Mangarara Formation: Exhumed remnants of a middle Miocene, temperate carbonate, submarine channel‐fan system on the eastern margin of Taranaki Basin, New Zealand

Abstract

The middle Miocene Mangarara Formation is a thin (1-60 m), laterally discontinuous unit of moderately to highly calcareous (40-90%) facies of sandy to pure limestone, bioclastic sandstone, and conglomerate that crops out in a few valleys in North Taranaki across the transition from King Country Basin into offshore Taranaki Basin. The unit occurs within hemipelagic (slope) mudstone of Manganui Formation, is strati graphic ally associated with redeposited sandstone of Moki Formation, and is overlain by redeposited volcaniclastic sandstone of Mohakatino Formation. The calcareous facies of the Mangarara Formation are interpreted to be mainly mass-emplaced deposits having channelised and sheet-like geometries, sedimentary structures supportive of redeposition, mixed environment fossil associations, and stratigraphic enclosure within bathyal mudrocks and fiysch. The carbonate component of the deposits consists mainly of bivalves, larger benthic foraminifers (especially Amphistegina), coralline red algae including rhodoliths (Lithothamnion and Mesophyllum), and bryozoans, a warm-temperate, shallow marine skeletal association. While sediment derivation was partly from an eastern contemporary shelf, the bulk of the skeletal carbonate is inferred to have been sourced from shoal carbonate factories around and upon isolated basement highs (Patea-Tongaporutu High) to the south. The Mangarara sediments were redeposited within slope gullies and broad open submarine channels and lobes in the vicinity of the channel-lobe transition zone of a submarine fan system. Different phases of sediment transport and deposition (lateral-accretion and aggradation stages) are identified in the channel infilling. Dual fan systems likely co-existed, one dominating and predominantly siliciclastic in nature (Moki Formation), and the other infrequent and involving the temperate calcareous deposits of Mangarara Formation. The Mangarara Formation is an outcrop analogue for middle Miocene-age carbonate slope-fan deposits elsewhere in subsurface Taranaki Basin, New Zealand.

The source is in the sink: Deep‐water deposition by a submarine volcanic arc, Taranaki Basin, New Zealand

“…The shallow, north/north‐west‐trending channels observed in the Mangarara Formation at the north end of Pahaoa Ridge (<1 km south‐east of section E; Fig. ; Puga‐Bernabéu et al ., ) are of particular interest in context with these dune deposits. Channel‐margin geometry was also documented at the contact between the Mohakatino and Mangarara formations at the Awakino Heads site (section E).…”

“…() suggests that the basement high was submerged, but lacks data to directly constrain the region of the basement high. The Mangarara and Tirua formations indicate that carbonate production was active at or near sea‐level in the vicinity of the Herangi High in middle Miocene time (early Langhian and late Serravallian, respectively), but the unconformity between the Mangarara Formation and overlying Mohakatino Formation represents up to 4·5 Myr, during which time carbonate production apparently shut off (Puga‐Bernabéu et al ., ). Furthermore, activity on the Taranaki Fault, which cores the Herangi High, ceased in the study area by middle Miocene time (Stagpoole & Nicol, ).…”

“…The base of the succession is Manganui Formation deep‐marine mudstone topped by the Tirua and Mangarara formations, deep‐marine channel (for example, Fig. ) and fan deposits of bioclastic sandstone and conglomerate reworked downslope from shelf carbonate factories that fringed emergent portions of the Herangi–Patea–Tongaporutu High (Nodder et al ., ,b; Puga‐Bernabéu et al ., ).…”

Heterozoan carbonate deposition on a steep basement escarpment (Late Miocene, Almería, south‐east Spain)

“…Sediment characteristics may locally influence the sediment redeposition type (Puga-Bernab eu et al, 2014) but, in the Almer ıa apron, variations in the skeletal associations in the source area did not change the depositional style in the lobes. Although the Almer ıa lobes are linked to feeder channels, these channels followed and filled fault-related canyons/depressions in the basement instead of cutting across previously accumulated deposits as in the channelized systems found in other temperate-water carbonate systems Vigorito et al, 2005;Puga-Bernab eu et al, 2009).…”

Origin and resedimentation of rhodoliths in the Late Paleocene flysch of the Polish Outer Carpathians

“…Detailed studies of Paleogene rhodoliths have generally been limited to occurrences in Upper Eocene to Oligocene strata, mainly in the Mediterranean region. Resedimented rhodoliths in flysch and the taxonomy of coralline algae from such deposits have seldom been investigated (Leszczyński 1978;Stockar 2000;Puga-Bernabéu et al 2009). …”