Late Neogene history of paleoproductivity and ice rafting south of Tasmania

2004 ◽  
pp. 253-272 ◽  
Author(s):  
Liselotte Diester-Haass ◽  
Stefan Nees
Keyword(s):  
Late Neogene ◽  
History Of ◽  
Ice Rafting

Stratophenetic tracing of phylogeny using SIMCA pattern recognition technique: a case study of the late Neogene planktic foraminiferaGloboconellaclade

Paleobiology ◽  
1994 ◽  
Vol 20 (1) ◽  
pp. 52-65 ◽  
Author(s):  
Kuo-Yen Wei
Keyword(s):  
Pattern Recognition ◽  
Morphological Variability ◽  
Principal Component ◽  
Pattern Recognition Technique ◽  
Evolutionary Patterns ◽  
Continuous Increase ◽  
Late Neogene ◽  
History Of ◽  
Classification Procedures ◽  
Recognition Technique

The Plio-Pleistocene planktic foraminiferal sequence of theGloborotalia(Globoconella)puncticulata-inflataclade in Deep Sea Drilling Project Site 588, dated at 4.36 Ma to 0.05 Ma, records the branching history of theG. inflatalineage from the ancestralG. puncticulatalineage. The gradational nature of the divergence and the enormous morphological variability inherent in theG. inflatalineage have elicited different views on taxonomy and phylogeny of this clade. A pattern recognition technique, soft independent modeling of class analog (SIMCA), was used as an objective quantitative stratophenetic methodology to reconstruct the phylogenetic history.Typical specimens of two species,G. puncticulataandG. inflata,were identified from a stratigraphic level dated at 2.76 Ma. Principal component models were built to characterize the morphometric patterns of the two morphotypes using SIMCA. TheGloboconellaspecimens of the next lower and higher adjacent stratigraphic levels were evaluated against the models and classified into one of the two morphotypes. The newly classified specimens were then used to build new models for further tracing of lineages in lower and upper sections, respectively. Progression of such training and classification procedures through stratigraphic intervals resulted in a reconstruction of the evolutionary patterns of the two lineages. Cladogenesis gave rise to the descendant lineage,G. inflata,at about 3.5 Ma. The two co-existing species,G. inflataandG. puncticulata,differ only in size and show similarity in most characters at the beginning of their divergence. Other characters began to diverge later, at various rates. The gradients between planktic and benthic foraminiferal δ18O values show a continuous increase during the late Pliocene. The succession fromG. puncticulatatoG. inflataduring the same time correlates with the progressively increased vertical stratification in temperature of surface waters.Globorotalia puncticulatabecame extinct at 2.35 Ma when the temperature gradient further increased, corresponding to the onset of extensive glaciation in the Northern Hemisphere.

The late Miocene to Pleistocene ice-rafting history of southeast Greenland

Boreas ◽  
2008 ◽  
Vol 31 (1) ◽  
pp. 28-35 ◽  
Author(s):  
KRISTEN E. K. ST. JOHN ◽  
LAWRENCE A. KRISSEK
Keyword(s):  
Late Miocene ◽  
History Of ◽  
Ice Rafting

Late Neogene marine Ostracoda from Tjörnes, Iceland

1991 ◽  
Vol 65 (5) ◽  
pp. 767-794 ◽  
Author(s):  
Thomas M. Cronin
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Warm Water ◽  
Early Pleistocene ◽  
The North ◽  
East Greenland Current ◽  
Late Neogene ◽  
History Of ◽  
Western Side ◽  
Glacial Tills

On the western side of the Tjörnes Peninsula in northern Iceland exposures of fossiliferous marine sediments, basalts, and glacial tills record the climatic history of this region of the North Atlantic Ocean. Seventy-five marine ostracode species were recovered from the Pliocene Tjörnes sediments and Quaternary sediments known as the Breidavik beds. The ostracode assemblages contain many warm-water genera that do not inhabit Iceland today and indicate early to middle Pliocene (4.5–3.0 Ma) winter and summer bottom-water temperatures that averaged 5–6°C and 14–16°C, respectively (maximum 20°C in summer, rarely below 3°C in winter except during a brief cooling 3.5–3.2 Ma). An intensified North Atlantic Drift and a diminished or absent East Greenland Current account for warm-water oceanographic conditions at 66°N. Late Pliocene marine climates were cooler with winter and summer averages of about 9°C and 8°C. Early Pleistocene ostracode assemblages dated at 1.7–1.3 Ma contain extant arctic–subarctic species that indicate winter and summer temperatures of about − 1.5°C and 4–5°C. New speciesBensonocythere eirikssoni, Robertsonites williamsi, Hemicythere rekaensis, Thaerocythere mayburyae, Thaerocythere whatleyi, Leptocythere tjornesensis, Tetracytherura bardarsoni, andCytheromorpha einarssoniare described.

Discussing the dating of ferruginous duricrusts: promises from mineralogy of supergene minerals with non-destructive microsampling

2020 ◽  
Author(s):  
Karina Marques ◽  
Thierry Allard ◽  
Guillaume Morin ◽  
Benoît Baptiste ◽  
Cécile Gautheron ◽  
...  
Keyword(s):  
Mineralogical Composition ◽  
Alluvial Fan ◽  
Secondary Minerals ◽  
Origin And Evolution ◽  
Late Neogene ◽  
Erosion History ◽  
Powder Samples ◽  
History Of ◽  
Different Populations ◽  
Fine Resolution

<p>Ferruginous duricrusts record a part of the Earth’s geodynamical and climatic history in tropical area, because they can be formed over a wide geologic period. However, the events and processes related to their formation, transformation and distribution are still obscure. This is mainly due to the complexity arising from their finely divided and polycrystalline nature together with the coexistence of various generations of supergene minerals, such as iron and aluminum oxides, oxyhydroxides or hydroxides (e.g. goethite, hematite and gibbsite) and kaolinite, even at microscopic scale. Classical mineralogical investigations are often realized using powders samples, which hinders subsequent analyses on the same sample, such as SEM or (U-Th)/He dating. Thus, the aim of this study was to propose a new way to investigate the mineralogy of supergene ferruginous samples on micrometric grains that will be analyzed by (U-Th)/He dating method. Prior to this analysis, we first compare the X-ray diffraction data of grains and small amounts of powders looking to reveal the mineralogical composition of populations of secondary minerals of a ferruginous duricrust by taking into account the heterogeneity of the material. Samples were collected from a ferruginous duricrust with pisolitic structure developed over epiclastic conglomerates and sandstones deposited by alluvial fan and fluvial streams from the Upper Cretaceous at the western Minas Gerais state (Brazil). The geomorphology of the study area is delineated by remnants of paleosurface (up to 1,000 m a.s.l.), which comprises an important record of long-term Brazilian continental history.Macroscopic facies recognized on duricrusts sections were described, which allowed the identification of various populations of secondary minerals. After this detailed description, grains (size < 0.5 mm) were collected and powder samples of each population were prepared by crushing. Overall, the results point out that the grain and powder samples could be used to identify mineralogical composition at fine resolution of secondary minerals from ferruginous duricrusts. In addition, XRD results are similar for both types of sample preparation, however the < 0.5 mm grain samples are more advantageous because they are not destructive and thus allow to get a finer description of the mineralogy of different populations and can subsequently be used for e.g. (U-Th)/He dating, providing critical information for interpreting and discussing the ages of iron oxides.</p><p><strong>Grant:</strong> 19/10708-7; 17/22292-4; 17/20788-2, São Paulo Research Foundation (FAPESP)</p><p><strong>References</strong></p><p>Allard, T., Gautheron, C., Riffel, S.B., Balan, E., Soares, B.F., Pinna-Jamme, R., Derycke, A., Morin G., Bueno, G.T., Nascimento, N., 2018. Combined dating of goethites and kaolinites from ferruginous duricrusts. Deciphering the Late Neogene erosion history of Central Amazonia. Chemical Geology 479, 136-150.</p><p>Monteiro, H.S., Vasconcelos, P.M.P., Farley, K.A., Spier, C.A., Mello, C.L., 2014. (U-Th)/He geochronology of goethite and the origin and evolution of cangas. Geochim. Cosmochim. Acta  131, 267–289.</p><p>Vasconcelos, P.M., Heim, J.A., Farley, K.A., Monteiro, H.S., Waltenberg, K., 2013. <sup>40</sup>Ar/<sup>39</sup>Ar and (U–Th)/He - <sup>4</sup>He/<sup>3</sup>He geochronology of landscape evolution and channel irondeposit genesis at LynnPeak, Western, Australia. Geochim. Cosmochim. Acta 117, 283-312.</p>

scholarly journals Late Neogene history of the laurel tree (LaurusL., Lauraceae) based on phylogeographical analyses of Mediterranean and Macaronesian populations

2009 ◽  
Vol 36 (7) ◽  
pp. 1270-1281 ◽  
Author(s):  
Francisco Rodríguez-Sánchez ◽  
Beatriz Guzmán ◽  
Alfredo Valido ◽  
Pablo Vargas ◽  
Juan Arroyo
Keyword(s):  
Late Neogene ◽  
History Of
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