Magnetic mineralogy in Barranca Tlalpan exposure paleosols, Tlaxcala, Mexico
Fuente:
Redalyc
Enregistré dans:
| Auteur principal: | |
|---|---|
| Format: | Artículo científico |
| Langue: | en |
| Publié: |
Universidad Nacional Autónoma de México
2004
|
| Sujets: | |
| Accès en ligne: | |
| Tags: |
Ajouter un tag
Pas de tags, Soyez le premier à ajouter un tag!
|
| _version_ | 1876465363984580608 |
|---|---|
| author | Ana Soler |
| author_facet | Ana Soler |
| contents | Magnetic mineralogy in Barranca Tlalpan exposure paleosols, Tlaxcala, Mexico Ana Soler Elizabeth Solleiro Rebolledo Beatriz Ortega Guerrero Sergey Sedov Ciencias de la Tierra paleosols central Mexico rock magnetic analysis The knowledge of past climatic and environmental conditions in central Mexico, interpretedextensively from lacustrine records, is restricted to the last ca. 50,000 years. The recent discovery of newlocalities of paleosol sequences in central Mexico and the reconnaissance of their usefulness as recordsof environmental change provides a new source of information about past climatic conditions for timesprior to the last full glacial. In this paper, we analyze the mineral magnetic properties of a sequence ofpaleosols developed in volcaniclastic deposits and evaluate these data as paleoenvironmental proxy.The sequence consists of a modern Phaeozem soil and seven late Quaternary Luvisol paleosols outcroppingin Barranca Tlalpan, Tlaxcala, Mexico. Rock magnetic analysis was used to study the concentration andtype of magnetic mineralogy. The mineral magnetic data, supported by soil morphological and chemicaldata, are interpreted to indicate that the paleosols can be grouped in three sets, each with distinctcharacteristics. The Red set paleosols P7 and P6 are the most weathered, and present the highest magneticconcentration composed of Ti-magnetite and ultrafine magnetite (<30 nm). The Brown set of paleosolsP5, P4 and P3, with few redoximorphic features, have coarser grains and lower concentrations of magneticminerals. The Gray set, paleosols P2 and P1, have abundant redoximorphic features including FeMnnodules, and have a multicomponent magnetic mineralogy of coarse size. Paleosols from the Red andBrown sets conserve evidence of neoformation of ultrafine magnetite grains in the Bt horizons, probablyderived from pedogenic processes. However, direct observations by microscopy and rock magnetismparameters point to a later destruction of this ultrafine fraction. We consider that even if pedogenicprocesses resulted in the formation of ultrafine magnetite, redoximorphic conditions under humid climatesare responsible of the destruction of magnetic minerals. Such conditions may have strongly prevailed inthe Gray set paleosols, whereas the Red set was probably developed under contrasting seasonalprecipitation climates, which favored the formation and preservation of pedogenic magnetic minerals. 2004 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57221114 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.1 Vol.21 |
| format | Artículo científico |
| id | redalyc_57221114 |
| institution | Redalyc |
| language | en |
| publishDate | 2004 |
| publisher | Universidad Nacional Autónoma de México |
| spellingShingle | Magnetic mineralogy in Barranca Tlalpan exposure paleosols, Tlaxcala, Mexico Ana Soler Ciencias de la Tierra paleosols central Mexico rock magnetic analysis Magnetic mineralogy in Barranca Tlalpan exposure paleosols, Tlaxcala, Mexico Ana Soler Elizabeth Solleiro Rebolledo Beatriz Ortega Guerrero Sergey Sedov Ciencias de la Tierra paleosols central Mexico rock magnetic analysis The knowledge of past climatic and environmental conditions in central Mexico, interpretedextensively from lacustrine records, is restricted to the last ca. 50,000 years. The recent discovery of newlocalities of paleosol sequences in central Mexico and the reconnaissance of their usefulness as recordsof environmental change provides a new source of information about past climatic conditions for timesprior to the last full glacial. In this paper, we analyze the mineral magnetic properties of a sequence ofpaleosols developed in volcaniclastic deposits and evaluate these data as paleoenvironmental proxy.The sequence consists of a modern Phaeozem soil and seven late Quaternary Luvisol paleosols outcroppingin Barranca Tlalpan, Tlaxcala, Mexico. Rock magnetic analysis was used to study the concentration andtype of magnetic mineralogy. The mineral magnetic data, supported by soil morphological and chemicaldata, are interpreted to indicate that the paleosols can be grouped in three sets, each with distinctcharacteristics. The Red set paleosols P7 and P6 are the most weathered, and present the highest magneticconcentration composed of Ti-magnetite and ultrafine magnetite (<30 nm). The Brown set of paleosolsP5, P4 and P3, with few redoximorphic features, have coarser grains and lower concentrations of magneticminerals. The Gray set, paleosols P2 and P1, have abundant redoximorphic features including FeMnnodules, and have a multicomponent magnetic mineralogy of coarse size. Paleosols from the Red andBrown sets conserve evidence of neoformation of ultrafine magnetite grains in the Bt horizons, probablyderived from pedogenic processes. However, direct observations by microscopy and rock magnetismparameters point to a later destruction of this ultrafine fraction. We consider that even if pedogenicprocesses resulted in the formation of ultrafine magnetite, redoximorphic conditions under humid climatesare responsible of the destruction of magnetic minerals. Such conditions may have strongly prevailed inthe Gray set paleosols, whereas the Red set was probably developed under contrasting seasonalprecipitation climates, which favored the formation and preservation of pedogenic magnetic minerals. 2004 artículo científico 1026-8774 https://www.redalyc.org/articulo.oa?id=57221114 en http://www.redalyc.org/revista.oa?id=572 Revista Mexicana de Ciencias Geológicas application/pdf Universidad Nacional Autónoma de México Revista Mexicana de Ciencias Geológicas (México) Num.1 Vol.21 |
| title | Magnetic mineralogy in Barranca Tlalpan exposure paleosols, Tlaxcala, Mexico |
| topic | Ciencias de la Tierra paleosols central Mexico rock magnetic analysis |
| url | https://www.redalyc.org/articulo.oa?id=57221114 |