Controls of pre-existing structures on clinoform architecture and the associated progradational system elements

摘要

There remains a limited understanding of the controls of pre-existing structures on the architecture of deep-water progradational sequences. In the Northern Taranaki Basin (NTB), New Zealand, Pliocene post-extensional sedimentary sequences overlie Miocene back-arc volcaniclastic units. We utilize seismic reflection datasets to investigate the relationships between the buried back-arc mound-shaped structures, and the spatio-temporal changes in clinoform architecture and the associated progradational system elements within the overlying continental slope margin sequences. Our results reveal the following: (a) buried mound-shaped structures in the northern domain of the study area, overlain by younging progression of shelf-to-basin prograding clinoforms; (b) folding of the deeper clinoforms that systematically decrease in magnitude with shallowing depth from the top of the seamounts; (c) overall, the N-S-trending continental slope margin evolves from a highly curvilinear/angular trend in the deeper clinoforms (Units 1 and 2) into a rectilinear geometry within the shallower post-extensional intervals (Unit 3 and shallower); (d) Units 1 and 2 characterized by dominance of stacked offlap breaks and over-steepened (7-10°) clinoform foreset slopes in the northern domain, and dominance of gently dipping foreset slopes (<6°) in the south; (e) Unit 3 shows very low (<5°) and intermediate (5-7°) foreset slopes across the entire survey; (f) in the northern domain, differential loading by prograding sequences about the buried seamounts and horst-graben structures induced a differential compaction of the deeper units, which influenced a temporal pinning of the prograding slope margin in pre-Unit 2 times and (g) wide, closely spaced channel incision into over-steepened slopes dominate the deeper prograding sequence in the northern domain, whereas narrower, straighter channels dominate the south. We show that the buried pre-existing structures constitute rigid buttresses that mo