INVESTIGADORES
TRIPALDI Alfonsina
congresos y reuniones científicas
Título:
Petrographic composition and provenance of modern eolian sand, Médanos Grandes, Northwestern Argentina
Autor/es:
CICCIOLI, P.L.; TRIPALDI, A.; FORMAN, S.L.
Lugar:
Santa Rosa, La Pampa, Argentina
Reunión:
Conferencia; VII International Conference Aeolian Research; 2010
Institución organizadora:
INTA
Resumen:
<!--
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0cm;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
p.MsoTitle, li.MsoTitle, div.MsoTitle
{margin:0cm;
margin-bottom:.0001pt;
text-align:center;
mso-pagination:widow-orphan;
font-size:12.0pt;
mso-bidi-font-size:10.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
mso-ansi-language:ES-MX;
font-weight:bold;
mso-bidi-font-weight:normal;
text-decoration:underline;
text-underline:single;}
@page Section1
{size:612.0pt 792.0pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;
mso-header-margin:36.0pt;
mso-footer-margin:36.0pt;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
<!--
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-parent:"";
margin:0cm;
margin-bottom:.0001pt;
mso-pagination:widow-orphan;
font-size:12.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";}
p.MsoTitle, li.MsoTitle, div.MsoTitle
{margin:0cm;
margin-bottom:.0001pt;
text-align:center;
mso-pagination:widow-orphan;
font-size:12.0pt;
mso-bidi-font-size:10.0pt;
font-family:"Times New Roman";
mso-fareast-font-family:"Times New Roman";
mso-ansi-language:ES-MX;
font-weight:bold;
mso-bidi-font-weight:normal;
text-decoration:underline;
text-underline:single;}
@page Section1
{size:612.0pt 792.0pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;
mso-header-margin:36.0pt;
mso-footer-margin:36.0pt;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
Landscapes of western Argentina
present several dune fields, many of them partially enclosed by high ranges of
the Andean domain. Médanos Grandes (MG) dune field (San Juan province) is bounded by the Sierra
de Pie de Palo to the north, a high massif of Precambrian-Lower Paleozoic
metasedimentary and metavolcanic rocks. Colluvial and fluvial deposits occur along
the east, west and southern margins (Bermejo and San Juan River
plains). To the northeast there is the Sierra de Valle Fértil, mostly composed
of Precambrian-Lower Paleozoic metasedimentary rocks, some non- to strongly
metamorphosed, mafic to acid igneous rocks and a Mesozoic sedimentary cover. Other
important sediment sources are the Andes (Upper
Paleozoic granites and sedimentary and volcanic successions of variable ages),
and the Precordillera (Paleozoic and Cenozoic sedimentary rocks with minor
Upper Paleozoic volcanites). Two sets of samples from MG were petrographically
studied. The first is middle to late Holocene aeolian sand that corresponds to
litharenites to feldspathic litharenites, dominated by metamorphic and volcanic
rock fragments and lesser amounts of quartz and feldspar. The second group,
probably < 100 years old sand, includes lithic feldsarenites to feldspathic
litharenites, with higher amounts of quartz and feldspars. Although the
tectonic environment of the source areas has not varied in the Holocene, the
two groups show compositional differences reflected, among others, in the QFL
and QmFL ratios. The Holocene sand portrays a provenance from undissected to
transitional arc, whereas the more recent sand plots in the dissected arc
field. This difference reflects a multiple and changing sediment sources due to
the aeolian reworking of the Bermejo and San Juan River
plains that collect volcanic-sedimentary and crystalline basement detritus.
