Late Permian Limestone Research Articles

Geochemistry of the new Permian-Triassic boundary section at Sitarička Glavica, Jadar block, Serbia

The new Permian-Triassic boundary section at Sitarička Glavica is unusual for the Alpine-Dinaride area, in that it is dominantly detrital in the early Triassic. It shows a change from late Permian limestones and shales with a diverse algal-brachiopod-echinoid-molluscan biota deposited in quieter normal marine water (unit 1), into similar sediments, with coarser calcisiltites and a reduced fauna (unit 2), into a post-extinction early Triassic calcareous micaceous siltstones and silty limestones (unit 3) with only molluscan fossils. The major element ratios to Al, reported previously, change little through the section, but with slightly higher ratios just above the extinction horizon (except for K) at the top of unit 2, and show moderate chemical weathering, and change to slightly less mature sediments above. Trace element ratios to Al show little consistent change, except for higher values of most ratios at the contact of units 1 and 2, where slight but temporary increases in TOC, δ13Corg and δ15Norg, and C/N, and decrease in δ34Spyrite occur. Low HFSE (Zr, Nb, REE, Th, U, Ta) values and ratios to other elements indicate that the resistant mineral containing these elements were somehow removed prior to deposition in residual lags by preferential wind erosion. Paleoredox indicators are inconsistent but anoxia seems present in unit 1 and 2 with mostly oxic conditions in unit 3 above. The geochemistry of this section does not show the concentrations of Ni and other elements attributed to Siberian Trap sources and evidence of volcanic input to the sediments is confined to below and above the extinction horizon. The main geochemical changes occur at the top of unit 1, corresponding with a faunal diversity decrease, but not extinction, and at the +5 metre horizon, which seems to- have no faunal changes associated with it. The carbon and other organic-related elements and isotopes indicate a terrestrial input of freshwater and organic matter just before the main negative spike in carbon isotopes, which greatly reduced the diversity of the fauna, and was shorty followed by an input of intermediate volcanic ash. The actual extinction and paleontological Permian-Triassic boundary occurred at the top of unit 2, and has little geochemical changes associated with it. These events can be recognized in other Alpine-Dinaride sections -. All Alpine-Dinaride sections also show a latest Permian ostracod-dominated horizon with a negative spike in organic carbon and sulphur isotopes that indicate an input of freshwater and land plant material, reducing the surface waters to almost brackish, followed by a return to normal salinities with the return of a reduced latest Permian fauna, accompanied by a gradual negative shift in carbonate carbon isotopes accompanied by input of intermediate volcanic material. The main extinction is accompanied by a drop in the difference between carbon and organic carbon isotopes, indicating less land plant input; but otherwise there is little geochemical change at this horizon.

The Chaqupacha Mississippi Valley-type Pb–Zn deposit, central Tibet: Ore formation in a fold and thrust belt of the India–Asia continental collision zone

The newly discovered Chaqupacha Mississippi Valley-type (MVT) Pb–Zn deposit in central Tibet has been found to be helpful for understanding MVT ore formation relative to tectonic evolution of a foreland fold and thrust belt. The deposit lies in the Tuotuohe area of the western Fenghuo Shan-Nangqian fold and thrust belt of the India–Asia continental collision zone. It contains NNW-striking and folded Late Permian strata including an upper clastic unit and an underlying limestone unit. The strata overlie late Oligocene clastic rocks through a south-dipping reverse fault that is associated with regional northward thrusting during the Paleogene. The Late Permian and late Oligocene strata are unconformably overlain by flat-lying early Miocene marl and mudstone of the Wudaoliang Formation. Lead and zinc ores are mainly hosted by pre-ore dissolution and collapse breccias in the Late Permian limestone. The style of mineralization is epigenetic, as shown by replacement of the pre-ore dissolution breccia matrix and open-space-fill by galena, sphalerite, calcite, and minor barite and pyrite. δ34S values of the main sulfide galena range from −27.5‰ to +12.6‰. These features, together with the lack of magmatic activity during the mineralization, suggest that Chaqupacha is an MVT deposit. Subordinate mineralization is also present in the early Miocene Wudaoliang Formation marl and the paleokarst breccia which contains matrix compositionally equivalent to strata of the Wudaoliang Formation. The mineralization shares similar mineral associations and textures with the pre-ore dissolution breccia-hosted mineralization. Thus, the Pb and Zn mineralization in the entire deposit probably resulted from the same mineralizing event, which is younger than the youngest ore-hosting rocks (i.e., the early Miocene Wudaoliang Formation). Considering that thrusting in the Tuotuohe area had ceased prior to deposition of the Wudaoliang Formation host rocks, the mineralization at Chaqupacha post-dated the regional deformation. The Chaqupacha deposit thus provides a good example of MVT mineralization in a foreland fold and thrust belt that post-dates regional thrusting.

Challenging the sensitivity limits of Paleomagnetism: Magnetostratigraphy of weakly magnetized Guadalupian–Lopingian (Permian) Limestone from Kyushu, Japan

Despite their utility for bio- and chemostratigraphy, many carbonate platform sequences have been difficult to analyze using paleomagnetic techniques due to their extraordinarily weak natural remanent magnetizations (NRMs). However, the physical processes of magnetization imply that stable NRMs can be preserved that are many orders of magnitude below our present measurement abilities. Recent advances in reducing the noise level of superconducting magnetometer systems, particularly the introduction of DC-SQUID sensors and development of a low-noise sample handling system using thin-walled quartz-glass vacuum tubes, have solved many of these instrumentation problems, increasing the effective sensitivity by a factor of nearly 50 over the previous techniques of SQUID moment magnetometry.Here we report the successful isolation of a two-polarity characteristic remanent magnetization from Middle–Late Permian limestone formed in the atoll of a mid-oceanic paleo-seamount, now preserved in the Jurassic accretionary complex in Japan, which had proved difficult to analyze in past studies. Paleothermometric indicators including Conodont Alteration Indices, carbonate petrology, and clumped isotope paleothermometry are consistent with peak burial temperatures close to 130°C, consistent with rock magnetic indicators suggesting fine-grained magnetite and hematite holds the NRM. The magnetic polarity pattern is in broad agreement with previous global magnetostratigraphic summaries from the interval of the Early–Middle Permian Kiaman Reversed Superchron and the Permian–Triassic mixed interval, and ties the Tethyan–Panthalassan fusuline zones to it. Elevated levels of hematite associated with the positive δ13Ccarb of the Kamura event argue for a brief spike in environmental oxygen. The results also place the paleo-seamount at a paleolatitude of ~12° S, in the middle of the Panthalassan Ocean, and imply a N/NW transport toward the Asian margin of Pangea during Triassic and Jurassic times, in accordance with the predicted trajectory from its tectono-sedimentary background. These developments should expand the applicability of magnetostratigraphic techniques to many additional portions of the Geological time scale.

Geochemistry of the Middle to Late Permian limestones from the marginal zone of an isolated platform (Laibin, South China)

Major, trace and rare earth elements were measured in 27 samples of the Middle to Late Permian limestones from the Tieqiao section located on the marginal zone of an isolated platform (Laibin, South China). Shale-normalized REE+Y patterns of all samples show notably negative Ce anomalies (0.21–0.66, average 0.33), slightly positive Gd anomalies (1.08–1.30, average 1.20), and positive Y anomalies with superchondritic Y/Ho ratios (36–91, average 55), which are consistent with those of modern shallow seawater. Their relative LREEs enrichment with higher NdSN/YbSN ratios (0.58–1.80) than those of modern shallow seawater (0.21–0.50) suggests complicated sources of REEs for all samples. Compared with geochemical features of sediments influenced by terrigenous particles and hydrothermal fluids, it is concluded that ambient shallow seawater was the primary source of REEs in these limestones. Comparing the indicators of REE+Y elements (ΣREE, NdSN/YbSN, Ce/Ce*, Gd/Gd*, Eu/Eu* and Y/Ho) in limestones with those in bedded cherts from the Tieqiao section, we consider that limestone and bedded chert have similar sources of REE+Y elements: ambient shallow seawater with more or less hydrothermal fluids. In addition, there is a completely negative correlation between CaCO3 and SiO2 contents in limestones and bedded cherts. These results imply that precipitation of CaCO3 was inhibited by that of SiO2 which was derived mainly from hydrothermal fluid, especially in bedded cherts from the Tieqiao section.

Paleomagnetic data from the Late Carboniferous-Late Permian rocks in eastern Tibet and their implications for tectonic evolution of the northern Qiangtang-Qamdo block

We report paleomagnetic results from the Late Carboniferous-Late Permian strata in eastern Tibet (China), and aim to clarify the tectonic and paleogeographic evolution of the northern Qiangtang-Qamdo block, which is the key to the study of plate boundary between the Gondwanaland and the Eurasia during the late Paleozoic. Two hundred and nineteen samples—including limestone, muddy siltstone, basalt, lava, and tuff—were collected at 24 sites in the Upper Carboniferous and Middle-Upper Permian successions. A systematic study of rock magnetism and paleomagnetism yields three reliable paleomagnetic pole positions. Both hematite and magnetite occurred in the Late Carboniferous limestone samples. The demagnetization curve shows a characteristic double-component, with the remanent magnetization (ChRM) exhibiting a positive polarity (negative inclination). In the Late Permian limestone, tuff, and basalt, magnetic information were recorded primarily in magnetite, although a small fraction of them was found in hematite in basalt. The demagnetization curve illustrates a double or single component, with the ChRM showing a negative polarity (positive inclination), which has passed the classic fold test successfully. The single polarity features of the ChRM directions of the Late Carboniferous and Middle-Late Permian rocks are respectively related to the Kiaman positive and reversed polarities under the stratigraphic coordinates. This, in turn, indicates that both ChRMs directions represent the original remanence directions. By comparison with the previously published paleomagnetic results from the late Paleozoic rocks in the northern Qiangtang Range, we suggest that: (1) Qamdo and northern Qiangtang block were independent of each other during the Late Carboniferous to the Early Permian periods. The north Lancangjiang ocean basin between the two blocks may have closed before the Middle Permian and been involved in the continent-continent collision stage in the Late Permian-Early Triassic periods. (2) The northern Qiangtang-Qamdo Block paleogeographically was situated at low to intermediate latitudes in the Southern Hemisphere in the Late Carboniferous-Late Permian periods, and began to displace northward in the Early Triassic, with an amount of more than 5000 km northward transport from its current location.

Deglacial variations of Sr and 87Sr/ 86Sr ratio recorded by a stalagmite from Central China and their association with past climate and environment

A low-resolution strontium isotopic ratio ( 87Sr/ 86Sr) record coupled with a high-resolution Sr concentration profile covering the last deglacial period were obtained for a stalagmite, SJ3, collected from Songjia Cave, northeast Sichuan province, Central China. Both Sr and 87Sr/ 86Sr display significant variations during the period between 20 and 10 ka, which correlate well with oxygen isotope records from Greenland ice cores and speleothems in the East Asian summer monsoon regime, with higher Sr and more radiogenic 87Sr/ 86Sr values occurring during cold-dry climatic phases and vice versa. The Sr in SJ3 shows a negative linear relationship between 87Sr/ 86Sr and 1/Sr, suggesting the binary mixing of two end-members, the host rock of Late Permian limestone with a relatively lower 87Sr/ 86Sr ratio (∼ 0.7071) and an exotic Sr source with a relatively radiogenic 87Sr/ 86Sr ratio (∼ 0.7109 deduced from the 87Sr/ 86Sr-1/Sr correlation). Atmospheric dust activity was suggested to be the most probable factor influencing the two indices. Because the carbonate fraction in wind-blown dust is enriched in Sr and has a more radiogenic 87Sr/ 86Sr ratio, enhanced atmospheric dust activity under stronger Asian winter monsoon which is associated with cold-dry climate would lead to higher Sr concentrations and more radiogenic 87Sr/ 86Sr ratios in SJ3 and vice versa. This interpretation is supported by the general parallelism of the two Sr indices to winter monsoon proxy from East Asia such as the dust flux and quartz median diameter in Luochuan loess profile during the same period. This study suggests that the speleothem 87Sr/ 86Sr ratio and Sr concentration, especially the former in northeastern Sichuan Province can be used to investigate the atmospheric dust activity and Asian winter monsoon.

Rare earth elements and yttrium in a stalagmite from Central China and potential paleoclimatic implications

In a pilot study, the rare earth elements and yttrium (REE when discussed without Y or REY with Y) were measured by inductively-coupled plasma mass spectrometry (ICP-MS) on a stalagmite (SJ3) from northeast Sichuan, Central China. This stalagmite was dated by the thermal ionization mass spectrometry (TIMS) 230Th method to between 38 and 10 thousand years before present (ka BP). The REY geochemical indices, including the concentrations, Lanthanum, Cerium and Yttrium anomalies and the fractionation between light and heavy REE (LREE and HREE), display significant stadial-interstadial changes corresponding to variations in past climates and environments. The North American Shale Composite (NASC)-normalized REY patterns for sub-samples of SJ3 display obvious negative Ce anomalies and positive Y anomalies. For most sub-samples, the LREE are relatively depleted relative to the HREE. La anomalies during relatively cold and dry climatic phases (including the last glacial maximum (LGM) and the period synchronous with Heinrich event one identified in the North Atlantic region) are usually positive, while the Ce and Y anomalies and the LREE-HREE fractionation are more pronounced. During relatively warm and humid phases the REY pattern displays an opposite signature. The REY sources for SJ3 include the overlying soil layer, which consists mainly of aeolian sediments, and the host rock of the Late Permian limestone. Source change may be the primary mechanism controlling the variations of the REY pattern for SJ3. The REY pattern for the youngest sub-sample from the top dirty section of SJ3, which is porous and rich in detrital materials, seems to be dominated by the overlying soil layer. The REY in sub-samples deposited during relatively cold and dry phases may come mainly from the host limestone and thus show patterns more similar to a marine signal. For the rest of the sub-samples, REY from both sources may be present. In addition to the sources, the REY pattern for SJ3 may also be influenced by REY mobilization from sources and transportation in groundwater, and prior carbonate deposition, all of which should be closely related with changes in climate and environment. Thus the REY pattern for speleothems might be a potential proxy for past climate and environment.

The Permian-Triassic boundary sections in northern Vietnam (Nhi Tao and Lung Cam sections): Carbon-isotope excursion and elemental variations indicate major anoxic event

Two Permian-Triassic boundary sections (Lung Cam and Nhi Tao) in shallow marine carbonates from northern Vietnam, near the border between Vietnam and China, were studied for major and trace elemental variations as well as carbon and oxygen isotopic compositions. At the Nhi Tao section, we observe a continuous transition from Late Permian limestones, siliceous limestones and microbial limestones (Dong Dang Formation) to Early Triassic limestones and dolomitic limestones (Hong Ngai Formation). At the Lung Cam section, a thin layer of shale (the uppermost part of the Dong Dang Formation-Late Permian) separates carbonate layers of the Dong Dang Formation (Late Permian) from those of the Hong Ngai Formation (Early Triassic). There is a clear negative shift of about 2.5–3‰ in the δ 13C values at both sections, beginning about 10 cm below the Permian-Triassic boundary as defined by paleontological and lithological data. The existence and extent of these excursions is compatible with introduction of 12C-rich deep ocean water onto the shallow carbonate platform. In the Nhi Tao section, this negative shift in δ 13C starts at about the same level as a change in magnetic susceptibility, indicating some input from terrestrial sources. The δ 13C curves shows evidence for a rapid reduction in biomass, which may be related to the extinction event, and the long-term reduction in δ 13C in the Early Triassic suggests long-term perturbation of the environment and slow recovery. The shift towards negative values indicates a reduction in carbon burial. The shape of the Ce/Ce* curve suggests that the redox conditions of depositional environments in both sections fluctuated, but that there was a decline in oxygenation with time, possibly into the anoxic range. Distinct negative anomalies coincide with the onset of the carbon isotope shifts, which might indicate additional influx of anoxic waters. The Th/U ratios in both sections are mainly less than 2, reinforcing this possibility. Upwelling of anoxic deep-ocean water onto the shallow carbonate platform at Nhi Tao and Lung Cam at the end of the Permian, with related disastrous consequences for the biosphere, is indicated by our data.

A LATE CHANGHSINGIAN (LATE PERMIAN) DEEPWATER BRACHIOPOD FAUNA FROM THE TALUNG FORMATION AT THE DONGPAN SECTION, SOUTHERN GUANGXI, SOUTH CHINA

Abstract This paper describes a unique deepwater brachiopod fauna from the upper part of the Talung Formation at the Dongpan Section, southern Guangxi, South China. This brachiopod fauna includes 10 species belonging to 10 genera. New taxa are Anidanthus mucronata n. sp., Dongpanoproductus elegans n. gen. and sp., Costatumulus dongpanensis n. sp., and Spinomarginifera semicircridge n. sp. This fauna is characterized by small, thin-shelled species with high abundance and low diversity, and therefore is different in generic and species composition from the coeval faunas of the Late Permian limestone facies in South China. The brachiopod fauna can be safely assigned to the latest Changhsingian as indicated by the presence of abundant Paracrurithyris pigmaea, the immediately underlying radiolarian Neoalbaillella optima Zone of late Changhsingian age, and the overlying ammonoid Ophiceras sp. cf. O. tingi Tien of the lowest Triassic. This fauna is most likely to have lived in a deepwater environment as indicate...

Foraminifers from the exotic Late Permian limestone pebbles in the Mesozoic low-grade sequence of the eastern Rhodope, Bulgaria: paleogeographic and paleotectonic consequences

Foraminifers from the exotic Late Permian limestone pebbles in the Mesozoic low-grade sequence of the eastern Rhodope, Bulgaria: paleogeographic and paleotectonic consequences

Paleomagnetic results from Saudi Arabia and the Permo-Triassic Pangea configuration

The Pangea configuration for the interval of Late Carboniferous to Early Jurassic is still debated: was it similar to the well known Wegenerian Pangea or did Gondwanaland move with respect to Laurussia along a major right-lateral lineament of several thousand kilometres during the Triassic, as suggested by Irving? We try here to answer this important question with the paleomagnetic study of well dated Permo-Triassic sediments from a borehole in Saudi Arabia. Sediments of the same age have also been sampled at the surface, but proved to be remagnetized, probably by a strong desert alteration. The paleomagnetic study of the bore-hole core yielded a high temperature component magnetization thought to be of primary origin carried either by magnetite (Late Permian limestones) or hematite (Early Triassic red shales) with antipodal normal and reversed inclinations. Its co-latitude and pole directions compare well with those from a selection of South American, African, Madagascar, and Moroccan poles. A new reliable pole west Gondwana with a mean age of 244 ± 11 m.y. is derived (λ = 53.4°N, Φ = 259.4°E, A 95 = 3.6 in West African coordinates), and its comparison with the Laurussian poles of same age window strongly suggests a Pangea in which the northern part of South America was facing the east of North America (Pangea B of Irving) at the Permo-Triassic boundary. A large right-lateral strike-slip movement of some 3500 km during the Triassic is thus required to reconstruct Pangea to its Jurassic pre-Atlantic opening position.

Paleomagnetic and rock magnetic investigations of the Changxing Permian‐Triassic section, Zhejiang Province, China

Paleomagnetic and rock magnetic experiments on the Triassic Yinkeng Formation and the Permian Changxing Formation sampled from the Permian‐Triassic type section, Changxing County, reveal that a high temperature primary direction is isolated in dolomitic samples from the Early Triassic but the Late Permian limestones samples appear to be remagnetized during the Jurassic. A Permian‐Triassic pole previously reported for the Changxing Formation from this section (Lin et al., 1985) is not in agreement with results from this study or other poles for that time interval reported for the Yangtze Block and may be remagnetized.

Discussion on structural evolution of Mesozoic Peninsular Malaysia

C. S. Hutchison and S. P. Sivam write: Harbury et al ‘ s 1990 paper is a useful contribution to our knowledge of the Mesozoic Tembeling Formation. However, the generalizations on stratigraphy and orogenesis for the whole Peninsular Malaysia are based on inadequate literature research and a general unfamiliarity with the region. Accordingly we feel obliged to bring to your attention the most obvious shortcomings of the paper. The timing of the Indosinian Orogeny of Southeast Asia ( Belov et al. 1986 ) traditionally was based on the widespread elimination of marine sedimention and general uplift by early Jurassic time. The predominantly Carnian-Norian strata (collectively called Upper Triassic flysch), were followed by predominantly Jurassic-Cretaceous molasse: the characteristically red Tembeling Group (Malaysia) and the Terrain Rouge (Indochina), and the non-oxidized Gagau Group and Tebak Formation (Malaysia) and the Grès Supérieurs of Indochina. The critical locality in Peninsular Malaysia is at Jengka Pass, where the gently dipping marine Tembeling Formation is late Triassic to early Jurassic, unconformably underlain by vertically bedded Late Permian limestone, shale and sandstone ( Ichikawa et al. 1966 ). This situation is an analogue of the western margin of the Khorat Basin of NE Thailand, where the Upper Triassic to earliest Jurassic Huai Hin Lat Formation unconformably overlies late Permian Saraburi Limestone ( Kon’no & Asama 1973 ). Jurassic redbeds succeed the Huai Hin Lat Formation, and in Peninsular Malaysia the marine Jengka Pass sequence is succeeded eastwards by continental redbed facies. The information of the foregoing paragraph has been distorted by Harbury et

Upper Permian conodonts from Hydra, Greece

Conodont faunas recovered from the upper 80 m of Late Permian limestones on the Greek island of Hydra (Idhra) include Neogondolella leveni (Kozur, Mostler, and Pjatakova), Neogondolella orientalis (Barskov and Koroleva), Hindeodus julfensis Sweet, Xaniognathus hydraensis n. sp., and Ellisonia sp. The conodonts occur with a rich assemblage of silicified brachiopods, fusulines, and other invertebrates. Diagnostic fusulines include Reichelina media Miklukho-Maklai and Palaeofusulina cf. P. prisca Deprat. The conodont and fusuline faunas are correlative with well-known faunas described from the lower part of the Ali Bashi Formation of the Djulfa region of Iran, and with similar faunas described from other regions of Central Asia. The presence of conodonts from the Neogondolella orientalis Zone of Kozur indicates that the age of the upper part of the Permian sequence on Hydra is early-middle Dzhulfian (Baisalian Substage).