TY - JOUR
T1 - The development of sheath folds in viscously stratified materials in simple shear conditions
T2 - An analogue approach
AU - Dell'Ertole, Damiano
AU - Schellart, Wouter P.
PY - 2013/11
Y1 - 2013/11
N2 - Sheath folds are highly non-cylindrical folds occurring in a variety of geological settings, and have been studied using different approaches. With the present work, we provide a quantitative analysis of the generation and development of sheath folds in a viscously layered system in simple shear conditions. The sheath folds develop from an initial non-cylindrical deflection located on the highly viscous layer. The analogue experiments investigated the influence of (1) variations in the viscosity ratio between the high viscosity layer and the matrix (ηhvl/ηm), (2) variations in the ratio between the amplitude of the initial deflection and the thickness of the high viscosity layer (Af/Thvl), and (3) progressive simple shear (γ). The results show that increases in ηhvl/ηm will produce progressively less elongated sheath folds, while increases in Af/Thvl will result in more elongated sheath folds. We present regime diagrams with ηhvl/ηm and Af/Thvl for different shear strains illustrating under which conditions sheath folds form. In case the original deflection amplitude and layer thickness as well as γ can be retrieved for sheath folds in nature, then their geometry can be used to quantify the effective ηhvl/ηm.
AB - Sheath folds are highly non-cylindrical folds occurring in a variety of geological settings, and have been studied using different approaches. With the present work, we provide a quantitative analysis of the generation and development of sheath folds in a viscously layered system in simple shear conditions. The sheath folds develop from an initial non-cylindrical deflection located on the highly viscous layer. The analogue experiments investigated the influence of (1) variations in the viscosity ratio between the high viscosity layer and the matrix (ηhvl/ηm), (2) variations in the ratio between the amplitude of the initial deflection and the thickness of the high viscosity layer (Af/Thvl), and (3) progressive simple shear (γ). The results show that increases in ηhvl/ηm will produce progressively less elongated sheath folds, while increases in Af/Thvl will result in more elongated sheath folds. We present regime diagrams with ηhvl/ηm and Af/Thvl for different shear strains illustrating under which conditions sheath folds form. In case the original deflection amplitude and layer thickness as well as γ can be retrieved for sheath folds in nature, then their geometry can be used to quantify the effective ηhvl/ηm.
KW - Analogue model
KW - Ductile deformation
KW - Sheath fold
KW - Simple shear
UR - http://www.scopus.com/inward/record.url?scp=84885349443&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84885349443&partnerID=8YFLogxK
U2 - 10.1016/j.jsg.2013.09.002
DO - 10.1016/j.jsg.2013.09.002
M3 - Article
AN - SCOPUS:84885349443
SN - 0191-8141
VL - 56
SP - 129
EP - 141
JO - Journal of Structural Geology
JF - Journal of Structural Geology
ER -