Ruth Mawson

Middle Palaeozoic extinction events: Faunal and isotopic data

Abstract At least 9 and possibly as many as 12 extinction events of global or near-global impact can be discriminated in the mid-Palaeozoic (earliest Silurian to Early Carboniferous) on the basis of brachiopod, coral, conodont and ammonoid data, and the history of carbonate build-ups. Isotopic data from whole-rock samples are presented for three of these events, based on Australian carbonate sequences constrained by conodont data. These data represent the initial phase of a more extensive investigation using C, O, S, Sr and Nd isotopic signatures derived from conodonts, articulate and inarticulate brachiopod shell, and fish remains from numerous Australian and European sequences. The aim of the project is to identify isotopic responses to extinction events, and address causes for these changes. In limestone sections analysed so far, variations in carbon isotope compositions on a whole-rock scale are most marked at horizons that can be correlated with times of significant reduction in biomass and diversity. This is despite the fact that the whole rocks are in fact multicomponent systems with respect to carbon, in part arising from diagenetic rearrangements of carbon distribution within the scale of the whole rock. Thus, the carbon isotope data do provide evidence on a whole-rock scale for fundamental changes in the global carbon cycle that are correlative with extinction events. It is, however, unlikely that the magnitude of the isotopic shift will be precisely documented from such whole-rock analyses. The oxygen isotope results are less obviously related to the times of carbon isotope excursion; this contrast in apparent resilience to post-depositional modification of pristine isotope compositions exemplifies the extreme caution needed in evaluating isotopic data from carbonates.

LITHOSTRATIGRAPHY, CONODONT BIOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENT OF THE MIDDLE DEVONIAN (GIVETIAN) TO EARLY CARBONIFEROUS (TOURNAISIAN) LIPAK FORMATION IN THE PIN VALLEY OF SPITI (NW INDIA)

Bed-by-bed lithostratigraphic sections combined with sequence stratigraphy and conodont biostratigraphy provide new information on the depositional environment and age of the Lipak Formation in the Pin Valley (Spiti). The formation comprises mixed siliciclastic and calcareous sediments at lower levels, richly fossiliferous limestones with two distinct sandstone incursions at higher levels, and dark mudstones followed by a thin siltstone interval. The upper limit of the Lipak Formation is defined by the angular unconformity below the sandstones of the Permian Gechang Formation. Lithologic correlation with sections in upper Lahaul indicates that, in the Pin Valley, the formation has been truncated just below its characteristic gypsum horizon. The lower boundary of the Lipak Formation is gradational from coastal arenites of the Muth Formation; the mappable boundary is drawn at the first appearance of dark carbonaceous, argillaceous siltstone and shale. Sedimentary structures, microfacies and conodont faunas indicate a general shallow marine depositional environment of the Lipak Formation in the Pin Valley; five sequence stratigraphic units have been distinguished. Conodont data demonstrate that the lowest 33 m of the Lipak Formation of the Pin Valley is mid to late Early varcus Subzone with characteristic species of Icriodus and Bipennatus . A previously unrecognised hiatus at c. 33 m above the base, at the boundary of sequence stratigraphic units S1 and S2, represents the interval Middle varcus Subzone to at least the end of the late Famennian Early expansa Zone. Because this hiatus does not correspond to a mappable boundary, no division of the Lipak Formation into named stratigraphic units is suggested, but we refer informally to the sediments represented by cycle S1 as Lipak A, and the sediments represented by cycles S2-S5 as Lipak B. Determination of S1 as Early varcus Subzone provides a maximum age for the gradationally underlying Muth Formation. At 75 m above the base of the composite Lipak Formation section, a 58 cm black to dark grey shale interval within late Famennian fossiliferous limestones conceivably correlates with the Hangenberg Event (end-Middle praesulcata Zone). Younger conodont faunas of the Lipak Formation -dominated by species of Clydagnathus with species of Bispathodus and Pseudopolygnathus also represented- is shown to extend to the mid-Tournaisian Early crenulata Zone.

Low-grade metamorphism in the Palaeozoic sequences of the Townsville hinterland, northeastern Australia*

The transition from diagenesis to low‐grade metamorphism for the Ordovician ‐ Early Carboniferous sequences of the Burdekin and Clarke River Basins and the Broken River ‐ Camel Creek region is characterised by b ‐cell dimension and Kübler Index (KI = illite crystallinity) of K‐white micas, clay‐mineral assemblages and conodont colour alteration index (CAI). Data indicate that: (i) there is a regional metamorphic pattern characterised by anchizonal conditions, with consistently higher grade in the Camel Creek region (or Subprovince); (ii) anomalies are explicable in terms of location relative to areas of differing intensity of deformation (e.g. the Ruxton Formation) and inferred greater depth of burial (e.g. southern versus northern outcrop tracts of Quinton Formation); (iii) the regional pattern in the Broken River ‐ Gray Creek area shows general alignment with the regional grain; (iv) there is a generalised north to south increase in CAI for the Broken River region (‘Top Hut’ to Broken River, 6), with higher values towards the Montgomery Range intrusions; (v) in the Burdekin Basin, there arehigher CAI values north of Mt Podge and ‘Star’, and lower values (

Late Ludfordian Correlations and the Lau Event

Changes in whole conodont faunas and δ13C values are combined to achieve high-resolution correlations of Upper Silurian successions in many areas (primarily Gotland, Skane, Lithuania, Bohemia, Austria, Sardinia and Queensland); other areas are correlated with lower precision. Four of the widely recognised subzones average considerably less than 0.1 Ma and a fifth interval less than 0.01 Ma. The main constraints on resolution and precision now achievable are the amount of, and the precision in, new or previously published data from each local section; centimetric scale collecting would be worthwhile in many sections. Some stratal characters are more widespread during certain intervals than might have been expected, for example, the presence of oncolites and algal coatings in the Icriodontid Zone and the lower part of the O. snajdri Zone. Similarly, the Dayia navicula bloom in the Upper P. siluricus Subzone was widespread. So also were muddy-sandy sediments followed by oolite low in the O. snajdri Zone; crinoids flourished widely when the lower part of the Lower Icriodontid Subzone was formed. Closely spaced samples show that, in some intervals, the now well-known δ13C spike was modified considerably by fluctuations; that is, it is not a smooth plateau. The best-documented fluctuations (19 analyses) are 2.5 smooth cycles with up to 2.7‰ in amplitude during ca 12,000 years or less in the base of the O. snajdri Zone. An enigma is the depletion of the spike in some sections, especially in the best Bohemian section.

LATE DEVONIAN-TOURNAISIAN CONODONTS FROM THE EASTERN KHYBER REGION, NORTH-WEST PAKISTAN

Conodonts (62 species and subspecies) from acid-leaching of 226 samples from four sections through the Ali Masjid Formation west of Misri Khel in the former South Khyber Agency, north-west Pakistan, are documented by illustrations and distributional data. These indicate that most of this unit, at least in that area, spans the interval Middle crepida Zone (low in the Famennian) to at least Early crenulata Zone (mid-Tournaisian), though a fauna from low in one of the sections produced conodonts indicative of the Late falsiovalis Zone (early Frasnian). Two major hiatuses are inferred: between the Late falsiovalis and Middle crepida zones, and between the Late expansa and Early duplicata zones. Coherence of the conodont biostratigraphy accords with lithologic alignments between the sections.

Devonian trilobites from the Shogrām Formation, Kurāgh, Chitral (NW Pakistan)

Late Devonian trilobites from horizons close to the Frasnian-Famennian boundary in the Shogrām Formation at Kurāgh, Chitral (NW Pakistan) are described. A new species of Asteropyginae, Neocalmonia chitralensis sp. nov., and a new subpecies, Neocalmonia batillifera orientalis subsp. nov., are described; these extend the range of Asteropyginae eastwards from Iran and southern Afghanistan. The Upper Kellwasser Event is located within KUR 19 of Talent et al. (1999).

Silicified Early Devonian (Lochkovian) brachiopods from Windellama, southeastern Australia

Silicified Early Devonian (Lochkovian;eurekaensis Zone) brachiopods from the Windellama Limestone of south-eastern Australia are documented. New taxa consist of one new genus, a schizophoriid,Pelecymya, type speciesP. caperata sp. nov., 9 other new species,Morinorhynchus trypeter, Asymmetrochonetes picketti, Hadrorhynchia? attinarum, Sphaerirhynchia? mastodon, Ambothyris? inopis. Howellella placeotextilis, Howellella alatextilis, Howellella legirupa, andReticulariopsis saginatus, and 2 new subspecies,Schizophoria antiqua erugata, andGypidula pelagica lunata. Though a typical Old World fauna, it has little resemblance to previously documented Late Silurian-Early Devonian (Ludlow-Lochkovian) brachiopod faunas, including silicified faunas, from elsewhere in Australia. Also documented are the poorly preserved brachiopods from the clastic and volcaniclastic Tangerong Formation (Early Devonian; ?Pragian) overlying the Windellama Limestone.KurzfassungSilifizierte Brachiopoden aus dem Unter-Devon (Lochkovium;eurekaensis-Zone) des Windellama-Kalksteins von SE-Australien werden dokumentiert. Als neues Taxon wird die schizophoriide GattungPelecymya n. gen. mit der Typus-ArtPelecymya caperata n. sp. beschrieben. Außerdem neun weitere Arten:Morinorhynchus trypeter n. sp.,Asymmetrochonetes picketti n. sp.,Hadrorhynchia? attinarum n. sp.,Sphaerirhynchia? mastodon n. sp.,Ambothyris? inopis n. sp.,Howellella placeotextilis n. sp.,Howellella alatextilis n. sp.,Howellella legirupa n. sp. undReticulariopsis saginatus n. sp. sowie die beiden UnterartenSchizophoria antiqua erugata n. subsp. undGypidula pelagica lunata n. subsp. Wenngleich diese Vergesellschaftung eine typische Fauna der ‘alten Welt’ darstellt, so zeigt sie doch wenig Ähnlichkeiten mit bereits früher beschriebenen Brachiopoden-Faunen des oberen Silur bis Unter-Devon (Ludlow-Lochkovium), einschließlich silifizierter Faunen, von anderen Fundorten Australiens. Ebenfalls dokumentiert werden die schlecht erhaltenen Brachiopoden der klastischen und vulkano-klastischen Tangerong Formation (Unter-Devon; ?Pragium), die den Windellama Kalkstein überlagert.

Teaching Paleontology with an Acid-Leaching Facility

Innovations as well as modifications of more traditional approaches to the teaching of undergraduate and graduate paleontology at Macquarie University have been developed to help teach large classes of internal students (traditional full-time day students, and part-time day and evening students) as well as external students (students who work largely at home, attending the university only for concentrated blocks of instruction and practical work on weekends or during university vacations). These modifications are aimed especially at our external students, many of whom are fundamentally biologists rather than earth scientists. Pivotal to this effort has been a large acid-leaching facility for extraction of silicified and phosphatic fossils, macro and micro. Use of this facility has made it possible to focus field work on collection of blocks for acid leaching, and laboratory work on identification of the resultant faunas to generic level, using the Treatise on Invertebrate Paleontology. With this have been...

Macquarie University's undergraduate degree in museum studies

In 2002, Macquarie University introduced a 4-year programme of study leading to a B.Sc./B.A. in Natural History, Culture and Museum Studies. The double degree programme covers speciality areas of particular interest to national, state and regional museums and for which Macquarie has a high reputation. This interdisciplinary degree is designed to: a) provide students with a modern background for the field of Museum Studies, b) allow students to qualify with coherencies (majors) in at least three segments of study, and c) allow students to develop strong generic skills in information management. Most of the Universitys museums are involved in the delivery of the degree programme. This creates opportunities for students to experience practical museum-based projects. The development of this undergraduate degree programme also enables the University to more effectively engage its museums with its academic mission and to encourage its museum staff to strive for appropriate standards of professionalism.

Teaching Reef Environments and Paleoecology on Contemporary and Quaternary Reefs

An account is given of two decades experience in running undergraduate, graduate, and popular courses in reef science focussed on zonation, bioturbation, and lithification of southwest Pacific reefs. The program can be readily adapted for other regions having coral cays with extensive reef flats, or regions with broad fringing or barrier reefs. Educational value is increased where contemporary and fossil reefs are closely juxtaposed, as for example in New Caledonia, Vanuatu, the Cook Islands, and French Polynesia.