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Distinct petrographic responses to basin reorganization across the Triassic-Jurassic boundary in the southwestern Barents Sea
Basin Research ( IF 3.2 ) Pub Date : 2020-02-12 , DOI: 10.1111/bre.12437
Lina H. Line 1 , Reidar Müller 1 , Tore G. Klausen 2 , Jens Jahren 1 , Helge Hellevang 1, 3
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[Abstract A general shift towards higher mineralogical and textural maturity changes the reservoir character across the Triassic–Jurassic transition in the southwestern Barents Sea basin (SWBSB), largely affecting the hydrocarbon prospectivity in the region. Petrographic and geochronological provenance data presented in this paper suggest that the shift from mineralogically immature to mature sandstones initiated during the deposition of the Norian–Rhaetian Fruholmen Formation, and varies with basin location. Strong contrasts between the Fruholmen Formation and underlying formations are associated with proximity to the rejuvenated Caledonian and Fennoscandian hinterlands and are mainly restricted to the southern basin margins. In the basin interior, subtle petrographic variations between the Fruholmen Formation and older Triassic sandstones reflect a distal position relative to the southern hinterland. The long‐lived misconception of a regional compositional contrast in the Arctic at the turn of the Norian can be attributed to higher sampling frequency associated with hydrocarbon exploration activity along the southern basin margins, and masking by increased annual precipitation and subsequent reworking during the Jurassic. Geothermal signatures and rearrangement of ferric clay material across the Carnian–Norian transition support a recycled origin for the Fruholmen Formation in the basin interior. As the closest tectonically active region at the time, the Novaya Zemlya fold‐and‐thrust belt represents the best provenance candidate for polycyclic components in Norian–Rhaetian strata. In addition to recycling in the hinterland during the Late Triassic, local erosion of exposed intrabasinal highs and platforms at the Triassic–Jurassic transition represents a second process where thermodynamically unstable mineral components originally sourced from the Uralides may be removed. Textural and mineralogical modification may also have occurred in marginal‐marine depositional environments during periods with elevated sea level. Mature sediment supply from the rejuvenated hinterland in the south, multiple cycles of reworking and gradual accumulation of polycyclic grains have likely led to the extreme compositional maturity registered in the Tubaen, Nordmela and Sto formations in the SWBSB. It is likely that increased annual precipitation since the latest Carnian had an amplifying effect on sandstone maturation across the Triassic–Jurassic boundary, but we consider the effect to be inferior compared to provenance shifts and reworking. Findings from this study are important for understanding compositional and textural maturity enhancement processes in siliciclastic sedimentary basins., Structural reorganization of the western Barents Sea basin and surrounding hinterland terrains resulted in a shift from compositionally immature to mature sandstones during the Late Triassic. ]

中文翻译:

巴伦支海西南部三叠纪-侏罗纪边界对盆地重组的不同岩相响应

[摘要] 巴伦支海盆地西南部 (SWBSB) 向更高矿物学和结构成熟度的普遍转变改变了三叠纪-侏罗纪过渡的储层特征,在很大程度上影响了该地区的油气勘探前景。本文提供的岩石学和地质年代学物源数据表明,在 Norian-Rhaetian Fruholmen 组沉积期间开始从矿物学未成熟到成熟砂岩的转变,并随盆地位置而变化。Fruholmen 地层和下伏地层之间的强烈对比与靠近复兴的 Caledonian 和 Fennoscandian 腹地有关,并且主要限于南部盆地边缘。在盆地内部,Fruholmen 组和较老的三叠纪砂岩之间细微的岩相变化反映了相对于南部腹地的远端位置。长期以来,人们对诺利阶之交北极区域组成对比的误解可归因于与盆地南部边缘的油气勘探活动相关的较高采样频率,以及侏罗纪期间年降水量增加和随后的改造所掩盖。跨越 Carnian-Norian 过渡的地热特征和铁质粘土材料的重新排列支持了盆地内部 Fruholmen 地层的回收来源。作为当时最近的构造活动区,新地岛褶皱冲断带代表了诺里安-雷蒂安地层多环组分的最佳候选物源。除了晚三叠世期间腹地的再循环外,三叠纪-侏罗纪过渡时期暴露的盆地内高压和平台的局部侵蚀代表了第二个过程,其中最初来自乌拉里德的热力学不稳定矿物成分可能被去除。在海平面升高期间,边缘海洋沉积环境中也可能发生结构和矿物学改变。来自南部复兴腹地的成熟沉积物供应,多环颗粒的多次再加工和逐渐积累可能导致 SWBSB 中的 Tubaen、Nordmela 和 Sto 地层的极端成分成熟度。自最近的卡尼阶以来,年降水量的增加可能对三叠纪-侏罗纪边界的砂岩成熟产生了放大作用,但我们认为与物源转移和再加工相比,这种影响要差一些。这项研究的发现对于理解硅质碎屑沉积盆地的成分和结构成熟度增强过程非常重要。巴伦支海西部盆地和周围腹地地形的结构重组导致晚三叠世期间从成分不成熟到成熟砂岩的转变。] 西巴伦支海盆地和周围腹地地形的结构重组导致晚三叠世期间从成分不成熟到成熟砂岩的转变。] 西巴伦支海盆地和周围腹地地形的结构重组导致晚三叠世期间从成分不成熟到成熟砂岩的转变。]
更新日期:2020-02-12
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