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- Schmitz, Birger, et al.
(författare)
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The Global Stratotype Sections and Points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain
- 2011
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Ingår i: Episodes. - 0705-3797. ; 34:4, s. 220-243
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Tidskriftsartikel (refereegranskat)abstract
- The global stratotype sections and points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages have been defined in the coastal cliff along the Itzurun Beach at the town of Zumaia in the Basque Country, northern Spain. In the hemipelagic section exposed at Zumaia the base of the Selandian Stage has been placed at the base of the Itzurun Formation, ca. 49 m above the Cretaceous/Paleogene boundary. At the base of the Selandian, marls replace the succession of Danian red limestone and limestone-marl couplets. The best marine, global correlation criterion for the basal Selandian is the second radiation of the important calcareous nannofossil group, the fasciculiths. Species such as Fasciculithus ulii, F. billii, F. janii, F. involutus, F. pileatus and F. tympaniformis have their first appearance in the interval from a few decimetres below up to 1.1 m above the base of the Selandian. The marker species for nannofossil Zone NP5, F. tympaniformis, first occurs 1.1 m above the base. Excellent cyclostratigraphy and magnetostratigraphy in the section creates farther correlation potential, with the base of the Selandiatz occuring 30 precession cycles (630 kyr) above the top of magnetochron C27n. Profound changes in sedimentology related to a major sea-level fall characterize the Danian-Selandian transition in sections along the margins of the North Atlantic. The base of the Thanetian Stage is placed in the same section ca. 78 m above the Cretaceous/Paleogene boundary. It is defined at a level 2.8 m or eight precession cycles above the base of the core of the distinct clay-rich interval associated with the Mid-Paleocene Biotic Event, and it corresponds to the base of magnetochron C26n in the section. The base of the Thanetian is not associated with any significant change in marine micro-fauna or flora. The calcareous nannofossil Zone NP6, marked by the first occurrence of Heliolithus kleinpelli starts ca. 6.5 m below the base of the Thanetian. The definitions of the global stratotype points for the bases of the Selandian and Thanetian stages are in good agreements with the definitions in the historical stratotype sections in Denmark and England, respectively.
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| 2. |
- Pujalte, Victoriano, et al.
(författare)
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Sea-level changes across the Paleocene-Eocene interval in the Spanish Pyrenees, and their possible relationship with North Atlantic magmatism
- 2014
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 393, s. 45-60
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Tidskriftsartikel (refereegranskat)abstract
- The issue of whether major and rapid global sea-level changes existed on a preglacial Earth can be resolved by the detailed study of the Paleocene-Eocene (P-E) interval, where a large and rapid carbon isotope excursion linked to an important global warming event, the Paleocene Eocene Thermal Maximum, allows for high-resolution correlation between terrestrial, coastal and marine settings. Based primarily on outcrop and borehole information from the Tremp-Graus Basin in the southern Spanish Pyrenees, it is shown that a sea-level fall of at least 20 m occurred less than 75 kyr prior to the PETM. This forced a seaward displacement of the shoreline of ca. 20 km, a widespread incision of valleys in the alluvial plains and the subaerial exposure and excavation of the adjacent marine carbonate platform. The subsequent sea-level rise caused the infilling of the incised valleys, a process completed before the onset of the PETM, and continued rising during and after the event, leading to the aggradation of the alluvial plain and eventually to the transgression of the whole Tremp-Graus Basin. However, the sea level did not regain its pre-fall position until near the end of the PETM. Therefore, although rising, the sea level was comparatively low in the southern Pyrenean area during most of the PETM. The pre-PETM sea-level fall has been reported in other basins of the southern Pyrenees, in the North Sea area, the Austrian Alps and in Egypt, and the subsequent sea-level rise has been documented in widely separated sites around the Earth, an evidence of their global (eustatic) scope. The causal mechanism(s) of the pre-PETM sea-level fall is (are) unresolved, although glacioeustasy may have played a role. The subsequent sea-level rise was most likely caused by tectonomagmatic activity in the North Atlantic. (C) 2013 Elsevier B.V. All rights reserved.
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