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Expedition 392 summary
Get PDFDuring International Ocean Discovery Program Expedition 392, three sites were drilled on the Agulhas Plateau and one site was drilled in the Transkei Basin in the Southwest Indian Ocean. This region was positioned at paleolatitudes of ~53°–61°S during the Late Cretaceous (van Hinsbergen et al., 2015) (100–66 Ma) and within the new and evolving gateway between the South Atlantic, Southern Ocean, and southern Indian Ocean basins. Recovery of basement rocks and sedimentary sequences from the Agulhas Plateau sites and a thick sedimentary sequence in the Transkei Basin provides a wealth of new data to (1) determine the nature, origin, and bathymetric evolution of the Agulhas Plateau; (2) significantly advance the understanding of how Cretaceous temperatures, ocean circulation, and sedimentation patterns evolved as CO2 levels rose and fell and the breakup of Gondwana progressed; (3) document long- and short-term paleoceanographic variability through the Late Cretaceous and Paleogene; and (4) investigate geochemical interactions between igneous rocks, sediments, and pore waters through the life cycle of a large igneous province (LIP). Importantly, postcruise analysis of Expedition 392 drill cores will allow testing of competing hypotheses concerning Agulhas Plateau LIP formation and the role of deep ocean circulation changes through southern gateways in influencing Late Cretaceous–early Paleogene climate evolution
Expedition 392 Preliminary Report: Agulhas Plateau Cretaceous Climate
Get PDFThe long-term climate transition from the Cretaceous greenhouse to the late Paleogene icehouse provides an opportunity to study changes in Earth system dynamics associated with large changes in global temperature and atmospheric CO2 levels. Elevated CO2 levels during the mid-Cretaceous supergreenhouse interval (~95–80 Ma) resulted in low meridional temperature gradients, and oceanic deposition during this time was punctuated by widespread episodes of severe anoxia termed oceanic anoxic events, resulting in enhanced burial of organic carbon in conjunction with transient carbon isotope and temperature excursions. The prolonged interval of mid-Cretaceous warmth and subsequent Late Cretaceous–Paleogene climate trends, as well as intervening short-lived climate excursions, are poorly documented in the southern high latitudes. International Ocean Discovery Program (IODP) Expedition 392 aims to drill five sites in the southwest Indian Ocean on the Agulhas Plateau and in the Transkei Basin, positioned at paleolatitudes of 65°–58°S during the Late Cretaceous (100–66 Ma) and in the new and evolving gateway between the South Atlantic, Southern Ocean, and southern Indian Ocean basins. Recovery of basement rocks and expanded sedimentary sequences from the Agulhas Plateau and Transkei Basin will provide a wealth of new data to (i) determine the nature and origin of the Agulhas Plateau and (ii) significantly advance the understanding of how Cretaceous temperatures, ocean circulation, and sedimentation patterns evolved as CO2 levels rose and fell and the breakup of Gondwana progressed. Importantly, Expedition 392 drilling will test competing hypotheses concerning Agulhas Plateau large igneous province formation and the role of deep ocean circulation changes through southern gateways in controlling Late Cretaceous–Paleogene climate evolution
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Resolución UNRN N° 392/2009. Contratar personal temporario
No full textFil: Universidad Nacional de Río Negro (U). Universidad Nacional de Río Negro. Río Negro, ArgentinaResolución UNRN N° 392/2009. Contratar personal temporariofals
Valentinian II coin, 375-392 AD
No full textValentinian IIVOT/X/MULT/XX in wreathNLAE 4EFKorbousThe Bill F. Kelso Collection of Ancient Coins contains coins from around the world. These ancient coins are from the following places and eras: Greece, Carthage, the Roman Republic and Empire, St. Constantine era, Byzantine, Arabic, China, and the Vandals. Also included are reference materials and photographs
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Cretaceous–Paleogene calcareous nannofossils from International Ocean Discovery Program Expedition 392 to the Agulhas Plateau, Southwest Indian Ocean
Get PDFInternational Ocean Discovery Program (IODP) Expedition 392 cored three sites on the Agulhas Plateau and one site in the Transkei Basin to address questions regarding the origin and timing of emplacement of Agulhas Plateau, as well as examine Southern Ocean climate history and opening of oceanic gateways from the Cretaceous through the Paleogene. Age models for the sites rely primarily on calcareous nannofossils and magnetostratigraphy, with dinoflagellates providing key events for some intervals, and additional contributions from planktonic foraminifers and diatoms. Site U1579, located in a basin on southern the central Agulhas Plateau, records a nearly continuous section dated to the Santonian to earliest Miocene. Dinoflagellates provide age control for the zeolitic sandstone and siltstone with glauconite at the base of the cored section. Above this, nannofossils are common to abundant and moderately preserved in upper Santonian to Maastrichtian calcareous chalks and the assemblages show Southern Ocean affinities. Paleogene nannofossils are abundant and moderately to well preserved. Sedimentation rates were lowest in the Eocene, which includes either condensed intervals or hiatuses. Nannofossils are well preserved in the Oligocene and assemblages consist of primarily mid-latitude species with occasional incursions of cold-water taxa. Site U1580 is also located on the southern Agulhas Plateau adjacent to a basement high. This site records several unconformities, and the lowermost part of the cored interval is interspersed with basalt layers interpreted as sills. The oldest sediment is likely uppermost Cenomanian in age. Overlying the shallowest basalt is Coniacian–Santonian silt- and sandstone with varying proportions of zeolites, glauconite, and carbonate. Sedimentation rates were very high (~10 cm/ky) during this time. Much of the early Campanian and mid-Maastrichtian is missing at this site. Paleocene nannofossils are moderately well preserved and suggest a continuous section with sedimentation rates of 1.5 cm/ky. Sedimentation rates increased in the late Paleocene to early Eocene, and nannofossils are quite well preserved through the Paleocene-Eocene Thermal Maximum and in the lower Eocene chalk/ooze. Site U1581 in the Transkei Basin includes a thick section of upper Campanian to Maastrichtian mudstone with occasional sandstone beds. Nannofossil are sparse but very well preserved through much of this interval, although preservation decreases with depth, concomitant with increasing siderite. The Cretaceous assemblages include both Southern Ocean and mid-latitude taxa. Reworking is common throughout the Cenozoic and this interval is also interspersed with hiatuses, especially in the Eocene and Miocene. Sedimentation appears to be more continuous from the latest Miocene to present, with sedimentation rates of ~2.8 cm/ky. Site U1582, cored on the northern Agulhas Plateau, includes only ~40 m of ooze and siliciclastic sediments overlying basement. Manganese nodules are common and the section is highly condensed, with at least 70 Myr represented. Future work will refine the age models for each site to provide a framework for the paleoclimatic and paleoceanographic studies planned by the expedition science party members
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