中国地质大学：《构造地质学》课程PPT教学课件（英文版）Lecture 13 dip isogons and fold system

Review of geometrical elements of folds 转折 面 A 拐 转折端 槽线 Geometric elements of folds inter-limb angle A.翼邵平直的稻皱的翼问角;以.弧形稻皱的翼闻角

Geometric elements of folds inter-limb angle Review of geometrical elements of folds

Classification of folds(continue) Based on four main features or properties I direction of closing and facing 2 attitude of axial surface 3 size of inter-limb angle, and 4 shape of profile 5 dip isogons

Classification of folds (continue) Based on four main features or properties: 1 direction of closing and facing 2 attitude of axial surface 3 size of inter-limb angle, and 4 shape of profile 5 dip isogons

A antiform B synform C neutral fold younger upwards-lacing older Facing towards the left Downwards-facing Classification of fold based on direction of closing and facing

Classification of fold based on direction of closing and facing Downwards-facing upwards-facing Facing towards the left

axial plane C overfold A upright B inclined crest ap for oil or gas nges D recumbent ough E Classification of folds based on the attitude of axial surface

Classification of folds based on the attitude of axial surface Trap for oil or gas

-180 Gentle O pen Close 120 Tight Isoclinal Classification of folds based on the inter-limb angle

Classification of folds based on the inter-limb angle Gentle Open Close Tight Isoclinal

A. Constant Bed Thickness perpendicular Fold surface B. Thickness constan A parallel B similar parallel to axial surface C. A common center of curvature D. Planar limbs and sharp angular C concentric D chevron Inge zone Classification of folds based on the fold profile

A . Constant Bed Thickness perpendicular to Fold surface B. Thickness constant parallel to axial surface C. A common center of curvature D. Planar limbs and sharp angular hinge zone Classification of folds based on the fold profile

Parallel folds Detachment zone

Parallel folds Detachment zone

The band is the zone in which the common short straight limb Bounded by the two adjacent fold surfaces Kink band Markedly asymmetric chevron with a very long limb and a very short limb

Kink band Markedly asymmetric chevron with a very long limb and a very short limb The band is the zone in which the common short straight limb Bounded by the two adjacent fold surfaces

Classification of folds based on shape of profile Variation in layer thickness

Classification of folds based on shape of profile • Variation in layer thickness

le perpendicular to the axial surface axial surface ta Method of measuring variation in layer thickness to in a fold. Measurement is made at the point where the tangent to the outer curve makes an angle a with the perpendicular to to the axial surface

the perpendicular to the axial surface Method of measuring variation in layer thickness t in a fold.Measurement is made at the point where the tangent to the outer curve makes an angle  with the perpendicular to the axial surface