By Steve Ogilvie and Turan Abdullayev (BP Caspian)

Asymmetrical folds have one limb that is steeper than the other (Fig. 1). These can be observed at an outcrop to the NW of Baku in Azerbaijan on Fig. 1 (on the Baku to Guba highway). These outcrops were dubbed as the Candy Cane Mountains by writer Mark Elliot due to the various colours observed (https://azerbaijan.travel/hike-candy-cane-mountains).

Our fold interpretation of this particular outcrop is given in Fig. 2. From right to left (N-S), the folding style varies from a simple asymmetrical fold to an overturned fold to a recumbent fold. Note how the individual fold axes become increasingly horizontal.

This change of fold styles can be interpreted as an increasing intensity of deformation resulting in the beds from one limb almost lying horizontally upon the equivalent beds of the other limb i.e., a recumbent fold. The older structures are on the left hand (S) side.

Note that the mechanical stratigraphy (alterating sands-shales-marls) will also impact how the rocks deform - there is a dominance of shale (ligher colours) causing it to deform in a ductile manner by folding.

Figure 1. Folds in outcrop at “Candy Cane Mountain” on road to Guba (at red star on map inset) in Azerbaijan. Cretaceous age sandstones (red beds due to iron oxide content) interbedded with shales and marls (lighter colours). Location of Baku given by black star.

Figure 2. Interpretation of the outcrop in Fig. 1. An evolution of folding style from N-S towards overturned and recumbent folds indicates an increasing level of deformation in this direction.