Accelerator Mass Spectrometry at Arizona: Geochronology of the Climatic Record and Connections with the Ocean

There are many diverse uses of accelerator mass spectrometry (AMS). 14C studies at our laboratory include much research related to paleoclimate, with 14C as a tracer of past changes in environmental conditions as observed in corals, marine sediments, and many terrestrial records. Terrestrial records can also show the influence of oceanic oscillations, whether they are short term, such as ENSO (El Niño/Southern Oscillation), or on the millennial time scale. In tracer applications, we have developed the use of 129I as well as 14C as tracers for nuclear pollution studies around radioactive waste dump sites, in collaboration with IAEA. We discuss some applications carried out in Tucson, AZ, for several of these fields and hope to give some idea of the breadth of these studies

RECONSTRUCTION OF 130-KYR RELATIVE GEOMAGNETIC INTENSITIES FROM Be-10 IN TWO CHINESE LOESS SECTIONS

Efforts to extract weak geomagnetic excursion signals from Chinese loess-paleosol 10Be have generally been unsuccessful due to the complexities of its accumulation, because the geomagnetic and climate (precipitation and dust) signals contained in loess-paleosol sequence are tightly overprinted. Here, we present a reconstruction of geomagnetic relative paleointensities for the past 130 kyr from 10Be records in 2 Chinese loess-paleosol sections using a correction based on the correlation of 10Be with magnetic susceptibility (SUS) to remove the climatic contamination. Both these records reveal the Laschamp and Blake events, which lie in the loess and paleosol (L1SS1 and S1SS3) horizons corresponding to mid-MIS 3 and 5e, respectively. The good agreement between our results and other geomagnetic intensities reconstructions from Atlantic and Pacific sediments indicates that our method is robust. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Cionodendron and related lithostrotionid genera from the Mississippian of eastern Australia: systematics, stratigraphy and evolution

Denayer, J. & Webb, G.E., 26.2.2015. Cionodendron and related lithostrotionid genera from the Mississippian of eastern Australia: systematics, stratigraphy and evolution. Alcheringa 39, xxx–xxx. ISSN 0311-5518. The Mississippian colonial rugose corals of eastern Australia are taxonomically reviewed and assigned to formal genera. Their homeomorphy with the Eurasian genera Siphonodendron and Lithostrotion but also Heterostrotion resulted from parallel evolution within the Lithostrotionidae. Fasciculate species are reassigned to Cionodendron, as they share a robust columella, septotheca and two series of tabellae. Based on common characters, three species groups are recognized: the C. columen Group (characterized by the occurrence of parricidal and non-parricidal increase), the C. hallense Group (development of second-order lonsdaleoid dissepiments) and the C. arundineum Group (lacking the previous characters). Fourteen species are recognized, one being new (C. smithi sp. nov.) and two documented for the first time in the area. The oldest species are late Tournaisian in age, but the genus is most diverse in the middle–late Visean. Several morphological lineages are recognized within the three groups. The massive species are classified in the newly erected genus Australastraea that likely evolved from one of the early species of Cionodendron in the early Visean. Eleven species were identified, two being newly described (A. arcifera, sp. nov., A. carinata sp. nov.) and two others documented for the first time. Australastraea is characterized by a septotheca that is commonly discontinuous, conferring a pseudo-cerioid or astreoid habit. Two morphological groups are identified: the A. wilkinsoni Group (small corallites with simple narrow dissepimentarium) and the A. columnare Group (large corallites with complex dissepimentarium). The small fasciculate species previously referred to Lithostrotion williamsi are here reassigned to the new genus Pickettodendron, which differs from Cionodendron by the lack of minor septa and presence of a complete tabularium but is, nevertheless, relatively closely related to that genus. Pickettodendron is represented by three species, one being new (P. nudum sp. nov.), and is restricted to the early (–‘middle’) Tournaisian. A polyphyletic origin of the Cionodendroninae is considered, with Cionodendron and Australastraea originated in a first species of Amygdalophyllum and Pickettodendron originated in a second one. The biostratigraphic value of the Cionodendroninae is currently limited owing to the poor stratigraphic coverage of appropriate facies but correlations were made possible by the identification of A. columellaris and C. consanguineum in the early Visean of New South Wales and Queensland, and A. columnare and A. sp. in the middle–late Visean of both states. The Cionodendroninae assemblages of eastern Australia are strongly endemic and possibly represent one of the scarce remains of the Panthalassa Province. Julien Denayer [[email protected]], Evolution and Diversity Dynamics Lab, Geology Department, University of Liège, B18, Allée du Six-Août, Sart Tilman, B-4000 Liège, Belgium; Gregory E. Webb [[email protected]], Integrated Palaeoenvironmental Research Group, School of Earth Sciences, University of Queensland, QLD 4072, St-Lucia, Australia