Integrated stratigraphy of the Waitakian-Otaian Stage boundary stratotype, Early Miocene, New Zealand

The base of the type section of the Otaian Stage at Bluecliffs, South Canterbury, is recognised as the stratotype for the boundary between the Waitakian and Otaian Stages. Principal problems with the boundary are the restriction of existing bioevent proxies to shelf and upper slope environments and its uncertain age. These topics are addressed by a multidisplinary study of a 125 m section about the boundary, which examines its lithostratigraphy, depositional setting, biostratigraphy, correlation, and geochronology. The lower siltstone lithofacies (0-38.5 m) was deposited at upper bathyal depths (200-600 m) in a marginal basin which was partially sheltered from fully oceanic circulation by a submarine high and islands. The site was covered by cool-temperate water and was probably adjacent to the Subtropical Convergence. This unit is succeeded by the banded lithofacies (38.5-106 m) and the upper siltstone lithofacies (basal 19 m studied). Paleodepth probably declined up-sequence, but deposition at shelf depths is not definitely indicated. A cyclic pattern of abundance spikes in benthic and planktonic foraminifera commences 9 m above base and extends to 73 m in the banded lithofacies. Oxygen isotope excursions (up to 2.08%) in Euuvigerina miozea and Cibicides novozelandicus are greatest within the interval containing the abundance spikes. The stage boundary occurs in the banded lithofacies at the highest abundance spike (73 m). Although condensed intervals might affect the completeness of the section, they are not associated with sedimentary discontinuities, and we consider that the section is suitable as a biostratigraphic reference. Spores, pollens, dinoflagellates, calcareous nannofossils, foraminifera, bryozoans, and ostracods are preserved near the boundary, but molluscs principally occur higher, in the shallower upper siltstone lithofacies. Siliceous microfossils are rare. There is considerable scope for further biostratigraphic research. The primary event marking the boundary at 73 m is the appearance of the benthic foraminifer Ehrenbergina marwicki. This is a distinctive and widely distributed event but is restricted to shelf and upper bathyal environments. Supplementary events in planktonic foraminifera and calcareous nannofossils were researched. Highest occurrences of Globigerina brazieri and G. euapertura are recorded at 47 and 58 m. There is a marked decline in relative abundance of Paragloborotalia spp. at 62 m. Helicosphaera carteri becomes more abundant than H. euphratis between 56 and 87 m. These events are not exact proxies for the boundary but they may usefully indicate proximity to it. They occur in the interval of prominent spikes in foraminiferal abundance. The Waitakian-Otaian boundary is dated at 21.7 Ma by strontium isotopes. Stable primary remanence could not be determined in a pilot paleomagnetic study of Bluecliffs specimens. However, specimens trended towards reversed polarity, and remagnetisation great circle analysis will allow directions to be calculated in future collections

LATE PALEOCENE IN THE OTWAY BASIN BIO STRATIGRAPHY AND AGE OF KEY MICRO FAUNAS

Volume: 94Start Page: 1End Page: 1

Foraminifera in Cenozoic paleoenvironments

Brian McGowra

Beyond the GSSP: New developments in chronostratigraphy - preface

Brian McGowranhttp://micropress.org/micropen/index.php?journal=S&action=detail&issue_id=37&page=

Scientific accomplishments of Reginald Claude Sprigg

Appointing R.C. Sprigg in 1949 as Head of the new Regional Mapping Section of the Geological Survey of South Australia was decisive to its rapid success and high national reputation. Sprigg had vast enthusiasm for all things in natural history and especially earth history, appreciation of the economic drive, the ability to frame deep and meaningful questions in feedback with geological mapping, strong grasp of the interplay between geo-structure and geo-history, and exemplary follow-through to completion (not invariably) as richly illustrated papers and regional and thematic maps. By age 35 he had changed the culture of South Australian Geology and departed the GSSA. in 1954 Sprigg moved on to geological and biological exploration in a spirit of private enterprise in economic development. Others expanded the research programs although from time to time he revisited his early interests in the light of developments in the earth sciences, such as the revolution in continental drift and plate tectonics and advances in late Neogene chronology and correlation. The earth-science of hydrocarbon exploration unified most of Sprigg's preoccupations in private enterprise with reviews and syntheses. His histories and popular works gave insights into the rapidly changing scientific, industrial and environmental-awareness scenes and into his view of his own contributions. ADELAIDE GEOSYNCLINE. At the outset of his career Sprigg achieved the most comprehensive advance in the geology of the complex and difficult Adelaide region in more than 150 years. The Mawson-Sprigg Adelaide System with its Torrensian, Sturtian and Marinoan Series was vintage Sprigg. He recognised the Adelaide miogeosyncline as a fossil continental terrace, much older than any that had been recognised hitherto. When his notions of flysch facies and the relationship of the Kanmantoo Group to the Adelaide System were clarified (with Bruno Campana) Sprigg realized that the Kanmantoo eugeosynclinal trough marked the initiation of the great Tasman Geosyncline of eastern Australia. EDIACARAN BIOTA. In a clear case of the prepared mind and the deliberate search, Sprigg had been alert for a decade to the necessary existence of animals without mineralised skeletons before he discovered the fossils which became the basis for the Ediacaran assemblage of animals of latest Precambrian age. He described and named 17 species of pelagic coelenterates (“jellyfish“) of which about one-third survived as recognized taxa and some as higher animals. He saw himself as much biologist as geologist, and his handling of the comparative morphology, taphonomy and reconstruction, taxonomy and biological inferences was confident and secure. LATE NEOGENE IN SOUTHERN AUSTRALIA. In employing the term “Kosciuskan epoch“ in his earliest work, Sprigg perceived the late uplift as being coeval with and part of the uplift of the highlands of southeastern Australia, and he sustained this view of neotectonic activity when it was unfashionable, as in petroleum exploration in Mesozoic-Cenozoic sedimentary basins. Finding strong indications of a cyclical pattern in the remarkably regular lateral succession of fossil beaches in the South-east of South Australia, he took the intuitive leap of explaining this regional pattern with the Milankovitch theory of ice ages, which were still be integrated with the geohistorical record. In due course geomagnetic and oxygen-isotopic stratigraphy would confirm his 1940s theory that the aeolianites record a punctuated succession of high sea levels (i.e., interglacials). (Subsequently Sprigg added the calcareous aeolianites to the counterclockwise whorl of siliciclastic dunes in a grand vision of windy, glacial Australia, but his initial theory is the survivor.) Predicting that the Pleis tocene River Murray might produce a canyon at the shelf edge, he convinced the Navy to make the necessary traverse and the canyons were found (the first on the australian margin). With S.A. Shepherd,...Brian McGowranhttp://adelaideaus.library.ingentaconnect.com/content/rssa/trssa/2013/00000137/00000001/art0000

Foraminiferal micropalaeontology in Adelaide 1950-1970: correlation and age determination in post-war mapping and subsurface exploration

In the 1940s the Cenozoic molluscan record was ceding to the foraminiferal as main biostratigraphic driver. The central scientific problems for the stratigraphy of the Cenozoic Erathem in southern Australia were a patchy biostratigraphic succession, very few links with the tropical IndoPacific region and the classical sections of Europe, and a fragile sense of stratigraphic relationships within and between the various sedimentary basins in southern Australia. In more specific terms the stratigraphic problems were (or were about to emerge as) the Miocene/Pliocene hiatus, the evolution of the Orbulina bioseries and the age of the Orbulina surface, the recognition and correlation of Oligocene strata, and discovering and dating fossil assemblages below the Upper Eocene. M.F. Glaessner at the University of Adelaide's Geology Department and N.H. Ludbrook at the Geological Survey of South Australia made and led substantial progress in these matters, and Glaessner also stimulated research in foraminiferal morphology and evolutionary taxonomy. The progress occurred in feedback with shifts in scientific style and emphasis. Glaessner brought a new rigour to the recognition of microfossil assemblages and events and the relationship of bio-zones to chrono-stages. Exploiting the superb collection by W.J. Parr, A.N. Carter laid the groundwork with a biozoning of the Upper Eocene to Middle Miocene composite succession, employing a mix of benthic and planktonic events. M. Wade developed strong insights into the internal morphology of foraminiferal shells and its taxonomic significance, the relationships between morphospecies as biological species and morphospecies as pragmatic biostratigraphic tools, and correlating across the tropical-temperate transitions through the Cenozoic. J.M. Lindsay developed subsurface stratigraphic micropalaeontology in hydrogeology and engineering geology into a fine art, sharpened the delineation of the Miocene-Pliocene unconformity, did most to solve the Oligocene problem and (with Ludbrook) strengthened the Eocene-Miocene biozonation. By ~1970 there was a perceptual shift from species' ranges, in which implicitly imperfect records are linked, to species' occurrences including datums. The shift clarified insights into such geohistorical phenomena as climatic shifts and transgressions and regressions. It was encouraged by the first persuasive, numerically calibrated geological time scale. Micropalaeontology continued and stratigraphic horizons expanded in both institutions but the first two decades comprise a natural phase in Adelaide.Brian Mcgowra

Organic evolutioin in deep time: Charles Darwin and the fossil record

The heart and soul of geology are to be found in rock relationships and earth history. The fossil record was central and critical to geology emerging as geohistory, the first historical science, from the speculative geotheories of the 18th Century. The key figure was Cuvier. In the process of shaping geohistory, Cuvier and palaeontology produced the second historical science, namely biohistory, including faunal and floral succession in deep time; and biohistory and geohistory have been intertwined for two centuries. lamarck kept alive the venerable theory of organic change, but evolution as heuristic scientific theory was stumbling. Even so, the fossil-based geological time scale was constructed in the six decades between Cuvier nailing bioextinction and Darwin nailing biospeciation. by about 1830, French molluscan palaeontology was building Tertiary stratigraphic succession, correlation and age determination in the palaeontological synthesis, i.e., biostratigraphy. Palaeontology revealed ancient and exotic life in a deep-time panorama of succession punctuated by extinctions and demanding explanation, but it contributed little to theory of evolutionary processes. Darwin’s world was lyell’s gradualist world and his appreciation of environmental change as an evolutionary forcing factor lessened as competition came to dominate his thinking. Darwin’s Darwinism comprised five theories. Two were historical theories (the world and its biospecies change in deep time; and common descent in branching evolution produces the tree of life) and both were widely accepted by the generation after Darwin. The other three were causal or nomothetic theories (respectively speciation; gradual change not saltational; and variational change by natural and sexual selection) and they were accepted only in the 20th Century. For its importance to our culture, Darwin’s historicist worldview, in the face of entrenched, ahistorical opinion as to what science really is, outweighs disputes about the importance of selection. As stratigraphy and palaeontology went global and highly successful on most criteria, their evolutionary direction went ‘anti-Darwinian’ in the later 19th Century, towards such theories as orthogenesis, saltationism and a resurgent ‘Neo-lamarckism’, mostly in Hyatt, Cope and Osborn in North America. This cluster of trends culminated a second time in the 1930s–1940s, in the macromutational typostrophism of the German synthesis, dominated by Schindewolf. Meanwhile there was a thin red line of Darwinian palaeontology down those decades from the 1860s to the 1920s. When population genetics emerged from decades of its own anti-Darwinism the Modern Synthesis was forged between natural history, genetics and palaeontology, the latter especially embodied by Simpson’s macroevolution. Darwin’s three causal theories came into their own in the 1930s–1950s in completing the Darwinian Revolution—or, as I prefer, installing the Darwinian Restoration. However, the Restoration was dominated by variational evolution, whilst practitioners of embryology and morphology, in the transformational mode of evolution, felt excluded. The roots of modern palaeobiology are firmly in the Darwinian Restoration and Simpsonian palaeontology and macroevolution. Modern palaeobiology (i) is thoroughly Darwinian in its historicism and variational evolution but (ii) is beyond Darwin in becoming pervasively hierarchical whilst (iii) reconciling with elements of the German Synthesis through collaboration with developmental genetics in evo-devo. Also (iv) we have gone beyond Darwin (and Simpson) primarily in the rise of micropalaeontology with its untold millions of specimens and in enormous progress in chronologically resolving and reconstructing bioevents and environmental shifts in the geological past. And (v) the tree of life is underlain by an anastomosing web of life. Deep-time palaeobiology becomes more autonomous as major soluble problems arise from the fossil record, utterly beyond the reach of shallow-time neontology. Securely embedded in thriving research programmes recovering the recorded history of life on earth, Darwinism lives!. © 2013 Taylor and Francis Group LLC. All rights reserved.Brian McGowra

The Australo-Antarctic Gulf and the Auversian facies shift

Three time lines through the neritic stratigraphic record distributed around the northern margin of the Australo-Antarctic Gulf (AAG) mark three fundamental shifts in global environments collectively comprising the Auversian facies shift. The three lines are: (1) the beginning: the Khirthar transgression and the onset of neritic carbonate accumulation in the Bartonian Age (preceding onset of the Middle Eocene climatic optimum [MECO]); (2) the midlife change (Bartonian-Priabonian transition): the shift from carbonate-rich to carbonate-poor, higher-nutrient environments under estuarine circulation, causing widespread dysaerobia culminating in opaline silicas; and (3) the Eocene-Oligocene = Priabonian-Rupelian boundary and glaciation during oxygen isotope event Oi-1, with return of improved ventilation in neritic environments and resumption of carbonate accumulation. Meanwhile, it was warm and very wet at ~60°S. In developing a scenario for the death of the AAG, the birth of the Southern Ocean, and the transition from Paleogene greenhouse Earth to Neogene icehouse Earth, the neritic record of the northern margin is more in accord with the “Dinocyst biogeographic hypothesis” than with the “Tasman gateway hypothesis.”Brian McGowranhttp://specialpapers.gsapubs.org/content/452/215.abstrac