Cenozoic stratigraphy of South Africa: current challenges and future possibilities

The Cenozoic stratigraphy of South Africa has developed over the past 166 years since geological mapping of the region was initiated. The current status of lithostratigraphy and the global chronostratigraphic framework is discussed in the context of the diverse Cenozoic regolith across the region. Geological mapping here utilizes lithostratigraphy to organise the Cenozoic deposits, although some extensive units are characterised informally using lithological descriptors. Although there are no formal biostratigraphic units, the allied use of “Land Mammal Ages” compiled from fossil type sites is described. An analogous archaeological cultural-historical “technocomplex” stratigraphy is outlined to subdivide stone age cultural material commonly associated with Quaternary deposits and has often been used as a relative dating framework. A summary table of Cenozoic regolith is presented, differentiating deposits into their terrain morphologically defined Geomorphic Province context as a means of correlating similar deposits across the subcontinent. For mapping units based on lithological characteristics, the use of lithodemic nomenclature to characterise units in each geomorphic province is proposed as a temporary measure to enhance inter-regional correlation and encourage further research that could lead to formal lithostratigraphic descriptions.

Palinostratigraphy and Paleoenvironments in the Gorodishchi Section (Middle Volga River Region, Kimmeridgian–Hauterivian)

—Eight dinocyst-based and three spore- and pollen-based biostratigraphic units are defined in the Kimmeridgian, Volgian, and Hauterivian of the Gorodishchi section, based on a biostratigraphic analysis of the successions of marine and terrestrial palynomorphs. Algological assemblages are described in more detail, and additional criteria for the definition of dinocyst zones established by previous researches are given. A more detailed biostratigraphic subdivision of the middle part of the Volgian is proposed. A local dinocyst zone in the Hauterivian and a biostratigraphic succession of spore–pollen units in the entire section are described for the first time. The research results demonstrate that the boundaries of many palynostratigraphic units exhibit a considerable correlation potential. Based on a biofacies analysis of the microphytoplankton, the dynamics of transgressive–regressive events is studied in relation to the accompanying oxygen and trophic conditions. Possible relationships between marine paleoenvironments and climatic changes reconstructed on the basis of spore–pol­len data are discussed.

A new geological map and review of the Middle Devonian rocks of Westray and Papa Westray, Orkney, Scotland

The Middle Devonian lacustrine sediments of Orkney, off the northeast Scottish mainland, are composed largely of the Lower and Upper Stromness Formations and overlying Rousay Formation. These three formations have been subdivided and defined by vertebrate biostratigraphic biozones with recent division of the Rousay Formation into three further units based on characteristic fish fossils. The division of the Rousay Formation has enabled a map to be constructed of the solid geology of the island of Westray, Orkney, based on fish identification, detailed logging of sedimentary cycles throughout the Rousay succession, parameters of divisional boundaries, and a survey of faults marking sinistral transtensional movement parallel to the Great Glen Fault. Post-Carboniferous shortening and basin inversion led to uplift, folding and reactivation of normal faults as reverse faults, to form a positive strike-slip flower structure in Westray. A suite of Permian igneous dykes intruded across Orkney include three minor offshoots in Westray. The resulting map is the first to make use of biostratigraphic units within the Rousay Flagstone which are now regarded as Members.

Upper Ordovician (Hirnantian) to Lower Silurian (Telychian, Llandovery) graptolite biostratigraphy of the Tielugou section, Shennongjia anticline, Hubei Province, China

The Tielugou section, Shennongjia Anticline, Hubei Province (China) includes a relatively complete succession of Hirnantian (latest Ordovician) to basal Telychian (Llandovery, early Silurian) graptolite faunas. The section shows the first record of a fauna of the late Aeronian Stimulograptus halli Biozone from South China, even though the index species was not reported. The Stimulograptus sedgwickii Biozone may not be represented, indicating a possible gap at the base of the Stimulograptus halli Biozone. The interval yields a number of taxa that are elsewhere reported to originate only in the Stimulograptus halli Biozone. The youngest graptolitic levels are included in the Spirograptus guerichi Biozone based on specimens of Parapetalolithus dignus and Parapetalolithus palmeus not known from earlier intervals. Spirograptus guerichi is not represented in the section. The Tielugou section provides the first detailed information on the faunas and thickness of the encountered biostratigraphic units for the Shennongija region.

Biostratigraphy of Upper Jurassic of the Valy clay pit (Samarskaya Luka) by ammonites, ostracods and dinocysts

The results of integrate biostratigraphic study of Upper Jurassic deposits of the clay pit near the village of Valy (Syzran district, Samara region) are presented. For the first time a bed-by-bed description was made and the subdivision of the section into zones, subzones and biohorizons by ammonites was established. Bauhini and Kitchini zones (Bayi subzone) are established in the Lower Kimeridgian, while Upper Kimmeridgian is represented by Autissiodorensis zone only. In the Lower Volgian Sokolovi and Pseudoscythica zones were recognized, while the Middle Volgian is represented by the Panderi zone. The age of the regionally developed unconformity at the base of the Trazovo Formation has been clarified. As in the sections located to the south from studied section, this unconformity is located in the base of the Autissiodorensis zone, overlying different Oxfordian and lower Kimmeridgian. For the first time for Kimmeridgian of Central Russia in the marlstone band of the Kitchini zone (bayi biohorizon) solitary corals conditionally attributed to the genus Trochocyathus were found. Along with corals other warm-water taxa (belemnites Hibolithes, rare ammonites Taramelliceras) were found in the same bed, suggesting deposition of this bed during the short-time warming event. 6 biostratigraphic units (zone and beds with fauna) were recognized by ostracods, along with 2 dinocyst-based units (assemblage and zone) which are compared with the stratigraphic subdivisions by these groups, previously proposed for the Kimeridgian and Volgian stages of the Russian Platform. The paleo-ecological analysis has allowed to assume, that sediments have accumulated in the conditions of warm shallow eutrophic basin with depth to 50 m, with gradual increase of eutrophy through time. At some levels, short-term episodes of severe shallowing or freshening are recorded by ostracods.

The Turonian-Coniacian deposits of the south-west of the Ulyanovsk-Saratov trough

Integrated study of a series of the Turonian and Coniacian complete geological records has revealed the stratigraphic completeness and specified the faunal contents of the deposits. The south and the southwest of the Ulyanovsk-Saratov trough have been shown to comprise the thickest beds of the studied interval represented by carbonate and carbonate-terrigenous rocks. Northwards, in the zone of the Saratov dislocations, the Turonian – Coniacian bodies are peculiar for terrigenous and terrigenous-carbonate compositions. The beds are ubiquitously monotonous, which complicates identifications at the stage and the substage levels. Distributions of the benthic foraminifer assemblages and the data on the finds of cephalopods, inoceramus, echinoderms, brachiopods and siliceous sponges have allowed to distinguish detailed biostratigraphic units at the level of biozones traced within the examined structural units. An attempt has been made to reconstruct the conditions in the marine environment.

On the non-marine stratigraphy and floras of north-eastern Russia

Some decisions of the Third Inter-departmental Regional Stratigraphic Meeting on Precambrian, Paleozoic and Mesozoic of North-eastern Russia (St. Petersburg, 2002) are analysed in the light of latest data obtained. It is shown that regional stratigraphic units (‘Horizons’) of non-marine Cretaceous recognised in this Meeting are in fact not the basic subdivisions, but rather specialised biostratigraphic units, namely ‘Beds with flora’. Ages of some of these units are specified, notably Beds with Arman Flora is Turonian–Coniacian, Beds with Amka Flora is Coniacian and Beds with Arkagala Flora is Santonian–Campanian. We recommend to keep the previous names for the Penzhina, Barykov and Koryak phases of floral development and for the corresponding stratigraphic units. An updated version of the non-marine Cretaceous stratigraphic chart of the Okhotsk-Chukotka structural-facial Region is proposed to discuss.

Integrated stratigraphy of the Upper Barremian–Aptian sediments from the south-eastern Crimea

Previous studies made in different parts of the world have shown that Barremian–Aptian times imply many difficulties in deciphering the biostratigraphy, microfossil evolution and correlation of bioevents. In an attempt to improve our knowledge of this period in a particular area of the Tethyan realm, we present the first integrated study of microbiota (including planktonic foraminifera, calcareous nannofossils, ostracods and palynomorphs) and magnetostratigraphy of the upper Barremian–Aptian sediments from south-eastern Crimea. The nannofossils display the classical Tethyan chain of bioevents in this interval, while the planktonic foraminifera demonstrate an incomplete succession of stratigraphically important taxa. Our study enabled the recognition of a series of biostratigraphic units by means of four groups of microfossils correlated to polarity chrons. The detailed analysis of the microfossil distribution led to a biostratigraphic characterization of the Barremian/Aptian transition and brought to light an interval, which may correspond to the OAE1a.

Famenian palynostratigraphy of the Volyn–Podillya margin of the East–Europian platform

Famenian carbonate-terrigenous deposits with thickness іn 300-580 m are widely distributed within the Volyn-Podillia margin of the East-European platform. It is the facies-varying complex of rocks, the stratification of which is very difficult because there are no faunal remains in the sediments (with the exception of the lower part). Therefore, during the study of this stratum, the palynological method and the palynostratigraphic division are very important. The main purposes of this study are to identify palynozones, distinguish their generalized description and to create a local scale of the palynological zonation - the vertical succesion of biozones. The material for research consists of more than 450 samples, selected from 31 boreholes. The main method is the facial-palynological analysis, or the method of palynoorictocenosis. This is the first study to perform the standardized description of the biostratigraphic units determined by the palynological data for the Famennian of the Volyn-Podillia margin of the East-European platform. In general, five palynozones are allocated in the Famennian. All palynozones are comprehensively documented thanks to numerous palynological data, characterized by a zonal spore assemblage, in the structure of which there are following categories of taxa: based on the vertical range characteristics - key, characteristic, transit ones; on the content - subdominant, accessory. According to spreading peculiarities of key and characteristic species the following types of bio-units are identified: the Range-Zone (two units) and the Concurent-Range Zone (three ones). General the Famenian deposits of the Volyn-Podillia margin of the East-European platform were palynologically subdivided into lebedianensis–magnificus (the oldest zone), varicornata, cassis–lupinovitchi, versabilis –hamulus, lepidophyta (the youngest unit) miospore zones. Palynozones with a thickness from 17 to 231 m are laterally widespreaded, recorded from a number of boreholes within Volyn-Podillya. They have a set of palynological features that allow easy recognition of deposits. Palynozones detail the sequence bedding, complement the paleontological characteristic and form the local palynological zonal scheme of the Famenian of the Volyn-Podillia margin of the East-European platform.

Biostratigraphy of the Bajocian-Bathonian boundary interval in northern Siberia: new data on belemnites from the Yuryung-Tumus peninsula

This paper presents a refined belemnite based biostratigraphy for the Bajocian-Bathonian transition in the Yuryung-Tumus peninsula (northern Siberia, Russia). A revision of the Siberian belemnite zonation is proposed. Herein two new belemnite biostratigraphic units are introduced: the Paramegateuthis subishmensis Zone (upper part of the Lower Bajocian) and the Paramegateuthis ishmensis Zone (Lower-Middle Bathonian boundary interval). Paramegateuthis subishmensis STOYANOVA-VERGILOVA, recorded for the first time in Siberia and previously only known from Bulgaria (Sub-Mediterranean domain), provides evidence for correlation of both the Boreal Boreiocephalites borealis and Cranocephalites gracilis ammonite zones with the standard Stephanoceras humphriesianum Zone. The new biostratigraphic data also result in an improved correlation based on belemnites for the Lower-Middle Bathonian of the Boreal (Siberia, North European Russia) and Subboreal (Central Russia) regions.