Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina

New outcrops of Middle Carboniferous glacigenic deposits found in the Guandacol Formation (western Paganzo Basin) are described in this paper. The study locality of Los Pozuelos Creek (northwestern Argentina) includes coarse-grained diamictites, rhythmites, laminated pebbly mudstones and shales that...

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Detalles Bibliográficos
Publicado: 2005
Materias:
Carboniferous
Gondwanic glaciation
Grounding-line system
Morainal banks
Northwestern Argentina
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v8_n2_p187_Marenssi
http://hdl.handle.net/20.500.12110/paper_1342937X_v8_n2_p187_Marenssi
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling paper:paper_1342937X_v8_n2_p187_Marenssi2023-06-08T16:10:38Z Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina Carboniferous Gondwanic glaciation Grounding-line system Morainal banks Northwestern Argentina New outcrops of Middle Carboniferous glacigenic deposits found in the Guandacol Formation (western Paganzo Basin) are described in this paper. The study locality of Los Pozuelos Creek (northwestern Argentina) includes coarse-grained diamictites, rhythmites, laminated pebbly mudstones and shales that represent an expanded column of the Gondwanic glaciation in this region. Thirteen lithofacies recorded at the measured section have been grouped into three facies associations. Facies Association I is composed of coarse-grained massive and stratified diamictites (lithofacies Dmm, Dms, Dmg, Dcs), laminated siltstones with dropstones (Fld) and interstratified sandstones and mudstones (Fl, Sr). These rocks represent both tillites and resedimented diamictites closely associated to small water bodies where laminated siltstones with dropstones and stratified sandstones and mudstones were deposited. Facies Association II comprises couplets of matrix-supported thinly bedded diamictites (Dmld) and laminated mudstones with dropstones (Fld). This facies association results from the combination of three different processes, subaqueous cohesionless debris flows, coeval rainout of ice-rafted debris and settling of fine-grained particles from supension. Finally, Facies Association III is made up of laminated mudstones without dropstones, thin marl levels and scarce fine- to very fine-grained sandstones. This assemblage clearly suggests sedimentation in a deep marine environment below the wave base. The architecture of t he glacigenic deposits has been investigated using photomosaic panels. The geometry of the depositional bodies and facies suggest that Los Pozuelos Creek outcrops exhibit a well preserved three-dimensional example of a grounding-line system. In particular, three different subenvironments of a morainal bank were interpreted: a bank-front, a bank-core and a bank-back. The bank-front assemblage is characterized by coarse-grained, mainly resedimented, diamictites grading laterally to prograding clinoforms composed of interbedded matrix-supported thinly bedded diamictite and mudstones. The bank-core assemblage is formed by a stacking of coarse-grained diamictites where at least five major erosional surfaces, bounding four multistory diamictite bodies, can be recognized. Finally, the bank-back assemblage corresponds to discontinuous intervals of striated lodgement till, and coarse-grained resedimented diamictites showing important post-depositional deformation. The retrogradational stacking of the morainal banks indicate an overall glacial retreat and a glacioeustatic sea-level rise. Erosional surfaces at the base of each morainal bank suggest intervening short term episodes of ice advance. The new data pr esented here confirm the existence of "true" tillites in western Paganzo Basin and suggest several (at least four) pulses of glacial advance and retreat during the Namurian glaciation in the region and permit a more refined interpretation of the glacial deposits in the Huaco area. © 2005 International Association for Gondwana Research, Japan. 2005 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v8_n2_p187_Marenssi http://hdl.handle.net/20.500.12110/paper_1342937X_v8_n2_p187_Marenssi
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Carboniferous
Gondwanic glaciation
Grounding-line system
Morainal banks
Northwestern Argentina
spellingShingle Carboniferous
Gondwanic glaciation
Grounding-line system
Morainal banks
Northwestern Argentina
Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina
topic_facet Carboniferous
Gondwanic glaciation
Grounding-line system
Morainal banks
Northwestern Argentina
description New outcrops of Middle Carboniferous glacigenic deposits found in the Guandacol Formation (western Paganzo Basin) are described in this paper. The study locality of Los Pozuelos Creek (northwestern Argentina) includes coarse-grained diamictites, rhythmites, laminated pebbly mudstones and shales that represent an expanded column of the Gondwanic glaciation in this region. Thirteen lithofacies recorded at the measured section have been grouped into three facies associations. Facies Association I is composed of coarse-grained massive and stratified diamictites (lithofacies Dmm, Dms, Dmg, Dcs), laminated siltstones with dropstones (Fld) and interstratified sandstones and mudstones (Fl, Sr). These rocks represent both tillites and resedimented diamictites closely associated to small water bodies where laminated siltstones with dropstones and stratified sandstones and mudstones were deposited. Facies Association II comprises couplets of matrix-supported thinly bedded diamictites (Dmld) and laminated mudstones with dropstones (Fld). This facies association results from the combination of three different processes, subaqueous cohesionless debris flows, coeval rainout of ice-rafted debris and settling of fine-grained particles from supension. Finally, Facies Association III is made up of laminated mudstones without dropstones, thin marl levels and scarce fine- to very fine-grained sandstones. This assemblage clearly suggests sedimentation in a deep marine environment below the wave base. The architecture of t he glacigenic deposits has been investigated using photomosaic panels. The geometry of the depositional bodies and facies suggest that Los Pozuelos Creek outcrops exhibit a well preserved three-dimensional example of a grounding-line system. In particular, three different subenvironments of a morainal bank were interpreted: a bank-front, a bank-core and a bank-back. The bank-front assemblage is characterized by coarse-grained, mainly resedimented, diamictites grading laterally to prograding clinoforms composed of interbedded matrix-supported thinly bedded diamictite and mudstones. The bank-core assemblage is formed by a stacking of coarse-grained diamictites where at least five major erosional surfaces, bounding four multistory diamictite bodies, can be recognized. Finally, the bank-back assemblage corresponds to discontinuous intervals of striated lodgement till, and coarse-grained resedimented diamictites showing important post-depositional deformation. The retrogradational stacking of the morainal banks indicate an overall glacial retreat and a glacioeustatic sea-level rise. Erosional surfaces at the base of each morainal bank suggest intervening short term episodes of ice advance. The new data pr esented here confirm the existence of "true" tillites in western Paganzo Basin and suggest several (at least four) pulses of glacial advance and retreat during the Namurian glaciation in the region and permit a more refined interpretation of the glacial deposits in the Huaco area. © 2005 International Association for Gondwana Research, Japan.
title Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina
title_short Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina
title_full Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina
title_fullStr Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina
title_full_unstemmed Facies and architecture of a carboniferous grounding-line system from the Guandacol Formation, Paganzo Basin, Northwestern Argentina
title_sort facies and architecture of a carboniferous grounding-line system from the guandacol formation, paganzo basin, northwestern argentina
publishDate 2005
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_1342937X_v8_n2_p187_Marenssi
http://hdl.handle.net/20.500.12110/paper_1342937X_v8_n2_p187_Marenssi
_version_ 1768543766388408320

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