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Detrital zircon U-Pb geochronology and geochemistry of the Riachuelos and Palma Sola beach sediments,Veracruz State,Gulf of Mexico:a new insight on palaeoenvironment

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Journal of Palaeogeography 2020年第4期9卷 495-521页

作者： John S.Armstrong-Altrin Unidad de Procesos Oceánicos y Costeros Instituto de Ciencias del Mar y LimnologíaUniversidad Nacional Autónoma de MéxicoCiudad UniversitariaCiudad de México 04510México

Zircons are abundant in the beach *** this study,surface microtexture,mineralogy,bulk sediment geochemistry,trace element composition and U−Pb isotopic geochronology of detrital zircons collected from the Riachuelos and Palma Sola beach areas,southwestern Gulf of Mexico were performed to infer the sediment provenance and *** zircon microtexture was categorized as mechanically-and/or chemically-induced *** weathering index values for the Riachuelos(~72−77)and Palma Sola(~71−74)beach sediments indicated moderate weathering of both of the two source *** major and trace element data of bulk sediments suggested passive margin settings for the two *** trace elemental ratios and chondrite-normalized rare earth element(REE)patterns of bulk sediments revealed that the sediments were likely sourced by felsic and intermediate igneous *** the zircon Th/U ratios(mostly more than 0.2)and zircon REE patterns(with negative Eu and positive Ce anomalies)suggested a magmatic origin for both of the beach sediments from these two *** distinct zircon age peaks respectively belonging to the Paleozoic and the Cenozoic were identified both in the Riachuelos and Palma Sola beach *** geochronology comparison research between the Riachuelos−Palma Sola beach sediments and potential source areas in SW Gulf of Mexico revealed that the source terrane supplied the Paleozoic zircons of this study was identified as the Mesa Central Province(MCP),and the Cenozoic zircons were transported from the nearby Eastern Alkaline Province(EAP).Moreover,although the Precambrian zircons were very few in the studied sediments,their geochronology and geochemistry results still could infer that they were contributed by the source terranes of Grenvillian igneous suites in the Oaxaca and the Chiapas Massif Complexes.

关键词： Detrital zircon beach sediment U-Pb dating Zircon grain morphology Microtexture Mineralogy Geochemistry Geochronology Gulf of Mexico

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Provenance of sediments from Barra del Tordo and Tesoro beaches, Tamaulipas State, northwestern Gulf of Mexico

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Journal of Palaeogeography 2021年第3期10卷 382-398页

作者： Mayla A.Ramos-Vazquez John S.Armstrong-Altrin Posgrado en Ciencias del Mar y Limnologpa Universidad Nacional Autonoma de MexicoCiudad UniversitariaCiudad de Mexico 04510Mexico Universidad Nacional Autonoma de Mexico Instituto de Ciencias del Mar y LimnologiaUnidad de Procesos Oceanicos y CosterosCiudad UniversitariaCiudad de Mexico 04510Mexico

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.

关键词： Geochemistry sedimentary provenance Zircon U–Pb beach sediment Rare earth elements Mexico

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Coastal landscape evolution tracked from late Holocene wave-cut benches in the Sinan Archipelago,Southwest Korea

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Geoscience Frontiers 2020年第1期11卷 293-301页

作者： Sung-Ja Choi Bokchul Kim Yong Sik Gihm Sanghoon Kwon Geology Division Korea Institute of Geoscience and Mineral ResourcesDaejeon34132Republic of Korea Department of Earth System Sciences Yonsei UniversitySeoul03722Republic of Korea School of Earth Sciences The Ohio State UniversityColumbusOH43210USA

Glacio-isostatic adjustment(GIA)and tectonic activity are important factors in the formation of marine *** Holocene wave-cut benches in the eastern part of the West Sea of Korea,also called the Yellow Sea,can be divided into two steps:531 cm above sea level(ASL)for the upper bench(T2)and 464-481 cm ASL for the lower bench(T1).sediments on the benches a re classified into four units,and are interpreted to be beach deposits acco rding to gravel shape,textu re,and seaward *** ove rlying sediment indicates that T2 was formed at approximately 530 cm ASL before 2900 yr BP,and T1 at approximately 460-480 cm ASL before 1520 yr *** Holocene(4000-2000 yr BP)relative sea level(RSL)curves based on GIA models are inconsistent with the wave-cut bench *** T1 and T2 benches to the RSL curves of the West Sea,the upper and the lower benches were uplifted by approximately 5-8 m and 4-7 m,*** the area is several hundred kilometers away from plate boundaries,the high frequency of earthquakes in the West Sea may have induced the uplift of wave-cut benches during the last 2000 *** indicate that the west coast of the Korean Peninsula(KP)should no longer be considered an area of subsidence,but be assigned to a regime of uplift during the late Holocene.

关键词： West Sea of Korea Yellow Sea Late Holocene Wave-cut benches beach sediment Uplift Tectonics

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