scholarly journals Zur Entstehung des Talkessels von La Paz/Bolivien und Umgebung

1979 ◽  
Vol 34 (1) ◽  
pp. 43-49 ◽  
Author(s):  
C. Villarroel ◽  
K. Graf

Abstract. The town of La Paz is situated between the Bolivian Highland (Altiplano) and the Central Mountain Range. These two landscape units were mostly formed during the Tertiary. But at their intermediate bordering zone, geomorphological forms have 'later been reshaped. At the end of the Pliocene, a peneplain was formed (the Altiplano of today) and got covered by volcanic ashes. Since the fossilization of mammals (Posnanskytherium) in the late Pliocene, a tektonical uplift of about 3300 ft. has taken place, and huge moraines built up covering the whole city area of today. The enormous La Paz Valley was eroded above all during the last interglacial period. During the last ice age, the glaciers reached the present upper city border only and melted away very rapidly 9800 years ago at the latest.

Science ◽  
2014 ◽  
Vol 346 (6216) ◽  
pp. 1514-1517 ◽  
Author(s):  
Christopher T. Hayes ◽  
Alfredo Martínez-García ◽  
Adam P. Hasenfratz ◽  
Samuel L. Jaccard ◽  
David A. Hodell ◽  
...  

During the last interglacial period, global temperatures were ~2°C warmer than at present and sea level was 6 to 8 meters higher. Southern Ocean sediments reveal a spike in authigenic uranium 127,000 years ago, within the last interglacial, reflecting decreased oxygenation of deep water by Antarctic Bottom Water (AABW). Unlike ice age reductions in AABW, the interglacial stagnation event appears decoupled from open ocean conditions and may have resulted from coastal freshening due to mass loss from the Antarctic ice sheet. AABW reduction coincided with increased North Atlantic Deep Water (NADW) formation, and the subsequent reinvigoration in AABW coincided with reduced NADW formation. Thus, alternation of deep water formation between the Antarctic and the North Atlantic, believed to characterize ice ages, apparently also occurs in warm climates.


1998 ◽  
Vol 17 (9-10) ◽  
pp. 963-985 ◽  
Author(s):  
Torben Fronval ◽  
Eystein Jansen ◽  
Haflidi Haflidason ◽  
Hans Petter Sejrup

2016 ◽  
Vol 12 (9) ◽  
pp. 1933-1948 ◽  
Author(s):  
Amaelle Landais ◽  
Valérie Masson-Delmotte ◽  
Emilie Capron ◽  
Petra M. Langebroek ◽  
Pepijn Bakker ◽  
...  

Abstract. The last interglacial period (LIG, ∼ 129–116 thousand years ago) provides the most recent case study of multimillennial polar warming above the preindustrial level and a response of the Greenland and Antarctic ice sheets to this warming, as well as a test bed for climate and ice sheet models. Past changes in Greenland ice sheet thickness and surface temperature during this period were recently derived from the North Greenland Eemian Ice Drilling (NEEM) ice core records, northwest Greenland. The NEEM paradox has emerged from an estimated large local warming above the preindustrial level (7.5 ± 1.8 °C at the deposition site 126 kyr ago without correction for any overall ice sheet altitude changes between the LIG and the preindustrial period) based on water isotopes, together with limited local ice thinning, suggesting more resilience of the real Greenland ice sheet than shown in some ice sheet models. Here, we provide an independent assessment of the average LIG Greenland surface warming using ice core air isotopic composition (δ15N) and relationships between accumulation rate and temperature. The LIG surface temperature at the upstream NEEM deposition site without ice sheet altitude correction is estimated to be warmer by +8.5 ± 2.5 °C compared to the preindustrial period. This temperature estimate is consistent with the 7.5 ± 1.8 °C warming initially determined from NEEM water isotopes but at the upper end of the preindustrial period to LIG temperature difference of +5.2 ± 2.3 °C obtained at the NGRIP (North Greenland Ice Core Project) site by the same method. Climate simulations performed with present-day ice sheet topography lead in general to a warming smaller than reconstructed, but sensitivity tests show that larger amplitudes (up to 5 °C) are produced in response to prescribed changes in sea ice extent and ice sheet topography.


1988 ◽  
Vol 10 ◽  
pp. 5-9 ◽  
Author(s):  
Claude F. Boutron ◽  
Clair C. Patterson ◽  
Claude Lorius ◽  
V.N. Petrov ◽  
N.I. Barkov

Concentrations of lead (Pb) have been measured by the ultra-clean isotope dilution mass spectrometry technique in various sections of the Antarctic Dome C and Vostok deep ice cores, whose ages range from 3.85 to 155 ka B.P., in order to assess the natural, pre-human, sources of this toxic heavy metal in the global troposphere. Pb concentrations were very low, as low as about 0.3 pg Pb/g during the Holocene and probably during the last interglacial and part of the last ice age. On the other hand, they were quite high, up to about 40 pg Pb/g, during the Last Glacial Maximum and at the end of the penultimate ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Pb in the global troposphere. Pb contribution from volcanoes is significant during periods of low Pb only. Contribution from the oceans is insignificant.


2010 ◽  
Vol 7 (3) ◽  
pp. 3969-3999 ◽  
Author(s):  
C. Albrecht ◽  
H. Vogel ◽  
T. Hauffe ◽  
T. Wilke

Abstract. Ancient Lake Ohrid is probably of early Pleistocene or Pliocene origin and amongst the few lakes in the world harboring an outstanding degree of endemic biodiversity. Although there is a long history of evolutionary research in Lake Ohrid, particularly on molluscs, a mollusc fossil record has been missing up to date. For the first time, gastropod and bivalve fossils are reported from the basal, calcareous part of a 2.6 m long sediment succession (core Co1200) from the north-eastern part of Lake Ohrid. Electron spin resonance (ESR) dating of mollusc shells from the same stratigraphic level yielded an age of 130±28 ka. Lithofacies III sediments, i.e. a subdivision of the stratigraphic unit comprising the basal succession of core Co1200 between 181.5–263 cm appeared solid, grayish-white, and consisted almost entirely of silt-sized endogenic calcite (CaCO3>70%) and intact and broken mollusc shells. Here we compare the faunal composition of the thanatocoenosis with recent mollusc associations in Lake Ohrid. A total of 13 mollusc species (9 gastropod and 4 bivalve species) could be identified within Lithofacies III sediments. The value of sediment core fossils for reconstructing palaeoenvironmental settings was evaluated. The agreement between sediment and palaeontological proxies was tested. The combined findings of the ecological study and the sediment characteristics suggest deposition in a shallow water environment during the Last Interglacial period. We tested for major faunal changes since the Last Interglacial period and searched for signs of extinction events. The fossil fauna exclusively included species also found in the present fauna, i.e. no extinction events are evident for this site since the Last Interglacial. The thanatocoenosis showed the highest similarity with recent Intermediate Layer (5–25 m) mollusc assemblages. The demonstrated existence of a mollusc fossil record in Lake Ohrid sediment cores also has great significance for future deep drilling projects. It can be hoped that a more far reaching mollusc fossil record will then be obtained, enabling insight into the early evolutionary history of Lake Ohrid.


Author(s):  
Hans Blumenberg

This chapter discusses Hans Blumenberg's essay “Advancing into Eternal Silence: A Century after the Sailing of the Fram” (1993). This essay was written three years before his death. It offers not just the philosophical reading of an episode in the history of polar expeditions ripe with significance, but draws on an anecdote to muse on the relationship between media-archaeology and nihilism. Blumenberg explains that humans are risky beings, and not just because they seek frontier-pushing adventures like the voyage adrift of the Fram. They are risky for the very reason that their biological origins lie in the narrow span of the last interglacial period, when they learned the ability to cope with life caught between the advancing and receding glaciers; the natural being was now pitted against nature.


Quaternary ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 6
Author(s):  
Christopher Satow ◽  
Katharine M. Grant ◽  
Sabine Wulf ◽  
Hartmut Schulz ◽  
Addison Mallon ◽  
...  

The Eemian was the last interglacial period (~130 to 115 ka BP) to precede the current interglacial. In Eastern Mediterranean marine sediments, it is marked by a well-developed and organic-rich “sapropel” layer (S5), which is thought to reflect an intensification and northward migration of the African monsoon rain belt over orbital timescales. However, despite the importance of these sediments, very little proxy-independent stratigraphic information is available to enable rigorous correlation of these sediments across the region. This paper presents the first detailed study of visible and non-visible (cryptotephra) layers found within these sediments at three marine coring sites: ODP Site 967B (Levantine Basin), KL51 (South East of Crete) and LC21 (Southern Aegean Sea). Major element analyses of the glass component were used to distinguish four distinct tephra events of Santorini (e.g., Vourvoulos eruption) and possible Anatolian provenance occurring during the formation of S5. Interpolation of core chronologies provides provisional eruption ages for the uppermost tephra (unknown Santorini, 121.8 ± 2.9 ka) and lowermost tephra (Anatolia or Kos/Yali/Nisyros, 126.4 ± 2.9 ka). These newly characterised tephra deposits have also been set into the regional tephrostratigraphy to illustrate the potential to precisely synchronise marine proxy records with their terrestrial counterparts, and also contribute to the establishment of a more detailed volcanic history of the Eastern Mediterranean.


Sign in / Sign up

Export Citation Format

Share Document