An ancient submarine canyon in the Oligocene‐Miocene of the western Niger Delta
An ancient submarine canyon in the Oligocene‐Miocene of the western Niger Delta
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DOI：
10.1111/j.1365-3091.1984.tb00887.x
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发表时间：
1984-12
期刊：
影响因子：
3.5
通讯作者：
S. W. Petters
中科院分区：
文献类型：
--
作者：
S. W. Petters
摘要：尼日尔三角洲西部地下的Agbada组中，出现了一层异常的晚渐新世-中新世早期厚石质海相页岩，这里称为Opuama页岩段。奥普玛页岩充填了一条深古河道，该河道被切割成始新世—早渐新世的海陆层。浮游和底栖有孔虫表明，在渐新世晚期至中新世早期的外陆架斜坡深度开始沉积，到中新世晚期，河道已充填到浅海浅海深度。这条通道被认为是海底形成的，被称为奥普阿玛峡谷。奥普阿玛峡谷形成于明显的早-中渐新世海平面下降时期，并被浊流切割。它是在渐新世晚期至中新世早期海平面上升期间被填满的。奥普阿马峡谷位于尼日尔三角洲西部回归线的位置支持了Burke（1972）的结论，即三角洲西部和东部（已知古代海底峡谷填充物的地方）回归线是古代海底峡谷的潜在地点。伯克的结论是基于他的观察，即现代三角洲的东部和西部的重新进入者是相对的海岸漂流汇聚并产生浊流切割海底峡谷的地区。
ABSTRACT An anomalous sequence of thick fossiliferous marine shale of late Oligocene-early Miocene age, here termed the Opuama Shale Member, occurs within the paralic Agbada Formation in the subsurface of the western Niger Delta. The Opuama Shale fills a deep palaeochannel which was cut into Eocene-early Oligocene paralic beds. Planktonic and benthic foraminifera suggest that deposition in the channel began in the late Oligocene-early Miocene at outer shelf-slope depths, and that by the late early Miocene the channel had filled to shallow neritic depths. The channel, which is believed to be of submarine origin, is termed the Opuama canyon. The Opuama canyon originated during the pronounced early-Middle Oligocene drop in sea-level, and was cut by turbidity currents. It was filled, during the major late Oligocene-early Miocene rise of sea-level. The location of the Opuama canyon in the western re-entrant of the Niger Delta supports Burke's (1972) conclusion that the western and eastern (where ancient submarine canyon fills are known) re-entrants of the delta are potential sites for ancient submarine canyons. Burke based his conclusion on the observation that the eastern and western re-entrants of the modern delta are areas where opposing longshore drifts converge and generate turbidity currents which cut submarine canyons.