The impact of tectonic activity on carbonate density-flow deposition along two sectors of the Apulia Carbonate Platform

IF 2 4区 地球科学 Q1 GEOLOGY
Gunnar Sçlen, L. Spalluto, I. Grunnaleite, Atle Jørgen Hestad Sande, N. B. Jensen, Per Olav Eide Svendsen, Gaetano Osso, Nicola Paoli, M. Talbot
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Abstract

Generation of thick megabreccias along carbonate platforms apparently relies on the establishment of overpressured zones in the margin and upper slope deposits (particularly during relative sea-level lowstands), but the main triggering mechanism is thought to be seismic tremors. Here, we present a detailed sedimentological analysis of carbonate density-flow deposits south and north of the Mattinata Fault, a major strike-slip fault zone in the Gargano Promontory (Italy). The analysis shows that in the southern sector the deposits of Albian–Cenomanian age (Monte S. Angelo Formation) are made up predominantly of thick and amalgamated debrites (megabreccias), whereas some 25 km to the north they are composed predominantly of prograding high-density turbidites. Moreover, detailed analysis of Maastrichtian slope deposits (Monte Acuto Limestones) from the southern sector shows that they make up a N–S-prograding system of coalesced lobes composed of high-density turbidites and subordinate debrites. We infer that preconditional factors (e.g., platform progradation, tectonic oversteepening, and high pore pressures in the margin and upper-slope deposits) for triggering the density flows varied along strike of the platform, but the main controlling factors were the activity of the prominent strike-slip Mattinata Fault and the propagation of tremor energy to its near- and far-field regions: large earthquakes triggered thick (up to 40 m) and amalgamated Albian–Cenomanian debrites in proximity (south of) to the fault, whereas the subdued effect of the tremors triggered thinner debrites (5–10 m) and rock falls in the far-field region north of the fault. Moreover, predominantly high-density turbidite deposits were emplaced in the far-field region during lower-magnitude earthquakes. During the Maastrichtian the thick succession of high-density turbidites and scattered thick debrites south of and adjacent to the Mattinata Fault may record an overall quiescent period of the fault. The results are of relevance for understanding the spatiotemporal distribution of density-flow deposition along carbonate platforms in tectonically active regions—in particular with respect to the activity of large strike-slip faults.
构造活动对阿普利亚碳酸盐岩台地两段碳酸盐岩密度流沉积的影响
沿碳酸盐岩台地厚巨型角砾岩的形成显然依赖于边缘和上斜坡沉积超压带的建立(特别是在相对海平面低洼时),但主要的触发机制被认为是地震震动。本文对意大利加尔加诺海峡(Gargano Promontory)主要走滑断裂带Mattinata断裂南侧和北侧的碳酸盐岩密度流沉积进行了详细的沉积学分析。分析表明,在南部地区,Albian-Cenomanian时代的沉积物(Monte S. Angelo组)主要由厚的和合并的碎屑(大角砾岩)组成,而在北部约25公里处,它们主要由推进的高密度浊积岩组成。此外,对南段马斯特里赫特斜坡沉积(Monte Acuto石灰石)的详细分析表明,它们构成了一个由高密度浊积岩和次级碎屑组成的n - s向递进的聚并裂片体系。我们推断,触发密度流的前提因素(如台地进动、构造过陡化、边缘和上斜坡沉积的高孔隙压力)沿台地走向变化,但主要控制因素是突出的走滑Mattinata断裂的活动和震颤能量向其近场和远场区域的传播。大地震在断层附近(南部)触发了厚的(高达40米)和混合的阿尔巴尼亚-塞诺曼尼亚碎屑,而地震的减弱作用则在断层北部的远场地区触发了较薄的碎屑(5-10米)和岩石坠落。此外,在低震级地震期间,高密度浊积岩沉积主要位于远场区。在马斯特里赫特时期,Mattinata断裂南部和附近高密度浊积岩的厚层演替和分散的厚层碎屑可能记录了该断裂的整体静止期。研究结果对于理解构造活动区沿碳酸盐岩台地的密度流沉积的时空分布,特别是对大型走滑断层的活动具有重要意义。
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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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