Impact of growth faults on mixed siliciclastic-carbonate-evaporite deposits during rift climax and reorganisation—Billefjorden Trough, Svalbard, Norway,Basin Research

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Impact of growth faults on mixed siliciclastic-carbonate-evaporite deposits during rift climax and reorganisation—Billefjorden Trough, Svalbard, Norway
Basin Research ( IF 2.8 ) Pub Date : 2021-06-04 , DOI: 10.1111/bre.12578
Aleksandra Smyrak‐Sikora _{1,

2} , Jakob B. Nicolaisen _{1,

3} , Alvar Braathen ₄ , Erik P. Johannessen ₅ , Snorre Olaussen ₁ , Lars Stemmerik _{1,

3}

Affiliation

Fault-controlled mixed siliciclastic-carbonate-evaporite depositional systems exhibit distinct sensitivity to tectonic and eustatic controls that are expressed in the sedimentary architecture. In the Upper Carboniferous Billefjorden Trough (Svalbard, Norway), up to 2,000 m of a warm and arid climate syn-rift basin fill comprises such depositional systems, documented in this study with traditional field techniques supported by helicopter- and ground-based LIDAR models. The basin evolved from siliciclastics-dominated red beds and paralic units that filled a symmetrical basin, to a rift climax half-graben with alluvial fans entering the basin along relay ramps of the master fault zone (Billefjorden fault zone). Faults located in the hanging wall dip-slope prevented the progradation of coarser material to the eastern part of the basin. Later, structural reorganisation in the dipslope led to the cessation of easternmost faults with deformation focusing along one major lineament (Løvehovden fault zone) antithetic to the master fault zone. The basin subsidence became more symmetrical, with main central depocentre and shallower platforms near the basin flanks. Footwall anticlines from faults displacement gradients were sensitive to periodical exposure and recorded dissolution breccias and footwall synclines preserved evaporites coupled with shallow marine siliciclastic deposits. Concurrently, thick gypsum/anhydrite deposits in the basin centre reflect glacio-eustatic lowstands, whereas evenly thick carbonate deposition characterises highstands. While most analysis of syn-rift basin fill is based on siliciclastics deposits, we here demonstrate the complexity of tectonism versus eustatic sea level changes in a mixed carbonate-evaporite syn-rift deposits. Tectonic influence is ascribed to the deposition of alluvial fans that prograded from the master fault towards the basin centre. On the dipslope glacio-eustatic signals outperformed tectonic influence on deposition. Sea level lowstands promoted deposition of red sabkha mudstones and gypsum/anhydrite, salinas evaporites or dissolution breccias, interbedded with highstand carbonate beds.

中文翻译：

裂谷高潮和重组过程中生长断层对混合硅质碎屑-碳酸盐-蒸发岩矿床的影响——Billefjorden 海槽，斯瓦尔巴群岛，挪威

断层控制的混合硅质碎屑-碳酸盐-蒸发岩沉积系统对沉积结构中表现出的构造和静压控制表现出明显的敏感性。在上石炭纪 Billefjorden 海槽（挪威斯瓦尔巴群岛），长达 2,000 米的温暖和干旱气候同裂谷盆地填充物包含此类沉积系统，本研究记录了直升机和地面 LIDAR 模型支持的传统现场技术. 盆地由以硅质碎屑岩为主的红层和充满对称盆地的近地单元演化为裂谷高潮半地堑，冲积扇沿主断层带（比勒峡湾断层带）的接力斜坡进入盆地。位于上盘倾角的断层阻止了较粗物质向盆地东部的进积。之后，倾角的结构重组导致最东断层停止，变形集中在与主断层带相对的一条主要线路（Løvehovden 断层带）。盆地下沉变得更加对称，主要的中央沉降中心和盆地两侧附近的较浅平台。断层位移梯度的下盘背斜对周期性暴露很敏感，记录的溶解角砾岩和下盘向斜保留了蒸发岩以及浅海硅质碎屑沉积物。同时，盆地中心厚厚的石膏/硬石膏沉积物反映了冰川 - 静静压低位，而均匀厚的碳酸盐沉积则是高位的特征。虽然大多数同裂谷盆地充填分析是基于硅质碎屑沉积物，我们在这里展示了混合碳酸盐蒸发岩同裂谷沉积物中构造作用与海平面变化的复杂性。构造影响归因于冲积扇的沉积，这些冲积扇从主断层向盆地中心前进。在倾角冰川静海信号优于构造对沉积的影响。海平面低位促进了红色 sabkha 泥岩和石膏/硬石膏、盐沼蒸发岩或溶解角砾岩的沉积，与高位碳酸盐岩床互层。

更新日期：2021-06-04

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