Review of the Neogene Biostratigraphy and Stratigraphy of the Los Angeles Basin and Implications for Basin Evolution: Chapter 4
Review of the Neogene Biostratigraphy and Stratigraphy of the Los Angeles Basin and Implications for Basin Evolution: Chapter 4
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洛杉矶盆地新近纪生物地层学和地层学回顾及其对盆地演化的启示：第四章
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发表时间：
1991
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通讯作者：
G. Blake
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作者：
G. Blake
洛杉矶盆地是加州大陆边缘的新近系盆地之一，它是由与复杂的扭动断裂机制有关的伸展作用形成的。这些伸展机制导致拉分构造，导致许多陆缘盆地在渐新世晚期至中新世早期迅速加深。在过去的60年里，洛杉矶盆地油田之间的生物地层对比框架一直基于Wissler(1943,1958)首次发表的海底有孔虫带和分区。这些生物地层单位被用来对比整个盆地的上、中、新统和上上新统碎屑岩储层。Wissler底栖有孔虫带(1943,1958)与Kleinpell中新世底栖有孔虫带(1938,1980)和纳特兰(1952)上新世-更新世有孔虫带相对应。随着其他微化石学科(例如硅质和钙质浮游微化石)的利用，已经开发出更精细的生物地层方案。浮游生物地层学与辐射时间尺度的相关性反过来又使底栖有孔虫地带性的对比和校准成为可能。应用这一新的生物地层学-年代地层学方案，现在可以用来限制标志着盆地发展的构造和沉积事件的时间和规模。通过与硅质微体化石、钙质超微化石、浮游有孔虫和放射性年代对比，确定了不同底栖有孔虫分带的年龄关系。End_Page 135-根据新近系沉积包厚度和底栖有孔虫带与其他化石群之间的年代地层关系，建立了三个区域剖面。这些区域剖面显示了中央盆地沉积中心在新近纪晚期的转移。前晚中新世沉积沿盆地边缘最厚，特别是在中央地块西北部的普恩特山和卡普斯特拉诺海湾。晚中新世至早更新世沉积的沉积物位于中央海槽中，以纽波特-英格尔伍德、圣莫尼卡-雷蒙德山和惠蒂埃断裂系统为界。不整合面和间断与每个构造块体有关。其中一些不整合是与构造生长或断层运动有关的局部事件。间歇期是由海洋化学或海底水流速度变化引起的地区性事件。中新世晚期至上新世早期的不整合与盆地东南部帕洛斯弗尔德斯丘陵地区和阿纳海姆鼻区的局部构造生长有关。中新世晚期出现的其他不整合与沿纽波特-英格尔伍德断层和惠蒂埃断层的运动有关。中新世晚期，在帕洛斯韦尔德斯丘陵和新港湾地区的蒙特利组内出现了一个间歇期。这种间歇被认为与与大陆和海洋冰川有关的气候和海洋事件有关。
The Los Angeles basin is one of the Neogene basins along the California continental margin that was formed by extension related to complex wrench-fault mechanisms. These extensional mechanisms caused the pull-apart tectonics that resulted in rapid deepening of many of the continental margin basins in the late Oligocene to early Miocene. For the last 60 years, the biostratigraphic framework for correlation between the oil fields of the Los Angeles basin has been based on the benthic foraminiferal zones and divisions first published by Wissler (1943, 1958). These biostratigraphic units are used to correlate the upper middle Miocene to upper Pliocene clastic reservoirs across the basin. The benthic foraminiferal zones of Wissler (1943, 1958) were correlated to the Miocene benthic foraminiferal zones of Kleinpell (1938, 1980) and the Pliocene-Pleistocene stages of Natland (1952). With the utilization of other microfossil disciplines (e.g., siliceous and calcareous planktonic microfossils), a more refined biostratigraphic scheme has been developed. Correlation of plankton biostratigraphies with the radiometric time scale has in turn allowed correlation and calibration of benthic foraminiferal zonations. Application of this new biostratigraphic-chronostratigraphic scheme can now be used to constrain the timing and magnitude of tectonic and depositional events marking basin development. Benthic foraminiferal assemblages from three stratigraphic sections, located around the margins of the Los Angeles basin, were correlated to siliceous microfossils, calcareous nannofossils, planktonic foraminifers, and radiometric dates to determine the age relationships of the different benthic foraminiferal zonations. End_Page 135------------------------ Three regional cross sections were constructed based on the thickness of the Neogene sedimentary package and based on the chronostratigraphic relationships between the benthic foraminiferal zones and the other fossil groups. These regional cross sections illustrate the shifting of the central basin depocenter through the late Neogene. The pre-late Miocene deposits are thickest along the basin margin, especially in the northwestern part of the central block, the Puente Hills, and the Capistrano embayment. The sediments that were deposited during the late Miocene through the early Pleistocene were deposited in the central trough, bounded by the Newport-Inglewood, Santa Monica-Raymond Hill, and the Whittier fault systems. Unconformities and hiatuses are associated with each tectonic block. Some of these unconformities are local events related to structural growth or fault movement. The hiatuses are regional events caused by changes in ocean chemistry or velocity of bottom currents. The unconformities that occur in the late Miocene to early Pliocene are related to local structural growth in the Palos Verdes Hills area and the Anaheim nose area of the southeastern portion of the basin. Other unconformities that occur in the late Miocene are related to movement along the Newport-Inglewood fault and the Whittier fault. In the late middle Miocene a hiatus occurs within the Monterey Formation in the Palos Verdes Hills and the Newport Bay area. This hiatus is thought to be related to climatic and oceanic events associated with continental and oceanic glaciation.