Charophyte Assemblages Research Articles

Stratigraphy and biostratigraphy (charophytes) of the marine-terrestrial transition in the Upper Eocene of the NE Ebro Basin (Catalonia, Spain)

The onset of endorheic sedimentation in the Ebro Basin is a prominent feature of the basin’s evolution and has recently been characterized as a rapid event occurring in the Early Priabonian. In the north-eastern part of the basin this event coincides with the deposition of the Artes Formation (Fm.), mainly built up by red beds of alluvial origin. The marine-continental boundary has been poorly studied up to now in the so-called Llucanes area, and what was previously thought to be the base of the Artes Fm. is actually a transitional unit, which we define as the Sant Boi Formation, which covers the underlying marine Milany Depositional Sequence and passes laterally to the Terminal Complex, extending over 15km along the eastern margin of the Ebro Basin. The Sant Boi Fm. is formed by up to 15-20m of alternating siltstones and lutite, grading upwards to brackish and lacustrine marls and lignite, and represents deposition in a brackish to freshwater floodplain. It is characterized biostratigraphically by the fossil charophyte assemblage Harrisichara lineata, Harrisichara vasiformis-tuberculata and Nodosochara jorbae, from the middle part of the Priabonian. In contrast, the overlying red beds of the Artes Fm. are characterized by assemblages containing Harrisichara tuberculata, Nodosochara jorbae and Lychnothamnus longus from the Late Priabonian. These results are largely consistent with recent magnetostratigraphic studies performed south of the studied area, and have enabled us to refine the stratigraphy of the marine-continental transition in the north-eastern Ebro Basin.

Discussion of Paleocene-Eocene Boundary of SanShui Basin

Core SB-01 , located in SanShui Basin, contained two ostracode assemblages and two charophyte assemblages. Ostracode assemblages included Sinocypris nitela-Cyprois buxinensis-Limnocythere honggangensis assemblages (89.0-73.38m) and Sinocypris nitela-Cyprois buxinensis-Limnocythere honggangensis assemblages(73.38-0m); Charophyte assemblages consisted of Peckichara subspherica-Rhabdochara jiangduensis assemblages (89.0-73.38m) and Gyrogona qianjiangica-Obtusochara brevicylindrica（73.38-53.75m）assemblages. At 73.38 core depth, the abrupt change of microfossil assemblages took place, and δ13C and δ18O values of bulk carbonates also changed rapidly, the former decreased and the latter enhanced respectively. It consisted with the geological records of the Paleocene- Eocene Thermal Maximum ( PETM), hence Paleocene-Eocene boundary of SanShui Basin should be roughly placed at 73.38m core depth.

Découverte de charophytes de l’Albien dans la Formation Kebar (Tunisie centrale) : implications paléoécologiques et paléobiogéographiques

In Tunisia, in the platform domain, the Aptian-Albian transition is associated with a major stratigraphic gap not precisely dated, which is related to the subaerial exposure of the Aptian Orbata platform. Locally, in central Tunisia (Jebel Kebar), this gap is substituted by the sedimentary records of the Kebar Formation. This formation provided a rich association of fossil charophytes, formed by Atopochara trivolvis trivolvis, Clavator harrisii zavialensis and Sphaerochara verticillata which allows attributing it to the late Aptian–early Albian interval (most probably early Albian). In addition, a new variety, Sphaerochara verticillata var. kebariensis, is described. The charophyte assemblage shows significant biogeographic affinities with a coeval flora found in the Iberian Peninsula. The Kebar Formation was previously regarded as exclusively nonmarine, but the presence of the assemblage of charophytes and associated ostracods described rather indicates a fluctuation between margino-littoral (lagoonal) and continental environments.

Revision of Late Tithonian charophytes from Lisbon and Sintra-Cascais (Portugal): taxonomy, biostratigraphy and palaeobiogeographical significance

Abstract. The re-evaluation of the charophyte content of ‘Purbeckian’ sediments from several sections around Lisbon (Olelas and Brouco) and Sintra-Cascais (Murches, Atrozela and Malveira-Guincho) revealed new palaeofloral associations from the Late Tithonian of the South Lusitanian Basin (Portugal). These sections contain Globator rectispirale, G. aff. nurrensis, Nodosoclavator bradleyi, Clavator reidi, Clypeator cf. discordis, Porochara maxima, and newly described occurrences of P. jaccardi, Mesochara harrisi and nodosoclavatoroide utricles. These revised data reinforce the evidence for assigning most of the studied deposits to a Late Tithonian age, instead of the formerly accepted wider interval Tithonian to Early Berriasian (‘Purbeckian’). Population analysis and statistics were applied in order to better assess population variation of the different species.The results of this study are relevant as they contribute to improve the biostratigraphical definition of the ‘Purbeckian’ formations of Portugal and allow more accurate palaeobiogeographical interpretations within the central Tethyan domain, by comparison of the identified charophyte assemblages with documented Jurassic–Cretaceous transition charophytes from other regions.

Charophytes from the Upper Paleocene of the Trans-Altai Gobi Desert (Mongolia)

Charophyte assemblage is described from the Naran Member of the Tsagaan sair section (Upper Paleocene). A new species, Mesochara cornuta, is described.

Triassic charophytes from Slovenia: palaeogeographic implications

Charophyte gyrogonites are reported for the first time from the Triassic of Slovenia and Southern Europe. They were found associated with Late Ladinian-Early Carnian conodonts in marine limestone of the Oblakov Vrh succession, in the northern part of the Outer Dinarides. The charophyte assemblage consists of rare gyrogonites belonging to genus Stenochara, which would probably have been transported to a marine depositional setting from their growing area, a freshwater or brackish environment located nearby. This confirms that smaller areas of palaeogeographic highs, with non- marine facies, occurred during the Triassic in the Adriatic-Dinaric Carbonate Platform and could be reached by charophytes after long-distance dispersal.

Palaeobiogeography of the genus Latochara (fossil Charophyta) in the Upper Jurassic of Southern Europe. New data from Oléron Island (France)

A charophyte assemblage including Latochara tenuicostata (PECK 1937) and Mesochara gr. voluta (PECK 1937) was found in the Lower Tithonian bone-bed 148 of the stratigraphic section at the Pointe de Chassiron, Oléron Island (Charente-Maritime, Southwestern France). This bed, which is well known for its rich and diverse fauna of tetrapods, was deposited in a margino-littoral environment of Purbeckian facies in the Late Jurassic Charente palaeogulf. The occurrence of Latochara at Oléron Island is the most southern location known in the distribution of this genus during the Late Jurassic. This suggests that the boundary between the charophyte Boreal and Tethyan provinces, defined on the basis of this distribution, is not solely determined by latitudinal (i.e. thermal) factors. Ecological factors such as salinity and competition with other charophyte families are hypothesized as alternative explanations.

Woodland in a fluvio-lacustrine environment on the dry Mongolian Plateau during the late Paleocene: Evidence from the mammal bearing Subeng section (Inner Mongolia, P.R. China)

In the understanding of the global faunal turnover during the Paleocene–Eocene transition, an important role has been attributed to the Asian continent, although the Asian fossil record for this period is still incomplete. Here we present a multidisciplinary study of the Subeng section (Inner Mongolia, P.R. China), integrating sedimentological, stratigraphical and diverse palaeontological data, in order to reconstruct the palaeoenvironment and to enhance the understanding of the late Paleocene communities that once thrived on the Mongolian Plateau. The Subeng section starts with the Maastrichtian Iren Dabasu Formation directly covered by the late Paleocene Nomogen Formation. This Nomogen Formation is composed of typical lacustrine deposits at the base, covered by fluvio-lacustrine deposits at the top. Both types of deposits provided rich ostracod and charophyte assemblages, closest to those of the Naran Member, Naran Bulak Formation of Mongolia. Palynomorphs from the lake sediments suggest a local flora at Subeng more wooded and closed than reported from elsewhere in this region. The fluvio-lacustrine deposits of the Nomogen Formation have yielded a vertebrate fauna especially rich in mammals. The mammal fauna from Subeng is close to that from Bayan Ulan and typical for the Gashatan Asian Land Mammal Age. The presence of reworked pedogenic carbonate nodules and mud aggregates suggests an at least seasonally dry regional climate. Combined sedimentological and palaeontological data suggest the late Paleocene Nomogen Formation at Subeng was an isolated woodland in a fluvio-lacustrine environment, representing a locally humid environment on the semi-arid Mongolian Plateau. The mammal fauna reflects these differences and shows a number of relatives to mammals from the more humid northeastern Chinese biotic province as well as some North American immigrants.

Quaternary charophytes from Salina del Bebedero, Argentina: their relation with extant taxa and palaeolimnological significance

Charophyte (Charales, green macroscopic algae) assemblages found in Quaternary shoreline sediments from Salina del Bebedero, Argentina, are described in detail, illustrated, and statistically analysed. Fossil gyrogonites, Late Pleistocene and Holocene in age, of Chara cf. hispida var. major (Hartman) Wood, Chara halina Garcia, Chara hornemannii Wallmann, Chara bulbillifera (Donterberg) Garcia, Lamprothamnium haesseliae Donterberg and Lamprothamnium succinctum (Braun ex Ascherson) Wood were identified. A comparison with extant charophyte species of similar ecological requirements allowed for an accurate systematical determination and provided useful data for complementary palaeoecological and palaeobiogeographical approaches. On this basis, a reconstruction of palaeo-salinities for the Salina del Bebedero lake, represented by eleven palaeo-beaches, is proposed. Also the associations of charophytes with the ostracods Cyprideis sp., Limnocythere sp., Pampacythere sp., Cypridopsis sp., Darwinula sp., Ilyocypris gibba (Randohr) Brady and Norman, and the foraminifers Ammonia sp., Elphidium gunteri Cole, Quinqueloculina sp., and one species of Discorbacea are analysed, since they are present in both the fossil and modern environments.

A charophyte flora from the Lower Pechelbronn Formation (?Upper Eocene/?Lower Oligocene) of Malsch south of Heidelberg (SW Germany)

Abstract. The Lower Pechelbronn Formation (?Upper Eocene/?Lower Oligocene) of Malsch (clay-pit ‘Am Viehweg’) yielded a moderately abundant charophyte assemblage. One new species, Chara rhenana sp. nov., is erected, two more species, Harrisichara lineata and Nitellopsis (Tectochara) cf. wonnacotti, are recorded in the Rhine Graben area for the first time. The Lower Pechelbronn Formation may be correlated to the Stephanochara vectensis zone (Riveline, 1986) and the mammalian level MP 20 (reference locality: St. Capraise; Schmidt-Kittler, 1987). The associated ostracod fauna clearly indicates a limnic depositional environment.

Correlation of Upper Jurassic-Lower Cretaceous continental sequences from the southern Biscay margin, northern Spain

Biostratigraphical data indicate that fresh-water carbonate deposits from the southern part of the the Cantabrian Basin, northern Spain are of earliest Cretaceous (Berriasian) age. Charophyte assemblages enable correlation with fresh-water carbonate rocks of the western Cameros Basin to the south. The charophytes also support correlation with Berriasian marginal marine carbonate sequences in the Jura Mountains, southern England and northern Germany, indicating that these continental carbonate rocks represent fresh-water equivalents of the 'Purbeckian' facies. The biostratigraphical correlation is enhanced by the parallel facies evolution observed in the Upper Jurassic-Berriasian of the Cameros and Cantabrian basins. Interpretation of these successions as non-marine depositional sequences permits member-scale correlation between the two basins. Further strong facies similarities in the overlying alluvial clastic rocks of the two areas suggest a revised correlation of the overlying Valanginian-Albian deposits. The two basins were connected at least intermittently during the Late Jurassic-Early Cretaceous; only during periods of higher sea-level did facies differences develop as a result of greater marine influence in the north. At other times, vast alluvial, lake and marsh systems extended over the region, leading to the deposition of genetically-related alluvial and lacustrine or palustrine deposits in these linked half-graben systems. In Cantabria and the Cameros Basin, strong lateral variations in facies, thickness and stratigraphy reflect erosion at the onset of Late Jurassic rifting, differential subsidence in the Early Cretaceous, and erosion beneath Aptian-Albian unconformities. Improved understanding of the successions described here may assist interpretation of similar Upper Jurassic-Lower Cretaceous sequences on the northern margin of the Biscay rift, such as those in the Wessex and North Celtic Sea basins.

Charophytes from Deccanintertrappean beds of peninsular India: Implications for age and correlation of Deccan volcanics

A taxonomically diverse charophyte assemblage from the Deccan intertrappean beds around Gurmatkal (District Gulbarga, Karnataka), and a corresponding assemblage from another intertrappean locality over 1500 Km to the north (Kora, District Kachchh, Gujarat), are described. The Gurmatkal assemblage comprises 8 genera and 10 species, whereas the Kachchh charophytes are assigned to 4 species. Several of the Gurmatkal taxa are common to other Deccan intertrappean localities of peninsular India. The assemblage includes cosmopolitan species such as Platychara perlata and P. compressa whose presence is consistent with a Late Cretaceous (Maastrichtian) age indicated unambiguously by associated ostracodes. Earlier age assignments (Upper Eocene-Oligocene) need to be discounted. Apparently there are no biostratigraphically resolvable temporal differences between the Gurmatkal intertrappean beds and those outcropping along the northwestern and eastern fringes of the Deccan volcanics.

Correlation of charophyte assemblages from the nonmarine Jurassic-Cretaceous transition of NW Germany

Based upon the first detailed study of the charophytes from the complete Upper Jurassic-lowermost Cretaceous (partly nonmarine) sequence of NW Germany, we distinguish eight successive assemblages which can be used as a local biozonation for the Lower Saxonian basin. Though charophytes cannot yet contribute to refined biozonations from the Oxfordian Korallenoolith up to the Tithonian Unterer Münder Mergel (assemblages 1–3) and in the late Berriasian-early Valanginian Wealden (assemblage 8), if compared with traditional ostracod/foraminifer biozones or palynozones, they are as useful as ostracods at the Jurassic-Cretaceous boundary (assemblages 4–5) and even better for correlation of the early Berriasian Serpulit and Purbeck (assemblages 6–7). Among other useful clavatoraceans, taxa principally from the Globator lineage present both short stratigraphic ranges and a large geographic distribution allowing: (a) the correlation of at least parts of the British lower Purbeck with the German Oberer Münder Mergel, Serpulit and Purbeck; (b) confirmation of the position of the Jurassic-Cretaceous boundary near the base of the Oberer Münder Mergel, as already proposed by ostracod workers; and (c) presentation of a more refined correlation of the assemblages from the Oberer Münder Mergel and Serpulit (Boreal realm) with the Early Berriasian biozones of the French and Swiss Jura (Tethyan realm).

Corrélation de la biozonation des Charophytes avec celle des Foraminifères (Orbitolinidés dans le Valanginien inférieur du Bassin du Maestrat (Castellò, Espagne)

A correlation between the biozonations of orbitolinidsand charophytes is established in the Lower Valanginian from the Polacos Formation (Maestrat basin, Castelló, east of Spain). This correlation is based on the presence of the charophyte association: Perimneste micrandra-Perimneste ancora (rare), Globator trochiliscoides (primitive), Embergerella stellata, Flabellochara harrisii and Porocharaceae in the levels underlaying and overlaying the banks with the orbitolinid Valdanchella miliani. This charophyte assemblage is similar to the flora of the “Olba zone” from Grambast (1974), which was hypothetically attributed to the Hauterivian. According to our correlation, the olba flora was atleast already existing in the Lower Valanginian. Provisionally, the biostratigraphic boundary between the Berriasian and the Valanginian can be characterized in the continental domain of Tethys by the disappearance of Globator nurrensis and the first appearance of Embergerella stellata. Uncertainty still exists in the chronostratigraphy of the charophyte biozonation during the Middle Valanginian to Upper Hauterivan time interval.

Freshwater fish otoliths from the Deccan Trap associated sedimentary (Cretaceous-Tertiary transition) beds of Rangapur, Hyderabad, District, Andhra Pradesh, India

The present paper describes 12 species of fish otoliths recovered by washing and screening processes from the Deccan Trap associated sedimentary (Intertrappean) beds exposed near Rangapur, Hyderabad District, Andhra Pradesh, India. The present collection of otoliths contains four major groups: Clupeomorpha (“ Clupeidarum” sp.), Osteoglossomorpha ( “Osteoglossidarum” deccanensis sp. nov., “O”. intertrappus sp. nov. and “Notopteridarum” nolfi sp. nov.), Protacanthopterygii (“Salmoniformorum” rectangulus sp. nov.), and Percomorpha ( Dapalis sp., “Apigonidarum” ovatus sp. nov., “Serranidarum” sp., “Percoideorum” ellipticus sp. nov., “P.” rangapurensis sp. nov., “ Percoideorum” sp. 1 and “ Percoideorum” sp. 2). This collection of otoliths represents freshwater lacustrine deposition of the sediments. The age of the Intertrappean beds is considered Uppermost Cretaceous to Palaeoncene on the basis of freshwater ostracode ( Paracypretta jonesi, Mongolianella hislopi and Candoniella sp.) and charophyte ( Platychara perlata and Nemegtichara sp.) assemblages.

The pleistocene palaeoenvironmental record of Lake Buchanan: An atypical Australian playa

Lake Buchanan is an “intermontane” playa located in subdued topography astride the Great Dividing Range in central Queensland. Undated multiple beach ridges on the western shore and cliffed lacustrine sediments on the eastern shore, both up to 5 m above the present lake-floor, attest to previous permanent-lake phases. Due to its position astride the continental divide for much of the Tertiary, Lake Buchanan probably escaped the acid weathering regime and attendant gypsum-formation of the continental interior. Present surface- and groundwaters (140–210% salinity) are atypical of other Australian salt lakes which are commonly Mg 2+-rich and similar to evaporated ocean water. For Lake Buchanan, ionic Ca 2+/Mg 2+ ≈, and the Sr 2+ (≈95 ppm) and F − (≈ 12 ppm) contents are very high, and Br − exceedingly low (<0.02 ppm). The unusual water compositions are considered to reflect the chemical composition of the attachment rocks which are Mesozoic and Tertiary clay-rich sandstones. This relationship argues against the universal applicability of marine aerosol transport and marine-salt recycling as sources of salts for Australian playas. Sediments cored from the lake floor are uniform non-laminated sandy clays composed of quartz (35 weight%), kaolinite (30%) and illite (25%). There is no primary chemically-precipitated carbonate or gypsum. Low-magnesium calcite occurs as a biogenic detritus of shelly fauna, charophyte gyrogonites and pedogenic nodules. Apart from the upper 20–50 cm, the sediment is devoid of organic carbon. A sequence of palaeosols indicates exposure of the lake floor during at least 13 episodes in the Pleistocene. For a 15-m core (BU-1), palaeomagnetic analysis has identified the Brunhes-Matuyama boundary (0.73 Ma) at 5.0 m; and probably the top of Jaramillo subchron (0.92 Ma) at 6.3 m. An extremely slow sedimentation rate of ≈7 m/Ma is indicated for the last 1 Ma. From 6.5 to 10.5 m in this core, intense iron-staining (pedogenesis) has confounded designation of palaeomagnetic polarity. Extrapolation might suggest an age of between 1.5 and 2 Ma for the base of this core. Fossil biota from BU-1 and BU-9 include abundant ostracods and charophyte remains, and less commonly gastropods, fish fragments and foraminifers. Water depth is interpreted from ostracod and charophyte assemblages. For the last 0.73 Ma we recognize four major wet phases. The early history of BU-1 (below 12 m, ≈16 Ma?) alternated between dry playa and shallow lake.