Sökning: "Oligocene"

Visar resultat 1 - 5 av 19 avhandlingar innehållade ordet Oligocene.

1. 1. Late Eocene through Oligocene calcareous nannofossils from the paleo-equatorial Pacific Ocean – taxonomy, preservation history, biochronology and evolution

   Författare :Teodora Blaj; Jan Backman; Jorijntje Henderiks; Isabella Raffi; Paul Bown; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; marine sediments; calcareous nannofossils; late Eocene; Oligocene; biochronology; evolution; morphometry; taxonomy; ODP Leg 199 Site 1218; paleo-equatorial Pacific Ocean; Historical geology and palaeontology; Historisk geologi och paleontologi; Marine Geoscience; marin geovetenskap;

   Sammanfattning : This study aims to unravel the ecological and evolutionary dynamics within the calcareous nannofossil communities at the Eocene/Oligocene (E/O) transition and during the Oligocene time when Cenozoic 'icehouse' conditions were established. The main question this study aims to answer is whether the changes in the nannofossil assemblages were controlled by intrinsic evolutionary trends or if the changes were controlled by environmental factors such as changes in temperature and nutrient availability in the surface water. LÄS MER

3. 2. The metamorphic history of Naxos (central Cyclades, Greece) : Deciphering the Oligocene and Miocene exhumation events

   Författare :Alexandre Peillod; Uwe Ring; Alasdair Skelton; Arne Willner; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Cycladic Blueschist Unit; exhumation; fluid flow; geothermobarometry; Hellenide orogen; Rb-Sr dating; subduction-zone metamorphism; Heat flow; Lower crust; extensional domain; Metamorphic core complex; Geology; geologi;

   Sammanfattning : High pressure, low temperature (HP-LT) rocks observed at the surface of the Earth are evidence ofpast subduction zones. Understanding the tectonics processes that control the exhumation of HP-LT metamorphic rocks in these subduction zones requires full comprehension of the pressure-temperature-time (P–T–t) cycle that the rocks experienced. LÄS MER

4. 3. The Greenhouse - Icehouse Transition : a dinoflagellate perspective

   Författare :Caroline A. van Mourik; Henk Brinkhuis; Malgorzata Moczydlowska-Vidal; Stockholms universitet; []
   Nyckelord :Eocene - Oligocene; dinoflagellate cysts; biostratigraphy; paleoecology; NATURAL SCIENCES; NATURVETENSKAP;

   Sammanfattning : Through the analysis of the stratigraphic and spatial distribution of organic walled dinoflagellate cysts (dinocysts) from climatologically and oceanographically key sites, this project aims to contribute to a better understanding of the Eocene-Oligocene (E/O) environmental changes and their timing. A central issue is to identify the global environmental changes which are responsible for the Eocene cooling and its underlying mechanisms with the focus on the Oligocene isotope-1 (Oi-1) event, thought to mark the onset of major Antarctic glaciation. LÄS MER

5. 4. Late Oligocene through late Miocene calcareous nannofossil biostratigraphy and biochronology

   Författare :Gunnar Olafsson; Stockholms universitet; []
   Nyckelord :;

   Sammanfattning : .... LÄS MER

7. 5. How were high-pressure rocks exhumed in Naxos, Greece?

   Författare :Alexandre Peillod; Uwe Ring; Johannes Glodny; Alasdair Skelton; Joakim Mansfeld; Jaroslaw Majka; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; extrusion wedge Naxos petrology metamorphism; Mineralogy; Petrology and Geochemistry; mineralogi; petrologi och geokemi;

   Sammanfattning : Combining petrological and geochronological data we were able to show that rocks in south Naxos completed a full blueschist-/greenschist-facies metamorphic loop in about 10 Myr, distinctly faster than hitherto believed. We show that the high-pressure rocks reached peak pressure (16.3±0.9 kbar - 619 ±32°C) between 40. LÄS MER