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Search Results: 1 - 10 of 356 matches for " Miocene "
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Diatoms from Middle Miocene Continental Deposits of Primorye  [PDF]
Olesya Yu. Likhacheva
Journal of Geoscience and Environment Protection (GEP) , 2014, DOI: 10.4236/gep.2014.23012
Abstract:

Diatoms from Middle Miocene deposits of Khanka Lake’s northwestern shore (Primorye) were studied using light and scanning microscopes. The analyses of diatom flora composition and species diversity showed that there was a dominace of several taxa that made possible the recognition of two diatom complexes. The lower complex differs from the upper one by higher species diversity, by presence of many subtropical diatoms and absence of pronounced dominant species. Differences between the complexes can be explained by the progressing climatic cooling and predominance of fluvial-lakustrine sedimentation over the typically lake one due to development of a wide system of river valleys.

Characterization and Origin of the Miocene Mudawwara-Quwayra Basaltic Dike, Southern Jordan  [PDF]
Hani Alnawafleh, Khaled Tarawneh, Khalil Ibrahim, Khitam Zghoul, Awad Titi, Rami Rawashdeh, Khaled Moumani, Ahmad Masri
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.68071
Abstract: Petrographic, mineralogical and geochemical investigations were carried out on representativesamples from the Mudawwara-Quwayra Dike (MQD) in southernJordan. The MQD intruded Paleozoic and Cretaceous rocks as sub-vertical basaltic plugs, striking NW-SE along a fault zone and extending for more than 100 km. The MQD forms irregularly positive features, and is represented by symmetrical, elliptical, elongated or circular hills. It comprises thin basaltic layers intercalatedwith pyroclastics and inclusions of different size and lithology, including limestone, sandstone, phosphate, quartzite, and marble. Petrographically, the rock exhibits phyric, porphyritic, vitrophyric and locally glomerophyritic textures manifested by plagioclase, clinopyroxene and rareolivine and set in a matrix of plagioclase, pyroxene, brown glass and opaque phases. Clinopyroxeneand olivine phenocyrsts show disequilibrium textures such as reaction/resorbed rims in theforms of corroded ends. The paragenetic sequence shows that olivine is the first phase to be crystallized and coexisting with pyroxene at sometime, while pyroxene continues crystallization. Plagioclase might have crystallized in contemporaneous later than the pyroxene. The MQD rocks are classifiedas basalt and exhibit a narrow range of silica with a unique subalkaline affinity. This is mostprobably attributed to assimilation of the abundant siliciclastic inclusions by the ascending magma. Emplacement of the MQD is attributed to regional phase of
New Data on the Upper Miocene Presence in the Aegean Region: The Geological Evolution of Spetses Island, Peloponnesus, Greece  [PDF]
Evdoxia E. Lykoudi
Open Journal of Geology (OJG) , 2014, DOI: 10.4236/ojg.2014.43006
Abstract:

Based on detailed geological and geomorphological mapping, sampling and micro-palaeontological determinations, both of the alpine and neogene formations, new data have been derived for Spetses Island (SW Aegean). The applied methodology provided results on the paleogeographic evolution for Spetses Island and the nearby land of Argolida peninsula as well. Based mainly on characteristic nannofossils, a Miocene age of the post-alpine formations is determined. It is the first time that miocene formations have been identified, not only in Spetses Island and Argolida, but in the whole area of Peloponnesus, where only Plio-pleistocene deposits have been described. This work also leads to the conclusion that Spetses Island is attached to the Argolida peninsula, forming an independent paleogeographic unit since Upper Miocene.

Analysis of Structure and Textures of Anhydrite Mineral in Gachsaran Formation in Gotvand Area, Iran  [PDF]
Maryam Marandi, Davood Jahani, Ali Uromeihy, Majid Karimpour Reihan
Open Journal of Geology (OJG) , 2017, DOI: 10.4236/ojg.2017.710099
Abstract: Minerals are deposited when evaporation is greater than atmospheric precipitation. Calcium sulfates are one of the most important evaporative minerals which have been expanding over the past few years. In the formation of these minerals, various sedimentary and diagenetic processes play a role from shallow ridges to deep water. The research investigated the types of evaporative minerals (with an emphasis on anhydrite) in Gachsaran Formation in Gotvand dam range (25 km north of Shoushtar city). Investigating the thin sections of evaporative samples of this formation led to the identification of various anhydrite textures. Also, the existence of the main phases of calcium sulfate and NaCl by XRD analyses on a number of samples. The formation of anhydrite, gypsum and halite minerals in Gachsaran Formation in Lagoon and Sabkha environments was identified texture. The most important textures were laths anhydrite, nodule, isolated, radial anhydrite crystals, and porphyroblastic gypsum crystals, most of which are formed at the same stage of precipitation or in the early stages of diagenesis.
Revisión del género Stegotherium Ameghino, 1887 (Mammalia, Xenarthra, Dasypodidae)
Fernicola,Juan Carlos; Vizcaíno,Sergio Fabián;
Ameghiniana , 2008,
Abstract: a taxonomic revision of the genus stegotherium ameghino is presented herein. the diagnoses of stegotherium tessellatum ameghino and stegotherium variegatum ameghino are emended, the validity of stegotherium simplex (ameghino) is tentatively maintained, and two new species stegotherium caroloameghinoi and stegotherium pascuali are erected. exhaustive study of the fossils collected and/or studied by the ameghino brothers has resulted in relocation of the type specimens, fossils that had been partially or completely misplaced, of stegotherium tessellatum and stegotherium variegatum.
Hallazgos de restos fósiles de Hyperoodon sp. (Cetacea, Ziphiidae) en las costas gallegas (NO Espa?a)
Miján,Ismael;
Revista de biología marina y oceanografía , 2007, DOI: 10.4067/S0718-19572007000300005
Abstract: the frequent finding of fossil data of cetaceans in the galician deep seas reveals us the existence of a very important cetacean paleontological deposit that placement is over 300 meters deep. moreover the discovering of globicephalinae rostra, mysticets tympanics and other rests highly degraded, the findings of two hyperoodon sp. skulls from miocene which are in a excellent conservation condition suppose one of the rare evidences of the primitive hyperoodon and probably it means new species no described yet more plesiomorfic than known ones in this genre
Whale vertebra from Miocene beds in Turje near Dol pri Hrastniku, Slovenia
Vasja Miku?
Geologija , 1998,
Abstract:
When did Sardinia rotate? Statistical evaluation of the paleomagnetic data
M. Todesco,L. Vigliotti
Annals of Geophysics , 1993, DOI: 10.4401/ag-4250
Abstract:
Chondrichthyan Fauna from the Pirabas Formation, Miocene of Northern Brazil, with Comments on Paleobiogeography
Márcia Aparecida Fernandes dos Reis
Anuário do Instituto de Geociências , 2005,
Abstract: The chondrichthyan fauna from the Pirabas Formation is redescribed. Only thirteen nominal taxa are considered valid. From these taxa, ten were reassigned to extant taxa (Carcharhinus sorrah, Carcharhinus perezii, Galeocerdo cuvier, Rhizoprionodon lalandii, Sphyrna sp., Hemipristis elongatus, Carcharodon carcharias, Isurus oxyrinchus, Nebrius ferrugineus, and indeterminate Myliobatidae), confirming the Neogene age of this formation. This elasmofauna is compared with other Caribbean and African Tertiary faunas.
Elaboration of the Hydro-Geophysics GIS Showing the Volubilis Depression and the Prerifains Ridges Structuration (Morocco North Occidental)  [PDF]
Asma Ben Moussa, Abdelaziz Mridekh, Bouabid El Mansouri, Ahmed Manar, Mohamed Chibout
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.66050
Abstract: We present a comparative analysis of electrical and gravity data on the Geographic Information System of the prerifaines ridges. At the Meso-Cenozo?c sequence, the geometry of the prerifaines ridges is fairly well known. However, the post-Miocene series remain to be characterized. In this perspective, we use a database composed of gravity and vertical electrical sounding profiles and geo-electrical sections in order to characterize this structuration. These data are calibrated by many oil and hydrogeological boreholes. Preliminary results lead to better understanding of the organization of its underlying structures in this area. The Gravimetric filtering results show that the area may be dissected by tree major faults striking NW-SE, NE-SW and N-S. All these faults have contributed, since Hercynian to Alpines orogenies, to the structuring of this area, being proved to be the deepest and can reach 4500 m. The comparison of gravity maps, geological and structural maps under Geographic Information System allows the identification of major structural directions and trends of the study area. It confirms some structural elements gathered from outcrops and define new ones. Results from this work show the importance of using various filtering and interpretation techniques in the analysis of gravity data. They also provide news insights into the deep structure of the study area.
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