Unconformity

This document summarizes a seminar on Ramsay classification of folds and folding mechanisms. It introduces Ramsay fold classification, which divides folds into three classes based on criteria like dip isogon patterns and curvature. Class 1 folds have convergent dip isogons and greater inner curvature. Mechanisms of folding discussed include buckling, which can form Class 1b folds of constant thickness, and bending due to intrusion or between boudins. Applications of the classification include hydrocarbon and salt dome exploration.

Structural geology is the study of the three-dimensional of the rock units with respect to their deformational histories, Structure is spatial and geometrical configuration of rock components. Structures are classified into two types: Primary structures. Secondary structures Primary structures Structures that form during deposition or crystallization of the rock, are the result of two processes: Settling of solid particles from fluid medium in which they have been suspended, in most of the sedimentary rocks. Crystallization of mineral grains from a liquid in which they have been dissolved as in igneous rocks.

This document discusses different types of faults, their classification, and characteristics. It begins by defining a fault and explaining their importance in geology. The main types of faults discussed are normal faults, thrust faults, strike-slip faults, and oblique faults. Criteria for identifying faults and the role of fluids in faulting are also summarized. Brittle faults occur in the upper crust and are characterized by fractures, while ductile faults at depth can form mylonite rocks. The document provides an overview of fault geometry and mechanics.

Unconformities represent gaps or missing time in the geologic record due to non-deposition or erosion. There are several types of unconformities that can form, such as angular unconformities, disconformities, and nonconformities. Unconformities are important as they provide information about periods of geologic activity, like folding or erosion of the land, and help place boundaries on geologic timescales. They can be identified in the field based on features like a lack of parallel bedding above and below the contact, presence of erosion surfaces, and fossils of widely different ages across the boundary.

There are two main forms of igneous rocks: 1) Extrusive rocks form from lava erupted at the Earth's surface and cool rapidly. They include lava flows, pyroclastic deposits like volcanic ash and tuff. 2) Intrusive rocks form from magma that cools below the surface. They can be concordant, forming sheets and domes parallel to layers, like sills and laccoliths, or discordant and cutting across layers, like dikes, batholiths, and volcanic necks.

Presentation focuses on the types of Rock cleavagrs, foliations and lineations. These types are also explained in brief.

A shear zone is a zone of strong deformation (with a high strain rate) surrounded by rocks with a lower state of finite strain. It is characterized by a length to width ratio of more than 5:1. In the Upper crust, where rock is brittle, the shear zone takes the form of a fracture called a fault. In the lower crust and mantle, the extreme conditions of pressure and temperature make the rock ductile. That is, the rock is capable of slowly deforming without fracture.

This lecture includes the brief description of types of fractures especially shear. contractional and tension fractures. Classification of faults

A fabric describes the spatial and geometric relationships that make up a rock at the microscopic to centimeter scale. It includes planar structures like bedding and cleavage, as well as the preferred orientation of minerals. Fabrics can be primary, forming during rock formation processes, or secondary and resulting from deformation. Foliation refers specifically to planar fabric and can develop through processes like cleavage, schistosity, and mylonitic foliation under increasing metamorphic conditions and deformation. Lineations describe linear fabric elements oriented in rocks, such as intersection lineations between planar features or mineral lineations showing preferred mineral alignments. Together, foliations and lineations define the tectonite class of a rock.