Abstract

A palynological study of 239 outcrop samples and their sedimentological context was undertaken on the Pliocene Productive Series in the Kirmaky and Yasamal valleys, eastern Azerbaijan. The Productive Series is primarily a representation of the palaeo-Volga and forms the main hydrocarbon-producing reservoirs in the South Caspian Basin. Most sands are interpreted as fluvial, based on sedimentary characteristics. Mudstone and siltstones often contain freshwater and brackish assemblages interpreted as ‘Caspian lake’ transgressions, indicative of rapid Caspian Sea level change during the Pliocene. Most samples contain rich assemblages including pollen, spores, dinoflagellate cysts, algae and fungal bodies. Common tree pollen elements include Pinus, Alnus, Betula, Carya, Juglans, Pterocarya, Quercus and Ulmus, which all occur in present-day vegetation or pollen records from the Caucasus or Urals. Herbaceous pollen includes Amaranthaceae, Asteraceae (including Artemisia), Ephedra and Poaceae, commonly found in the drier Caspian regions. The dinoflagellate cysts include ‘Peri-paratethyan endemic’ taxa such as Caspidinium rugosum and Spiniferites cruciformis. ‘Pannonian’ species such as Thalassiphora balcanica, Romanodinium areolatum and Spiniferites oblongus confirm the persistence of these taxa into the early Pliocene in Eastern Paratethys, around five million years later than their first documented presence in Central Paratethys. ‘Caspian lake’ influences diminish up-section, as indicated by a progression from brackish to freshwater and sub-aerial conditions. Productive Series deposition was mainly driven by the combined effects of lake level and catchment climate. The principal hydrocarbon reservoir sands were deposited as a result of increased catchment humidity, whereas drying conditions led to reduced coarse clastic input and deposition of alluvial plain mudstones. Productive Series deposition terminated with the onset of the marine-influenced Akchagyl Series, which spans the Plio-Pleistocene boundary. The lowermost sediments of the Akchagyl Series are freshwater in origin and grade up-section into marine beds containing dinoflagellate cysts of Arctic affinity.

摘要

在阿塞拜疆东部的 Kirmaky 和 ​​Yasamal 山谷的上新世生产系列中对 239 个露头样品及其沉积学背景进行了孢粉学研究。生产系列主要是古伏尔加河的代表，形成了南里海盆地的主要产油气储层。根据沉积特征，大多数砂岩被解释为河流砂岩。泥岩和粉砂岩通常包含淡水和半咸水组合，被解释为“里海湖”海侵，表明在上新世期间里海海平面迅速变化。大多数样品含有丰富的组合，包括花粉、孢子、甲藻囊肿、藻类和真菌体。常见的树花粉成分包括松、桤木、桦木、Carya、Juglans、Pterocarya、Quercus和Ulmus，它们都出现在现今高加索或乌拉尔的植被或花粉记录中。草本花粉包括苋科、菊科（包括蒿属）、麻黄和禾本科，常见于较干燥的里海地区。甲藻囊肿包括'Peri-paratethyan地方性'分类群，例如Caspidinium rugosum和Spiniferites cruciformis。'Pannonian' 物种，如Thalassiphora balcanica、Romanodinium areolatum和Spiniferites oblongus证实了这些分类群在东帕特提斯的上新世早期的持续存在，比它们在中央帕特提斯的首次记录存在晚了大约 500 万年。“里海湖”的影响逐渐减弱，从微咸水到淡水和亚空气条件的进展表明。生产系列沉积主要受湖泊水位和集水区气候的综合影响。由于集水区湿度增加，主要的碳氢化合物储层砂层沉积，而干燥条件导致粗碎屑输入减少和冲积平原泥岩沉积。生产系列沉积随着受海洋影响的 Akchagyl 系列的开始而终止，该系列跨越上新世-更新世边界。