(1976). Authorship and discrimination of formations in the Permian Productus Creek Group, Southland. New Zealand Journal of Geology and Geophysics: Vol. 19, No. 1, pp. 149-151.
Abstract Rare fossils including the gastropod Peruvispira aff. imbricata Waterhouse and the bivalve Atomodesma aff. marwicki Waterhouse indicate a late Lower Permian age for the middle part of the Greenhills Group. Plerophyllum aff. timorense Gerth occurs in a lower horizon of the Greenhills Group. Bands of marble containing shell prisms, rare radiolarians, and other microfossils occur in the upper part of the section.
The Santee River of North Carolina and South Carolina emptied into the sea 75 km west of its modern mouth when the shoreline was 15 to 21 m above present sea level in early Pleistocene time. For a short time, the river deposited a fluviomarine delta lobe (volume 5 cu km) that covered 400 sq km near Summerville, South Carolina, 35 km northwest of Charleston. The Summerville lobe was abandoned before the late Pleistocene, and the sea has not covered the area since then. The original wave-constructed ridge-and-swale topography is still visible; drill holes have revealed the subsurface lithofacies relationships. In the modern Santee delta and the chenier plain of Louisiana, similar topography and patterns of lithofacies reflect alternating dominance of flood-plain deposition nd shoreface redistribution. Paleontology, paleomagnetic stratigraphy, and sediment mineralogy contribute to the age determination of the Summerville lobe. On the basis of fossil pollen and invertebrates identified by U.S. Geological Survey paleontologists, the Summerville lobe deposits are tentatively believed to be equivalent in age to the Waccamaw Formation (late Pliocene and early Pleistocene) of northern South Carolina. Surficial heavy- and light-mineral suites are more mature, and thus older, than paleontologically dated late Pleistocene shoreline deposits nearby. Less weathered mineral suites below the water table in the Summerville lobe reflect the Piedmont (Santee River) source of the sediment. Preliminary paleomagnetic data are compatible with this age determination. End_of_Article - Last_Page 452------------
Gorge Saddle is one low point on a drainage divide between Fiordland and the Southland Plain. Eastward sloping Quaternary terraces east of the divide and westward sloping terraces to the west contain granitic pebbles which could have been deriVed only from the west. This suggests doming at the present divide concurrent with transport from the west.
Abstract In middle and late Permian time, the Productus Creek area of South land, New Zealand, was the site of simultaneous accumulation of shallow marine, biogenic carbonate and immature volcanogenic sediments. The prismatic shell fragments of the bivalve Atomodesma formed the major limestones; this suggests a well-established bank environment. Less extensive calcareous Bryozoa banks succeeded the Atomodesma banks, and were covered in turn by a prograding conglomerate in late Permian time. Trends in fossil assemblages, clay mineralogy, sediment sizes, and sediment thicknesses suggest a nearby Permian shore line north-west of Productus Creek. Two hypothetical transgression-regression models of the Productus Creek Group are discussed: (a) a migrating delta and (b) eustatic sea-level variation which takes into account contemporaneous glacial events in Australia and elsewhere. One new informal formation, the Weetwood Formation, is named, and the Mangarewa, Elsdun, and Hawtel Formations are redefined.
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 thin 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.
ABSTRACT Mollusks tend to break down mechanically to three basic microarchitectural units: layers (500-250µ), sublayers (32-4µ), and unit crystals (0.5-.125µ). In natural environments the size distribution of carbonate in sediments differs from that produced artificially because of selective dispersal by waves and tidal currents. In the inner continental shelf off west Florida, the particles smaller than 500µ, produced mainly in the wave zone, tend to accumulate on the outer shelf and in the lagoons. The breaker zone contains most of the coarser particles.
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