MACNBR   00242
MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Major floristic trends in Patagonia during the late Paleogene-early Neogene: evidence from spores and pollen grains
Autor/es:
BARREDA, V.; PALAZZESI, L.
Lugar:
Bonn
Reunión:
Congreso; 12th International Palynological Congress; 2008
Resumen:
<!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;
mso-font-charset:0;
mso-generic-font-family:roman;
mso-font-pitch:variable;
mso-font-signature:-1610611985 1107304683 0 0 159 0;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;
mso-font-charset:0;
mso-generic-font-family:swiss;
mso-font-pitch:variable;
mso-font-signature:-1610611985 1073750139 0 0 159 0;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{mso-style-unhide:no;
mso-style-qformat:yes;
mso-style-parent:"";
margin-top:0cm;
margin-right:0cm;
margin-bottom:10.0pt;
margin-left:0cm;
line-height:115%;
mso-pagination:widow-orphan;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-font-family:Calibri;
mso-bidi-font-family:"Times New Roman";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-unhide:no;
color:blue;
text-decoration:underline;
text-underline:single;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-noshow:yes;
mso-style-priority:99;
color:purple;
mso-themecolor:followedhyperlink;
text-decoration:underline;
text-underline:single;}
.MsoChpDefault
{mso-style-type:export-only;
mso-default-props:yes;
font-size:10.0pt;
mso-ansi-font-size:10.0pt;
mso-bidi-font-size:10.0pt;
mso-ascii-font-family:Calibri;
mso-fareast-font-family:Calibri;
mso-hansi-font-family:Calibri;}
@page Section1
{size:612.0pt 792.0pt;
margin:70.85pt 3.0cm 70.85pt 3.0cm;
mso-header-margin:35.4pt;
mso-footer-margin:35.4pt;
mso-paper-source:0;}
div.Section1
{page:Section1;}
-->
Major floristic trends in Patagonia during the late
Paleogene-early Neogene: evidence from spores and pollen grains
Viviana Barreda,
Luis Palazzesi
Sección Paleopalinología, División
Paleobotánica, Museo Argentino de Ciencias Naturales "Bernardino
Rivadavia", CONICET. Av. Ángel Gallardo 470, C1405DJR, Buenos Aires,
Argentina. vbarreda@macn.gov.ar;
lpalazzesi@macn.gov.ar
Patagonian vegetation faced major changes in composition,
structure and distribution during the late Paleogene-early Neogene. The
fragmentation of temperate rainforests and the expansion of sclerophyllous
communities in eastern Patagonia are the most important turnovers. Fossil
pollen records suggest that Paleogene landscapes were dominated by a Gondwanic group
of families comprised mainly by Nothofagaceae, Podocarpaceae and Araucariaceae,
along with Gunneraceae, Cunoniaceae and Proteaceae. By the Early Miocene rainforest
taxa began to decline, some species became extinct (Lagarostrobos, Microcachrys,
Nothofagus subgenus Brassospora) and others were confined to
moister enclaves (Araucariaceae, Nothofagus
subgenus Fuscospora). A new vegetation
type composed by drought-tolerant plants progressively spread during the
Neogene; Asteraceae (Nassauviinae, Chuquiraga),
Calyceraceae (Boopis), Fabaceae (Caesalpinea, Anadenanthera, Prosopis),
Anacardiaceae (Schinus), Poaceae,
Chenopodiaceae, Convolvulaceae (Cressa)
were among the most characteristic families. Some of them may have evolved from
humid or sub humid ancestors as an adaptation to the new conditions (Asteraceae
Barnadesioideae); others may have dispersed into eastern Patagonia from Neotropical
bordering regions (Fabaceae Caesalpinoideae). The fragmentation of the
rainforest communities was probably related to major global (cooling trend) and
regional (Andean uplift) events, which would have led to a progressive
desertification of the eastern Andean region. Such conditions allowed low trees
and shrubs of Celtidaceae (Celtis),
Anacardicaceae (Schinus) and Fabaceae
(Prosopis, Prosopidastrum) to grow and expand by the Late Miocene. Many of
these sclerophyllous taxa are today restricted to the seasonally dry forests of
the Chaco Domain and might have derived from these Miocene ancestors.