Joints and unconformity

The document discusses key concepts related to the geometry and elements of rock folding. It defines folding as the bending of rock strata due to compressional forces, which results in a wavy formation of the earth's surface known as folds. Folds are described by their form and orientation. Key elements of folds discussed include limbs, which are the segments of rock beds between the crest and troughs of a fold, and hinge lines, which connect the points of maximum curvature in a folded sequence. The document also defines axial planes, fold axes, plunge, and features such as crests, troughs, and inflection points.

Joints are cracks or fractures in rocks that divide the rock mass into blocks. They form due to tensile and compressive stresses from processes like cooling/crystallization of igneous rocks, erosion, seismic activity, and tectonic plate movement. Joints can be systematic or non-systematic, and are classified by their orientation, geometry, and origin. Joints are important both geologically and economically, as they influence groundwater flow, quarrying, tunnel construction, and more.

structural geology- lineations and foliations, their types, characteristics with examples and figures.

The document discusses various types of sedimentary structures classified based on their formation process. Primary structures form during deposition without external forces, while secondary structures form after deposition due to forces. Examples of primary structures include ripple marks, cross-bedding and flaser bedding. Secondary structures include sole marks, tool marks and groove marks formed by erosion. Chemical structures also form via processes like dissolution and precipitation. Sedimentary structures provide clues about depositional environments and sediment transport directions.

Structural geology is the study of the architecture and geometry of the Earth's crust and the processes that have shaped it. It involves analyzing how rock bodies deform in response to tectonic stresses. Structural analysis generally involves descriptive, kinematic, and dynamic analysis. Descriptive analysis describes rock structures like folds and faults. Kinematic analysis evaluates strain and changes in shape and orientation of rocks. Dynamic analysis reconstructs the stresses that caused rock deformation and failure. Stresses in rocks can be tensile, compressive, or shear stresses. Stress is analyzed using concepts like the stress tensor, Mohr's circle diagrams, and the orientation of maximum shear stresses. The main sources of stress that drive deformation are the motions of tectonic

This document discusses the classification of joints in rocks. It describes two main classifications: geometrical and genetic. Geometrical classification is based on the orientation of joints relative to rock beds and includes strike, dip, oblique, and bedding joints. Genetic classification considers the forces that formed the joints, dividing them into tension, shear, and compression joints. Joints are important in civil engineering and geology as they can cause weaknesses in rocks and influence landslides.

This document defines sequence stratigraphy and discusses its basic concepts. Sequence stratigraphy studies genetically related rock units bounded by unconformities. It is based on dividing strata into sequences bounded by sea level changes. Key concepts discussed include depositional sequences, parasequences, flooding surfaces, system tracts, accommodation space, and the importance of sequence stratigraphy for understanding basin evolution and resource exploration.

This document discusses the geometric classification of folds in geology. It defines what folds are and describes their key features like hinge lines, axial planes, limbs, and amplitudes. It then categorizes folds based on various criteria such as the sense of curvature (anticline, syncline), direction of younging (anticlinal, synclinal), symmetry (symmetrical, asymmetrical), nature of the hinge line (cylindrical, non-cylindrical), plunge, interlimb angle, thickness, orientation, and shape of the hinge. It provides examples of different fold types and discusses parasitic folds. The document serves as a comprehensive overview of how folds are classified geometrically in structural geology.

This document defines and describes different types of lineations found in deformed rocks, which are linear structures that occur repetitively. It discusses three main types of lineations: form lineations related to geological structures like folds, boudins, and slickenlines; surface lineations defined by intersections or slip; and mineral lineations caused by the preferred orientation of mineral grains or aggregates. Specific examples of each lineation type are provided, and the usefulness of lineations in structural analysis to determine strain and slip directions is explained.

Rock fabric is defined as the total sum of grain shape, size, and configuration in a rock. Foliation is a planar fabric that can include cleavage, which refers to spaced, aligned planar or curviplanar surfaces associated with folds. Lineation is a linear fabric that represents the subparallel alignment of elongate elements within a rock. Both foliation and lineation can be primary features that formed during the original igneous or sedimentary processes or can be secondary features formed by metamorphism.

This document defines and describes the key elements of faults in geology. It discusses fault plane, fault line, strike, dip, hanging wall, footwall, throw, heave, net slip, rake, and hade. Elements such as strike and dip are used to characterize the orientation of the fault plane. Hanging wall and footwall refer to the rock blocks separated by the fault. Throw, heave and net slip describe the displacement components. Understanding these fault elements aids in field study and identification of fault types.

The document discusses different types of unconformities: - Angular unconformity occurs when rock layers above and below are not parallel due to erosion and deposition over a long period of time with changes in bedding orientation. - Nonconformity separates older crystalline rocks from overlying younger sedimentary or volcanic rocks, representing a long period of erosion. - Disconformity has parallel bedding above and below, separated by erosion over some time. - Local unconformity is similar to a disconformity but represents only a short period of non-deposition over a small area.