Isotope constraints and radiocarbon age applied to late holocene landscape evolution due to San marcos fault activity, Cordoba, argentina.

MASSABIE, A.; PANARELLO, H.0.; CEGARRA, M.; CORDERO OTERO, R R; LO FORTE, G.; SANGUINETTI, A.; VALENCIO, S. A.

Salvador Bahía

Congreso; IV South American Sympusium on Isotope Geology; 2003

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0mm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} p.MsoBodyText, li.MsoBodyText, div.MsoBodyText {margin:0mm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 30.0mm 70.85pt 30.0mm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Validity of 1,800±140 bp radiocarbon age of  the carbonate in the organic soil laying on SMF is supported by δ13C = -3.2‰ and d18O = -5.4 ‰ values in equilibrium with circulating water and atmosphere in open system conditions.  Late Holocene activity of SMF determined direct landscape modifications due to its barrier effect over surface and under surface water flow in the San Marcos Sierra foothills area of Córdoba, Central Argentina. Based on radiocarbon ages, isotope analyses and morphostructural control of Late Quaternary fluvial and phreatic deposits, two final neotectonic activity steps of SMF are placed between 4,000 – 2,000 bp. The first step could be constraint between 4,000 – 3,000 bp. It controled the avulsion of  River Quilpo associated with a (2,560±120 bp) transitory lacustrine paleoenvironment due to neotectonic damming up in the foot wall block of SMF.  The second SMF neotectonic step around 2,000 bp, lengthend to the northwest  a transverse local watershed over River de la Costa banks introducing an aditional modification of Late Holocene fluvial lanscape around San Marcos Sierra foothills of Cordoba. Two direct paleoenvironmental evidences of the last SMF tip point displacement to the northwest have been detected: firstly the tectonicaly controled attitude of  erosive planes on both sides of  fault scarp, and secondly the flow path changes of phreatic water in Level III over SMF hanging wall block which caused massive carbonate precipitation (1,800±140 bp) due to groundwater evaporation in the atmosphere.