Abstract The Lower Miocene (lower Aquitanian) Hadrukh Formation (30–65 m thick), Al-Lidam area, Eastern Province, Saudi Arabia, was cored to examine sequence development within a non-marine siliciclastic-prone coastal plain in a semi-arid distal foreland setting. Facies are dominated by structureless quartz sands (terrestrial sand-sheets/shrub-coppice dunes or nebkhas), along with gypsiferous/calcareous quartz sands and gypsites (inland sabkhas), brecciated and sheet-cracked sandy carbonates/calcareous sands (palustrine), and some coarse lithic-clast quartz sands (fluvial) and associated paleosol-capped red and green-gray mudrock (interfluves). However, they lack the intercalated eolian laminated and cross-bedded sands of this hyper-arid region today, reflecting semi-arid Early Miocene conditions. Spectral analysis of core gamma-ray logs shows astronomical forcing within the eccentricity, obliquity and precessional bands. Tuning indicates the Hadrukh Formation is a composite sequence (∼1.3 myr duration) containing three (400 kyr) major sequences and eight minor sequences. Fluvial facies are locally developed at the base and near the top of the composite sequence. Massive sand sheet facies dominate the sequences, and sandy evaporitic facies and palustrine sandy carbonates are best developed in upper parts of sequences but interfinger within short distances with other facies. Subsidence and differential warping caused thickness and facies variation but the succession shows a strong astronomical signal. Astronomical forcing controlled semi-arid vs. more humid phases of deposition, as well as the position of base level, elevation of the ground-water table and presumably density of shrub cover. The three major sequence boundaries developed during 400 kyr eccentricity minima and cooling, while minor sequence boundaries formed during short eccentricity (100 kyr) cooling events.

中文翻译：

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沙特阿拉伯东部下中新世 Hadrukh 组陆地块状砂层、内陆 sabkha 和沼泽单元的天文强迫层序发育

摘要 沙特阿拉伯东部省 Al-Lidam 地区的下中新世（下阿基坦阶）Hadrukh 组（30-65 m 厚）被取芯，以检查半干旱区非海相硅质碎屑倾向沿海平原内的层序发育。远端前陆环境。相主要是无结构的石英砂（陆地砂层/灌木丛沙丘或nebkhas），以及含石膏/钙质石英砂和石膏岩（内陆sabkhas），角砾状和片状裂隙砂质碳酸盐/钙质砂（沼泽），和一些粗碎屑石英砂（河流）和相关的古土壤覆盖的红色和绿灰色泥岩（间流）。然而，它们缺乏今天这个超干旱地区的夹层风积层和交错层沙，反映了半干旱早中新世条件。核心伽马射线测井的光谱分析显示了偏心率、倾角和岁差带内的天文强迫。调谐表明 Hadrukh 组是一个复合层序（持续时间约 1.3 myr），包含三个（400 kyr）主要层序和八个次要层序。在复合层序的底部和顶部附近局部发育河流相。层序以块状砂板相为主，层序上部发育砂质蒸发相和沼泽砂质碳酸盐岩，与其他相在短距离内相交。沉降和差异翘曲导致厚度和相变，但序列显示出强烈的天文信号。天文强迫控制的半干旱与更潮湿的沉积阶段，以及基准面的位置，地下水位的高度和推测的灌木覆盖密度。三个主要层序边界在 400 kyr 偏心率最小值和冷却期间形成，而次要层序边界在短偏心率（100 kyr）冷却事件期间形成。