Controls on bioturbation and sediment distribution in carbonate shoreface deposits: insights from heterogeneity in Pleistocene and recent strata

IF 2 4区 地球科学 Q1 GEOLOGY
Alexa Goers, S. Hasiotis, E. Rankey
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引用次数: 0

Abstract

Burrowing organisms alter sedimentary textures, influence cement distribution, and affect petrophysical characteristics of carbonate strata. Although many descriptions of carbonate successions reference bioturbation, quantitative data on spatial variability of trace fossils is rare, and fewer studies address trace-fossil influence on postdepositional modification of sedimentary deposits, which can affect petrophysical properties. To address these unknowns and determine the controls on ichnology in carbonate shoreface successions, this study evaluates the along- and across-strike distribution of sediment and bioturbation in recent, Holocene, and Pleistocene shoreface deposits on the leeward margin of Crooked-Acklins Platform (CAP), southern Bahamas. To the north, the extant margin shelf is characterized by poorly to moderately sorted, very fine–fine, skeletal-peloid-ooid sand with an average of 16% mud (less than 62.5 µm) that is moderately to intensely bioturbated (ii3–6). Trace assemblages are diverse , and include horizontal tracks and trails, abundant horizontal deposit-feeding and locomotion traces, as well as dwelling and resting burrows attributable to the proximal Cruziana Ichnofacies. In marked contrast, margin shelf deposits to the south are well-sorted, medium ooid-peloid sand with less than 1% mud, and display a range of bioturbation, from nonbioturbated to moderately intense bioturbation (ii1–4). Trace-fossil assemblages exhibit low ichnodiversity, dominated by vertical dwelling burrows with reinforced wall lining attributable to the Skolithos Ichnofacies. Holocene and Pleistocene strata show similar proximal-to-distal and along-strike variations in sediment attributes, ichnodiversity, and bioturbation. These trends reflect a progressive, north–to-south increase in energy reflecting the change in margin orientation relative to the direction of dominant wave energy, analogous to the recent system. This study provides data for an integrated sedimentologic-ichnologic conceptual model for proces ses and patterns of sediment accumulation on carbonate shorefaces, and are distinct from siliciclastic analogs.
碳酸盐滨面沉积中生物扰动和沉积物分布的控制:来自更新世和新近地层非均质性的启示
穴居生物改变了沉积结构,影响了胶结物的分布,影响了碳酸盐岩地层的岩石物理特征。尽管许多碳酸盐序列的描述都参考了生物扰动,但关于微量化石空间变异性的定量数据很少,而且很少有研究涉及微量化石对沉积沉积物沉积后改造的影响,而沉积后改造会影响岩石物理性质。为了解决这些未知问题并确定碳酸盐滨面序列的技术控制因素,本研究评估了巴哈马南部弯曲-阿克林斯台地(CAP)背风边缘新近、全新世和更新世滨面沉积物的沿走向和跨走向分布和生物扰动。在北部,现存的边缘陆架的特征是分选差至中等,非常细,骨-球状砂,平均为16%的泥(小于62.5µm),中度至强烈的生物扰动(i3 - 6)。痕迹组合多样,包括水平痕迹和轨迹,丰富的水平采食和运动痕迹,以及可归因于近端克鲁齐亚纳岩相的居住和休息洞穴。与之形成鲜明对比的是,南部的边缘陆架沉积物为分选良好的中鲕粒砂,泥含量低于1%,并表现出从非生物扰动到中等强度生物扰动的一系列生物扰动(i1 - 4)。微量化石组合表现出较低的技术多样性,以垂直居住洞穴为主,壁衬增强,这可归因于斯科利索鱼相。全新世和更新世地层在沉积物属性、生物多样性和生物扰动方面表现出相似的近端到远端和沿走向变化。这些趋势反映了一个递进的,从北向南的能量增加,反映了相对于主导波能方向的边缘方向的变化,类似于最近的系统。该研究为碳酸盐岩岸面沉积过程和沉积模式的综合沉积学-技术概念模型提供了数据,并与硅-塑性类似物不同。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
3.80
自引率
5.00%
发文量
50
审稿时长
3 months
期刊介绍: The journal is broad and international in scope and welcomes contributions that further the fundamental understanding of sedimentary processes, the origin of sedimentary deposits, the workings of sedimentary systems, and the records of earth history contained within sedimentary rocks.
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