| 1. |
- Payros, Aitor, et al.
(författare)
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Mid- latitude alluvial and hydroclimatic changes during the Paleocene–Eocene Thermal Maximum as recorded in the Tremp- Graus Basin, Spain
- 2022
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Ingår i: Sedimentary Geology. - : Elsevier BV. - 0037-0738. ; 435
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Tidskriftsartikel (refereegranskat)abstract
- A short episode (~170 kyr) of extremely high global temperatures that occurred ~56 Ma, known as the Paleocene–Eocene Thermal Maximum, is widely considered an ancient analogue of the ongoing anthropogenic warming. This ancient hyperthermal event consisted of three phases, onset, core and recovery, which are respectively represented in the mid-latitude south Pyrenean Tremp-Graus Basin by three successive terrestrial units, the Claret Conglomerate, the Yellowish Soils and the Gypsum-rich Unit, each of them recording a different sedimentary response to evolving climatic and hydrological regimes. The Claret Conglomerate is mainly made up of calcareous conglomerates and is acknowledged to record an abrupt hydrological change during the onset phase. This unit most likely formed in an alluvial megafan, an interpretation here reinforced with new architectural information and by comparison with naturally occurring small-scale fan-like accumulations. Assuming the similarity between the onset of the Paleocene–Eocene Thermal Maximum and the anthropogenic warming, recent hydrological and meteorological data from mid-latitude Spain were compiled for comparison purposes. This comparison concurs with published modelling results about hydroclimate changes in the Pyrenees during the hyperthermal event, postulating an enhancement of seasonal contrast with augmented frequency and intensity of floods but no significant change in total rain. Furthermore, the comparison suggests that the Claret Conglomerate accumulated during extreme rainfall episodes that mainly occurred in autumn. The Yellowish Soils are mostly composed of silty marls with ubiquitous small-sized carbonate nodules and intercalated calcarenites. The marls were deposited in floodplains and the calcarenites in point bars and crevasse splays of meandering rivers. The scarcity of conglomerates entails a near absence of strong currents, and the carbonate nodules perennial or seasonal arid conditions. These nodules occur within cumulate palaeosols, the development of which required regular sedimentary increments during inundations on the floodplains. Sedimentation rates of siliciclastic material on the floodplains increased significantly during the core of the hyperthermal event, as well as at river outlets in coastal settings, which shows that erosion was accelerated and rules out the occurrence of protective, dense vegetation. Combined, these characteristics suggest persistent very dry summers, but a smooth wet season without intense precipitation events. Lastly, the profusion of gypsum in the youngest unit is clear proof of an arid climate during the recovery of the hyperthermal event. In essence, the studied deposits provide a unique window into the sequence of hydroclimatic change during the rise, peak and decline of an ancient global warming event in a mid-latitude terrestrial setting, against which ongoing climate-change data and future projections can be compared.
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| 2. |
- Pujalte, Victoriano, et al.
(författare)
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A rapid sedimentary response to the Paleocene-Eocene Thermal Maximum hydrological change : New data from alluvial units of the Tremp-Graus Basin (Spanish Pyrenees)
- 2022
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 589
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Tidskriftsartikel (refereegranskat)abstract
- A massive emission of light carbon about 56 Ma, recorded in marine and terrestrial sediments by a negative carbon isotope excursion (CIE), caused a short-lived (~170 kyr) global warming event known as the Paleocene–Eocene Thermal Maximum (PETM). The onset and core of this event is represented in the south Pyrenean Tremp-Graus Basin by two successive alluvial units, the Claret Conglomerate (CC) and the Yellowish Soils, which represent laterally juxtaposed depositional environments. It is generally agreed that these units record a dramatic increase in seasonal rain and an increased intra-annual humidity gradient during the PETM, but the timing of the sedimentary response to this hydrological change is a matter of debate. Some authors maintain that the CC was developed during the early, most intense phase of the carbon emission, others that its formation lagged by 16.5 ± 7.5 kyr behind the onset of the PETM. The latter claim was mainly based on the assumption that in two sections of this basin, Claret and Tendrui, the onset of the CIE occurs 3 and 8 m below the base of the CC, respectively. Here we show that in some zones between these two sections the CC was not deposited and the Yellowish Soil unit rests directly and conformably on the underlying Esplugafreda Formation. New δ13Corg data from this intervening zone provide evidence that the onset of the CIE is situated just ~1 m below the Yellowish Soils. In adjacent sections the CC erosional base cuts down deeper than 5 m, thus removing or obscuring the chemostratigraphically-defined base of the PETM. A tentative estimate based on averaged sedimentation rates indicates that ~3.8 kyr, or less, may have elapsed from the onset of the CIE to the arrival of PETM alluvium into the Claret-Tendrui study area, less than half of the lowest estimate of previous authors. Since the study area was situated about 15 km from the source area, our new estimate supports a rapid response of the sedimentary system to the hydrological change at the onset of the PETM.
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| 3. |
- 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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