Deformation–sedimentation feedback and the development of anomalously thick aggradational turbidite lobes: Outcrop and subsurface examples from the Hikurangi Margin, New Zealand

Abstract

Concepts of the interaction between autogenic (e.g., flow process) and allogenic (e.g., tectonics) controls on sedimentation have advanced to a state that allows the controlling forces to be distinguished. Here we examine outcropping and subsurface Neogene deep-marine clastic systems that traversed the Hikurangi subduction margin via thrust-bounded trench-slope basins, providing an opportunity to examine the interplay of structural deformation and deep-marine sedimentation. Sedimentary logging and mapping of Miocene outcrops from the exhumed portion of the subduction wedge record heavily amalgamated, sand-rich lobe complexes, up to 200 m thick, which accumulated behind NE–SW-oriented growth structures. There was no significant deposition from low-density parts of the gravity flows in the basin center, although lateral fringes demonstrate fining and thinning indicative of deposits from low-density flows. Seismic data from the offshore portion of the margin show analogous lobate reflector geometries. These deposits accumulate into complexes up to 5 km wide, 8 km long, and 300 m thick, comparable in scale with the outcropping lobes on this margin. Mapping reveals lobe complexes that are vertically stacked behind thrusts. These results illustrate repeated trapping of the sandier parts of turbidity currents to form aggradational lobe complexes, with the finer-grained suspended load bypassing to areas downstream. However, the repeated development of lobes characterized by partial bypass implies that a feedback mechanism operates to perpetuate a partial confinement condition, via rejuvenation of accommodation. The mechanism proposed is a coupling of sediment loading and deformation rate, such that load-driven subsidence focuses stress on basin-bounding faults and perpetuates generation of accommodation in the basin, hence modulating tectonic forcing. Recognition of such a mechanism has implications for understanding the tectono-stratigraphic evolution of deep-marine fold and thrust belts and the distribution of resources within them.

Depositional Model for Turbidite Lobes in Complex Slope Settings Along Transform Margins: The Motta San Giovanni Formation (Miocene—Calabria, Italy)

“…Data are extracted from Pirmez et al (2000), Bruhn et al (2003), Moraes et al (2004), Prélat et al (2009, 2010, and is locally accumulated. Such bypass and overspill processes are typical of intraslope sub-basins as also described from other geological contexts (Sinclair and Tomasso, 2002;Prather, 2003;McArthur et al, 2021). Studied lobe fringes record few bipartite beds, which are diagnostic for basin floor lobe fringe deposits (Hodgson, 2009).…”

“…These perched lobes are also described as confined lobes, of which an important literature is available from outcrop, with for example the world class Annot Sandstones, France (Joseph et al, 2000;Guillocheau et al, 2004;Joseph and Lomas, 2004;Etienne et al, 2012), the Sorbas basin, Spain (Kleverlaan, 1989;Postma and Kleverlaan, 2018) or the Hikurangi margin, New Zealand (Burgreen and Graham, 2014;McArthur et al, 2021), and from modern system such as the Golo system, East Corsica (Gervais et al, 2004(Gervais et al, , 2006Deptuck et al, 2008).…”

Relating seafloor geomorphology to subsurface architecture: How mass‐transport deposits and knickpoint‐zones build the stratigraphy of the deep‐water Hikurangi Channel

“…Deceleration may lead to the formation of more chaotic, yet still weakly‐confined, flow deposits. Anomalously high‐amplitude reflectors observed above sheet deposits with variable amplitudes may reflect sand‐rich deposits from weakly‐confined flows (McArthur et al ., 2021) after initial MTD‐margin topography was healed, leaving a less severe reduction in longitudinal gradient. These deposits formed immediately prior to, and during, re‐incision and may mark the transition from incised sheet to terrace deposits.…”

“…The trench fill decreases in thickness from ca 6 km in the south‐west to ca 1 km in the north‐east (Lewis et al ., 1998; Barnes et al ., 2010; Plaza‐Faverola et al ., 2012). The fill dominantly comprises turbidites resulting from overbank deposition from the Hikurangi Channel, and transverse drainage networks that traversed the bounding slope (Lewis, 1994; Lewis et al ., 1998; Mountjoy et al ., 2009; McArthur et al ., 2021).…”

Evolution of a Fault-Controlled, Deep-Water Sub-Basin, Tabernas, SE Spain

“…Nonetheless outcrop examples where tectonic control of sea floor gradients can be demonstrated are rare. Amongst those described are tectonically-forced lateral migration of channels and fans in the Ainsa Basin, northern Spain (Pickering and Corregidor, 2005;Tek et al, 2020), flow stripping across an emergent fault-scarp in the Annot Basin (Tomasso and Sinclair 2004), sandy lobes aggrading behind thrust-related folds in a trench slope setting on the Hikurangi Margin (McArthur et al, 2021), changes in bed type related to tectonic evolution of the Apennines foredeep (Tinterri and Muzzi Magalhaes, 2011;Tinterri and Piazza, 2019) and evidence for faulting on the floor of late Miocene basins in SE Spain (Haughton, 2000;Hodgson and Haughton, 2004). The study reported here builds on the first recognition of an important intrabasinal fault zone traversing the floor of the southern Tabernas Basin, SE Spain (Haughton, 2000).…”