87Sr/86Sr in gypsic soils of hyperarid settings as an altitude proxy: results for northern Chile (19-24ºS) and paleoaltimetry applications

COSENTINO, N. J.; JORDAN, T. E.

Florencia

Conferencia; Goldschmidt Conference; 2013

Quantification of uplift of a continentalsurface relative to sea level is challenging. We have developed a new altimeterproxy based on the 87Sr/86Sr ratio of incipient soils inhyperarid settings like those present in the Atacama Desert. The proposed altimeter is based on the firstorder topographic control on the extent of coastal fog [1]. Atmosphericadvection brings offshore-generated stratocumulus clouds to the continent,generating fog that on geologically recent timescales (103-104yrs) has averaged base and top altitudes of 300 and 1150 m.a.s.l.,respectively. In the hyperarid desert, calcium sulfateaccumulates on the surface, progressively forming saline soil [2]. Samples ofAtacama?s incipient soils reveal 87Sr/86Sr valuesclustering in two altitudinal domains (Figure 1); seawater 87Sr/86Sr(0.70916) is distinctively higher than the ratio for Atacama?s incipient soils outsideof the fog zone (0.70733). We are investigating the use of this relationship to deducelate Miocene-Pliocene topographic history of theNazca/South America forearc. Based on results of dated paleosols in the study area we reach apreliminary interpretation: ³ 400 m local uplift has occurred since 5 Ma.<style>&lt;!-- /* 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:3 0 0 0 1 0;}@font-face{font-family:Times;panose-1:2 0 5 0 0 0 0 0 0 0;mso-font-charset:0;mso-generic-font-family:auto;mso-font-pitch:variable;mso-font-signature:-536870145 1342185562 0 0 415 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin:0cm;margin-bottom:.0001pt;line-height:14.0pt;mso-line-height-rule:exactly;mso-pagination:widow-orphan;font-size:10.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:"Times New Roman";mso-ansi-language:EN-GB;}p.BODYTEXT, li.BODYTEXT, div.BODYTEXT{mso-style-name:"BODY TEXT";mso-style-unhide:no;mso-style-parent:"";margin:0cm;margin-bottom:.0001pt;text-align:justify;text-indent:14.2pt;line-height:11.0pt;mso-line-height-rule:exactly;mso-pagination:widow-orphan;tab-stops:14.2pt;font-size:9.0pt;mso-bidi-font-size:10.0pt;font-family:Times;mso-fareast-font-family:"Times New Roman";mso-bidi-font-family:"Times New Roman";mso-ansi-language:EN-GB;mso-no-proof:yes;}.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;}@page WordSection1{size:612.0pt 792.0pt;margin:72.0pt 72.0pt 72.0pt 72.0pt;mso-header-margin:36.0pt;mso-footer-margin:36.0pt;mso-paper-source:0;}div.WordSection1{page:WordSection1;}--&gt;<!-- /* 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:3 0 0 0 1 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin:0cm;margin-bottom:.0001pt;line-height:14.0pt;mso-line-height-rule:exactly;mso-pagination:widow-orphan;font-size:10.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:"Times New Roman";mso-ansi-language:EN-GB;}.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;}@page WordSection1{size:612.0pt 792.0pt;margin:72.0pt 72.0pt 72.0pt 72.0pt;mso-header-margin:36.0pt;mso-footer-margin:36.0pt;mso-paper-source:0;}div.WordSection1{page:WordSection1;}-->