Geochemical analysis by means of XRF and ICP\|AES was carried out on 35 selected samples. Major and trace elements were determined. They were: CaCO\-3, P\-2O\-5, Fe\-2O\-3, TiO\-2, SiO\-2, Al\-2O\-3, CaO, K\-2O, MnO, ...Geochemical analysis by means of XRF and ICP\|AES was carried out on 35 selected samples. Major and trace elements were determined. They were: CaCO\-3, P\-2O\-5, Fe\-2O\-3, TiO\-2, SiO\-2, Al\-2O\-3, CaO, K\-2O, MnO, Rb, Cs, Ga, Zr, Ta, Nb, Sr, Ba, Cr, Ni, Zn, Pb, Cu, V and B. The country rocks studied were of sandy\|muddy lithofacies, belonging to a typical tide marine transgressive heterolithic succession of Middle Miocene age. They are called the Ituzaingó Formation. The formation outcrops in northeastern Argentina on the left of the Paraná River Valley. The depositional setting largely depends on the outstanding internal structures and textures (i.e., herringbone cross stratification, tidal bundles, reactivation surfaces). In the study area, loessial friable sediment was used as geochemical background because it overlies shallow marine sediments. The results show significant differences. Boron is absent in loessial sediments. On the other hand, several trace elements such as vanadium and chromium are concentrated in the shallow marine sediments. These results may be useful to discern uncertain beds in the area studied.展开更多
Littoral siliciclastic shallow marine horizontal conformable beds (a heterolithic succession), Middle to Late Miocene, outcropping in northeastern Argentina (Ituzaingó Formation) and overlying transitional confor...Littoral siliciclastic shallow marine horizontal conformable beds (a heterolithic succession), Middle to Late Miocene, outcropping in northeastern Argentina (Ituzaingó Formation) and overlying transitional conformable horizontal regolithic mantle-rock bed derived from them (the Pampean and Post-Pampean Formations), were geochemically analyzed. The focus of this study is placed on the application of geochemical parameter and signature analyses related with the aforementioned geological units, which are of subcontinental extension into South America. The encountered results show an outstandingly similar geochemical behaviour between them. The main conclusion is that regolithic mantle-rock beds were derived from the littoral shallow marine mudstone (silty-argillaceous) beds. This is in oposition to previous aeolian processes proposed early in the 50’s and later. These mudstone beds constitute important sections of the littoral shallow marine sequence beds (outcropping HST parasequence). Such regolitization proposed for the Pampean and Post-Pampean Formations predominantly developed in-situ during the Late Pleistocene and Holocene. The main erosional and mobilized agents were the surface free water (pluvial, fluvial and laminar water sheets) and vadose water. So, the wind flows and/or the immense air flow hurricanes are of insignificant sedimentological influence. Otherwise, there is not a proved appropiate sandy-silty reservoir for a reasonable support of the “aeolian hypothesis”, as well as clear aeolian structures settled in the regolithic mantle-rock bed. In spite of these lines of equality textural-structural evidence, the geochemical values for both major elements and trace elements, demonstrate that the Miocene heterolithic marine succession was the mother rock of the overlying regolithic mantle-rock bed, which was formed as an in-situ mantle-rock bed.展开更多
文摘Geochemical analysis by means of XRF and ICP\|AES was carried out on 35 selected samples. Major and trace elements were determined. They were: CaCO\-3, P\-2O\-5, Fe\-2O\-3, TiO\-2, SiO\-2, Al\-2O\-3, CaO, K\-2O, MnO, Rb, Cs, Ga, Zr, Ta, Nb, Sr, Ba, Cr, Ni, Zn, Pb, Cu, V and B. The country rocks studied were of sandy\|muddy lithofacies, belonging to a typical tide marine transgressive heterolithic succession of Middle Miocene age. They are called the Ituzaingó Formation. The formation outcrops in northeastern Argentina on the left of the Paraná River Valley. The depositional setting largely depends on the outstanding internal structures and textures (i.e., herringbone cross stratification, tidal bundles, reactivation surfaces). In the study area, loessial friable sediment was used as geochemical background because it overlies shallow marine sediments. The results show significant differences. Boron is absent in loessial sediments. On the other hand, several trace elements such as vanadium and chromium are concentrated in the shallow marine sediments. These results may be useful to discern uncertain beds in the area studied.
文摘Littoral siliciclastic shallow marine horizontal conformable beds (a heterolithic succession), Middle to Late Miocene, outcropping in northeastern Argentina (Ituzaingó Formation) and overlying transitional conformable horizontal regolithic mantle-rock bed derived from them (the Pampean and Post-Pampean Formations), were geochemically analyzed. The focus of this study is placed on the application of geochemical parameter and signature analyses related with the aforementioned geological units, which are of subcontinental extension into South America. The encountered results show an outstandingly similar geochemical behaviour between them. The main conclusion is that regolithic mantle-rock beds were derived from the littoral shallow marine mudstone (silty-argillaceous) beds. This is in oposition to previous aeolian processes proposed early in the 50’s and later. These mudstone beds constitute important sections of the littoral shallow marine sequence beds (outcropping HST parasequence). Such regolitization proposed for the Pampean and Post-Pampean Formations predominantly developed in-situ during the Late Pleistocene and Holocene. The main erosional and mobilized agents were the surface free water (pluvial, fluvial and laminar water sheets) and vadose water. So, the wind flows and/or the immense air flow hurricanes are of insignificant sedimentological influence. Otherwise, there is not a proved appropiate sandy-silty reservoir for a reasonable support of the “aeolian hypothesis”, as well as clear aeolian structures settled in the regolithic mantle-rock bed. In spite of these lines of equality textural-structural evidence, the geochemical values for both major elements and trace elements, demonstrate that the Miocene heterolithic marine succession was the mother rock of the overlying regolithic mantle-rock bed, which was formed as an in-situ mantle-rock bed.
