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Tectonostratigraphic evolution, palaeogeography and main petroleum plays of the Nuussuaq Basin: An outcrop analogue for the Cretaceous–Palaeogene rift basins offshore West Greenland
Marine and Petroleum Geology ( IF 3.7 ) Pub Date : 2021-03-31 , DOI: 10.1016/j.marpetgeo.2021.105047
Gregers Dam , Martin Sønderholm

The onshore Nuussuaq Basin in central West Greenland comprises a complete Albian–Paleocene succession and as such represents the only complete rift succession outcrop analogue for the Cretaceous–Palaeogene offshore frontier basins in West Greenland. The basin fill reflects five tectonostratigraphic phases: 1) Pre-rift, 2) Albian – Early Cenomanian Early Rift, 3) Early Cenomanian – Early Campanian Thermal Subsidence, 4) Early Campanian – Early Paleocene Late Rift, and 5) Early Paleocene – Late Eocene Break-up and Drift. In addition, the succession is divided into nine tectonostratigraphic sequences (TSSs), each representing a specific configuration of depositional elements resulting mainly from tectonic events, which caused major palaeogeographic reconstruction of the basin and therefore critical to the petroleum systems. The sequences are bounded by unconformities or, in one case, by a major flooding phase. The Early Rift Phase in the Nuussuaq Basin was initiated in the Albian with development of half-grabens along N–S directed extensional faults. This phase was characterised by continued growth along extensional faults and embraces three TSSs (TSS1–3). They are characterised by alluvial fan, fan-delta and lacustrine sedimentation, wave- and tidal-dominated deltaic deposition, followed by a major fall in relative sea level and canyon incision. Oil seeps indicate presence of a lacustrine/brackish-water source rock at depth. During the following Late Cenomanian – Early Campanian Thermal Subsidence Phase a regional marine drowning of the basin took place with deposition of organic-rich mudstones, followed by re-establishment of deltaic deposition in the Coniacian–Santonian (TSS4). The Early Campanian – Early Paleocene Late Rift Phase was associated with a change in stress regime, formation of NW–SE directed extensional faults, uplift of highs and a major change in depositional environments from deltaic deposition to deposition from gravity flows in a confined system of slope channels and canyons. During the initial phase, structurally-controlled turbidite channels were established in a NW–SE trending graben-like structure that acted as conduits for sediment transport into the offshore areas (TSS5). This was followed by several phases of major uplift resulting from the rise of the Proto-Icelandic Mantle Plume prior to continental break-up eventually leading to the deposition of two structurally controlled TSSs (TSS6–7) characterised by the formation of submarine and subaerial canyons that acted as conduits for huge amounts of sediments transported into the offshore areas. The Nuussuaq Basin experienced significant subsidence during the initial phase of break-up volcanism with deposition of organic-rich Lower Paleocene marine mudstones blanketing the basin followed by a thick succession of Paleocene–Eocene volcanic rocks referred to as the West Greenland Basalt Province (TSS8–9). Volcanism gradually spread eastwards eventually blocking the connection to the sea stemming up a large lake between the prograding volcanic front and the cratonic mainland to the east. Finally, when the volcanic rocks covered the entire basin, rivers were redirected, and sediments were deposited in the offshore Sisimiut Basin to the south and the Melville Bay Basin to the north. During this latest rifting and break-up phase, the Nuussuaq Basin was aborted and terminated as a failed rift basin.

Four main plays have been defined based on the tectonostratigraphic subdivision: An Early Rift Play, a Thermal Subsidence Play, a Late Rift Play and a Break-up and Drift Play. The Early Rift Play has alluvial and estuarine sandstones as reservoir, Albian lacustrine/brackish-water mudstones as source rock and Cenomanian–Turonian mudstones as seal. The Thermal Subsidence Play has deltaic and shallow marine sandstones as reservoirs, Cenomanian–Turonian mudstones as source and Campanian mudstones as seal. The Late Rift Play has incised valley, submarine canyon and turbidite sandstones as reservoirs, and Campanian and Paleocene mudstones as seal and source. The Break-up and Drift Play is subdivided into three sub-plays, including: a Lacustrine Sub-play, an Intra-basaltic Siliciclastic Sub-play and a Fractured Volcanic Sub-play. The Lacustrine Sub-play has fluvio-deltaic sandstones as reservoir and intra-formational lacustrine and delta-plain mudstones as seal. The Intra-basaltic Siliciclastic Sub-play comprise fluvial and lacustrine sandstones as reservoir and volcaniclastic or siliciclastic mudstones as seal. The Fractured Volcanic Sub-play comprises fractured, porous volcanic rocks as reservoir and intra-basaltic mudstones or tight fine-grained volcanic rocks as seal. All three sub-plays require vertical or long-distance migration of hydrocarbons from deeper-seated Cretaceous – Lower Paleocene kitchens. Because the tectonostratigraphic phases recognised in the Nuussuaq Basin can also be applied to the regional seismic mapping offshore Greenland the implications of the Nuussuaq Basin plays can be applied to the frontier offshore basins.



中文翻译:

Nuussuaq盆地的构造地层演化,古地理和主要石油矿床:西格陵兰近海的白垩纪-古近纪裂谷盆地的露头类似物

西格陵兰中部的陆上Nuussuaq盆地包括完整的阿尔比亚-古新世演替,因此代表了西格陵兰白垩纪-古近纪近海边境盆地唯一的完整的裂谷演替露头类似物。盆地填充反映了构造地层的五个阶段:1)裂谷前,2)阿尔比亚–早西诺曼期早裂谷,3)早西诺曼尼亚–早坎潘期热沉降,4)早坎潘尼期–早古新世晚期裂谷,和5)早新世–晚晚期始新世破裂和漂移。另外,该演替被划分为九个构造地层序列(TSSs),每个序列代表主要由构造事件引起的沉积元素的特定构造,这些构造事件导致了盆地的主要古地理重建,因此对石油系统至关重要。序列受不整合面的限制,或者在一种情况下受主要淹没阶段的限制。Nuussuaq盆地的早期裂谷阶段始于阿尔比亚,沿NS向伸展性断层发育了半岩。这个阶段的特征是沿着伸展断层继续生长,包括三个TSS(TSS1-3)。它们的特征是冲积扇,扇三角洲和湖相沉积,波浪和潮汐为主的三角洲沉积,随后是相对海平面和峡谷切口的大幅下降。油渗出表明在深处存在湖相/微咸水源岩。在随后的西诺曼尼亚晚期-坎帕尼亚早期热沉降阶段,该盆地发生了区域性溺水事件,沉积了富含有机物的泥岩,然后在Coniacian–Santonian(TSS4)中重新建立三角洲沉积。早坎潘期—新世晚期裂谷期与应力状态的变化,西北—东南向伸展断层的形成,高隆起以及沉积环境的重大变化(从三角洲沉积到重力流在有限密闭系统中的沉积)有关。斜坡通道和峡谷。在初始阶段,在NW–SE趋势grab带状结构中建立了结构受控的浊积通道,充当了泥沙输送到近海区域(TSS5)的管道。随后是原始冰岛幔幔羽在大陆解体之前上升而导致的几个主要隆升阶段,最终导致两个结构受控的TSS(TSS6-7)沉积,其特征是形成了海底和空中峡谷充当输送到近海区域的大量沉积物的管道。Nuussuaq盆地在破裂火山作用的初期经历了沉陷,沉积了覆盖该盆地的富含有机质的下古新世海相泥岩,随后又形成了厚厚的古新世-始新统火山岩,被称为西格陵兰玄武岩省(TSS8– 9)。火山逐渐向东扩散,最终阻止了与大海的连接,从而在不断发展的火山前沿与东部的克拉通大陆之间形成了一个大湖。最后,当火山岩覆盖整个盆地时,河流被重新定向,沉积物沉积在南部的西西缪特盆地和北部的梅尔维尔湾盆地中。在最近的裂谷和破碎阶段,Nuussuaq盆地被中止并终止为破裂的裂谷盆地。

根据构造地层划分,已定义了四个主要层次:早期裂谷层次,热沉陷层次,晚期裂谷层次和破碎与漂移层次。早期的裂谷带以冲积和河口砂岩为储层,以阿尔比亚湖相/微咸水为泥质烃源岩,并以塞诺曼尼亚-突尼斯为泥质岩层。热沉层以三角洲和浅海相砂岩为储层,西诺曼-Turonian泥岩为源,Campanian泥岩为海豹。晚裂谷盆地已切开了山谷,海底峡谷和浊积砂岩作为储层,而坎帕尼亚和古新世的泥岩作为海豹和水源。分手和漂流剧分为三个子剧,包括:Lacustrine子剧,玄武岩内硅质碎屑子剧和断裂的火山子剧。Lacustrine子层以河流-三角洲砂岩为储集层,内部构造湖相和三角洲平原泥岩为海豹。玄武岩内碎屑岩子层包括河床和湖相砂岩作为储层,火山碎屑或硅弹性泥岩作为封层。裂隙火山岩层包括裂隙的多孔火山岩作为储层,玄武质内的泥岩或致密的细粒火山岩作为海豹。所有这三个子层都需要从较深的白垩纪–下古新世厨房中垂直或长距离迁移烃类。由于在Nuussuaq盆地中认识到的构造地层阶段也可以应用于格陵兰岛近海区域地震测绘,因此Nuussuaq盆地的作用可以应用于边境近海盆地。

更新日期:2021-04-12
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