Biozones

Se trata de un trabajo de tesis en el cerro El Santísimo, Arivechi, Sonora, México, estudiando la geología del lugar centrandose en la paleontología de la secuencia de rocas calcáreas del Ordovícico Inferior al Superior mediante la identificación de conodontos y de sus respectivas biozonas, útil para el registro fósil del phylum Chordata en el NW de México.

The Mio-Pliocene deposits of Djebel Diss (Mostaganem, Northwestern Algeria) are mainly constituted of marls including gypsy-calcareous beds with whitish limestone and stromatolithic limestone, closely comparable to those of the Murdjadjo carbonate platform. The sample analysis from studied sections (Djebel Aizeub, Sidi Abd Allâh, Douar Amarna) revealed successive planktonic foraminifera bio-events allowing to identify six biozones (Neogloboquadrina acostaensis p.p., Sphaeroidinellopsis seminulina, Globorotalia. margaritae, G. puncticulata-G. margaritae, G. puncticulata and G. aemiliana p.p.), ranging from the Lower Tortonian to the Piacenzian stages. Thus, yellowish sandy marls and blue marls are attributed to the lower Tortonian (N. acostaensis p.p.), the Trubi marls to the Zanclean (S. seminulina, G. margaritae, G. puncticulata-G. margaritae) and to the Piacenzian stages (G. puncticulata and G. aemiliana p.p.). An important stratigraphic gap, corresponding to the upper Tortonian a...

Benthic foraminiferal assemblages from Nordaustlandet, Svalbard, are described for the first time with the objective of reconstructing the palaeoenvironmental conditions in the area during the late Quaternary. Investigations were carried out on marine deposits exposed along the southern shores of Murchisonfjorden. Five foraminiferal assemblages (A1–A5), representing different palaeoenvironmental conditions, were identified from the marine intervals, i.e., the Cassidulina reniforme–Elphidium albiumbilicatum assemblage (A1) from the Early Weichselian, the Islandiella helenae–Cibicides lobatulus assemblage (A2) from the Early Weichselian, the Cibicides lobatulus–Cassidulina reniforme assemblage (A3) from marine isotope stage 3, the Elphidium albiumbilicatum assemblage (A4) from the early Holocene and the Astrononion gallowayi assemblage (A5) from the mid-Holocene. Assemblages A1–A5 are compared with modern and fossil Quaternary assemblages from Arctic regions. Particularly notable is the fact that a well-defined Middle Weichselian assemblage in Svalbard is described for the first time, i.e., the Cibicides lobatulus–Cassidulina reniforme assemblage. All the assemblages from Nordaustlandet represent glacier-distal, inner-shelf environments with an open connection to the ocean. The results reveal the occurrence of three marine intervals (ice-free periods) in the north-western part of Nordaustlandet during the Weichselian, as well as ice-free conditions during most of the Holocene. A comparison of the assemblages from Nordaustlandet with previously published foraminiferal zones from onshore sections elsewhere in Svalbard show some degree of similarity, but also show considerable variation in species compositions, presumably caused by local environmental differences.

The last twenty years have seen important findings in the area of paleoanthropology. The topic of man evolution fascinated scientist since Linnaeus (1758). The findings of several new genera and new species enabled the reconstruction of evolutionary trends. These trends lead to the identification of the unique living species Homo sapiens Linnaeus, 1758 (Hominidae: Homininae), starting from the splitting between Homininae and Paninae. The history of hominins' evolution was a very long one. During time the entire group took several evolutionary directions, showing an high adaptive capacity to the changes of the paleoenvironmental conditions.
Coppens (2013) provided an interesting sub-division of geological time using fossil of hominins. From geological and paleoecological settings, this author distinguished four temporal phases to re-arrange the chronostratigraphic distribution of species of Hominidae by correlating homologous part of fossils and by analyzing paleontological associations. Each phase is characterized by taxonomic and ecological homogeneity, bio-events and evolutionary degree of taxa belonging to a well defined phyletic lines (Palombo & Valli, 2003-04). Those groups may be considered a sort of continental biozones. The aim of this project is to demonstrate the validity of these phases as biozones marked by hominins.

Coppens Y. (2013) - Hominid evolution and the emergence of the genus Homo. In "Neurosciences and the Human Person: New Persperctives of Human Activities", Pontifical Academy of Science. Scripta varia, 121: 1-15.

Linnaeus C. (1758). Systema naturae per regna tria naturae, secundum classis, ordines, genera, species cum characteribus, differentiis, synonymis, locis. 10th ed. Vol. 1. Laurentii Salvii, Stockholm, Sweden.

Palombo M.R., Valli A.M.F. (2003-04) - Remarks on the biochronology of mammalian faunal complexes from the Pliocene to the middle Pleistocene in France. Geol. Romana, 37: 145-163.

In the scope of the ratification of an international reference boundary for the Rupelian-Chattian transition, it is important to evaluate both stages in their original stratotype areas. In this study, quantitative analysis of benthic foraminifera of several boreholes in the historical Rupelian stratotype area enables recognition of biostratigraphic events in the upper Rupelian and the Chattian; we present a coherent bio-stratigraphic scheme for the Oligocene southern North Sea Basin. The Rupelian-Chattian interval is subdivided into eleven biozones, of which the lowermost four (interval I-IV) were defined by GRIMM & STEURBAUT (2001) and the overlying seven (interval V-XI) are newly defined herein. A correlation between the Oligocene benthic foraminiferal zonation scheme for the southern North Sea Basin and the adjacent areas is established. Finally, some potential problems for the future decision on an international reference boundary for the Rupelian-Chattian are discussed.

L’étude de la succession des calpionelles, sur plusieurs coupes levées dans l’alternance marno-calcaire du Berriasien du domaine rifain externe (Prérif et Mésorif), a permis de caractériser les différentes zones et sous-zones de calpionelles et d’apporter des précisions biostratigraphiques sur les zones B et C. La zone B a été subdivisée en trois sous-zones (B1, B2, B3), la zone C en deux sous-zones (C1, C2). Les trois sous-zones de la zone D (D1, D2, D3) ont été bien caractérisées.

Abstract: The ‘punctata Event’ (Early–Middle Frasnian transition , Late Devonian) was recently recognized as yet another episode of major geochemical perturbations associated with the Middle-Late Devonian ecosystem readjustments which culminated in the Frasnian-Fammenian (F/F) mass extinction event, one of five largest of the Phanerozoic. We report variations in total organic carbon (TOC), magnetic susceptibility (MS), major, minor and trace element proxies (for changes in detrital input, bioproductivity and redox conditions) across the P.punctata conodont biozone in the Western Canada Sedimentary Basin (Western Laurussia). Geochemical proxies and MS display similar trends, suggesting an intimate interdependence. The data is thus evaluated within 1) a regional sequence stratigraphic perspective and 2) the marine-terrestrial teleconnections model (Algeo & Sheckler, 1998), whereby the rise and expansion of arborescent vascular land plants (the first ‘true’ forests) results in a transi...

Les changements observes dans les associations des genres de conodontes, ou biofacies a conodontes, s'effectuent de maniere rapide et synchrone sur des durees inferieures a la duree d'une zone a conodontes. La resolution obtenue en suivant l'evolution de ces changements est donc beaucoup plus fine que celle basee sur la biozonation et a permis de localiser la base de l'evenement Kellwasser superieur quand il n'est pas lithologiquement visible et de mieux caler des sediments non fossiliferes.

A 4190-yr varve record from lake Saki (Crimea) was recently re -analyzed using five different spectral methods, applied both overall and to separate segments of the record (Xanthakis et al., 1995a). Here we consider its palaeoclimatic implications, spanning much of the Holocene Subboreal and Subatlantic biozones, and compare the spectra with those of planetary- sola r orbital and radiation periodicities. Linkage is found with both the data on harmonics of the Earth -Moon Milankovitch parameters, and with harmonics and resonances of (a) the major planets, (b) the proxy solar activity record disclosed by 14 C flux in the Stuiver and Braziunas dendroscronological record, and (c) the long-term observations of geomagnetics and auroras. The most significant (>95%) of the Xanthakis et al data are in the ranges 20-25, 44-46, 57-67, 120-130 and 200-250 yr (Liritzis and Fairbridge, 1998). All of these clusters are strongly represented in the spectra of both palaeoclimatic and astronomic fr...

Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with 40Ar/39Ar ages. Some 230 million years ago

Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with 40Ar/39Ar ages. Some 230 million years ago

Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with 40Ar/39Ar ages. Some 230 million years ago in the Late Triassic (mid Carnian), the earliest dinosaurs were the dominant terrestrial carnivores and small herbivores in southwestern Pangaea. The extinction of nondinosaurian herbivores is sequential and is not linked to an increase in dinosaurian diversity, which weakens the predominant scenario for dinosaurian ascendancy as opportunistic replacement.

Benthic foraminiferal assemblages from Nordaustlandet, Svalbard, are described for the first time with the objective of reconstructing the palaeoenvironmental conditions in the area during the late Quaternary. Investigations were carried out on marine deposits exposed along the southern shores of Murchisonfjorden. Five foraminiferal assemblages (A1–A5), representing different palaeoenvironmental conditions, were identified from the marine intervals, i.e., the Cassidulina reniforme–Elphidium albiumbilicatum assemblage (A1) from the Early Weichselian, the Islandiella helenae–Cibicides lobatulus assemblage (A2) from the Early Weichselian, the Cibicides lobatulus–Cassidulina reniforme assemblage (A3) from marine isotope stage 3, the Elphidium albiumbilicatum assemblage (A4) from the early Holocene and the Astrononion gallowayi assemblage (A5) from the mid-Holocene. Assemblages A1–A5 are compared with modern and fossil Quaternary assemblages from Arctic regions. Particularly notable is the fact that a well-defined Middle Weichselian assemblage in Svalbard is described for the first time, i.e., the Cibicides lobatulus–Cassidulina reniforme assemblage. All the assemblages from Nordaustlandet represent glacier-distal, inner-shelf environments with an open connection to the ocean. The results reveal the occurrence of three marine intervals (ice-free periods) in the north-western part of Nordaustlandet during the Weichselian, as well as ice-free conditions during most of the Holocene. A comparison of the assemblages from Nordaustlandet with previously published foraminiferal zones from onshore sections elsewhere in Svalbard show some degree of similarity, but also show considerable variation in species compositions, presumably caused by local environmental differences.