The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in...The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in an area;Once the rocks of an area undergo polyphase of deformation, the boudins get modified and can no longer help in determining the deformational evidences. The present study involves identification of various types of boudins their classification and morphology as per existing status of knowledge and their role in determining the type of deformation in Neem Ka Thana belt, Proterozoic rocks of North Delhi fold belt. The study of symmetric, asymmetric and modified boudins in the area enabled the author to deduce that the rocks in above belt have suffered a ployphase deformation marked with flattening type of progressive deformation during the first phase (DF1) of deformation and the second phase (DF2) with a time gap, has produced modified boudins and folded boudin structures with the largely same axis of deformation in both these deformations.展开更多
Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks migh...Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks might be critical to the formation of limestone conglomerates.According to detailed field measurement and laboratory analyses (thin section observation and XRD analysis),four types of ribbon rocks are classified,i.e.,limestone and marlstone couplet (L-M),limestone and shale couplet (L-S),thin-bedded lime mudstone (Ltb),and laminated limestone and marlstone couplet (Cl).These ribbon rocks were mostly deposited in low-energy subtidal environments (below fair-weather wave base).Ribbon rocks exhibit various subtle deformation structures such as intrastratal cracks and "boudin" structures.Differential cementation of carbonate and argillaceous layers during early diagenesis is a prerequisite condition for the deformation of ribbon rock under compaction.Ribbon rocks would be deformed into limestone conglomerates under differential compaction that might be triggered by external forces such as storm and earthquake.展开更多
文摘The boudins can be of symmetric as well as asymmetric type and can help in determining shear sense and help unfold the deformational history, hence are important structure for recognizing the history of deformation in an area;Once the rocks of an area undergo polyphase of deformation, the boudins get modified and can no longer help in determining the deformational evidences. The present study involves identification of various types of boudins their classification and morphology as per existing status of knowledge and their role in determining the type of deformation in Neem Ka Thana belt, Proterozoic rocks of North Delhi fold belt. The study of symmetric, asymmetric and modified boudins in the area enabled the author to deduce that the rocks in above belt have suffered a ployphase deformation marked with flattening type of progressive deformation during the first phase (DF1) of deformation and the second phase (DF2) with a time gap, has produced modified boudins and folded boudin structures with the largely same axis of deformation in both these deformations.
基金supported by National Natural Science Foundation of China (Grant No.40972043)Natural Science Foundation of Shandong Province (Grant No.Y2008E02)Scientific Program of Shandong Provincial Education Department (Grant No.G08LD01)
文摘Ribbon rocks are characterized by an alternation of millimeter-to centimeter-thick limestone and argillaceous deposits (marlstone or shale).The sedimentary processes and diagenetic characteristics of ribbon rocks might be critical to the formation of limestone conglomerates.According to detailed field measurement and laboratory analyses (thin section observation and XRD analysis),four types of ribbon rocks are classified,i.e.,limestone and marlstone couplet (L-M),limestone and shale couplet (L-S),thin-bedded lime mudstone (Ltb),and laminated limestone and marlstone couplet (Cl).These ribbon rocks were mostly deposited in low-energy subtidal environments (below fair-weather wave base).Ribbon rocks exhibit various subtle deformation structures such as intrastratal cracks and "boudin" structures.Differential cementation of carbonate and argillaceous layers during early diagenesis is a prerequisite condition for the deformation of ribbon rock under compaction.Ribbon rocks would be deformed into limestone conglomerates under differential compaction that might be triggered by external forces such as storm and earthquake.
