AMBIENTUM BIOETHICA BIOLOGIA CHEMIA DIGITALIA DRAMATICA EDUCATIO ARTIS GYMNAST. ENGINEERING EPHEMERIDES EUROPAEA GEOGRAPHIA GEOLOGIA HISTORIA HISTORIA ARTIUM INFORMATICA IURISPRUDENTIA MATHEMATICA MUSICA NEGOTIA OECONOMICA PHILOLOGIA PHILOSOPHIA PHYSICA POLITICA PSYCHOLOGIA-PAEDAGOGIA SOCIOLOGIA THEOLOGIA CATHOLICA THEOLOGIA CATHOLICA LATIN THEOLOGIA GR.-CATH. VARAD THEOLOGIA ORTHODOXA THEOLOGIA REF. TRANSYLVAN
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STUDIA GEOLOGIA - Ediţia nr.2 din 2010 | |||||||
Articol: |
PAST SURFACE CONDITIONS AND SPELEOGENESIS AS INFERRED FROM CAVE SEDIMENTS IN THE GREAT CAVE OF SALITRARI MOUNTAIN (SW ROMANIA). Autori: . |
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Rezumat: In one of the passages in the Great
Cave of Șălitrari Mountain the floor is
completely covered by an alluvial deposit at least 6 m in thickness, ranging
from boulders, and cobbles, to sand and clay, topped by a layer of dry bat
guano. Sediment and mineral samples collected from six profiles underwent broad
analyses to determine their petrological and mineralogical makeup, grain-size
distribution, and paleoclimatic significance. The complicated facies alternation
suggests frequent changes in the former stream’s hydrological parameters, with
frequent flooding, leading to the hypothesis that the climate was somewhat
wetter than today. Both the mineralogical composition of the sediment (ranging
from quartz, mica, gypsum, phosphates, and calcite to garnet, zircon, titanite,
olivine, serpentine, tourmaline, sphalerite, pyrite/chalcopyrite, and
feldspars) and the petrological composition of the larger clasts (limestone,
sandstone, mudstone, granitoids, serpentinite, amphibolite, diorite, gneiss,
quartzite, microconglomerate, and schist) ascribe the potential source rocks to
an area with contrasting lithologies, such as amphibolites, felsic and basic
metaigneous, and metasedimentary rocks, mixed with a variety of detritic rocks.
These rock types are not entirely comprised by the catchment area of the modern
Presacina Brook, thus implying that due either to hydrological conditions, or
to changes in the base level caused by river down cutting or active tectonics,
the former source area was much more extensive. Based on morphological and
sedimentological criteria, the cave started under pipe-full flow conditions,
and further evolved during a prolonged and complex vadose phase. Evidence to
support the existence of hypogene conditions is also present. Once the
underground stream left the cave and most of the sediment was removed,
speleothem precipitation was initiated. In this contribution we put forward
evidence that argue for an extra-basinal origin of some of the alluvial
sediments, an uncommon fact documented in few cave environments so far. |
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