摘要:

Rb‐Sr and K‐Ar age determinations agree with palaeobotanical evidence in assigning an age of 270 Ma (Lower Permian) to the Nychum Volcanics, North Queensland. Geological and geochemical evidence (moderate ‐REE, La/Yb, Th, Zr/Y, Hf/Yb, Sc/Ni) indicate that the volcanics were erupted on a thin, active continental margin. Five magma groups are present: high‐alumina basalts, andesite‐dacites, acid rocks, tholeiitic andesites, and pitchstone with a high La/Yb ratio. The high‐alumina basalts and calc‐alkaline andesites have a parent‐daughter (source rock‐partial melt) relationship. The acid rocks share high HREE, Zr, Hf, Zn, Sc, Fe/Mg and low Al with, and may be fractionated from, the tholeiitic subduction‐zone andesites. Low‐pressure fractional crystallisation is evident in all five magma groups.

ISSN:0016-7614    

DOI:10.1080/00167618208729221

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The abrupt appearance of animal fossils at the end of the Precambrian can be explained in two ways—either as the initial explosion of animal life, or as the explosive appearance of fossilisable animals. Evidence from the oxygen‐binding proteins of living animals supports the latter view, since it points to a billion year history for the lower invertebrate phyla. It was the rise of large, muscular and/or mineralised animals that caused the Cambrian explosion, and the best explanation for their appearance seems to be a sharp increase in the oxygen content of the atmosphere.

ISSN:0016-7614    

DOI:10.1080/00167618208729222

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The Warrabin Trough in SW Queensland contains up to 3000 m of Devonian sedimentary rocks, and is a structural remnant of the formerly widespread Adavale Basin. Seismic data recently obtained by the Bureau of Mineral Resources enable reinterpretation of existing poorer quality seismic data, so that the structural framework and most of the trough margin can be mapped.

ISSN:0016-7614    

DOI:10.1080/00167618208729223

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Silcretes on the N.S.W. coast near Ulladulla have long been attributed to. a sub‐basaltic origin, but field evidence is at odds with all variations of the sub‐basaltic hypothesis, and one site shows good evidence that the basalt post‐dates the silcrete. K‐Ar ages averaging 29.7 ± 0.5 Ma from the basalts provide a minimum age for silcrete development in this area. Furthermore, the K‐Ar dates, together with evidence for an erosional rather than tectonic origin of the coastal lowland, demonstrate that the adjacent tablelands reached their present elevation prior to the mid‐Oligocene.

ISSN:0016-7614    

DOI:10.1080/00167618208729224

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The Dorrigo Plateau is covered by basalt, which is a remnant of the 18 Ma old Ebor Volcano. The centre of this volcano is an intrusion in the Bellinger Valley. The volcano was erupted on a palaeoplain of moderate relief. Subsequent uplift and tilting led to erosion of the Nambucca Beds, together with much of the volcano, and creation of a major escarpment, part of the Great Escarpment of eastern Australia. In this area the Great Escarpment is younger than 18 Ma.

ISSN:0016-7614    

DOI:10.1080/00167618208729225

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In late Pleistocene time Lake Dieri (ancestral ‘Greater Lake Eyre') was permanently filled during a wet climatic phase. Towards the close of Pleistocene time the watertable fell, Lake Dieri dried up, and its sediments deflated. Later the watertable rose, establishing ephemeral Lake Eyre in the deflated area, and Holocene sedimentation commenced. At about this time Lake Eyre tilted to the south and three sedimentary environments developed: (1)a saline playa environmentwithout saltcrusts in the northern end of the lake, where water drains away before wholly evaporating; (2)a terminal salina environmentin the south end, where evaporation of brines leaves saltcrusts overlying gypseous sediments; and (3) asaline flocculation environmentbetween the playa and salina environments, where sediments are deposited by flocculation when muddy floodwater from the north meets highly saline water of the southern salina.

ISSN:0016-7614    

DOI:10.1080/00167618208729226

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Chemical analyses of mafic to felsic metavolcanic rocks below and within fault slices of the Peel Fault System at Glenrock Station, N.S.W., show that several magmatic suites are present. The mafic metavolcanic rocks intercalated with volcanogenic sediments and calc‐alkaline volcanic rocks of the Tamworth Group are island arc tholeiites. Dolerites that intrude the sediments have tholeiitic or transitional characteristics. Ordovician‐Devonian(?) sediments, lithologically similar to the Woolomin Beds, contain island arc and intraplate‐intrusive rocks, and ocean floor, tholeiitic basalt. A sequence thrust over these beds contains calc‐alkaline volcanic rocks and mafic metavolcanic rocks of island arc character, which are poorer in Ti than the Tamworth Group mafic rocks. The source area for some of the volcanic rocks in the Tamworth Group may be to the east of the Peel Fault System.

ISSN:0016-7614    

DOI:10.1080/00167618208729227

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Although a 1972 dredging by USNSEltaninfrom the submarine Naturaliste Plateau was reported to yield rocks of continental origin, a re‐examination of the dredge haul shows that the rock clasts are in fact altered tholeiitic basalts. They have affinities both with MOR basalts and, especially, within‐plate basalts. Petrographically they correlate most closely with the Bunbury Tholeiitic Suite on the Australian mainland to the east. The basalts are reworked cobbles in a manganiferous Quaternary slump mass, which contains a quartz‐rich, felsic, detrital mineral suite with a granite‐gneiss provenance. The basalt cobbles were part of a basal conglomerate, which covered large areas of the Plateau. It is suggested that this was laid down from nearby elevated volcanic structures formed during the inception of seafloor spreading and the separation of Greater India from Australia at about 122 Ma BP.

ISSN:0016-7614    

DOI:10.1080/00167618208729228

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Limestones in the Palmers Oakey District, N.S.W., range in age from Middle Silurian to Early Devonian. They occur as sheet‐like, bioclastic beds and/or isolated clasts in three facies: a volcaniclastic facies, a mudstone‐limestone facies, and a limestone‐mudstone breccia facies. Multielement conodont taxa, not previously reported from Australia, includeKockelella absidata, Kockelella stauros, Ozarkodina asymmetrica, Ozarkodina stygia, Ozarkodina transitans, Pseudooneotodus bicornis,andPseudooneotodus tricornis.

ISSN:0016-7614    

DOI:10.1080/00167618208729229

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

ISSN:0016-7614    

DOI:10.1080/00167618208729230

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor