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- Larsson, Linda, et al.
(författare)
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Miocene climate evolution of northern Europe: A palynological investigation from Denmark
- 2011
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 1872-616X .- 0031-0182. ; 309:3-4, s. 161-175
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Tidskriftsartikel (refereegranskat)abstract
- A palynological investigation has been conducted on Lower-Upper Miocene sediments from Jylland, Denmark, corresponding to the time interval of about 19 to 8 Ma. The sediments, derived from the Sdr. Vium drill core, were deposited in marine to marginal-marine environments, as shown by the relatively high abundance of dinoflagellate cysts in all samples. Nevertheless, rich and diverse pollen assemblages occur throughout the succession and the palynological analysis reveals that coastal areas of the study area were during the Miocene dominated by Taxodium swamp forests that also hosted terrestrial angiosperms such as Nyssa, Betula, Alms and elements of the Myricaceae. Further inland, a mixed deciduous-evergreen forest prevailed. In areas with better drained soils, or on elevated areas, gymnospermous conifer forests prevailed including taxa such as Pinus, Sequoia and Sciadopitys. Overall, the climate in the study area was warm temperate during major parts of the Miocene with mean annual temperatures between 15.5 and 20 degrees C. By employing the Coexistence Approach combined with the method of allocating taxa into standardized climatic groups, four different climatic Miocene events are detected within the studied succession correlated to the coeval climate record of northwestern Europe. The oldest event is a cooling during the earlier Burdigalian, at approximately 19 Ma, coinciding with the MBi-1 oxygen isotope excursion. At ca. 18.5 Ma (in mid-Burdigalian) a warming phase is reconstructed, characterized by the highest precipitation rates observed in the sedimentary succession. A warming trend, starting in the latest Burdigalian, corresponds to the globally recognized Middle Miocene Climatic Optimum (MMCO) while a longer-term late Neogene cooling was initiated in the mid Serravallian, about 13 Ma. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Larsson, Linda, et al.
(författare)
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Vegetation and climate in the latest Oligocene-earliest Miocene in Jylland, Denmark
- 2010
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Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 159:3-4, s. 166-176
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Tidskriftsartikel (refereegranskat)abstract
- Two exposures in Jylland, Denmark, encompassing beds of latest Oligocene to earliest Miocene age (latest Chattian-early Aquitanian) yielded well-preserved palynofloras. The assemblages indicate that Jylland was covered by extensive Taxodiaceae swamp forests in the mid-Cenozoic. Besides a Taxodiaceae-Cupressaceae association, which was overwhelmingly dominant, other common plants in this habitat were Alnus, Nyssa, Betula, Salix, Cyrilla and Myrica. Most of the trees and shrubs are well adapted to swamps and thrive under more or less flooded conditions in modern bald cypress swamps of the southeastern North America. Vegetation composition indicates that a warm-temperate climate prevailed in Denmark during the Oligocene-Miocene transition. According to calculations using the Coexistence Approach, the mean annual temperature during this time span ranged from 15.6 to 16.6 degrees C. An increase to 16.5-21.1 degrees C is inferred from the palynoflora in the upper part of the section. The earlier, cooler period possibly reflects global cooling associated with the Mi-1 glaciation event at the Oligocene-Miocene boundary. No data from the very coldest part of the Mi-I event has been recorded, as this is represented by a gravel layer (representing a hiatus) in the lowermost part of the studied succession. The length of the missing time is not known precisely, but is probably in the order of some hundred thousand years. Correlation with the well-established chronostratigraphic and sequence stratigraphic framework for the studied succession reveals that the most distinctive change in palynoflora probably reflects a shift in depositional facies (due to an increase in sea level) rather than direct climatic change. The sea-level rise is herein interpreted to be eustatic and related to melting of Antarctic ice caps at the end of the Mi-1 glaciation event. (C) 2010 Elsevier B.V. All rights reserved.
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| 3. |
- Lindstrom, Sofie, et al.
(författare)
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Intense and widespread seismicity during the end-Triassic mass extinction due to emplacement of a large igneous province
- 2015
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Ingår i: Geology. - 0091-7613. ; 43:5, s. 387-390
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Tidskriftsartikel (refereegranskat)abstract
- Multiple levels of earthquake-induced soft-sediment deformations (seismites) are concentrated in the end-Triassic mass extinction interval across Europe. The repetitive nature of the seismites rules out an origin by an extraterrestrial impact. Instead, this intense seismic activity is linked to the formation of the Central Atlantic magmatic province (CAMP). By the earliest Jurassic the seismic activity had ceased, while extrusive volcanism still continued and biotic recovery was on its way. This suggests that magmatic intrusions into sedimentary strata during early stages of CAMP formation caused emission of gases (SO2, halocarbons, polycyclic aromatic hydrocarbons) that may have played a major part in the biotic crisis.
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