Texture, mineralogy, geochemistry, and 14C ages of two deep-sea sediment cores （GM6 and GM7） recovered in the southwestern Gulf of Mexico were investigated to infer their provenance and depositional condition. The s...Texture, mineralogy, geochemistry, and 14C ages of two deep-sea sediment cores （GM6 and GM7） recovered in the southwestern Gulf of Mexico were investigated to infer their provenance and depositional condition. The sediments are enriched in fine-grained silt and clay and poor in sand content. Mineralogically, the sediments consist of quartz, calcite, smectite, and kaolinite. Based on the ]4C data, the age of the GM6 and GM7 sediment cores were calculated as 23,615 cal yrs. BP and 19,007 cal yrs. BP, respectively. The weathering indices such as chemical index of alteration （CIA）, chemical index of weathering （CIW）, and plagioclase index of alteration （PIA） in GM6 （56-69, 60-74, and 6]-73, respectively） and GM7 （54-69, 57-76, and 55-74, respectively） cores revealed a moderate-to-high intensity of weathering. The rare earth element （REE） patterns suggested that the sediments were derived mostly by the weathering of intermediate rocks, exposed along the coastal regions of the Gulf of Mexico. The trace elemental ratios like V/Cr （〈2）, Ni/Co （〈2）, and Cu/Zn （〈1）, authigenic uranium content （〈1）, and Ce anomaly （Ce/Ce＊ ≤1） suggested that the sediments were deposited under an oxic condition, which was also revealed by the benthic foraminiferal assemblages throughout the GM6 and GM7 sediment cores.展开更多
The mineralogy, bulk sediment geochemical composition, and U–Pb ages of detrital zircons retrieved from the Barra del Tordo(Tordo) and Tesoro beach sediments in the northwestern Gulf of Mexico were analyzed to determ...The mineralogy, bulk sediment geochemical composition, and U–Pb ages of detrital zircons retrieved from the Barra del Tordo(Tordo) and Tesoro beach sediments in the northwestern Gulf of Mexico were analyzed to determine their provenance. The beach sediments are mainly composed of quartz, ilmenite, magnetite, titanite,zircon, and anorthite. The weathering proxies such as the Chemical Index of Alteration(CIA), Chemical Index of Weathering(CIW), and Plagioclase Index of Alteration(PIA), reveal a moderate-to-high intensity of weathering in the source area. The chondrite-normalized rare earth element(REE) patterns are similar to felsic igneous rocks, with large negative europium anomaly(Eu/Eu^(*)= ~ 0.47–0.80 and ~ 0.57–0.67 in the Tordo and Tesoro beach sediments,respectively).Three major zircon U–Pb age groups are identified in the Tordo and Tesoro beach sediments, i.e., Proterozoic(~2039–595 Ma), Mesozoic(~ 244–70.3 Ma), and Cenozoic(~ 65.9–1.2 Ma). The differences of the zircon age spectrum between the Tordo and Tesoro beach sediments are not significant. The comparison of zircon U–Pb ages in this study with ages of potential source terranes suggests that the Mesozoic and Cenozoic zircons of the studied Tordo and Tesoro beach sediments were derived from the Eastern Alkaline Province(EAP) and Mesa Central Province(MCP). Similarly, the likely sources for the Proterozoic zircons were the Sierra Madre Oriental(SMOr) and Oaxaquia in the northwestern Gulf of Mexico. The results of this study further indicate that the sediments delivered to the beaches by rivers and redistributed by longshore currents were crucial in determining the sediment provenance.展开更多
基金the partial financial assistance provided by the DGAPA-PAPIIT(No:IN106117)the Institute of Marine Sciences and Limnology(ICML),UNAM,Internal(No.616)projects+2 种基金DGAPA-PAPIIT,UNAM for the Bachelor degree scholarship(No:IN106117)the Posgrado en Ciencias del Mar y Limnologia(PCML)postgraduate program and to CONACyT for a doctoral fellowship(No.595593/308610)the support received by the Project"FACIES-PEMEX-PEP No:420401851"
文摘Texture, mineralogy, geochemistry, and 14C ages of two deep-sea sediment cores （GM6 and GM7） recovered in the southwestern Gulf of Mexico were investigated to infer their provenance and depositional condition. The sediments are enriched in fine-grained silt and clay and poor in sand content. Mineralogically, the sediments consist of quartz, calcite, smectite, and kaolinite. Based on the ]4C data, the age of the GM6 and GM7 sediment cores were calculated as 23,615 cal yrs. BP and 19,007 cal yrs. BP, respectively. The weathering indices such as chemical index of alteration （CIA）, chemical index of weathering （CIW）, and plagioclase index of alteration （PIA） in GM6 （56-69, 60-74, and 6]-73, respectively） and GM7 （54-69, 57-76, and 55-74, respectively） cores revealed a moderate-to-high intensity of weathering. The rare earth element （REE） patterns suggested that the sediments were derived mostly by the weathering of intermediate rocks, exposed along the coastal regions of the Gulf of Mexico. The trace elemental ratios like V/Cr （〈2）, Ni/Co （〈2）, and Cu/Zn （〈1）, authigenic uranium content （〈1）, and Ce anomaly （Ce/Ce＊ ≤1） suggested that the sediments were deposited under an oxic condition, which was also revealed by the benthic foraminiferal assemblages throughout the GM6 and GM7 sediment cores.
基金Consejo Nacional de Ciencia y Tecnologia (CONACy T),Project Number A1-S-21287Direccion General de Asuntos del Personal Academico (DGAPA)—Programa de Apoyo a Proyectos de Investigacion e Innovación Tecnologia (PAPIIT),Project Number IN107020Instituto de Ciencias del Mar y Limnologia Institutional Fund Number 616。
文摘The mineralogy, bulk sediment geochemical composition, and U–Pb ages of detrital zircons retrieved from the Barra del Tordo(Tordo) and Tesoro beach sediments in the northwestern Gulf of Mexico were analyzed to determine their provenance. The beach sediments are mainly composed of quartz, ilmenite, magnetite, titanite,zircon, and anorthite. The weathering proxies such as the Chemical Index of Alteration(CIA), Chemical Index of Weathering(CIW), and Plagioclase Index of Alteration(PIA), reveal a moderate-to-high intensity of weathering in the source area. The chondrite-normalized rare earth element(REE) patterns are similar to felsic igneous rocks, with large negative europium anomaly(Eu/Eu^(*)= ~ 0.47–0.80 and ~ 0.57–0.67 in the Tordo and Tesoro beach sediments,respectively).Three major zircon U–Pb age groups are identified in the Tordo and Tesoro beach sediments, i.e., Proterozoic(~2039–595 Ma), Mesozoic(~ 244–70.3 Ma), and Cenozoic(~ 65.9–1.2 Ma). The differences of the zircon age spectrum between the Tordo and Tesoro beach sediments are not significant. The comparison of zircon U–Pb ages in this study with ages of potential source terranes suggests that the Mesozoic and Cenozoic zircons of the studied Tordo and Tesoro beach sediments were derived from the Eastern Alkaline Province(EAP) and Mesa Central Province(MCP). Similarly, the likely sources for the Proterozoic zircons were the Sierra Madre Oriental(SMOr) and Oaxaquia in the northwestern Gulf of Mexico. The results of this study further indicate that the sediments delivered to the beaches by rivers and redistributed by longshore currents were crucial in determining the sediment provenance.
