Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations

/pdf/global-continental-and-ocean-basin-reconstructions-since-200-huopwd2ldv.pdf

Global continental and ocean basin reconstructions since 200 Ma

The Southern Hemisphere has traditionally been considered as having a fundamentally vicariant history. The common trans-Pacific disjunctions are usually explained by the sequential breakup of the supercontinent Gondwana during the last 165 million years, causing successive division of an ancestral biota. However, recent biogeographic studies, based on molecular estimates and more accurate paleogeographic reconstructions, indicate that dispersal may have been more important than traditionally assumed. We examined the relative roles played by vicariance and dispersal in shaping Southern Hemisphere biotas by analyzing a large data set of 54 animal and 19 plant phylogenies, including marsupials, ratites, and southern beeches (1,393 terminals). Parsimony-based tree fitting in conjunction with permutation tests was used to examine to what extent Southern Hemisphere biogeographic patterns fit the breakup sequence of Gondwana and to identify concordant dispersal patterns. Consistent with other studies, the animal data are congruent with the geological sequence of Gondwana breakup: (Africa(New Zealand(southern South America, Australia))). Trans-Antarctic dispersal (Australia southern South America) is also significantly more frequent than any other dispersal event in animals, which may be explained by the long period of geological contact between Australia and South America via Antarctica. In contrast, the dominant pattern in plants, (southern South America(Australia, New Zealand)), is better explained by dispersal, particularly the prevalence of trans-Tasman dispersal between New Zealand and Australia. Our results also confirm the hybrid origin of the South American biota: there has been surprisingly little biotic exchange between the northern tropical and the southern temperate regions of South America, especially for animals.

/pdf/southern-hemisphere-biogeography-inferred-by-event-based-1a73hz0gec.pdf

Southern Hemisphere Biogeography Inferred by Event-Based Models: Plant versus Animal Patterns

https://www.utdallas.edu/~rjstern/egypt/PDFs/Cenozoic%20Red%20Sea/BosworthRedSeaJAES05.pdf

The Red Sea and Gulf of Aden Basins

The concept of 'Gondwana', an ancient Southern Hemisphere supercontinent, is firmly established in geological and biogeographical models of Earth history. The term Gondwana (Gondwanaland of some authors) derives from the recognition by workers at the Indian Geological Survey in the mid- to late 19th century of a distinctive sedimentary sequence preserved in east central India. This succession, now known to range in age from Permian to Cretaceous, is lithologically and palaeontologically similar to coeval non-marine sedimentary successions developed in most of the Southern Hemisphere continents suggesting former continuity of these landmasses. Palaeomagnetic data and tectonic reconstructions suggest that the main assembly of Gondwana took place around the beginning of the Palaeozoic in near-equatorial latitudes and that the supercontinent as a whole shifted into high southern latitudes, allowing widespread glaciation by the end of the Carboniferous. From Carboniferous to Cretaceous times the southern continents had broadly similar floras but some species-level provincialism is apparent at all times. The break-up of Gondwana initiated during the Jurassic (at about 180 million years ago) and this process is continuing. The earliest rifting (crustal attenuation) within the supercontinent initiated in the west (between South America and Africa) and in general terms the rifting pattern propagated eastward with major phases of continental fragmentation in the Early Cretaceous and Late Cretaceous to Paleogene. Gondwanan floras show radical turnovers near the end of the Carboniferous, end of the Permian and the end of the Triassic that appear to be unrelated to isolation or fragmentation of the supercontinent. Throughout the late Palaeozoic and Mesozoic the high-latitude southern floras maintained a distinctly different composition to the palaeoequatorial and boreal regions even though they remained in physical connection with Laurasia for much of this time. Gondwanan floras of the Jurassic and Early Cretaceous (times immediately preceding and during break-up) were dominated by araucarian and podocarp conifers and a range of enigmatic seed-fern groups. Angiosperms became established in the region as early as the Aptian (before the final break-up events) and steadily diversified during the Cretaceous, apparently at the expense of many seed-fern groups. Hypotheses invoking vicariance or long distance dispersal to account for the biogeographic patterns evident in the floras of Southern Hemisphere continents all rely on a firm understanding of the timing and sequence of Gondwanan continental breakup. This paper aims to summarise the current understanding of the geochronological framework of Gondwanan breakup against which these biogeographic models may be tested. Most phytogeographic studies deal with the extant, angiosperm-dominated floras of these landmasses. This paper also presents an overview of pre-Cenozoic, gymnosperm-dominated, floristic provincialism in Gondwana. It documents the broad succession of pre-angiosperm floras, highlights the distinctive elements of the Early Cretaceous Gondwanan floras immediately preceding the appearance of angiosperms and suggests that latitudinal controls strongly influenced the composition of Gondwanan floras through time even in the absence of marine barriers between Gondwana and the northern continents. Go na br nd prn ti l S.ou

The breakup history of Gondwana and its impact on pre-Cenozoic floristic provincialism

Identification of a sequence of east-west trending magnetic anomalies of Mesozoic age in the western Somali Basin helps define the position of Madagascar in the Gondwana reconstruction. The anomalies are symmetric about ancient ridge segments and are flanked to the north and south by the Jurassic magnetic quiet zone. The motion of Madagascar relative to Africa was from the north and began in the middle Jurassic, about the same time as the initial breakup of Gondwanaland. Sea-floor spreading ceased when Madagascar assumed its present position in the Early Cretaceous.

https://science.sciencemag.org/content/sci/220/4592/67.full.pdf

The Separation of Madagascar and Africa

Palaeomagnetic samples have been collected on eight islands of the New Hebrides island arc. Data are presented for 31 stable sites out of 46 with ages ranging from Pleistocene to early Late Miocene. These data show 30° clockwise rotation of the arc commencing 6 m.y. BP. Synthetic polar wander paths corresponding to microplate rotation may be computed from known major plate polar wander paths. Thus a physiographically reasonable reconstruction of the New Hebrides plate is shown to have a polar wander path which compares well with the observed data. A reconstruction of a pre-Late Miocene double arc, consisting of the Solomons, New Hebrides-Vityaz, Fiji and Lau-Tonga island arcs, is possible which supports in terarc geological correlations and which suggests Plio?Pleistocene growth of the North Fiji Basin by r-r-r triple junction development concomitant with the development of the Lau Basin.

Analysis of palaeomagnetic data from the New Hebrides

(1975). Part 2. Younger Pacifics arcs and the eastern marginal seas: Arc reversals, and a tectonic model for the North Fiji Basin. Exploration Geophysics: Vol. 6, No. 2-3, pp. 47-49.

Part 2. Younger Pacifics arcs and the eastern marginal seas: Arc reversals, and a tectonic model for the North Fiji Basin

Geohistory analysis is a technique for plotting the cumulative subsidence of various chronostratigraphic horizons encountered in an exploration well or section. The intervals between horizons are corrected for sediment compaction and are plotted relative to an estimated ancient seabed (or land surface) as a function of geological time. Speed and precision have been added to this procedure by automatic computer processing and plotting. A variable eustatic sealevel datum has also been introduced. Accurate quantitative assessment of depth sub-seabed (or subsurface) of any horizon may be combined with a model of heatflow history for the well location to compute a maturation integral and theoretical vitrinite reflectance for that horizon as a function of geological time. Comparison of theory with present observations may be used to refine the model heatflow history. Palaeomaturation may be readily assessed. An offshore Perth Basin example is used to illustrate the effects of palaeosealevel, palaeoheatflow and unconformities and hiatuses. Analysis of a cross-section through three wells is used to demonstrate the potential for accurate calculation of a palinspastic section, palaeomaturation and migration direction. Geohistory analysis is demonstrated to be an essential tool in rigorous basin evaluation.

Recent advances in burial and thermal geohistory analysis

Seafloor spreading in the Coral Sea Basin is dated by Deep Sea Drilling Project Site 287 as Early Eocene (51 my bp). This requires normal rifting and breakup of an extended Australian continent including the Queensland. Papuan and Louisiade Plateaus as well as the Cretaceous portions of East Papua. A reconstruction based on continental and plateau margin physiography and Papua-New Guinea geology points to a pole of relative opening at lat. 11.3° S., long. 141.3° E. This results in left-lateral transform motion along the Moresby Trough and Bismarck-Lagaip Fault Zones through breakup, plus the deformation of the Owen Stanley sediment pile, and emplacement of the Papuan Ultramafic Belt. Following initiation of sea-floor spreading, subsidence commenced at what are now the marginal plateaus bordering the Coral Sea Basin. A widespread unconformity spanning the late Eocene-mid Ollgocene can be recognised on all plateaus as well as in the basin proper. This is attributed to the commencement of a significant equatorial circulation pattern in the deepening basin and over the subsided plateaus. Stabilisation of this equatorial circulation pattern permitted coral reef development on residual basement highs on the marginal plateaus and eventually) on the subsiding Queensland continental shelf and Papuan stable platform areas in the late Oligocene-early Miocene. On the basis of seismic refraction and gravity evidence, rift valley sequences up to 3 km thick are inferred beneath the Queensland and Townsville Troughs and bordering the Queensland and Papuan Plateaus. Though seismic refraction data are lacking, similar sequences are also inferred beneath parts of the Eastern and Marion Plateaus. Bligh Trough and Louisiade Rise. The age of this pre-breakup rifting is suggested to be mid Cretaceous-Palaeocene although direct evidence is absent. Gravity modelling over the Queensland Trough, Plateau and Coral Sea Basin supports the interpretation from seismic reflection and refraction data. Continental crustal structure with a deep metamorphic layer is indicated for the Queensland Trough and Plateau with a depth to the Moho of 22-28 km. The continental/ocean crust transition occurs towards the base of the continental slope at a water depth of up to 4.5 km along the Queensland Plateau. Crust beneath the Coral Sea abyssal plain is oceanic with a depth to mantle of 11-13 km.

/pdf/queensland-plateau-and-coral-sea-basin-stratigraphy-48s3u8cnmm.pdf

David A. Falvey

Papers

The Separation of Madagascar and Africa

Analysis of palaeomagnetic data from the New Hebrides

Part 2. Younger Pacifics arcs and the eastern marginal seas: Arc reversals, and a tectonic model for the North Fiji Basin

Recent advances in burial and thermal geohistory analysis

Queensland plateau and coral sea basin stratigraphy, structure and tectonics