International Commission On Stratigraphy Research Articles

QUESTIONS STUDYING OF THE PALEOCENE SEDIMENTARY COMPLEX OF THE CRIMEA AND KERCH PENINSULA

Actualized stratigraphic scheme of Paleocene deposits of the Crimea and Kerch peninsula is presented in the article. This scheme has been made based on the results of compilation and analysis of data of litology and paleontology, of using biostratigraphic developments of different micro and macro fossils and of modern views in stratigraphy. Research has been carried out within requirements of Stratigraphical Code of Ukraine (2012). Modern International Stratigraphic Chart (2012-2014) and modernized Regional stratigraphic Scale of Paleogene of Ukraine (2013) were accepted in the proposed scheme. Description and litologicalpaleontological characteristics of 13 local units of Paleocene as part of the Belokamenskian and Kachian regional stages are given. Stratigraphical volume, spreading and age of described suites and series were clarified. 5 new local units have been described in the article for the first time. Among them the Bondarenkovo suite (Belokamenskian regiostage), the Akbulat suite and the Kolodyazna series (Kachian regiostage) were proposed in the scheme of the Kerch peninsula; the Kubalach suite (Belokamenskian regiostage) and series of sandstones and siltstones (Kachian regiostage) were proposed in the scheme of the Plainland Crimea; the Kubalach suite (Belokamenskian regiostage) was propodes in the scheme of Crimea’ foothills. Duration of hiatuses, reduction of stratigraphic volume of local stratas in peripheral sections of sedimentary basins are shown at these stratigraphic schemes.

Cenozoic tectonic subsidence in deepwater sags in the Pearl River Mouth Basin, northern South China Sea

The Cenozoic tectonic subsidence of the deepwater area in the Pearl River Mouth Basin, northern South China Sea is studied by subsidence analysis via backstripping calculations based on data of newly interpreted sequence boundaries. In the subsidence analysis local porosity–depth parameters were estimated based on well data, the paleo-water depth parameters and lithology were estimated for all grid nodes based on well data and sedimentary system maps, and ages of sequence boundaries were adjusted according to the International Chronostratigraphic Chart v2013/01. Sensitivity analysis shows that these are essential to ensure the quality of the subsidence analysis in the slope areas. Maps of tectonic subsidence rates of 18 Cenozoic sequences were constructed and spatial–temporal variations of the tectonic subsidence were discussed. The subsidence was restricted in the Baiyun and Liwan Sags before 30 Ma and extended to uplifts after 30 Ma. This indicates that the 30 Ma unconformity is the breakup unconformity that separated the syn-rift and post-rift sequences. Four substages of post-rift subsidence were identified by cyclic changes in the rate and pattern of tectonic subsidence at boundaries of 23.3 Ma, 17.2 Ma and 11.9 Ma, respectively. Anomalous post-rifting tectonic subsidence was significant and totaled to ~ 1200 m at the center of the Baiyun Sag, and punctuated by rapid subsidence and uplift events. The Baiyun Event was manifested in the study area by a short-lived uplift event in 23.9–23.3 Ma followed by a short-lived rapid subsidence in 23.3–19.8 Ma in the central study area. This localized rapid subsidence caused northward jump and anti-clockwise rotation of the shelf break. Two-order teeterboard (seesaw)-like subsidence was observed in the study area in the post-rifting stage, suggesting elastic deformations of the crust and lithosphere. • Tectonic subsidence of deepwater sags estimated via backstripping on newest data • Maps and histograms of subsidence rate for 18 Cenozoic sequences are constructed. • Results indicate that the 30 Ma unconformity is the breakup unconformity. • Cyclic anomalous post-rift subsidence of ~ 1200 m confirmed for central Baiyun Sag • Baiyun event near Oligoc./Mioc. boundary is evidenced by rapid local subsidence.

The ‘Anthropocene’ as a ratified unit in the ICS International Chronostratigraphic Chart: fundamental issues that must be addressed by the Task Group

Abstract The proposal that the ‘Anthropocene’ should be ratified as a unit of the International Chronostratigraphic Chart/Geological Time Scale deserves serious consideration by the International Commission on Stratigraphy (ICS). The ‘Anthropocene’ task group within the ICS Subcommission on Quaternary Stratigraphy is responsible for producing a recommendation to be evaluated and considered for approval at high levels in the ICS organization. It must consider the rank and extent of the unit as well as a GSSP or GSSA that defines its lower boundary or beginning. Furthermore, the task group must address several questions related to the proposed unit and the nature of the ICS chart/timescale that are unique to it. Is the ‘Anthropocene’ a concept in search of a distinct stratigraphic record? Should it be defined on a stratigraphic signal or on a date in human history? Is the ‘Anthropocene’ a unit of Earth history or human history or primarily a future projection? Is the ‘Anthropocene’ useful as a chronostratigraphic unit on geological maps? Has the perceived change to a human-dominated Earth system overwhelmed the natural Earth system? What is the conceptual basis of the International Chronostratigraphic Chart/Geologic Time Scale? Will the term ‘Anthropocene’ have value even if not ratified as a formal unit?

Geosites of International Significance in the UNESCO WHS Lena Pillars Nature Park (Sakha Republic, Russia)

The Lena Pillars Nature Park belonging to the Sakha Republic (Yakutiya) is situated in the southeastern Siberian Platform on the right bank of the middle Lena River. The park is mainly known for the almost continuous chain of fancy pillar-like carbonate weathering outliers spreading along the right bank of the Lena River and banks of its tributaries Botoma and Sinyaya. However, the main reason of the ultimate importance of the park is that it represents a pivotal evidence of relatively rapid evolutionary development and growth of the skeleton and soft-bodied fauna and algae diversity, which took place about 541–509 Ma ago. This event is well known in the scientific world as the "Cambrian Explosion". The International Union of Nature Conservation included it into the list of key evolutionary events in the Earth's history. Numerous geosites of different types and significance levels are located in the park, and six of them are of international importance. They are highly representative in terms of stratigraphy, paleontology, paleoecology, and geomorphology. Stratigraphic geosites demonstrate nearly a continuous record of the Upper Ediacaran–Middle Cambrian deposits. Before the 1990s, stratotypes of the Lower Cambrian stages were used for standardization of the Lower Cambrian in the International Stratigraphic Chart. Paleontological geosites are mainly represented by fossil localities of the Early Cambrian, characterized by high level of preservation and diversity. Sinsk localities of the Early Cambrian biota are listed among the Cambrian Lagerstattens. Many geosites are objects of paleoecological investigations because their deposits were formed in synchronously existing parts of a former single paleobasin (inner lagoon, transitional reef, and outer abyssal) with different physical and chemical parameters. Geomorphologic sites represent different types of permafrost karst, as well as weathering outliers of columnar shape, the so-called Lena Pillars. The scientific and aesthetic value of the Lena Pillars Nature Park is globally recognized, and in 2012 it was inscribed into UNESCO WHL based on the criteria vii and viii.

The ICS International Chronostratigraphic Chart

The International Commission on Stratigraphy (ICS) has a long tradition of producing international charts that communicate higher-order divisions of geological time and actual knowledge on the absolute numerical ages of their boundaries. The primary objective of ICS is to define precisely a global standard set of time-correlative units (Systems, Series, and Stages) for stratigraphic successions worldwide. These units are, in turn, the basis for the Periods, Epochs and Ages of the Geological Time Scale. Setting an international global standard is fundamental for expressing geological knowledge. It is also of considerable pragmatic importance as it provides the framework through which regional-scale higher-resolution divisions can be linked, equated and collated. This is a status update on the International Chronostratigraphic Chart and the ICS website www.stratigraphy.org.

Correlation of regional stage of the neogene of the Central and Eastern Paratethys (Ukraine, Russia, Azerbaijan and Georgia) with the International stratigraphic chart

Using integral methodical basis (bio, litho, cyclo- magnetostratigraphy), the authors prove the validity of the correlations Paratethys. The detailed analysis of the microplankton occurrence (plankton foraminifers, nannoplankton, dinocysts) in the Neogene sediments of the Central and Eastern Paratethys, new data obtained during the drilling of the Azov-Black Sea area, allowed to prove and establish the boundaries of the Neogene 10 associations of marine plankton (correlation levels). Besides biostratigraphic used sedimentological, seismic-, cyclo-, magnetostratigraphic, tectonic, morphostructural criteria. The influence of the structure on the stratigraphic manifestations of volcanism are analyzed, particularly mud. As a result were proved and the boundaries and scope of regional, local (installed diachronism) Neogene units of the Central and Eastern Paratethys within Ukraine. Correlation with coeval units of Neogene sediments Romania, Poland, Slovakia, Bulgaria, South Russia, Georgia, Azerbaijan, as well as with the international stratigraphic scale. 
 Interregional stratigraphic scale of the Neogene sediments of the Central and Eastern Paratethys Ukraine are presented.

Geobiodiversity Database: a comprehensive section-based integration of stratigraphic and paleontological data

The Geobiodiversity Database (GBDB – www.geobiodiversity.com), an integrated system for the management and analysis of stratigraphic and paleontological information, was started in 2006 and became available online in 2007. Its goal is to facilitate regional and global scientific collaborations focused on regional and global correlation, quantitative stratigraphy, systematics, biodiversity dynamics, paleogeography and paleoecology. It is unique among global, public access databases in that it is a section-based online database system, incorporating data from a wide range of disciplines of stratigraphy and paleontology, with inherent interrelationship between different kinds of data sets. It provides the capability of completely digitizing raw data, as well as integrating of different interpretations to the same paleontological and stratigraphic content. Several Windows-based visualization and analysis applications, either fully integrated with the database or supported by subset-export functions, have been developed to make the database more useful as a scientific and educational tool. The GBDB became the formal database of the International Commission on Stratigraphy (ICS) in August 2012 at the 34th International Geological Congress in Brisbane, and will produce comprehensive and authoritative web-based stratigraphic information service for global geoscientists, educators and the public.

A futurist perspective on the Anthropocene

An important feature of the ongoing debate about the acceptance of the Anthropocene as a formal chronostratigraphic unit with the same rank as the Holocene (epoch) has been either the existence or the lack of a Global Stratotype Section and Point (GSSP). In addition, the utility of the Anthropocene as a stratigraphic unit has also been questioned. In this paper, it is proposed that the discovery of the GSSP may not be a major problem and could only be a matter of time. However, the term Anthropocene itself, defined on the basis of the stratigraphic expression of human activities (e.g. large-scale agriculture and land clearance, accelerated release of greenhouse gases to the atmosphere) may significantly impact the current stratigraphic framework guided by the International Commission on Stratigraphy (ICS). Indeed, the formal usage of this term can not only lead to stratigraphic and terminological inconsistencies but can also influence the future development of the established chronostratigraphic scheme. These points should be considered by the ICS Anthropocene Working Group before making a final decision. The stratigraphic status of the Anthropocene, however, is a formal issue that should not affect current and future research on human-induced environmental and sedimentary changes, including their stratigraphic imprint. The message is twofold: leave the formal chronostratigraphic aspects to the ICS, and keep producing and organizing knowledge independently of the formal debate. Doing so would require the development of a parallel and likely transitory chronological system without formal stratigraphic value, from which the term Anthropocene would be, at least temporarily, excluded.

Recent advances in the study of the Mesoproterozoic geochronology in the North China Craton

The Mesoproterozoic successions in the North China Craton (NCC) and the Qinling–Qilian–Kunlun Orogens have been revised using the new and highly reliable age data. Many Proterozoic strata in the Qinling–Qilian–Kunlun Orogens, such as the Qinling, Jinshuikou and Beidahe groups that have been ascribed to be Paleoproterozoic are actually of Mesoproterozoic Era. The most significant advances are recent geochronological studies on the Mesoproterozoic stratigraphy and magmatic events in the NCC. The boundary age between the Dahongyu Formation and the overlying Gaoyuzhuang Formation is well constrained to be ∼1600Ma, corresponding to the boundary age between Statherian and Calymmian. The boundary between the Tieling Formation and the overlying Xiamaling Formation is best positioned at ∼1400Ma, which is coeval with the boundary between Calymmian and Ectasian, and is about 400Myrs older than the conventional value of 1000Ma originally defined by the All China Commission of Stratigraphy. Hence the Jixianian System, including the Gaoyuzhuang, Yangzhuang, Wumishan, Hongshuizhuang and Tieling formations in ascending order, is comparable with the Calymmian System in the International Stratigraphic Chart. The lower boundary of the Changchengian System, the first system of the Mesoproterozoic in China Regional Stratigraphic Chart, also needs revision from the conventional 1800Ma to ∼1650Ma well constrained by the zircon U–Pb ages 1673±10Ma (LA-MC-ICP-MS) and 1669±20Ma (SHRIMP) of a granite-porphyry dike that was overlain unconformably by the basal conglomerate of the Changzhougou Formation, the first formation of the Changchengian System. Therefore, the earliest Mesoproterozoic sequence in the NCC represented by the Changchengian and Jixianian Systems in the Yanliao Aulacogen is identical to that of the Vindhyan Supergroup in Central Indian and the Riphean Series in Russia. On the other hand, a series of 1.8–1.6Ga anorogenic magmatic records were well-preserved around the NCC, which marked the initial rifting of the Columbia Supercontinent in the NCC. The magmatic events can thus be subdivided into three phases with peaks at ca 1.77Ga, ca 1.70Ga and ca 1.63Ga, respectively. In addition to 1.8–1.6Ga magmatic events, some minor volcanic eruptions at ca 1.56Ga and 1.44Ga, and wide-spread bi-modal magmatic intrusions at 1.35–1.32Ga have been recognized in the northern NCC, marking the continued rifting of the Columbia Supercontinent since ∼1.8Ga.

Formal subdivision of the Holocene Series/Epoch: a Discussion Paper by a Working Group of INTIMATE (Integration of ice‐core, marine and terrestrial records) and the Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy)

AbstractThis discussion paper, by a Working Group of INTIMATE (Integration of ice‐core, marine and terrestrial records) and the Subcommision on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), considers the prospects for a formal subdivision of the Holocene Series/Epoch. Although previous attempts to subdivide the Holocene have proved inconclusive, recent developments in Quaternary stratigraphy, notably the definition of the Pleistocene–Holocene boundary and the emergence of formal subdivisions of the Pleistocene Series/Epoch, mean that it may be timely to revisit this matter. The Quaternary literature reveals a widespread but variable informal usage of a tripartite division of the Holocene (‘early’, ‘middle’ or ‘mid’, and ‘late’), and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology. We propose an Early–Middle Holocene Boundary at 8200 a BP and a Middle–Late Holocene Boundary at 4200 a BP, each of which is linked to a Global Stratotype Section and Point (GSSP). Should the proposal find a broad measure of support from the Quaternary community, a submission will be made to the International Union of Geological Sciences (IUGS), via the SQS and the ICS, for formal ratification of this subdivision of the Holocene Series/Epoch. Copyright © 2012 John Wiley & Sons, Ltd.

Orbital cycles analysis and its genesis significance for the sequence hierarchy: A case study of Carboniferous Karashayi Formation, Central Tarim basin

The Carboniferous Karashayi (卡拉沙依) Formation of Tarim basin formed in the epi- continental sea shelf environment where the evolution of basins is pediocratic. As an important reservoir-forming combination, the Carboniferous Karashayi Formation consist of clastic rocks, car- bonate rocks and gypsum rocks, which show clear sedimentary cyclicity. According to paleontology research and stratigraphic correlation, Karashayi Formation corresponds to Visean and Serpukhovian in international stratigraphic chart with a time limit about ±27 Ma. The sequence stratigraphic study for the Karashayi Formation is rough because of the difficulty to identify the unconformity surfaces. The current study mostly divides it into three or four 3rd sequences. However, this partition cannot meet the geological crossing correlation. At the theory aspect of sequence stratigraphy, the genesis of the 3rd sequence is also a disputed problem. Cyclostratigraphy study of the Natural Gamma-Ray Log, Spontaneous Potential Log and other logging curves has been taken out by spectrum analysis and wavelet analysis, etc.. For Well Shun6 and Well Zhong1 in Tazhong (塔中) and neighbouring area, combined core observation and base level analysis, the Karashayi Formation was divided into 9 or 11 sequence stratigraphic units. Continuous constraints of each sequence is about ±2.40 Ma, correspond- ing to astronomical cycle formed by three parameters of Earth orbit. Accompanied by the historical division of 3rd sequences, the formation mechanism of 3rd sequences was possibly forced by the 2.4 Ma astro-

Geochronological correlation of the main coal interval in Brazilian Lower Permian: Radiometric dating of tonstein and calibration of biostratigraphic framework

The radiometric age of 291 ± 1.2 Ma obtained through single-crystal zircon U–Pb ages (Sensitive High Resolution Ion MicroProbe – SHRIMP II) of tonsteins from the Leão-Butiá Coalfield, southern Paraná Basin (Rio Grande do Sul state), associated with previous SHRIMP II radiometric data obtained from tonsteins from the western (Candiota Coalfield) and eastern (Faxinal and Leão-Butiá coalfields) borders of the basin indicate that the mean age of the main peat-forming interval is 291.0 ± 1.3 Ma. In a regional context, the mean age represents a consistent geochronological correlation for the uppermost and more important coal seams in southern Brazilian coalfields, but this assumption does not establish an ash fall origin from a single volcanic event. According to the International Stratigraphic Chart, the interval is dated as middle Sakmarian. The coal palynofloras are included in the Protohaploxypinus goraiensis Subzone within the palynostratigraphic framework for the Brazilian Paraná Basin. Formal relationships are also established with the Glossopteris–Rhodeopteridium Zone within the phytostratigraphic chart for the Lower Permian of southern Brazilian Paraná Basin.

The Early and early Middle Pleistocene context of human occupation and lowland glaciation in Britain and northern Europe

This paper reviews the stratigraphical and environmental contexts of early human occupation and lowland glaciation in Britain and northern Europe. It highlights the fragmentary nature of most of the critical sequences and the inadequacy of existing stratigraphical frameworks. The earliest archaeology known from NW Europe has been reported from Happisburgh 3, a site on the Norfolk coast. The flint artefacts from here were recovered from sediments previously assigned to the Pastonian Stage of the Early Pleistocene. However, the mammalian assemblage from Happisburgh 3 differs from other local sites attributed to the ‘Pastonian’, indicating a younger age within the Early Pleistocene. The sediments have reversed palaeomagnetic polarity and have palynological features inviting correlation with the Leerdam interglacial in the Dutch ‘Bavelian Complex’. The interglacials of the British ‘Cromerian Complex’ are compared and their archaeological record reviewed. At most of these sites, the archaeology includes hand-axes associated with a mammalian assemblage containing the water vole Arvicola but at Pakefield, Suffolk, a core-and-flake industry is associated with the ancestral Mimomys savini. This, together with the even older record from Happisburgh 3, indicates earlier periods of human occupation than previously known from NW Europe. At least five temperate episodes with distinct faunal assemblages are now recognized in the British early Middle Pleistocene but these are unlikely to equate directly with odd-numbered stages of the marine isotope record. This biostratigraphical framework conflicts with a ‘New glacial stratigraphy’ for East Anglia, which proposes glaciations during MIS 16, 12, 10 and 6. Evidence is reviewed from Sidestrand and Trimingham, where datable organic sediments occur directly beneath and above the Middle Pleistocene glacial succession, indicating that it was emplaced entirely during the Anglian glacial stage (MIS 12). A new stratigraphical framework is provided ranking British sites in order of relative age, which is then compared with a revised scheme for the Dutch late Early and early Middle Pleistocene succession. The revisions involve the relocation of the Waardenburg interglacial (‘Interglacial 1’) to the ‘Bavelian Complex’ and the use of the Brunhes-Matuyama palaeomagnetic reversal to define both the base of the Dutch ‘Cromerian Complex’ and the Early/Middle Pleistocene boundary. Moreover, following recent re-interpretation, the Noordbergum interglacial (‘Interglacial IV’) and ‘Glacial C’ are removed from the ‘Cromerian Complex’ and are correlated with MIS 11 and MIS 12 respectively. This scheme imposes greater consistency between the British and Dutch successions, as well as conformity with guidelines recommended by the International Stratigraphic Commission.

Sr isotopic characteristic of neoproterozoic carbonate sediments from the southern Yenisei Ridge

This paper presents the first Sr isotopic data for the Late Precambrian carbonate rocks of the southern Yenisei Ridge. Their geochemical study allowed estimation of the degree of secondary alterations and gave the possibility to reveal rocks with a less disturbed Rb-Sr isotopic system. The Sr isotopic data indicated Neoproterozoic sedimentation of the rocks about 1070–750 Ma ago. Sr and C isotopic data showed that carbonate rocks of the Sukhoi Pit, Tungusik, and Shirokino groups are Late Riphean and could be comparable with sedimentary sequences of three Precambrian key sections of the Northern Eurasia: the subsequent Derevnino, Burovaya, and Shorikha formations from the Turukhansk Uplift, the Lakhanda Group from the Uchur-Maya region, and the Karatav Group from the South Urals. All studied carbonate rocks are older than 750 Ma and, according to the International Stratigraphic Chart, accumulated prior to global glaciations in the Cryogenian. This is evident from sedimentological study indicating the absence of tillite horizons in the studied sections. δ13C values in the sections vary from +0.4 up to +5.3‰, which testifies to the absence of periods of great cold.

Serpukhovian Stage (Carboniferous) in type area: Sedimentology, mineralogy, geochemistry, and section correlation

This paper delivers bed by bed descriptions and detailed correlation of the sections Novogurovskii, Dashkovka, and Zaborie of the type area of Serpukhovian Stage of the International Stratigraphic Chart. Above a weakly expressed Forino Unconformity discovered in the lower Tarussian, no subaerial unconcormities can be confirmed up to the top of Steshevian. The basinal character of the Steshevian lobata montmorillonite shale unit is demonstrated. Oxygen minimum and perhaps greatest Early Serpukhovian highstand is revealed by geochemistry and trace fossil association in the lower part of the lobata shale. The paleogeographic model of the “Steshevian basin” outlined in this paper involves suppression of photozoan carbonate production in front of a low-energy delta causing development of a shallow depression in the surrounding carbonate platform. In the Steshevian black shale unit, upward change from lobata montmorillonites to shallower marine palygorskites is explained by evaporative pumping of magnesium and silica in basinal water under progressive climatic aridization.

The problems of reforming of the International Stratigraphic Chart in terms of evolution of ecosystems (by the example of the Lower Paleozoic)

The hierarchial structure and conceptual bases of the International Stratigraphic Chart (ISC) were created during the first eight sessions of the International Geological Congress (IGC) (1878–1900) by the systematization and unification of mainly the West European regional stratigraphic references, except the Permian and, partly, Carboniferous systems with stratotypes in the Russian territory. In the next stage, the structure was refined and supplemented by on the basis of the same principles. Since the middle 1980s, a radical ISC reforming has been performed in the framework of the International Commission on Stratigraphy (ICS), which revealed the contradictory tendencies in the development of modern stratigraphy. They are expressed first of all in the principal difference between the new methodology of the “rational” substantiation of global stratigraphic references adopted by the ICS and the real practice of the development of their regional equivalents based not on the choice of chronometric markers for global correlations but on the revealing of natural geohistorical stages in the evolution of ecosystems, using the total set of paleontological, sedimentological, and isotope-chronometric data. The new approach is based mainly on the concept of the self-sufficiency of limiting types, i.e., monotaxon markers for graduating the ISC, which replace the stratotypes of subunits, their integral complex characteristics, reflecting the trends and periodicity of the Earth's evolution. The negative consequences of this “rational” substantiation and revision of the stratigraphic references of the ISC are particularly obvious by the example of innovations in the subdivision of the Cambrian and Ordovician systems on the comparison of the new series and stages adopted by the ICS with the global ecosystem rebuildings in the Early Paleozoic.

The Middle Ordovician litho- and biostratigraphy of northwestern Gorny Altai

The structure of the Lower–Middle Ordovician Tuloi and Karasa Formations, which occur widely in northeastern Gorny Altai, has been studied. A bed-by-bed description of a new section of the boundary sediments between these stratigraphic units has been given. The graptolite, trilobite, and brachiopod assemblages typical of the Tuloi and Karasa Formations have been analyzed. Graptolite zones and subzones have been recognized, which permit correlating the stratotype and key sections of these local stratigraphic units with the stages of the International Stratigraphic Chart (ISC). The Karasa Formation occupies a considerably larger stratigraphic volume than presumed: It spans the late Arenig and the entire Llanvirn (including the Llandeilo) of the British standard, which is used in Russia (=Upper Dapingian–Darriwilian of the new Ordovician standard in the ISC). Finally, the paper discusses the suggested changes in the names of regional stratigraphic units (horizons) in the Ordovician stratigraphic chart of the western Altai–Sayan fold belt.

Japanese notation for chronostratigraphic and geochronologic units

There exist problems regarding the Japanese notation for chronostratigraphic and geochronologic units, as proposed by Japanese Industrial Standards (JIS). The first problem is the inappropriate translation into Japanese of the terms “Lower/Early, Middle/Middle, and Upper/Late” applied to Series/Epoch units in the International Stratigraphic Chart. The second problem is the inappropriate word order of System/Period units and Series/Epoch units. These problems can be overcome by using logical notation in which the terms “Lower/Early, Middle/Middle, and Upper/Late” for Series/Epoch units are translated as “kabutou/kose, chubutou/chuse, and joubutou/shinse” in Japanese. Although the Geological Society of Japan recommends the use of the JIS-style notation, the revised notation (as summarized here) is more logical and appropriate.

The Paleoproterozoic in the South-American continent: Diversity in the geologic time

Abstract The Paleoproterozoic blocks and terranes that constiture of the South-American continent basement register rock-forming events (orogeny and taphrogeny) clustered in the four different periods as defined by the International Stratigraphic Chart (IUGS/UNESCO 2004). There are some particular cases for which rifting and drifting events precede the processes of convergent interaction between lithospheric plates, representing therefore examples of Wilson Cycles. In other cases, the records of extensional processes and those of convergent interaction of lithospheric plates (orogenies) are either concurrent in time (with difficult discrimination between them) or concurrent in the geographic-geologic space (they occur in different and separated domains), privileging different regions. The four periods of rock-forming events discussed here (Siderian, Rhyacian, Orosirian, Statherian) are mainly recorded and recognizable for most of the cratonic domains of the continent, but they are gradually being identified within the Paleoproterozoic basement blocks (”inliers”) in the large Neoproterozoic (Brasiliano) provinces of the continent. In the latter, such discrimination is much more difficult due to the overprint of the Brasiliano thermo-dynamic processes. For many years (in the recent past), the word “Transamazonian” (event, orogeny, cycle) had been used to cover indiscriminately all these many different Paleoproterozoic events, of the four different periods. With the present discrimination of the four major stages (periods) on time of rock-forming processes (igneous, metamorphic and sedimentary assemblages) the term Transamazonian has naturally become obsolete, and its usage is no longer advisable.

Early Cretaceous stratigraphy and SHRIMP U-Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet

Wan, X., Scott, R., Chen, W., Gao, L. & Zhang, Y. 2011: Early Cretaceous stratigraphy and SHRIMP U-Pb age constrain the Valanginian–Hauterivian boundary in southern Tibet. Lethaia, Vol. 44, pp. 231–244. The Late Jurassic to the Early Cretaceous marine strata are extensively distributed in southern Tibet. In Gyangze, the strata are divided into the Weimei and Jiabula formations. In Nagarze, they are divided into the Weimei and Sangxiu formations. Previous work has reported diverse ammonite species of Haplophylloceras and Himalayites in the Weimei Formation, and a few species of Spiticeras in the lower Jiabula and Sangxiu formations. The present study has found the bivalve Inoceramus and nannofossil assemblages in the lower Jiabula and Sangxiu formations. The nannofossil assemblage of Nannoconus steimannii steinmannii, N. steinmannii minor and Watznaueria barnesae indicates Berriasian age, and the Calcicalathina oblongata–Speetonia colligata assemblage is Valanginian in age. Numerical ages for the Jiabula and Jiabula-goukou sections in Gyangze have been interpolated by comparing the fossil ranges with ages calibrated in other sections. The correlation experiment plots fossil ranges in the two sections to the CRET1 Database. The estimated rate of sediment accumulation of the lower Sangxiu Formation is 22.6 m/myr. The Jurassic–Cretaceous (J/K) boundary is at the bottom of the Jiabula Formation in Gyangze, and the base of the Sangxiu Formation in Nagarze. The boundary is marked by the appearance of the ammonite Spiticeras and the nannofossil assemblage of Nannoconus st. steinmannii–N. st. minor–Watznaueria barnesae. The radiometric age in Tibet is the first to be integrated with upper Valanginian fossils. The volcanic rocks of the upper Sangxiu Formation are dated at 136 ± 3.0 Ma deduced from zircon SHRIMP age of rhyolite. By consideration of the rate of sediment accumulation of the underlying sedimentary deposits, the J/K boundary in the Gyangze–Nagarze area is approximately 145 Ma as suggested by the newly issued International Stratigraphic Chart, and the Valanginian/Hauterivian boundary lies between 134 Ma and 136 Ma. □ Biostratigraphy, graphic plot, Jurassic/Cretaceous boundary, nannofossil, SHRIMP U-Pb age, Southern Tibet, Valanginian/Hauterivian boundary.