| 1. |
- Feurdean, Angelica, et al.
(author)
-
Younger Dryas to mid-Holocene environmental history of the lowlands of NW Transylvania, Romania
- 2007
-
In: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 68:3, s. 364-378
-
Journal article (peer-reviewed)abstract
- Pollen, micro-charcoal and total carbon analyses on sediments from the Turbuta palaeolake, in the Transylvanian Basin of NW Romania, reveal Younger Dryas to mid-Holocene environmental changes. The chronostratigraphy relies on AMS 14C measurements on organic matter and U/Th TIMS datings of snail shells. Results indicate the presence of Pinus and Betula open woodlands with small populations of Picea, Ulmus, Alnus and Salix before 12,000 cal yr BP. A fairly abrupt replacement of Pinus and Betula by Ulmus-dominated woodlands at ca. 11,900 cal. yr BP likely represents competition effects of vegetation driven by climate warming at the onset of the Holocene. By 11,000 cal yr BP, the woodlands were increasingly diverse and dense with the expansion of Quercus, Fraxinus and Tilia, the establishment of Corylus and the decline of upland herbaceous and shrubs taxa. The marked expansion of Quercus accompanied by Tilia between 10,500 and 8000 cal yr BP could be the result of low effective moisture associated with both low elevation of the site and with regional change towards a drier climate. At 10,000 cal yr BP, Corylus spread across the region, and by 8000 cal yr BP it replaced Quercus as a dominant forest constituent, with only little representation of Picea abies. Carpinus became established around 5500 cal yr BP, but it was only a minor constituent in local woodlands until ca. 5000 cal yr BP. Results from this study also indicate that the woodlands in the lowlands of Turbuta were never closed.
|
|
| 2. |
- Lascu, Ioan, et al.
(author)
-
A Late Glacial paleolake record from an up-dammed river valley in northern Transylvania, Romania
- 2015
-
In: Quaternary International. - : Elsevier BV. - 1040-6182 .- 1873-4553. ; 388, s. 87-96
-
Journal article (peer-reviewed)abstract
- Lake sediments from the Magherus, Valley in the lowlands of northern Transylvania provide new evidence of paleoenvironmental development in Romania during the Late Glacial. The studied sediments were deposited as a result of the damming of a small river valley following a series of mass wasting events that occurred during the deglaciation period. A continuous sedimentary sequence belonging to the former lake is preserved in the banks of the stream, and contains evidence of paleoenvironmental changes associated with the Late Glacial Interstadial (Bolling-Allerod or Greenland Interstadial 1, GI-1) and the Late Glacial Stadial (Younger Dryas or Greenland Stadial 1, GS-1), implying that the hallmark climatic episodes of northwestern Europe are also expressed in Eastern Europe. We employ a multiproxy approach based on the analysis of sediment composition and texture, mineral magnetism, organic macrofossils, and radiocarbon dating. The reconstructed paleoenvironmental evolution at the site captures the warm and humid conditions associated with GI-1, as well as the subsequent cooling concomitant with the onset of GS-1. These climatic events are paralleled by vegetation shifts in the region, as deduced from comparisons with pollen sequences from Magherus, and neighboring locations in Transylvania and the Carpathians. The Late Glacial Interstadial was warmer and wetter, as evidenced by increased organic matter content in the lake, decreased erosion in the catchment, development of palustrine plant communities in the proximity of the lake, and expansion of spruce during the Allerod (GI-1c-a). The Late Glacial Stadial was colder and dryer, as indicated by low sedimentary organic matter content, an increase in erosion markers, and the decline of spruce and its replacement by birch. The landscape was more open, as herbs and grasses also expanded during this time. These fluctuations imply that Late Glacial climatic events are well expressed not only in upland areas of Romania, but also in lowland regions such as the Transylvanian Basin, where climatic effects are expected to be more muted.
|
|
| 3. |
- Persoiu, Aurel, et al.
(author)
-
Holocene winter climate variability in Central and Eastern Europe
- 2017
-
In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
-
Journal article (peer-reviewed)abstract
- Among abundant reconstructions of Holocene climate in Europe, only a handful has addressed winter conditions, and most of these are restricted in length and/or resolution. Here we present a record of late autumn through early winter air temperature and moisture source changes in East-Central Europe for the Holocene, based on stable isotopic analysis of an ice core recovered from a cave in the Romanian Carpathian Mountains. During the past 10,000 years, reconstructed temperature changes followed insolation, with a minimum in the early Holocene, followed by gradual and continuous increase towards the mid-to-late-Holocene peak (between 4-2 kcal BP), and finally by a decrease after 0.8 kcal BP towards a minimum during the Little Ice Age (AD 1300-1850). Reconstructed early Holocene atmospheric circulation patterns were similar to those characteristics of the negative phase of the North Atlantic Oscillation (NAO), while in the late Holocene they resembled those prevailing in the positive NAO phase. The transition between the two regimes occurred abruptly at around 4.7 kcal BP. Remarkably, the widespread cooling at 8.2 kcal BP is not seen very well as a temperature change, but as a shift in moisture source, suggesting weaker westerlies and increased Mediterranean cyclones penetrating northward at this time.
|
|
| 4. |
- Persoiu, Aurel, et al.
(author)
-
Stable isotope behavior during cave ice formation by water freezing in Scarisoara Ice Cave, Romania
- 2011
-
In: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116, s. D02111-
-
Journal article (peer-reviewed)abstract
- Recently, a series of studies have targeted the stable isotopic composition of cave ice as a possible source of paleoclimatic information, but none presented an explanation for the way in which the external climatic signal is transferred to cave ice. While the relation between the stable isotopic composition of precipitation and drip water can be relatively easily determined, a more complex problem arises, i.e., the possible alteration of the primary climatic signal recorded by the oxygen and hydrogen stable isotopes during the freezing of water to form cave ice. Here we report the results of the first detailed investigations of the oxygen and hydrogen stable isotope behavior during the formation of ice in Scarisoara Ice Cave. Samples of ice align on a straight line with a slope lower than 8 in a delta(18)O-delta(2)H plot, characteristic for ice formed by the freezing of water. A model is presented for the reconstruction of the initial isotopic composition of water, despite the complexity induced by kinetic effects during early stages of freezing. These results are consistent with ice that forms by the downward freezing of a stagnant pool of water, under kinetic conditions in the initial stages of the process, and isotopic equilibrium thereafter. As ice caves are described in many parts of the world, otherwise poorly represented in ice-based paleoclimatology, the results of this study could open a new direction in paleoclimatic research so that an array of significant paleoclimate data can be developed on the basis of their study.
|
|
