A constitutive model for mechanical and chemo‐mechanical compaction in sedimentary basins and finite element analysis

Compaction and associated fluid flow are fundamental processes in sedimentary basin deformation. Purely mechanical compaction originates mainly from pore fluid expulsion and rearrangement of solid particles during burial, while chemo‐mechanical compaction results from Intergranular Pressure‐Solution (IPS) and represents a major mechanism of deformation in sedimentary basins during diagenesis. The aim of the present contribution is to provide a comprehensive 3D framework for constitutive and numerical modeling of purely mechanical and chemo‐mechanical compaction in sedimentary basins. Extending the concepts that have been previously proposed for the modeling of purely mechanical compaction in finite poroplasticity, deformation by IPS is addressed herein by means of additional viscoplastic terms in the state equations of the porous material. The finite element model integrates the poroplastic and poroviscoplastic components of deformation at large strains. The corresponding implementation allows for numerical simulation of sediments accretion/erosion periods by progressive activation/deactivation of the gravity forces within a fictitious closed material system. Validation of the numerical approach is assessed by means of comparison with closed‐form solutions derived in the context of a simplified compaction model. The last part of the paper presents the results of numerical basin simulation performed in one dimensional setting, demonstrating the ability of the modeling to capture the main features in elastoplastic and viscoplastic compaction. Copyright © 2016 John Wiley & Sons, Ltd.     

Holocene cool‐water carbonate and terrigenous sediments from southern Spencer Gulf,South Australia

Holocene sediments from southern Spencer Gulf are cool‐water carbonate‐rich gravels and sands, dominated by molluscs and Bryozoa. Five sedimentary fades are recognized: (i) molluscan gravel; (ii) branching coralline‐algal gravel, associated with shallow partially protected environments; (iii) molluscan‐biyozoan sand; (iv) mixed bioclastic sand, representative of the deeper central region of the lower gulf; and (v) bryozoan gravel, an isolated fades developed in a semi‐protected micro‐environment. The southern gulf is characterized by complex oceanographic conditions together with variations in water depth and substrate. The sediments share the characteristics of both the southern shelf and upper Spencer Gulf. Grain‐size distribution and sedimentary facies are controlled by a combination of all the above processes. Past sea level fluctuations are recognized from sea floor strand‐line deposits. The relic component of the palimpsest sediments has eroded from the Pleistocene aeolianite dunes. The sediments, therefore, reflect both the modern marine and past environments.     

应用粒度分析辨别某些第四纪混杂堆积成因初探

本文从粒度特征分析了青海昆仑山垭口地区的第四纪混杂堆积和甘肃武都泥石流堆积以及贡嘎山海洋性冰川的现代冰碛之间的差异性,明显看出,由于各种第四纪混杂堆积的搬运介质、搬运过程及沉积过程不同,第四纪混杂堆积的粒度特征存在明显的不同。沉积物的粒度特征反映了沉积环境。因此,用粒度特征来辨别各种第四纪混杂堆积也是一种行之有效的方法。     

云南白显矿床钡镁锰矿的矿物学研究

云南白显锰矿产于中三叠统法郎组地层中,其主要矿石矿物是钡镁锰矿。矿物属沉积成因,结晶细微,局部呈沿c轴延长的细小柱状和纤维状。矿物点群2/m,常见单形:斜方柱{110}、平行双面{100}和{001}。晶胞参数:a_0=0.9758nm,b_0=0.2848nm,c_0=0.9640nm,β=88.98°,V=0.26786nm~3,Z=1。矿物反射率为18.60～25.65,相对密度3.67,文中还列出了红外光谱和差热分析新资料。     

福建省下二叠统童子岩组风暴沉积特征

本文详细研究了福建省早二叠世童子岩期含煤岩系中风暴沉积的分布层位及沉积相序特征，在此基础上，对童子岩组风暴沉积的古地理环境进行了初步探讨。     

华南变质基底的组成、边界与构造演化（研究综述）

本文据作者调查并综合有关资料，就华南变质基底的组成结构、边界性质、构造型式及演化过程作了较全面阐述；就板溪群是否为构造混杂岩，及其所代表的地质体性质作了深入分析和讨论，作者认为：华南可能存在晚太古－早元古统一变质基底，中元古末至印支期为板块活动期，印支期后，由于受太平洋板块作用影响而进入新的构造活动期。     

济阳坳陷上第三系的沉积特征及沉积相的纵向演化规律

本文根据岩性特征、沉积构造、砂体厚度和测井曲线特征等资料，对4口岩心井进行了沉积相分析，详细研究了不同时期的河流类型及沉积相的演化规律，从而认为济阳凹陷上第三系沉积大体经历了3个阶段：早期的冲积扇一辫状河阶段，中期的辫状河一低弯度曲流河阶段及晚期的高弯度曲流河阶段，同时分析了不同砂体的油气储集性能。     

济阳坳陷上第三系馆陶组上段沉积相研究

利用地质资料、测井资料、地震资料及分析化验资料对济阳坳陷上第三系馆陶组上段岩相古地理特征进行了全面系统地研究。首先从岩性、沉积结构和构造、砂体形态、电性特征、地震反射等方面论证馆陶组上段为山麓洪积相和河流相沉积，其中它们又可进一步细分为10种亚相或微相。其次，详细论述了沉积相的平面展布，同时还指出了油气分布与沉积相带的关系。此外，本文还指出馆陶组上段沉积期的物源方向、河流流向、最终汇水区及当时的古气候条件等。     

沉积鲕石和尿路结石若干特征的对比研究

本文从仿生学的思路出发，将几种沉积鲕石、核形石、结核等从其结构、成分和形成条件等方面与四种常见尿路结石进行对比研究。认为这些产物虽然发生在自然界或人体内两种截然不同的环境中，但是在研究其形成机理时，彼此有许多可以互相借鉴之处。沉积鲕石、核形石的分层结构和再结晶交代现象等，可以对比应用于尿石的形成和发育机理的解释；同时，尿路结石形成理论中的局部过饱和以及取向附生学说，也可引进于沉积鲕石、核形石和结核的形成理论中。此外，本文首次介绍了热发光方法研究沉积鲕石和尿路结石的成果，并认为这一研究方法仍有继续深入探讨其应用范围的潜力。