--> ABSTRACT: Morphologic Variability of Clinoforms within the Giant Foresets Formation of the Northern Taranaki Basin, New Zealand, by Salazar, Migdalys; Moscardelli, Lorena G.; Wood, Lesli; #90142 (2012)

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Morphologic Variability of Clinoforms within the Giant Foresets Formation of the Northern Taranaki Basin, New Zealand

Salazar, Migdalys *1; Moscardelli, Lorena G.2; Wood, Lesli 2
(1) Jackson School of Geosciences, The University of Texas at Austin, Austin, TX.
(2) Bureau of Economic Geology, The University of Texas at Austin, Austin, TX.

Morphological variations within continental-margin clinoforms hold the clue to understanding sediment dispersal and composition, as well as transport mechanisms affecting the shelf margin region of a given basin. In this study, variations in clinoform morphologies within the Plio-Pleistocene Giant Foresets Formation were documented by interpreting clinoform architectures in an along-dip regional 2D seismic line, located in the northern portion of the Taranaki Basin. Seismic stratigraphic interpretations and paleontological studies from four wells were combined to document individual clinoform parameters such as front height and length, progradational and aggradational rates, and clinoform front declivity and its variation with depth (declivity profile). Three distinct clinoform morphologies were identified: gentle and smooth (low-angle, linear geometry), steep and rough (concave), and sigmoidal (convex-to-concave). The best curve fittings for these slope profiles correspond to linear, exponential, and Gaussian distribution functions, respectively.

These observations suggest three main periods of clinoform development exist within the Giant Foresets Formation. The first period, characterized by linear to gently arcuate clinoform foresets and the absence of canyons on the rollover region, is probably associated with moderate to high sediment input. This period is most likely related to a low degree of canyon incision during the late Pliocene (Waipipian to Lower Nukumanian stages). Steeper and dissected clinoforms developed within the middle portion of the stratigraphic succession are representative of the second period of development and associated with a higher degree of canyon incision and sediment bypass toward the basin. Increase in the critical slope angle during the Upper Nukumanian stage disturbed the previous planar surfaces, starting mass movements that reached their maximum development at 1.63 Ma. Changes in clinoform declivity through time suggest that slope angles greater than 5 degrees are characteristic of incised/failed clinoform fronts in the Taranaki Basin. Finally, sediment supply increased again during the deposition of the shallower, oversteepened section. More rounded, smooth transition between topsets and foresets could be associated to an increasing role of alongshore currents and an increased chance to preserve sediments in the roll-over region of the clinoforms (shelf-break).

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California