Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay

The boundary between the Mercedes (Late Cretaceous) and Asencio (Eocene) formations has been a subject of controversy in the past. The morphological evidence about the contact between both formations obtained in this paper indicate that the geochemical weathering processes that took place during the...

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Autores principales: Morrás, H., Tófalo, O.R., Sánchez-Bettucci, L.
Formato: JOUR
Materias:
Columnar structures
Cretaceous-paleogene boundary
Ferrugination
Uruguay
Weathering
column
Cretaceous
Eocene
field survey
fragmentation
paleosol
sandstone
water erosion
weathering
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_01019082_v29_n4_p487_Morras
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_01019082_v29_n4_p487_Morras2023-10-03T14:57:23Z Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay Morrás, H. Tófalo, O.R. Sánchez-Bettucci, L. Columnar structures Cretaceous-paleogene boundary Ferrugination Uruguay Weathering column Cretaceous Eocene field survey fragmentation paleosol sandstone water erosion weathering Uruguay The boundary between the Mercedes (Late Cretaceous) and Asencio (Eocene) formations has been a subject of controversy in the past. The morphological evidence about the contact between both formations obtained in this paper indicate that the geochemical weathering processes that took place during the early Eocene forming the paleosols found in the Asencio Fm. would have penetrated deeply in the light coloured sandstones of the top of the Mercedes Fm. This is shown by a transitional level composed of a marked irregular boundary, where ferruginous materials co-exist with relicts of the greyish sandstone, as well as with pouches of ferrugination within the body of the Mercedes Fm., several meters below that boundary. Likewise, the obtained evidence shows also that the nodular strata present at the base of the Asencio Fm. are the result of the weathering of the greyish sandstones of the Mercedes Fm., due to their fragmentation and ferrugination. As a consequence, it is herein proposed that the columnar structures of the so-called Gruta del Palacio and other similar sites correspond to that transition level at the top of the Mercedes Fm.; the nuclei of the columns would be composed of the ferruginous tongues whereas the hollows would be the result of the selective water erosion of the sandstone. On the base of the field evidence, the stratigraphical nomenclature of the cited levels is discussed. Fil:Tófalo, O.R. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Sánchez-Bettucci, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_01019082_v29_n4_p487_Morras
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Columnar structures
Cretaceous-paleogene boundary
Ferrugination
Uruguay
Weathering
column
Cretaceous
Eocene
field survey
fragmentation
paleosol
sandstone
water erosion
weathering
Uruguay
spellingShingle Columnar structures
Cretaceous-paleogene boundary
Ferrugination
Uruguay
Weathering
column
Cretaceous
Eocene
field survey
fragmentation
paleosol
sandstone
water erosion
weathering
Uruguay
Morrás, H.
Tófalo, O.R.
Sánchez-Bettucci, L.
Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay
topic_facet Columnar structures
Cretaceous-paleogene boundary
Ferrugination
Uruguay
Weathering
column
Cretaceous
Eocene
field survey
fragmentation
paleosol
sandstone
water erosion
weathering
Uruguay
description The boundary between the Mercedes (Late Cretaceous) and Asencio (Eocene) formations has been a subject of controversy in the past. The morphological evidence about the contact between both formations obtained in this paper indicate that the geochemical weathering processes that took place during the early Eocene forming the paleosols found in the Asencio Fm. would have penetrated deeply in the light coloured sandstones of the top of the Mercedes Fm. This is shown by a transitional level composed of a marked irregular boundary, where ferruginous materials co-exist with relicts of the greyish sandstone, as well as with pouches of ferrugination within the body of the Mercedes Fm., several meters below that boundary. Likewise, the obtained evidence shows also that the nodular strata present at the base of the Asencio Fm. are the result of the weathering of the greyish sandstones of the Mercedes Fm., due to their fragmentation and ferrugination. As a consequence, it is herein proposed that the columnar structures of the so-called Gruta del Palacio and other similar sites correspond to that transition level at the top of the Mercedes Fm.; the nuclei of the columns would be composed of the ferruginous tongues whereas the hollows would be the result of the selective water erosion of the sandstone. On the base of the field evidence, the stratigraphical nomenclature of the cited levels is discussed.
format JOUR
author Morrás, H.
Tófalo, O.R.
Sánchez-Bettucci, L.
author_facet Morrás, H.
Tófalo, O.R.
Sánchez-Bettucci, L.
author_sort Morrás, H.
title Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay
title_short Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay
title_full Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay
title_fullStr Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay
title_full_unstemmed Weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern Uruguay
title_sort weathering processes at the boundary between the mercedes (cretaceous) and asencio (eocene) formations, southwestern uruguay
url http://hdl.handle.net/20.500.12110/paper_01019082_v29_n4_p487_Morras
work_keys_str_mv AT morrash weatheringprocessesattheboundarybetweenthemercedescretaceousandasencioeoceneformationssouthwesternuruguay
AT tofaloor weatheringprocessesattheboundarybetweenthemercedescretaceousandasencioeoceneformationssouthwesternuruguay
AT sanchezbettuccil weatheringprocessesattheboundarybetweenthemercedescretaceousandasencioeoceneformationssouthwesternuruguay
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