状态转变的趋势。在这里和其他地方,边界上缺乏一致的元素地球化学变化,伴随着显著的同位素变化,这表明大气和海洋化学,而不是物源和海平面变化等物理变化,驱动了二叠纪-三叠纪的环境变化和物种灭绝。
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引用次数: 0
The origin of boulders in the Neoproterozoic of Eastern Sayan Ranges, south-west Siberia: Glacial transport versus winnowed concretions 西伯利亚西南部东萨扬山脉新元古代巨石的起源:冰川搬运与风化结核
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-03-19 DOI: 10.1002/dep2.188
Dmitrii Aleksandrov

The Cryogenian geological record of Siberia is scarce and ambiguous. Late Neoproterozoic strata of presumed glaciogenic origin of the Marnya Formation, Oselok Group cropping out along the Uda River in the Eastern Sayan Ranges, south-western Siberia has received considerable attention due to the presence of at least three distinctive diamictite units. The lower diamictite unit (Karapchetui Member) is in subvertical contact (previously interpreted as a glacial valley) with stratigraphically older strata of the Tagul and Ipsit formations of the Karagas Group, and is represented by a wedge-shaped unit of breccia that hosts numerous ellipsoidal sandstone bodies (previously thought to be boulders). The boulders are here reinterpreted as early diagenetic quartz and feldspar-cemented sandstone concretions exhumed and redeposited from the Ipsit Formation when the latter was still uncemented and easily erodible. Tectonic compression, reverse faulting and localised continuous syndepositional uplift led to exhumation of the concretions, whereas subsequent extension, reactivation of the fault and ‘negative inversion’ of the basin produced accommodation space for redeposition of the exhumed concretions. In the process of redeposition, exfoliating concretions produced abundant debris that provided clasts for the breccia deposit. The Karapchetui diamictite, therefore, can serve as a sedimentary archive of late Neoproterozoic tectonic activity at the south-western margin of the Siberian Craton.

西伯利亚的成冰纪地质记录稀少且模糊不清。西伯利亚西南部萨扬山脉东部乌达河沿岸的Oselok群Marnya组推测为冰川成因的新元古代晚期地层,由于存在至少三个独特的杂岩单元,受到了相当大的关注。下部杂岩单元(Karapchetui段)与卡拉加斯群的Tagul和Ipsit地层的地层较老地层处于近垂直接触(以前被解释为冰川谷),并以一个楔形角砾岩单元为代表,该单元包含许多椭球状砂岩体(以前被认为是巨石)。在这里,巨石被重新解释为早期成岩石英和长石胶结砂岩结核,它们是从Ipsit组挖掘和重新沉积的,当时后者仍然未胶结且易受侵蚀。构造挤压、逆断层作用和局部连续同沉积隆起导致结核的折返,而随后的伸展、断层的复活和盆地的“负反转”为折返结核的再沉积提供了容纳空间。在再沉积过程中,剥落的结核产生了丰富的碎屑,为角砾岩矿床提供了碎屑。因此,Karapchetui杂岩可以作为西伯利亚克拉通西南边缘新元古代晚期构造活动的沉积档案。
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引用次数: 1
Chemostratigraphic characteristics of trace elements, biomarkers and clay mineralogy indicating environmental conditions within Aptian sediments of the Organyà Basin, North-east Spain, prior to the onset of OAE 1a 微量元素、生物标志物和粘土矿物学的化学地层特征表明了OAE 1a爆发前西班牙东北部奥加尼阿盆地阿普特阶沉积物中的环境条件
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-03-18 DOI: 10.1002/dep2.186
Carlos Herdocia, Florentin J-M. R. Maurrasse

Shifting palaeoceanographic and palaeoclimatic conditions together with fluctuating eustatic sea levels during the Early Cretaceous Aptian stage led to a globally widespread deposition of organic-rich marine sediments designated Oceanic Anoxic Event 1a. Here a detailed lithostratigraphic and geochemical study is presented for 35.6 m of the Cabó Formation, part of the Organyà Basin, North-east Spain, to assess intermittent periods of enhanced organic carbon preservation in Lower Aptian sediments preceding Oceanic Anoxic Event 1a. The Organyà area contains well-exposed outcrops of Mesozoic black to dark grey marlstones and limestones with variable amount of organic matter (OM) indicative of oxygen-deficient conditions. Previous work in a section near the town of Organyà focussed on lithostratigraphy and biostratigraphy and assigned a Barremian–Aptian age. This study aims to provide an updated age based on carbon isotope correlation established elsewhere, and assess the chemostratigraphic characteristics of the Barremian–Aptian to clarify environmental changes regarding oxygen deficient conditions in the basin at that time. The δ13Corg values fluctuate from −22.1 to −24.4‰ showing concurrence with results at the El Pui section west of the studied section. Chemostratigraphic correlation of the δ13Corg reveals that the section is within segment C2, in the Lower Aptian. Redox-sensitive trace elements (V, Ni, Co, Cr, Cu, Mo) indicate heightened dysoxic conditions at five organic-rich layers, here designated carbonaceous layers (TOC >2%), associated with enhanced terrigenous fluxes coincident with increased major elements (Al, Si and Ti) during these intervals. Biomarkers from six levels showed n-alkane distributions with chain lengths from nC14 to nC34, mostly below nC21 indicating a predominance of marine-derived OM. Climate conditions inferred from variable smectite, and kaolinite content suggests fluctuating humid-warm conditions. The results thus reveal that the Organyà Basin experienced intervals of distinct oxygen-poor conditions prior to the onset of Oceanic Anoxic Event 1a.

早白垩世Aptian时期古海洋学和古气候条件的变化以及海平面的波动导致了全球范围内富有机海洋沉积物的沉积,被称为海洋缺氧事件1a。本文对西班牙东北部organy盆地Cabó组35.6 m的地层进行了详细的岩石地层学和地球化学研究,以评估海洋缺氧事件1a之前下Aptian沉积物中有机碳保存增强的间歇期。有机质区发育出露良好的中生代黑色至深灰色泥灰岩和灰岩,有机质含量变化,显示出缺氧条件。以前在organyo镇附近的一个地区的工作主要集中在岩石地层学和生物地层学上,并确定了巴雷米亚-阿普提亚时代。本研究旨在基于其他地区建立的碳同位素对比提供一个更新的时代,并评估巴雷米亚—阿普田的化学地层特征,以澄清当时盆地缺氧条件的环境变化。δ13Corg值在- 22.1 ~ - 24.4‰之间波动,与研究剖面以西El Pui剖面的结果一致。δ13Corg化学地层对比表明,该剖面位于下阿普天统C2段。氧化还原敏感微量元素(V、Ni、Co、Cr、Cu、Mo)表明,在5个富有机质层(这里指定为碳质层(TOC含量为2%))中,氧化还原敏感微量元素(V、Ni、Co、Cr、Cu、Mo)的缺氧条件加剧,在这些区间内,陆源通量增强,主要元素(Al、Si和Ti)增加。6个水平的生物标志物显示,正构烷烃链长分布在nC14 - nC34之间,大部分低于nC21,表明海洋来源的OM占主导地位。从蒙脱石和高岭石含量的变化推断出的气候条件表明湿热条件的波动。结果表明,在海洋缺氧事件1a发生之前,有机盆地经历了不同的缺氧条件。
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引用次数: 1
Channel-lobe transition zone development in tectonically active settings: Implications for hybrid bed development 构造活动环境中的河道-波瓣过渡带发育:对混合床发育的影响
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-02-18 DOI: 10.1002/dep2.180
Hannah L. Brooks, Makoto Ito, Valentin Zuchuat, Jeff Peakall, David M. Hodgson

Channel-lobe transition zones are dynamic areas located between deepwater channels and lobes. Presented here is a rare example of an exhumed channel-lobe transition zone from an active-margin setting, in the Kazusa forearc Basin, Boso Peninsula, Japan. This Plio-Pleistocene outcrop exposes a thick (tens of metres) channel-lobe transition zone succession with excellent dating control, in contrast to existing poorly dated studies of thinner (metres) deposits in tectonically quiescent settings. This high-resolution outcrop permits the roles of climate and associated relative sea-level changes on stratigraphic architecture to be assessed. Three development stages are recognised with an overall coarsening-upward then fining-upwards trend. Each stage is interpreted to record one obliquity-driven glacioeustatic sea-level fall-then-rise cycle, based on comparison with published data. Deposition of the thickest and coarsest strata, Stage 2, is interpreted to record the end of a period of relative sea-level fall. The thinner and finer strata of Stages 1 and 3 formed during interglacial periods where the stronger Kuroshio Oceanic Current, coupled to increased monsoonally driven tropical cyclone frequency and intensity, likely resulted in inhibited downslope sediment transfer. A key aspect of channel-lobe transition zone deposits in this case is the presence of a diverse range of hybrid beds, in contrast to previous work where they have primarily been associated with lobe fringes. Here hybrid bed characteristics, and grain-size variations, are used to assess the relative importance of longitudinal and vertical segregation processes, and compared to existing models. Compared to channel-lobe transition zones in tectonically quiescent basin-fills, this channel-lobe transition zone shows less evidence of bypassing flows (i.e. thicker stratigraphy, more isolated scour-fills, fewer bypass lags) and has significantly more hybrid beds. These features may be common in active basin channel-lobe transition zones due to: high subsidence rates; high sedimentation rates; and disequilibrium of tectonically active slopes. This disequilibrium could rejuvenate erodible mud-rich substrate, leading to mud-rich flows arriving at the channel-lobe transition zone, and decelerating rapidly, forming hybrid beds.

航道-波瓣过渡区是位于深水航道和波瓣之间的动态区域。这里展示了一个罕见的例子,显示了日本博须半岛Kazusa弧前盆地活动边缘环境中的剥露河道-波瓣过渡带。与现有的对构造静止环境中较薄(米)矿床的年代测定较差的研究相比,该上新世-更新世露头暴露了一个具有良好年代控制的厚(数十米)槽瓣过渡带序列。这种高分辨率露头允许评估气候和相关的相对海平面变化对地层结构的作用。识别出三个发育阶段,总体呈先粗后细的上升趋势。根据与已公布数据的比较,每个阶段都被解释为记录了一个倾斜驱动的冰川海平面下降-然后上升周期。第2阶段最厚和最粗糙地层的沉积被解释为记录了一段相对海平面下降期的结束。第1和第3阶段的较薄和较细地层形成于间冰期,在间冰期,更强的黑潮洋流,加上季风驱动的热带气旋频率和强度的增加,可能导致下坡沉积物转移受到抑制。在这种情况下,通道-波瓣过渡带沉积物的一个关键方面是存在各种各样的混合床,而之前的工作主要与波瓣边缘有关。在这里,混合床特征和粒度变化用于评估纵向和垂直偏析过程的相对重要性,并与现有模型进行比较。与构造静止盆地填充物中的槽-叶过渡带相比,该槽-叶转换带显示出较少的旁通流证据(即较厚的地层、更孤立的冲刷填充物、更少的旁通滞后),并且具有明显更多的混合床。这些特征可能在活动盆地-河道-凸角过渡带中很常见,原因是:高沉降率;高沉降率;以及构造活动斜坡的不平衡。这种不平衡可能使易受侵蚀的富泥基底恢复活力,导致富泥流到达河道-波瓣过渡带,并迅速减速,形成混合床。
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引用次数: 10
Reconstructing lake bottom water temperatures and their seasonal variability in the Dead Sea Basin during MIS5e MIS5e期间死海盆地湖底水温及其季节变化的重建
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-02-13 DOI: 10.1002/dep2.185
Niels S. Brall, Véronique Gardien, Daniel Ariztegui, Philippe Sorrel, Emmanuel Guillerm, Frédéric Caupin

Interglacial periods are characterised by thick accumulations of halite units in the Dead Sea Basin. During these intervals, small water droplets (fluid inclusions, FIs) were entrapped in the halite crystals which serve as windows to estimate the chemistry and physical properties of the primary lake water conditions. Brillouin spectroscopy is used here to reconstruct annual resolution temperatures from a halite core section in the Dead Sea Basin during the onset of Marine Isotope Stage 5e (ca 130 ka) of the Last Interglacial. Lake bottom temperatures can be inferred based on the occurrence of coarse/fine halite facies, as observed today with the formation of equivalent halite facies during winter/summer seasons in the Dead Sea. A recurring increase in lake bottom temperatures is found along the direction of coarse halite layers in three successive years. Moreover, low FI entrapment temperatures were detected in layers of fine (cumulate) halite facies. These results imply a twofold stronger seasonality in the Dead Sea Basin compared to today, with colder winters at the onset of Marine Isotope Stage 5e. The results therefore highlight the potential of using cyclic salt deposits to reconstruct seasonal temperature variability for numerous evaporitic environments in the geological record.

冰川间时期的特点是死海盆地的岩盐单元堆积较厚。在这些时间段内,小水滴(流体包裹体,FIs)被捕获在岩盐晶体中,岩盐晶体充当了估计主要湖水条件的化学和物理性质的窗口。在最后一次冰间期海洋同位素5e阶段(约130ka)开始期间,布里渊光谱用于重建死海盆地岩盐岩芯剖面的年分辨率温度。湖底温度可以根据粗/细岩盐相的出现来推断,正如今天在死海冬季/夏季形成等效岩盐相时所观察到的那样。湖底温度连续三年沿粗石盐层方向反复升高。此外,在细(堆积)岩盐相的地层中检测到低FI包埋温度。这些结果表明,与今天相比,死海盆地的季节性强了两倍,海洋同位素第5e阶段开始时的冬天更冷。因此,研究结果突出了利用循环盐层重建地质记录中众多蒸发环境的季节性温度变化的潜力。
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引用次数: 4
Depth-limiting resistant layers restrict dimensions and positions of estuarine channels and bars 深度限制阻力层限制河口河道和坝的尺寸和位置
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-02-07 DOI: 10.1002/dep2.184
Harm Jan Pierik, Jasper R. F. W. Leuven, Freek S. Busschers, Marc P. Hijma, Maarten G. Kleinhans

Estuaries comprise channels vital for economic activity and bars as valuable habitats. They are increasingly under human-induced pressures (e.g. sea-level rise and dredging), resulting in morphological changes that affect navigability, flood safety and ecology. Antecedent geology may strongly steer how estuary channels will adapt to these pressures, but is surprisingly absent in most models. Here geological data and a unique bathymetry dataset covering 200 years from the Ems-Dollard estuary (Netherlands/Germany) were used to demonstrate how local resistant layers force the position and dimensions of confluences and bars on the scale of an entire estuary. These layers limit channel depth and consequently cause widening, resulting in mid-channel bar formation and increased channel curvature. This could lead to unexpected estuary widening and may cause land loss in densely populated areas. With increasing channel volume (as may happen again under future sea-level rise), resistant layers in the estuary's substrate become more exposed, which enhances their effects. Many systems around the world contain shallow resistant layers that potentially constrain estuary channel dimensions and steer bank erosion. This highlights that resistant layer effects are important to consider as part of mixed depositional processes in coastal environments. It is therefore necessary to globally account for the effects of inherited resistant layers in the possible response of estuaries to sea-level rise and increased tidal penetration.

河口包括对经济活动至关重要的河道和作为宝贵栖息地的沙洲。它们越来越多地受到人为压力(如海平面上升和疏浚)的影响,从而导致影响通航、洪水安全和生态的形态变化。以前的地质可能会强烈地引导河口航道如何适应这些压力,但令人惊讶的是,在大多数模型中都没有。在这里,地质数据和独特的水深测量数据集涵盖了200年的Ems - Dollard河口(荷兰/德国),以证明当地的抵抗层如何在整个河口的尺度上强迫汇合处和沙洲的位置和尺寸。这些层限制了河道深度,从而导致河道加宽,导致河道中部沙洲的形成和河道曲率的增加。这可能会导致意想不到的河口拓宽,并可能导致人口稠密地区的土地流失。随着河道体积的增加(在未来海平面上升的情况下可能会再次发生),河口底物中的抵抗层变得更加暴露,这增强了它们的作用。世界上许多系统都含有浅层抵抗层,这可能会限制河口航道的规模,并引导河岸侵蚀。这突出表明,作为海岸环境中混合沉积过程的一部分,抵抗层效应是很重要的。因此,有必要在全球范围内考虑在河口对海平面上升和潮汐渗透增加的可能反应中遗传抗性层的影响。
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引用次数: 3
Impacts of Severe Tropical Cyclone Olwyn and the biogeomorphic response, Hamelin Pool, Shark Bay, Western Australia 强烈热带气旋奥尔温的影响和生物形态反应,西澳大利亚鲨鱼湾哈梅林池
IF 2.4 3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2022-02-07 DOI: 10.1002/dep2.183
Thérèse E. Morris, Stephen N. Morris, Peter R.C.S. Fearns, Aditya Chopra, Mehrooz F. Aspandair, Lindsay B. Collins, Micheal J. O'Leary, Pieter T. Visscher

Storm disturbance and recovery of the peritidal benthic microbial ecosystem occurs as part of the natural climate regime in Shark Bay. However, tropical cyclone and winter storm frequency and intensity are known to be changing due to climate forcing. Presented here is an analysis of the biogeomorphic response of the benthic microbial ecosystem within the intertidal to upper subtidal zone and the beach face coquina deposits of Hamelin Pool, to the passage of Category 3 Severe Tropical Cyclone Olwyn (13 March 2015). Storm effects (initial response to 40 days post-event) include: erosional sculpting of sediments, mats and structures; deposition and winnowing of sediments; accumulation of mucilaginous products into flocs, slurries and sludges; along with limited development of new coquina deposits in the beach face. Medium (15 months) term observations include: mat recovery and changes with transformation of mucilage deposits into new subtidal gelatinous mats, intertidal transitional mats and low-elevation microbial structures. Observations suggest that this disturbance had both positive (the floc-to-mat biogeomorphic storm response) and negative feedbacks (enhanced bioturbation), which impact the development of stromatolite forming microbial mats and microbialite structures.

风暴扰动和潮旁底栖微生物生态系统的恢复是鲨鱼湾自然气候制度的一部分。然而,众所周知,热带气旋和冬季风暴的频率和强度由于气候强迫而发生变化。本文分析了3级强热带气旋Olwyn(2015年3月13日)通过时潮间带底栖微生物生态系统对潮下带和Hamelin Pool海滩面coquina沉积物的生物地貌响应。风暴效应(事件发生后40天的初始反应)包括:沉积物、席子和结构的侵蚀雕刻;沉积物的沉积和筛分;黏液产物积聚成絮凝体、浆液和污泥;与此同时,滩涂面新矿床的开发有限。中期(15个月)的观测包括:垫层恢复和随着黏液沉积物转变为新的潮下胶状垫、潮间带过渡垫和低海拔微生物结构而发生的变化。观测结果表明,这种扰动具有正反馈(浮冰-席生物地貌风暴响应)和负反馈(生物扰动增强),影响叠层石形成微生物席和微生物岩结构的发育。
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引用次数: 1
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Depositional Record
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