Initiation of the Western Interior foreland basin
Initiation of the Western Interior foreland basin
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西部内陆前陆盆地的形成
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
A. Miall
中科院分区：
文献类型：
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作者：
A. Miall
在本期《地质学》中，Fuentes等人。(2009年，第379页)提出了一个新的沉降图和碎屑锆石的年龄数据，这有助于限制蒙大拿州(美国)前陆盆地的形成日期。他们提供了这些数据作为解决关于西部内陆开始前陆盆地沉积的争议的证据。然而，他们的讨论提出了一个问题，即什么地质资料构成了前陆盆地沉积风格的确凿证据，因此应该用什么标准来确定它的开始。前陆盆地的一个有用定义是，它是毗邻和平行于山带发展的凹陷。前陆盆地的形成是因为与山脉带的演化相关的地壳增厚所产生的物质导致岩石圈弯曲，这一过程被称为岩石圈扩张。在会聚板块边缘，前陆盆地发育在边缘弧后面(弧后型或前陆型；约旦，1995)或靠近碰撞带的下行大陆板块上方(周边型或前前陆型；Miall，1995)。向下的隆起伴随着基底前隆起的抬升，通常距离褶皱冲断带几百公里，在此之后有一个被称为背隆盆地的浅凹陷。关于阿尔伯塔省南部的前陆盆地，普赖斯(1973)首先阐明了地壳负荷和盆地形成之间的关系，随后Beaumont(1981)对艾伯塔省盆地进行了模拟，证明了外部负荷、地壳凹陷的形成及其同构造沉积作用之间的定量联系。Jordan(1981)论证了前陆盆地沉降和沉积类型的另一个关键标准：盆地地貌具有独特的等厚格局，平行于山前伸展，断面不对称，沉积中心靠近同期褶皱冲断带，其隆起为近端沉积源。Cross(1986)使用这一标准来区分前陆盆地的沉降和地壳下地幔负荷引起的盆地沉降，这产生了更广泛的盆地沉降模式。西部内陆盆地(艾伯塔盆地和落基山脉盆地是其中的一部分)是由于盘古板块运动学的一级变化而形成的弧后盆地。这块超级大陆在奥陶纪和二叠纪之间由多个板块汇聚和缝合而成，在三叠纪开始通过裂谷作用碎裂，到中侏罗世早期，洋壳在现在的美国大西洋海岸附近形成。北美大陆开始了一个漫长的西北向漂移过程，使板块相对于Pacifi c板块向西移动了约70°经度，向北移动了约40°纬度，直到古新世，随后轨迹发生变化，随后向南漂移了约10°，直到今天(Engebretson等人，1985)。有许多迹象表明，与板块运动学的这种变化有关的岩浆、构造沉降和沉积模式发生了一级变化。来自隆起的弧形或造山带的西风碎屑的首次出现，长期以来一直被认为是西部内陆前陆盆地开始形成的时间。在盆地建立之前，西部大陆边缘具有微地斜特征，沉积物来自东部来源(克拉通和加拿大盾)。罗恩·布莱基和我(在迈尔，2008)，指定
In this issue of Geology, Fuentes et al. (2009, p. 379) present a new subsidence plot and age data from detrital zircons that help to constrain the date of initiation of the foreland basin in Montana (United States). They offer these data as evidence for the resolution of a controversy regarding the initiation of foreland basin sedimentation in the Western Interior. However, their discussion raises the question of what geological data constitute the defi nitive evidence of the foreland basin style of sedimentation, and therefore the criteria that should be used to defi ne its commencement. A useful defi nition of a foreland basin is that it is a depression that develops adjacent and parallel to a mountain belt. Foreland basins form because the mass created by crustal thickening associated with the evolution of a mountain belt causes the lithosphere to bend, by a process known as lithospheric fl exure. At convergent plate margins, foreland basins develop behind the marginal arc (retroarc or retroforeland type; Jordan, 1995) or above the downgoing continental plate adjacent to a collision zone (peripheral or proforeland type; Miall, 1995). The downward fl exure is accompanied by the uplift of a forebulge in the basement, typically a few hundred kilometers out from the fold-thrust belt, and beyond that there is a shallow depression called the backbulge basin. The relationship between crustal loading and basin formation was fi rst articulated by Price (1973) with respect to the foreland basin of southern Alberta, and subsequent modeling of the Alberta Basin by Beaumont (1981) demonstrated the quantitative link between fl exural loading, the formation of a crustal depression, and its fi lling by syntectonic sedimentation. Jordan (1981) demonstrated another key criterion for the defi nition of the foreland basin style of subsidence and sedimentation: the distinctive isopach pattern of the basin fi ll, elongated parallel to the mountain front and asymmetric in cross section, with a depocenter located close to the contemporaneous fold-thrust belt, the uplift of which serves as the proximal sediment source. Cross (1986) used this criterion to distinguish foreland basin subsidence from that due to subcrustal mantle loading, which yields a much broader, wider pattern of basinal subsidence. The Western Interior basin (of which the Alberta basin and the Rocky Mountain basin are parts) was initiated as a retroarc basin as a result of a fi rst-order change in the plate kinematics of Pangea. This supercontinent, assembled by multiple plate convergence and suture between Ordovician and Permian time, began to fragment by rifting in the Triassic, and by early Middle Jurassic time, oceanic crust was forming off what is now the Atlantic coast of the United States. The North American continent began a long process of northwestward drift, which carried the plate some 70° of longitude westward, relative to the Pacifi c plate, and, some 40° of latitude northward until Paleocene time, followed by a change in trajectory and a subsequent southward drift of ~10° up to the present day (Engebretson et al., 1985). There are numerous indicators of a fi rst-order change in magmatic, tectonic subsidence and sedimentation patterns associated with this change in plate kinematics. The fi rst appearance of westerly-derived detritus from a rising arc or orogen has long been accepted as providing the timing of initiation of the Western Interior foreland basin. Prior to the establishment of the basin, the western continental margin was miogeoclinal in character, with sediment derived from easterly sources (the craton and the Canadian Shield). Ron Blakey and I (in Miall, 2008), designated the