Anomalous passive subsidence of deep‐water sedimentary basins: a prearc basin example, southern New Caledonia Trough and Taranaki Basin, New Zealand

Abstract

Stratigraphic data from petroleum wells and seismic reflection analysis reveal two distinct episodes of subsidence in the southern New Caledonia Trough and deep-water Taranaki Basin. Tectonic subsidence of~2.5 km was related to Cretaceous rift faulting and post-rift thermal subsidence, and 1.5 km of anomalous passive tectonic subsidence occurred during Cenozoic time. Pure-shear stretching by factors of up to 2 is estimated for the first phase of subsidence from the exponential decay of post-rift subsidence. The second subsidence event occured~40 Ma after rifting ceased, and was not associated with faulting in the upper crust. Eocene subsidence patterns indicate northward tilting of the basin, followed by rapid regional subsidence during the Oligocene and Early Miocene. The resulting basin is 300-500 km wide and over 2000 km long, includes part of Taranaki Basin, and is not easily explained by any classic model of lithosphere deformation or cooling. The spatial scale of the basin, paucity of Cenozoic crustal faulting, and magnitudes of subsidence suggest a regional process that acted from below, probably originating within the upper mantle. This process was likely associated with inception of nearby Australia-Pacific plate convergence, which ultimately formed the Tonga-Kermadec subduction zone. Our study demonstrates that shallow-water environments persisted for longer and their associated sedimentary sequences are hence thicker than would be predicted by any rift basin model that produces such large values of subsidence and an equivalent water depth. We suggest that convective processes within the upper mantle can influence the sedimentary facies distribution and thermal architecture of deep-water basins, and that not all deepwater basins are simply the evolved products of the same processes that produce shallow-water sedimentary basins. This may be particularly true during the inception of subduction zones, and we suggest the term 'prearc' basin to describe this tectonic setting.Correspondence: Jan Baur, Total S.A.,

Tectonic controls on Miocene sedimentation in the Southern Taranaki Basin and implications for New Zealand plate boundary deformation

“…Deposition of Late Cretaceous terrestrial to marginal‐marine sediments occurred in isolated sub‐basins in the STB that were controlled by NE to N‐trending normal faults until cessation of localised rifting by the end of the Paleocene (King & Thrasher, ; Reilly et al, ; Strogen et al, ). The basin then underwent passive thermal subsidence until the Late Eocene (King, ; King & Thrasher, ), followed by the onset of regional subsidence from the Early Oligocene (Baur, Sutherland, & Stern, ; Holt & Stern, ; Strogen et al, ). This subsidence resulted in basin deepening with maximum marine inundation between ca.…”

“…30 and 20 Ma (Hood et al, ; King & Thrasher, ; Strogen et al, ); only the Early Miocene part of this interval is considered here. A deepening of the basin was likely caused by both wider regional lithospheric‐driven plate boundary processes (Baur et al, ; Holt & Stern, ) as well as more localised downwarping in the foot‐wall of the TFS, producing a narrow foredeep close to the faults (Strogen et al, , their figure ). Maximum flooding of Zealandia occurred in the latest Oligocene–earliest Miocene (Waitakian, ca.…”

“…Rapid subsidence of the STB commenced at about ca. 35–30 Ma (Hayward & Wood, ; Strogen et al, ; Figure ) and is interpreted to reflect a combination of regional plate‐boundary scale subsidence and subsidence in the foot‐wall of the TFS associated with inception of the Australia‐Pacific plate boundary through New Zealand (Baur et al, ; Holt & Stern, ; Stagpoole & Nicol, ; Strogen et al, ). A range of potential mechanisms could account for the regional (plate boundary scale) subsidence including, frictional resistance to slip on the subduction thrust (e.g.…”

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“…Ocean currents predicted by model simulations also could be substantially wrong if paleobathymetry is not depicted accurately (e.g., if parts of the Tasman Frontier were much shallower than today during the early Eocene). There are indications that large vertical movements in the Tasman Frontier occurred during the early Eocene (Baur et al, 2014;Sutherland et al, 2010).…”

Integrated reservoir characterization of the Paleocene Farewell Formation, Taranaki Basin, New Zealand, using petrophysical and petrographical analyses

“…This formed the Tasman Sea and numerous extensional basins on the New Zealand subcontinent, which include an intra-plate rift that formed the Taranaki Rift, which later developed into the Taranaki Basin during the late Cretaceous (Baur et al 2014;Kroeger et al 2013;Thrasher 1992). The Taranaki Basin evolved in three distinct phases: (1) initial rifting phase in the mid-Cretaceous-Paleocene, associated with the breakup of Gondwana, (2) Eocene-early Oligocene passive margin, post-rift thermal contraction and regional subsidence, and (3) Oligocene-recent active marginal basin in response to development of the Australia-Pacific convergent plate boundary through New Zealand (King and Thrasher 1996).…”