Timing of Turbidite Sedimentation on the Mississippi Fan
Timing of Turbidite Sedimentation on the Mississippi Fan
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DOI：
10.1306/bdff8e16-1718-11d7-8645000102c1865d
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发表时间：
1993-07
期刊：
影响因子：
3.5
通讯作者：
V. Kolla;M. Perlmutter
中科院分区：
文献类型：
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作者：
V. Kolla;M. Perlmutter
密西西比扇上的砂质浊积岩沉积始于末次冰期-上升旋回期间海平面下降和相对最低值阶段，在海平面上升中后期直至全新世（距今12000 - 11000年）或稍晚的时期，其沉积作用十分显著。有几个因素表明砂质浊积岩沉积的晚期延续：(1)随着海平面的上升，密西西比峡谷向陆地延伸到大陆架中部的深度；(2)在海平面上升期间，冰川融水排放和沉积物负荷（卵石到粘土大小）直接由密西西比河输送到峡谷的顶端，(3)在峡谷向陆地侵蚀的过程中，可能会持续拦截海岸漂移；(4)峡谷顶部陡峭的坡度有利于沉积中心的滑塌和浊流的形成；(5)峡谷内缺乏预期的粗粒度岩性和三角洲地层格局，表明沉积物绕过峡谷进入深水。本文推断的密西西比扇晚期倾向于砂质浊积沉积与13285±650年B.P.之后亚马逊扇中部砂质浊积的出现以及直到全新世为止深海其他地方的大量浊积和碎屑沉积相一致。在海平面上升中后期的易砂浊积沉积与层序-地层模式的普遍认知相反。这种认识假定浊积岩和扇状沉积主要发生在海平面下降、最大低点和海平面上升早期。重要砂质浊积岩沉积的后期延续将影响地下地层校准、沉积体系推断和储层预测的概念。
Sandy turbidite sedimentation on the Mississippi Fan, initiated during the falling and maximum relative lowstand stages of sea level during the last glacio-eustatic cycle, was significant well into the mid to late sea level rise until the Holocene, 12,000-11,000 yr B.P. or slightly thereafter. Several factors suggest this late continuation of sandy turbidite sedimentation: (1) landward extension of the Mississippi Canyon into the mid-shelf water depths as sea level rose, (2) a major increase in glacial meltwater discharge and sediment loads (pebble to clay size) delivered directly to the head of the canyon by the Mississippi River during the rising sea level, (3) probable persistent interception of longshore drift by the canyon as it eroded landward, (4) steep gradients a the head of the canyon that favored slumping of depocenters and formation of turbidity currents, and (5) absence of expected coarse-grained lithologies and deltaic stratal patterns within the canyon, indicating sediment bypass through the canyon into deep water. The late sand-prone turbidite sedimentation inferred herein for the Mississippi Fan is compatible with the occurrence of sandy turbidites in the middle Amazon Fan subsequent to 13,285 ±650 yr B.P. and significant deposition of turbidites and clastics until the Holocene elsewhere in the deep ocean. Sand-prone turbidite sedimentation into the middle/late rise of sea level is in contrast to the common perception of sequence-stratigraphic models. This perception assumes that turbidite and fan sedimentation occurs mainly during alling, maximum lowstand, and early rise of sea level. Late continuation of significant sandy turbidite sedimentation will impact concepts of subsurface stratigraphic calibration, inferences of depositional systems, and reservoir predictions.