Age of Growth Faulting in Southeast Louisiana

ABSTRACT The times and amounts of expansion of the downthrown sections of growth faults in southeast Louisiana were studied. This provided a means of analysing the time and rate of growth fault movement. The rate of growth fault movement increases from the time of inception of faulting until a maximum rate is reached and then decreases to the time of cessation of fault movement. Superimposed on this cycle are numerous minor irregularities in the rate of movement which are a possible means of fault identification in complexly faulted areas. The age of maximum growth fault movement was determined throughout southeast Louisiana and discrete areas were defined on the basis of similar times of maximum fault activity. Within each area thus defined, the age of maximum growth of the domal uplifts was generally the same as that of the faulting. The geographic location and time of structural activity of these areas clearly show the basinward migration of growth fault movement in time. The general east-west trend of these areas of synchronous structural activity is interrupted in the northern portions of Jefferson and Plaquemines Parishes. This region acted as a buttress around which these structural trends were deflected. The superposition of several ages of faulting in southern Terrebonne Parish resulted in an anomalously large amount of subsidence and deposition in this area and formed the Terrebonne Trough. Because of the intimate relationship between structure and stratigraphy in the Miocene of south Louisiana, a knowledge of the time of structural activity is necessary to the understanding of the regional distribution of lithofacies.