|Johansen, Ståle Emil
|Omosanya, Kamaldeen Olakunle
|This study investigated the geological evolution of the northernmost areas of the Tara-naki Basin, and was based on a combination of seismic data (a combination of 2D linesand a 3D volume) and one well. The interpretation was subdivided into two parts. Thefirst part looked at the basin evolution linked to strata below the prograding shelf, and wascompared to adjacent areas further south with more information available in literature.The study of the pre-prograding shelf strata showed two separate extensional events, thepresence of a volcanic environment, and an angular unconformity. The two extensionalevents were correlated to the literature, and is linked to a failed Late Cretaceous rift andPliocene back-arc extension. The igneous extrusives and intrusives were related to theformation of an andesitic volcanic arc during mid- to late Miocene. Some of the dataindicated that igneous activity might have lasted longer in the northern parts of the basin.The angular unconformity could not be correlated with findings in literature.The second part analyzed the prograding shelf only, using qualitative methods andquantitative methods. Investigation of the Pliocene-Pleistocene prograding shelf showedthat the shelf edge advanced approximately 18 km in average along the studied lines overa period of 2.4 myr. The trajectory is flat to slightly descending during deposition ofclinothem bodies C1-C4, which promoted a significant advance of the shelf-slope-basinplatform. Topsets are are only slightly developed, and most of the sediments were dis-tributed on the slope and in the basin. The strong progradation was attributed to the largequantity of sediments sourced from the uplifted and subsequently eroded hinterland.Clinothem bodies C5-C8 was characterized by an overall ascending regressive trajec-tory, and marked a clear change in the interplay between sediment supply and relativesea-level changes. The rise in relative sea-level created significant accommodation spaceon the shelf, and promoted the formation of thick topsets. The change from a flat to as-cending trajectory was most likely a response to a decreasing supply of sediments.Clinothem C1-C4 were deposited over an approximate time span of 0.6 myr. This isin contrast to C5-C8, which were deposited over a time span of approximately 1.8 myr.This suggests that erosion and supply of sediments were initially high during depositionof C1-C4, followed by a subsequent decrease that facilitated accommodation on the shelf.The shelf-edge trajectory appears to be closely linked to both the shelf-edge advanceand the overall foreset inflection angle. The shelf-edge advance was significantly higherduring flat and descending regressive conditions than ascending regressive conditions.
|Seismic Interpretation of the Northernmost Areas of the Taranaki Basin, NZ
|Norges teknisk-naturvitenskapelige universitet, Fakultet for ingeniørvitenskap,Institutt for geovitenskap og petroleum