Triassic rocks of the Black Forest-Haldon area, Mackenzie Country, South Island, New Zealand

Abstract

Tightly folded marine sedimentary rocks, most or all of Triassic age, form the low hills on the north-east shore of Lake Benmore. They are separated from foliated sandstone and phyllite above and to the east by the Black Forest Thrust, which dips gently eastward.The sedimentary sequence in rocks known to be Triassic is, from the base: large lenticular sandstone bodies separated by subordinate finer-grained rocks; smaller sandstone lenses enveloped by siltstone and by.Jhin alternations of sandstone and siltstone which are commonly graded; and homogeneous siltstone with a few graded sandstone beds. The first two associations make up the Haldon Formation; the last is the Spurs Siltstone, The Haldon Formation is interpreted as an accumulation of channel sands and interchannel deposits formed in the upper part of a submarine fan. The Spurs Siltstone was deposited after this portion of the fan became inactive.The Middle Triassic pterioid Daonella and other fossils were found in the uppermost Haldon Formation. The tube fossil Torlessia was found at two localities, one at about the same horizon as Daonella and one at a lower horizon.Sandstone and fine-grained turbidites forming two outlying hills are named the Mount Maggie Formation.Haldon and Spurs Formations (and probably Mt Maggie Formation) are deformed into two interfering sets of folds. The first set consists of basically east-striking and mostly east-facing tight, steeply plunging folds with limbs steeply inclined to the south. The second set consists of a shallowly plunging, north-trending, open anticline to the west and a north-trending, tight synclinal fold belt to the east which is probably also shallowly plunging. Siltstone in the latter contains fracture cleavage and is locally overturned under the Black Forest Thrust. GEOLOGIC SETTINGThe Mackenzie Plain is an intermontane basin partially filled with the outwash and moraine of extensive Pleistocene glaciers. It is a dry area with thin soil and few trees. The land is divided mostly into large sheepruns established as early as the 1860s.The study area consists of roughly 38 krn" at the southern end of the Mackenzie Plain and just east of Lake Benmore (Fig. 1), lying wholly within Black Forest and Haldon stations and including both homesteads (Fig. 2). Isolated bedrock hills to the north poke up through the Pleistocene outwash and give way to more continuous rugged topography to the south. Elevations range from 360m (1183ft) to 960m 0158ft). The hills are tussock-covered and have slopes generally of 30°Or less. Rough tracks extend up most of the larger gullies and a private road follows Black Forest Stream. We saw no' 'evidence that the study area itself has been glaciated. Exposure is adequate for tracing beds on ridges and north-facing slopes if information is also gleaned from float. Exposure on south-facing slopes is mostly poor, and bedrock in most valleys is covered by alluvium. There are few natural exposures suitable for detailed measured sections.We found that the physiography is controlled by...

The Triassic Marine Biota of Eastern Indonesia and its Interregional and Global Correlation: A Review

“…Terebellina mackayi was reported for the first time from the Misool Archipelago by Jaworski (1915), then by Wanner (1931), and lately by Hasibuan (1991Hasibuan ( , 2007b from the same area. Terebellina mackayi was first described by Bather (1905) from New Zealand and its age ranges possibly from Ladinian to Norian (Campbell and Waren, 1965;Force and Force, 1978;Begg et al, 1983). The species probably also occur in Thailand within Carnian strata and Ladinian strata with Daonella in Malaysia (Grant-Mackie pers.…”