Source-to-sink constraints on tectonic and sedimentary evolution of the western Central Range and Cenderawasih Bay (Indonesia)

Abstract

The island of New Guinea is the result of continent-arc collision that began building the island's Central Range during the late Miocene. Recent studies have shown that rapid subduction, uplift and exhumation events took place in response to rapid, oblique convergence between the Pacific and the Australian plates. The tectonic and sedimentary evolution of Cenderawasih Bay, in the northwestern part of the New Guinea Island is still poorly understood: this bay links a major structural block, the Kepala Burung block, to the island's Central Ranges. Previous studies have shown that Cenderawasih Bay contains a thick (> 8 km) sequence of undated sediments. One hypothesis claims that the embayment resulted from a 3 Ma opening created by anticlockwise rotation of the Kepala Burung block with respect to the northern rim of the Australian plate. Alternatively, the current configuration of Cenderawasih Bay could have resulted from the southwest drift of a slice of volcanics and oceanic crust between 8 and 6 Ma. We test these hypotheses using i) a geomorphologic analysis of the drainage network dynamics, ii) a reassessment of available thermochronological data, and iii) seismic lines interpretation. We suggest that sediments started to accumulate in Cenderawasih Bay and onshore in the Waipoga Basin in the late Miocene since the inception of growth of the Central Range, beginning at 12 Ma, resulting in sediment accumulation of up to 12200 m. This evidence is more consistent with the second hypothesis, and the volume of sediment accumulated means it is unlikely that the embayment was the result of recent (2-3 Ma) rotation of structural blocks. At first order, we predict that infilling is mainly composed of siliciclastics sourced in the graphite-bearing Ruffaer Metamorphic Belt and its equivalent in the Weyland Overthrust. Ophiolites, volcanic arc rocks and diorites contribute minor proportions. From the unroofing paths in the Central Range we deduce two rates of solid phase accumulation (SPAR) since 12 Ma, the first one at a mean SPAR ranging between 0.12-0.25 mm/a with a maximum SPAR of 0.23-0.58 mm/a, and the second during the last 3 Ma, at a mean SPAR ranging between 0.93-1.62 mm/a and with a maximum SPAR between 2.13-3.17 mm/a, i.e., 6700-10000 m of Plio-Pleistocene sediment accumulation. Local transtensional tectonics may explain these unusually high rates of sedimentation in an overall sinistral oblique convergence setting.

Modelling of drainage dynamics influence on sediment routing system in a fold‐and‐thrust belt

“…In the Central Range of the island of New Guinea, the rapidly eroding southern flank ( E max_CR = 1.7 mm/a) contrasts with the slowly eroding central high plateau ( E min_CR < 0.7 mm/a) (Weiland & Cloos, ), in a similar way as seen in our experiments. Considering the rate of differential erosion and the mean slope of the south flank, the main drainage divide would migrate towards the centre of the Central Range at ~10 −2 m/a (Babault et al., ). Using the minimum and maximum erosion rates in the Central Range to calculate the incision rate ratio R cr * , we obtain values ranging from 5 × 10 4 ( I min_mod / E min_CR ) to 6 × 10 5 ( I max_mod / E max_CR ) (very close to the R mn * ratio previously calculated using the Atlas of Morocco and Himalaya cases).…”

“…Equation gives a simple way to calculate from incision rates and mean slopes the velocity of divide migration into a slowly eroding and highly elevated smooth erosional surface subjected to a constant uplift rate. This equation has been applied to the Central Range of New Guinea (Babault et al., ). When corrected for a non‐null erosion rate in the longitudinal‐dominated drainage network, the mean celerity of divide migration ( C pred ) in Equation becomes (Babault et al., ):…”

“…3D view to the West of the western Central Range of the New Guinea Island and cross section of the Irian Fold Belt from Kendrick (). Normalized steepness indices of rivers are in colour (Babault et al.,). Yellow dots: location of published AFT data (Weiland & Cloos, ).…”

“…This equation has been applied to the Central Range of New Guinea (Babault et al, 2018). When corrected for a non-null erosion rate in the longitudinal-dominated drainage network, the mean celerity of divide migration (C pred ) in Equation 2 becomes (Babault et al, 2018):…”

“…Hence, ongoing deformation should lead eventually to a reorganization from early longitudinal rivers to transverse ones, and rock-type-related erodibility may F I G U R E 1 2 3D view to the West of the western Central Range of the New Guinea Island and cross section of the Irian Fold Belt from Kendrick (2000). Normalized steepness indices of rivers are in colour (Babault et al,2018). Yellow dots: location of published AFT data (Weiland & Cloos, 1996).…”