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Upper Cretaceous-Upper Eocene mud-dominated turbidites of the Belaga Formation, Sarawak (Malaysia): 30Ma of paleogeographic, paleoclimate and tectonic stability in Sundaland
Marine and Petroleum Geology ( IF 4.2 ) Pub Date : 2021-01-08 , DOI: 10.1016/j.marpetgeo.2021.104897
Hassan Baioumy , Ahmed Mohamed Ahmed Salim , Nisar Ahmed , Maame Maisie , Khaled Al-Kahtany

The Upper Cretaceous-Upper Eocene Belaga Formation is characterized by thick deep-water sediments that were accumulated as one of the biggest ancient submarine fans covering a time interval of 30 Ma. Although the Belaga Formation is the extensively investigated formation in the Rajang Group, its source and tectonic setting are still arguable. This study utilizes, for the first time, detailed mineralogical and geochemical investigations on sediments from the Belga Formation to examine its origin. The Belaga Formation is subdivided into five members that are made of seven lithofacies dominated by mudstone. Clay fractions from the mudstones of the five members are composed of illite (40–60 wt %), kaolinite (30–45 wt %) and chlorite (5–15 wt %). Al2O3/TiO2 ratios and calculated SiO2 (wt. %) as well as Zr–TiO2, Al2O3–TiO2, SiO2–Al2O3/TiO2 and Cecn-La/Ybcn plots suggested felsic to intermediate igneous source rocks for all members probably the Lower-Upper Cretaceous granites and tonalities of the Schwaner Mountains situated southwest of the studied area. The abundance of kaolinite, Sr/Cu ratios, C-values, Sr/Cu ratios, Sr/Cu versus Ga/Rb plot and high Chemical Index Alteration (CIA) indicate warm and humid paleoclimate throughout the formation of the Belaga Formation. Geochemical proxies from the major oxides (SiO2–K2O/Na2O, K2O/Na2O–SiO2/Al2O3 binary plots and CaO–Na2O–K2O ternary plot), trace elements (Sc/Cr–La/Y discrimination diagram) and uniform REE patterns with distinct Eu negative anomalies propose a mature passive margin tectonic setting for the five members of the Belaga Formation. Facies analysis indicate typical turbidite sequences in all members. Domination of mudstone and the passive margin tectonic setting suggest a channel-levee complex without lobes submarine fan model (Type III) for these turbidites. Stability in source area composition, paleoclimate, palaeogeography and tectonic setting of Sundaland during the Late Cretaceous-Late Eocene (~30 Ma) indicated from sedimentology and geochemical proxies is consistent with the global paleogeographic and paleoclimatic models for this area during this period. Due to their geological and economic importance as potential hydrocarbon source in the region an all over the world, results of this study provide new insights for the architecture and sedimentology of turbidites.



中文翻译:

马来西亚砂拉越Belaga组的上白垩统-上新世上以泥浆为主的浊度:桑达兰古地理,古气候和构造稳定性为30Ma

上白垩统-上新世贝拉加组的特征是厚厚的深水沉积物,这些沉积物是时间间隔为30 Ma的最大的古代海底扇之一。尽管Belaga组是Rajang组中经过广泛研究的组,但其来源和构造背景仍有待商ar。这项研究首次利用对Belga地层沉积物的详细矿物学和地球化学研究来检查其成因。Belaga地层被细分为5个成员,这些成员由以泥岩为主的7个岩相组成。来自五个成员的泥岩中的粘土馏分由伊利石(40–60 wt%),高岭石(30–45 wt%)和绿泥石(5–15 wt%)组成。Al 2 O 3 / TiO 2比率和计算的SiO 2(wt。%)以及Zr-TiO 2,Al 2 O 3 -TiO 2,SiO 2 -Al 2 O 3 / TiO 2和Ce cn -La / Yb cn地块表明,对于所有成员,可能是从下到上白垩纪花岗岩,以及位于研究区域西南部的施万纳山脉的色调,为长至火成岩烃源岩。高岭石的丰度,Sr / Cu比,C值,Sr / Cu比,Sr / Cu与Ga / Rb曲线以及高化学指数变化(CIA)表明,整个Belaga地层都存在温暖和潮湿的古气候。主要氧化物(SiO 2 –K 2 O / Na 2 O,K 2 O / Na 2 O–SiO 2 / Al 2 O 3二元图和CaO–Na 2 O–K 2的地球化学代理)三元图),痕量元素(Sc / Cr-La / Y判别图)和具有明显Eu负异常的均匀REE模式,为Belaga组的五个成员提出了成熟的被动边缘构造背景。相分析表明在所有成员中典型的浊积岩序列。泥岩的控制和被动边缘构造背景表明,对于这些浊质,没有堤状潜艇扇形模型(III型)的河堤复合体。从沉积学和地球化学代理表明,晚白垩世-晚始新世(〜30 Ma)期间,苏达兰的源区组成,古气候,古地理和构造环境的稳定性与该地区的全球古地理和古气候模型一致。

更新日期:2021-01-28
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