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Upper Cambrian (upper + cambrian)

Distribution by Scientific Domains
Earth and Environmental Science100%

Selected Abstracts

LATE CAMBRIAN PLECTRONOCERID NAUTILOIDS AND THEIR ROLE IN CEPHALOPOD EVOLUTION

PALAEONTOLOGY, Issue 6 2007
HARRY MUTVEI
Abstract:, Numerous plectronocerid nautiloids appear in the Upper Cambrian of China. We have restudied their siphuncular structure, first described some 20 years ago. The siphuncle is characterized by: (1) long and holochoanitic septal necks dorsally but short and recurved necks laterally and ventrally; (2) strongly expanded connecting rings laterally; (3) two calcified layers in each connecting ring, outer spherulitic-prismatic and inner compact, the latter perforated by numerous pore canals; and (4) highly oblique siphuncular segments. The strongly expanded lateral sides of the connecting rings, together with the highly oblique course of the siphuncular segments, considerably enlarged the surface area of the connecting rings in each chamber, thereby increasing the transport capacity of cameral liquid. Thus, from their first appearance, plectronocerid nautiloids had developed a siphuncle for the replacement of cameral liquid with gases, and this system had a better and a more sophisticated design than that seen in stratigraphically younger nautiloids. However, their small orthoconic or slightly cyrtoconic shells were not well adapted for jet-powered swimming. [source]

Cambrian Fossil Embryos from Western Hunan, South China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009
Xiping DONG
Abstract: The exquisitely preserved fossil embryos of Markuelia recovered from the limestones of the Middle Cambrian Haoqiao Formation and Upper Cambrian Bitiao formation in western Hunan, South China are described and illustrated in detail for the first time. A new species Markuelia elegans sp. nov. is established based mainly on embryos from the Upper Cambrian. A few of animal's resting eggs, which are comparable with those of the Ediacaran Doushantuo Formation, have been also found in the Upper Cambrian of western Hunan. The membrane of one egg from the uppermost Cambrian has been replaced by pyrite and the overgrowth of the pyrite crystals exhibits a unique inorganic pattern termed herein ,Pseudoembryo'. The taphonomic setting in deeper water with possible strong reducing conditions promoted the excellent preservation for the Markuelia specimens. The study of Markuelia provides not only constraint on the anatomy, affinity, embryonic development and phylogenetic significance of this wormlike animal and but also opens a new window onto the evolution and development of the earliest animals. [source]

Vestrogothia spinata (Phosphatocopina, Crustacea), Fossils of Orsten-type Preservation from the Upper Cambrian of Western Hunan, South China

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2009
Zheng LIU
Abstract: Fossils of Orsten-type preservation represented by the crustacean Skaracarida and Phosphatocopida were found in western Hunan, South China in 2005, including the important phosphatocopid species Vestrogothia spinata based on exquisitely preserved soft-bodied specimens that allow the first growth stage to be reestablished. The taxonomy of Vestrogothia spinata is revised employing the character of a two-divided limb stem of the mandible. A new foundation for the phytogeny of the Phosphatocopina using mandible characters related to crustacean appendages is postulated. Vestrogothia spinata has only previously been found from Sweden. [source]

Magnetostratigraphic constraints on the Gondwanan origin of North China: Cambrian/Ordovician boundary results

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2002
Zhenyu Yang
Summary A significant gap in the middle Palaeozoic apparent polar wander (APW) path precludes polarity definition of the early Palaeozoic palaeopole for North China. This problem can in part be resolved by the intercontinental correlation of magnetic polarity patterns across small time intervals. A magnetostratigraphic study was carried out on upper Cambrian to lower Ordovician sediments near Zhaogezhuang (long. 118.5°E, lat. 39.7°N), North China. After stepwise thermal or thermal and alternating field demagnetizations, a characteristic magnetic component with normal and antipodal reversed directions was identified. These data, drawn from 49 samples, yield a north palaeopole at long. 294.6°E, lat. 32.9°N (dp = 3.0°, dm = 5.3°). A concordant magnetic polarity pattern around the Cambrian,Ordovician boundary and lowest Ordovician obtained from different continents favours a Southern Hemisphere origin (,17°) formation site. Using the Cambrian,Ordovician APW paths between North China and Gondwana, we suggest that the North China block (NCB) was part of Gondwana during the Cambro,lowest Ordovician, and started breaking away from Gondwana in the lower Ordovician. This finding is contrary to some palaeomagnetic models where the NCB was quite separate from Gondwana in the late Proterozoic, and was attached to the ,Pacific' side of Antarctica. [source]

Cambrian high-resolution biostratigraphy and carbon isotope chemostratigraphy in Scania, Sweden: first record of the SPICE and DICE excursions in Scandinavia

LETHAIA, Issue 1 2009
PER AHLBERG
A core drilling (Andrarum-3), from the classical locality at Andrarum, Scania, southernmost Sweden, penetrated a 28.90-m-thick Cambrian succession. The core comprises dark grey to black, finely laminated mudstones and shales with early concretionary carbonate lenses (stinkstones or orsten) and a few primary carbonate beds. The middle Cambrian (provisional Series 3) part of the core comprises 17.35 m, whereas the Furongian Series (upper Cambrian) part covers the remaining 11.55 m. Nineteen trilobite and two phosphatocopine genera are present in the middle Cambrian, whereas the less diverse Furongian interval yielded four trilobite and three phosphatocopine genera. Other, less frequent, faunal elements include conodonts (s. l.), brachiopods, sponge spicules, bradoriids, and coprolites. Trilobites and phosphatocopines were used to subdivide the core into seven biozones ranging from the Ptychagnostus atavus Zone to the Parabolina spinulosa Zone (P. spinulosa Subzone). Carbon isotopic analyses (,13Corg) through the core show two important excursions, the negative DrumIan Carbon isotope Excursion (DICE) in the Pt. atavus Zone, and the Steptoean Positive Carbon Isotope Excursion (SPICE) beginning near the first appearance of Glyptagnostus reticulatus and extending upward into the Olenus and Agnostus (Homagnostus) obesus Zone. The DICE displays a peak value, in the samples at hand, of ,30.45,,13Corg in the lower part of the P. atavus Zone. The ,13Corg values increase through the overlying L. laevigata and A. pisiformis zones and display peak values of c. ,28.00,,13Corg in the lowermost Furongian Olenus wahlenbergi and O. attenuatus subzones. Thereafter the values decrease significantly through the O. scanicus Subzone. Both isotopic excursions have been documented from several palaeocontinents, but never before from Baltica. Moreover, for the first time these excursions are recorded from organic matter in an alum shale setting. The recorded shift of +1.50,2.00,,13Corg is approximately half the magnitude of the SPICE documented from other regions. This discrepancy may be related to temporal variations in the type, origin, or diagenesis of the organic fraction analysed. [source]