Comparison of upwards splaying and upwards merging segmented normal faults

•We present examples of normal faults that splay upwards or merge upwards.•The upwards-merging example evolved differently than previously published relay ramp models.•Stepping normal faults can merge upwards, even though displacement decreases.•Linkage between stepping normal faults is therefore not simply proportional to displacement.•The examples presented are from the Columbus Basin, Trinidad.

A common model for normal fault growth involves a single fault at depth splaying upwards into a series of en-echelon segments. This model is applied to faults as well as a range of extension fractures, including veins, joints and igneous dykes. Examples of splaying growth fault systems in the Columbus Basin, offshore Trinidad, are presented. They include the commonly described upwards splaying type, but also one fault zone with an upward change from disconnected overlapping synthetic faults to a continuous fault. One fault zone with high-displacement fault segments is separated by a relay ramp at depth, becomes breached higher up, developing into a continuous fault at its upper part, where displacements are least. This example suggests that whilst kinematic linkage typically precedes geometric linkage in the evolution of relay ramps, low-displacement parts of a fault system may be geometrically linked whereas higher displacement areas are only kinematically linked.

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