Late Palaeogene Research Articles

Tertiary to recent oblique convergence and wrenching of the Central Dinarides: Constraints from a palaeostress study

The late Eocene to Neogene tectonic evolution of the Dinarides is characterised by shortening and orogen-parallel wrenching superposed on the late Cretaceous and Eocene double-vergent orogenic system. The Central Dinarides exposes NW-trending tectonic units, which were transported towards the Adria/Apulian microcontinent during late Cretaceous–Palaeogene times. These units were also affected by subsequent processes of late Palaeogene to Neogene shortening, Neogene extension and subsidence of intramontane sedimentary basins and Pliocene–Quaternary surface uplift and denudation. The intramontane basins likely relate to formation of the Pannonian basin. Major dextral SE-trending strike-slip faults are mostly parallel to boundaries of major tectonic units and suggest dextral orogen-parallel wrenching of the whole Central Dinarides during the Neogene indentation of the Apulian microplate into the Alps and back-arc type extension in the Pannonian basin. These fault systems have been evaluated with the standard palaeostress techniques. We report four palaeostress tensor groups, which are tentatively ordered in a succession from oldest to youngest: (1) Palaeostress tensor group 1 (D 1) of likely late Eocene age indicates E–W shortening accommodated by reverse and strike-slip faults. (2) Palaeostress tensor group 2 (D 2) comprises N/NW-trending dextral and W/WSW-trending sinistral strike-slip faults, as well as WNW-striking reverse faults. These indicate NE–SW contraction and subordinate NW–SE extension related to Oligocene to early Miocene shortening of the Dinaric orogenic wedge. (3) Palaeostress tensor group 3a (D 3a) comprises mainly NW-trending normal faults, which indicate early/middle Miocene NE–SW extension related to syn-rift extension in the Pannonian basin. The subsequent palaeostress tensor group 3b (D 3b) includes NE-trending, SE-dipping normal faults indicating NW–SE extension, which is likely related to further extension in the Pannonian basin. (4) Palaeostress tensor group 4 (D 4) is characterised by mainly NW-trending dextral and NE-trending sinistral strike-slip faults. Together, with some E-trending reverse faults, they indicate roughly N–S shortening and dextral wrenching during late Miocene to Quaternary. This is partly consistent with the present-day kinematics, with motion of the Adriatic microplate constrained by GPS data and earthquake focal mechanisms. The north–north-westward motion and counterclockwise rotation of the Adriatic microplate significantly contribute the shortening and present-day wrenching in the Central Dinarides.

Cenozoic alongslope processes and sedimentation on the NW European Atlantic margin

Based on studies of sediment accumulations deposited from-and erode by-alongslope flowing ocean currents on the European continental margin from Porcupine (Ireland) to Lofoten (Norway), the evolution of the Cenozoic paleocirculation was reconstructed as part of the STRATAGEM project. There is evidence of ocean current-controlled erosion and deposition in the Rockall Trough, in the Faeroe-Shetland Channel and on the Vøring Plateau since the late Eocene, although the circulation pattern remains ambiguous. The late Palaeogene flow in the Rockall Trough was almost probably driven by southerly-derived Tethyan Outflow Water. The extent and strength of any northerly-derived flow is uncertain. From the early Neogene (early-mid-Miocene), there was a massive regional expansion of contourite drift development both in the North Atlantic and in the Norwegian-Greenland Sea. This was most probably related to the development of the Faroe Conduit, the opening of the Fram Strait and the general subsidence of the Greenland-Scotland Ridge. These may have combined to cause a considerable acceleration in the exchange and overflow of deep waters between the Arctic and Atlantic Oceans. An early late Neogene (late early Pliocene) regional erosional event has been ascribed to a vigorous pulse of bottom-current activity, most probably the result of a global reorganisation of ocean currents associated with the closure of the Central American Seaway. During the late Neogene, contourites and sediment drifts developed in deep-water basins, between units of glacigenic sediments as well as infill of several paleo-slide scars. These sediments were derived from areas of bottom-current erosion as well as from the development of Plio-Pleistocene prograding sediment wedges, incorporating the extensive sediment supply derived from shelf-wide ice sheets. Presently a profound winnowing prevails along the shelf and upper slope due to the inflowing currents of Atlantic water. Depocentres of sediments derived from the winnowing are located (locally) in lower slope embayments and in slide scars.

Reconstructing the Mesozoic–Cenozoic exhumation history of the Irish Sea basin system using apatite fission track analysis and vitrinite reflectance data

This paper summarizes new and recent apatite fission track analysis and vitrinite reflectance results from across the Irish Sea basin system and its margins, which provide new constraints on the magnitude and timing of post-Palaeozoic exhumation across this area. In particular, these results suggest that this region has experienced a complex, multi-phase exhumation history. Distinct episodes of kilometre-scale exhumation occurred during the early Cretaceous, early Palaeogene and late Palaeogene–Neogene times, with the overall magnitude of exhumation in each episode decreasing over time. Regional early Cretaceous exhumation removed up to 3 km of section from the Irish Sea basins, and appears to be related to incipient Atlantic rifting. Early Palaeogene exhumation attained up to 2 km and was driven by a combination of localized tectonic inversion and regional epeirogenic uplift, although early Palaeogene palaeotemperatures within parts of the Irish Sea basin systemare dominated by non-burial-related processes. A final phase of exhumation, related to late Palaeogene– Neogene tectonic inversion, uniformly removed c . 1 km of section from this region. Given that these exhumation episodes coincide temporally with important periods of deformation at pre-existing or incipient plate boundaries, events at plate margins are interpreted to have exerted the primary control on the Mesozoic–Cenozoic exhumation of the Irish Sea basin system.

On the origin and development of Artemisia (Asteraceae) in the geological past

Fossil records combined with phytogeographical data reveal that Artemisia L. possibly originated from the existing arid or subarid area of temperate Asia in the mid-Tertiary. The earliest recorded Asteraceae pollen grains are mostly ornamented with medium to long spines, whereas Artemisia L. with short spinules is recorded slightly later. It may be deduced that the latter evolved from the former. Pollen morphological data confirm the coexistence of the two pollen patterns in the subtribe Artemisiinae containing Artemisia L. The development and evolution of the genus suggest three major stages in its history. Artemisia L. did not become abundant until the Middle to Late Miocene in spite of its earlier presence in the Late Palaeogene. Its representation remained low even though there are many records of the genus in the Late Miocene around the world. The Pliocene was an important time for the development of angiosperm herbs including Artemisia L., and the Quaternary has been a major period for the diversification and further worldwide expansion of the genus. The origin and subsequent development of Artemisia L. are considered to be closely related with increased environmental variation, including global climate changes and some important tectonic movements. © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society, 2004, 145, 331–336.

High-resolution sequence stratigraphy as a tool in hydrogeological exploration in the Atacama Desert

With water shortages becoming increasinglycommon globally, there is a need forincreasingly sophisticated methods oflocating groundwater reservoirs in more complex environments. High-resolution sequence stratigraphy, long used in the oil industry offers the prospect of a new tool for hydrogeological exploration. Recent exploration for groundwater in the Late Palaeogene and Neogene fore-arc basins of northern Chile in the Atacama Desert is used as an example of the application of this technique. The analysis of a second order sequence spanning the continental Early Oligocene to Miocene sediments and volcanics of the Calama and Turi Basins allows the identification of two aquifers separated by an aquiclude and provides valuable insight into reservoir properties and preferential flow paths within the aquifers, which can be matched with the results of pumping tests.

Tertiary stratigraphy and basin evolution of southern Sabah: implications for the tectono-stratigraphic evolution of Sabah, Malaysia

Integrated surface mapping, dating and radar image interpretation of strata in southern Sabah (northern Borneo) has made it possible to revise the lithostratigraphy, chronostratigraphy, structure and tectonic evolution of the area. The recognition in the field of an Early Miocene regional unconformity, which may be equivalent to the Deep Regional Unconformity recognised offshore, has allowed the development of a stratigraphic framework of groups and formations which correspond to stages in the sedimentary basin development of the area. Below the Early Miocene unconformity the succession can be resolved into deposits of an accretionary complex of Eocene age overlying an ophiolitic basement, and late Palaeogene deep water succession which formed in a forearc basin. The late Palaeogene deposits underwent syn-depositional deformation, including the development of extensive m~langes, all of which can be demonstrated to lie below the unconformity in this area. Some localised limestone deposition occurred during the period of uplift and erosion in the Early Miocene, following which there was an influx of clastic sediments deposited in delta and pro-deltaic environments in the Middle Miocene. These deltaic to shallow marine deposits are now recognised as forming two coarsening­ upward successions, mapped as the Tanjong and Kapilit Formations. Their map distribution have been revised. The total thickness of these two formations in the southern Sabah Basin amounts to 6,000 m, only half of the previous estimates. The Tanjong and Kapilit Formations are deformed into broad NW-SE-trending synclines separated by narrow anticlines. The anticlines are sub-parallel to major faults and associated with high angle reverse faults, and positive flower structures. Secondary fold-faults formed oblique to the major faults. The structural style suggests that the NW-SE trending faults acted as major left-lateral transpressional zones. The faults may in part be reactivated basement structures. The Early Miocene unconformity is interpreted to be the result of deformation and uplift following underthrusting of continental crust of the South China Sea which terminated Paleogene subduction beneath North Borneo. Renewed subsidence is related here to rifting in the Sulu Sea which led to the development of a major Miocene depocentre above the older forearc accretionary complex. The major transpressional deformation probably occurred during the Late Pliocene, and is possibly related to propagation of deformation from Sulawesi towards NW Sabah. This strike-slip deformation which uplifted the area is termed here the Meliau Orogeny. Renewed extension during the Quaternary has caused some sequence repetition. The 'circular basins' of the Meliau, Malibau and Tidung areas, are interpreted as remnants of a single large basin, deformed in the NW-SE trending transpressional fault zones.

Break Up of Australia-India-Madagascar Block, Opening of the Indian Ocean and Continental Accretion in Southeast Asia With Special Reference to the Characteristics of the Peri-Indian Collision Zones

Linear belts of Gondwana basins developed in the Indian continent since Late Palaeozoic along favoured sites of Precambrian weak zones like cratonic sutures and reactivated mobile belts. The Tibetan and Sibumasu - West Yunnan continental blocks, that were located adjacent to proto-Himalayan part of the Indian continent, rifted and drifted from the northern margin of the East Gondwanic Indo-Australian continent, during Late Palaeozoic, when the said northern margin was under glacial or cool climatic condition and rift-drift tectonic setting. The Indo-Burma-Andaman (IBA), Sikule, Lolotoi blocks were also rifted and drifted from the same northern margin during Late Jurassic. This was followed by the break-up of the Australia-India-Madagascar continental block during the Cretaceous. The activity was associated with hot spot related volcanism and opening up of the Indian Ocean. The Late Cretaceous and Tertiary phases of opening of the Arabian Sea succeeded the Early Cretaceous phase of opening of the Bay of Bengal, part of the Indian Ocean. The Palaeo- and Neo-Tethyan sutures in Tibet, Yunnan, Laos, Thailand and Vietnam reveal the complex opening and closing history of the Tethys. The IBA block rotated clockwise from its initial E-W orientation because of 90°E and adjacent dextral transcurrent fault movements caused due to faster northward movement of the Indian plate relative to that of Australia. The India-Tibet terminal collision during Early-Middle Eocene initiated Himalayan orogenesis and contemporaneously there was foreland basin development that was accompanied with sporadic but laterally extensive continental-flood-basalt (CFB) type and related volcanism. The Paleogene rocks of the Himalayan foreland basin are involved in tectonism and are mostly concealed under older rocks. The Mesozoic-Early Eocene ophiolite terrane on IBA does not represent the eastern suture of the Indian plate but occurs as klippe on IBA, caused due to oblique collision between Sibumasu and IBA during Late Oligocene. Post-collisional indentation of Y-shaped Indian continent into the Asian collage produced Himalayan syntaxes, clockwise rotation of the Sibumasu block which was then sutured to the Tibetan and SE Asian blocks, and tectonic extrusion of the Indochina block along the Ailao Shan Red River (ASRR) shear zone. Highly potassic magmatic rocks were emplaced during Late Palaeogene at the oroclinally flexed marginal parts of the South China continental lithosphere. These magmatic bodies were dislocated by the ASRR left lateral shear zone soon afterwards. Petrogenetic and tectonic processes that generated the Eocene CFB volcanics at the Himalayan foreland basin may have also produced Late Palaeogene magmatism from outer parts of the Namche-Barwa Syntaxis. Their site-specific location and time sequence suggest them to be genetically related to the India-Asia collision process and Indian continent's indentation-induced syntaxial buckling. Deep mantle-reaching fractures were apparently produced during India-Asia terminal collision at the strongly flexed leading brittle edge of the Indian continental lithosphere, and possibly later in time at the outer oroclinally bent marginal parts of the rigid South China continental lithosphere, generating typical magma. The subduction zone that developed along the western margin of IBA due to oblique convergence between the IBA and the Indian plate is still active. The northern end of IBA ultimately collided with the NE prolongation of the Indian continent and was accreted to it during Mio-Pliocene. The Shillong massif was uplifted and overthrust over the Bengal Basin located over its passive margin to the south, whereas, the Eocene distal shelf sediments of IBA were overthrust over the Tertiary shelf of the Indian continent.

Petrochemical characteristics of the Mesozoic-Cenozoic volcanic rock in Huanghua basin

Based on the data from typical core sampling, combined with K-Ar dating, petrochemistry, trace elemental geochemistry and isotopic compositions of the Mesozoic-Cenozoic volcanic rock in the Huanghua basin, Bohai region, the geochemical features of the volcanic rock were studied. The rocks fall into four groups: Cenozoic basalt, Mesozoic late Cretaceous basaltic-trachyandesite, Mesozoic late Cretaceous trachy-dacite and liparite, and Mesozoic early Triassic dacite. The distribution pattern of the main elemental abundance of late Mesozoic shows a typical bimodal. Chronologically, for the volcanic rock, the amount of SiO2 decreases gradually, the contents of Fe2O3,FeO,CaO,MgO,TiO2,P2O5 and MnO increase little by little. The Cenozoic basalt is derived from the asthenospheric mantle. The late Cretaceous basaltic-trachy-andesite is derived from the enriched lithospheric mantle. In late Cretaceous and early Palaeogene, the felsic volcanic rock may be derived from fractional melting of the crust.

Palaeogene-Neogene/present day(?) growth folding in the Bahamian foreland of the Cuban fold and thrust belt

The Santaren Anticline constitutes the frontal termination of the Cuban fold and thrust belt within the Bahamian foreland. New well and seismic data allow us to constrain in detail the evolution of this anticline. Pre-growth and syntectonic (partly post-tectonic?) units, separated by a major unconformity, are associated with the Santaren Anticline. Their geometrical features are consistent with a detachment fold. The precise age of the beginning of fold growth remains unknown. However, the complete record of well-dated syntectonic sediments documents its kinematic evolution from Mid-Eocene to Pliocene/present day, and reveals an approximately constant and very slow growth rate from Early Miocene to Pliocene/present day. The timing of evolution of the Santaren Anticline is not consistent with previous models that postulate that deformation associated with the Cuban fold and thrust belt ended in the Eocene. Our data suggest that the most external part of the Cuban fold and thrust belt was still being deformed under a compressional regime during the late Palaeogene, Neogene and probably during the Quaternary. We propose that this folding may result from compressive stresses transmitted approximately 400 km northwards from the actual plate boundary, as a result of slow convergence between the N and S American plates.

Ophiuroid diversity in the type area of the Maastrichtian Stage

With the exception of holothurians, all Late Cretaceous (Campanian–Maastrichtian) and Early Palaeogene (Danian) echinoderms from the extended type area of the Maastrichtian Stage are currently being revised. In addition to a handful of taxa described previously in the literature, many new genera and species of brittle star and basket star (Ophiuroidea) have been recognised in recent years. In fact, the study area is one of the very few regions in the world that have yielded diverse ophiuroid faunas of latest Cretaceous age. Of note also is the fact that many of the new taxa are based on more or less complete specimens, i.e., discs preserving (portions of) arms, making generic assignment much more reliable. The various ophiuroid groups recognised are briefly discussed and selected specimens are illustrated in order to document the diversity. Formal descriptions will be published elsewhere. Ophiuroid taxa described by Berry (1938), as based on poorly preserved material from the Late Maastrichtian of the area, are briefly commented upon.

Early Tertiary basin formation and the development of Lacustrine and quasi-lacustrine/marine source rocks on the Sunda Shelf of SE Asia

Abstract The Tertiary basins of the Sunda Shelf of SE Asia were formed in the ?Mid- to Late Eocene and accumulated thick intervals of syn-rift lacustrine and low salinity organic rich shales throughout the Late Palaeogene. Towards the end of the Oligocene and into the Early Miocene marine transgression occurred throughout the region. A change to deep open marine sedimentation followed by a general shallowing and deposition throughout the Neogene, of great thicknesses of marginal marine and paralic sediments. The syn-rift sediments are the most important hydrocarbon source rocks in this region, although precise dating of them is difficult due to the long-ranging nature of the palynomorphs and the paucity of the microfauna. However characteristics of the depositional environments and nature of the source rocks deposited within separate provincial basins that were wholly or partially landlocked can be assessed from a detailed examination of the isolated palynomorph and kerogen assemblages. A classification of lacustrine depositional environments within the region on this basis is presented.

Geological framework of the South Tasman Rise, south of Tasmania, and its sedimentary basins

The South Tasman Rise is a continental fragment of 200 000 km2 lying south of Tasmania and surrounded on three sides by Late Cretaceous and Palaeogene oceanic crust, which assumed its present configuration in the Palaeogene. The western side of the rise is dominated by the Tasman Escarpment, the northernmost part of the Tasman Fracture Zone. The South Tasman Rise consists of three structural blocks, linked to Tasmania by thinned continental crust, that moved southward with Antarctica from Tasmania in the Late Cretaceous. All have been affected by northwest‐southeast strike‐slip motion in the Late Cretaceous and north‐south extension in the Tertiary. The western block moved from west of Tasmania, had the longest and most intense tectonism, and consists of large basement highs and the complex Ninene Basin. Basins on all three blocks are generally fault‐controlled and are believed to contain Late Cretaceous to Early Oligocene detrital non‐marine and shallow‐marine sedimentary rocks, and Late Oligocene and younger bathyal to pelagic chalk and ooze. The Ninene Basin is more extensive and generally somewhat thicker (up to 5 km) than basins on the other two blocks. Basins on all three blocks have long‐term petroleum potential but only the central block is in presently drillable water depths.

RELATIONSHIPS BETWEEN HYDROCARBON GENERATION, COAL TYPE AND RANK FOR MIDDLE EOCENE COALS, BULLER COALFIELD, NEW ZEALAND

The Buller Coalfield in the northern portion of the Paparoa Trough (NW South Island, New Zealand) contains a middle Eocene bituminous coal‐bearing succession that exhibits marked variations in both coal rank and type. The across‐basin rank changes result from differential late Palaeogene subsidence of the Paparoa Trough and subsequent inversion. Superimposed upon coalification trends are down‐seam variations in coal type, evidenced by isorank variation in conventional chemical parameters. These type variations are not a consequence of changes in maceral group proportions, which are dominated by vitrinite.Forty‐eight coal samples from fifteen drillholes through the Brunner Coal Measures have been examined for vitrinite reflectance, proximate analysis, specific energy, and sulphur content. Total Organic Carbon (TOC), Rock‐Eval properties and the bulk composition of the bitumen were also determined.All the coals analysed lie within the high volatile bituminous B to medium volatile bituminous coalification stages. Variation in analytical properties within this suite, and more specifically within serial samples, provides insights into the nature of the organic matter comprising the coals. While TOC varies systematically with ash content, reflecting proximity of the depositional mires to fluvial systems, values increase with rank (68–86% ash free). The Hydrogen Index (HI) decreases from 334 to 190 mg hydrocarbons/g TOC over a range of 429 to 470 d̀C Tmax, analogous to the volatile matter content and vitrinite reflectance, respectively. The more perhydrous coal samples at a given rank are characterised by depressed Tmax/vitrinite reflectance and elevated Hi/volatile matter contents.Bitumen and sulphur contents are not the primary control onperhydrous characteristics. The bitumen content crudely corresponds to the S1 peak plus the initial portion of the S2 peak liberated under low temperatures during Rock‐Eval pyrolysis; however, the bulk of the generative potential is associated with the residual kerogen fraction. Suggate (S) Rank and maximum palaeotemperature appear to be the best indicators of coal rank.A period of significant hydrocarbon generation and release begins at Tmax∼440d̀C for the Buller coals. The main oil “window” is defined by the interval 440–455d̀C Tmax or 0.8–1.1% vitrinite reflectance (Romax), and by correlation to maximum palaeo‐temperatures, 125–155d̀C. This is further substantiated by mass balance considerations, which indicate that hydrocarbon generation (Petroleum Generation Index (PG1) > 0.1) was occurring in the coals at a maturity level of O. 7–0.9 % Romax (Tmax 440–444 d̀C) with an increase in PGI between ∼0.9 and 1.1% Romax (∼Tmax 445–455 d̀C). Between PGI 0.1 and 0.4, the expulsion efficiency rapidly increased, presumably due to generation and expulsion of the bulk of the oil.

Does Continuous Compressive Tectonic Regime Exist During Late Palaeogene to Late Neogene in NW Central Anatolia, Turkey? Preliminary Observations

The suggested continuous Late Palaeogene to Late Neogene compressional regime in NW central Anatolia has been investigated by the field observations coclude that in all locations, especially aroun Yuva village, the relationship between the basement and Neogene units does not satisfactorily show a compressional regime and therfore the claim of the continuous compressive tectonic regime in the NW central Anatolia is questionable.

Origin and timing of siderite and calcite concretions in late Palaeogene non- to marginal-marine facies of the Te Kuiti Group, New Zealand

The Late Eocene-earliest Miocene Te Kuiti Group represents an overall transgressive sequence of formations ranging upwards from non-marine coal measure facies through marginal-marine low-energy shoreline siliciclastic sediments to fully-marine mixed siliciclastic-carbonate deposits. Concretionary structures are common in the lowest formations of the group, being dominantly sideritic in the non-marine to brackish sediment facies (Waikato Coal Measures and Glen Afton Claystone) and calcitic in the more marine-influenced sediments (Rotowaro Siltstone). The geochemistry of the carbonate cements within these early diagenetic concretions records the change from carbonate precipitation from purely meteoric fluids to precipitation from marine fluids, and a shifting source of carbonate carbon across this transition.Siderite precipitation in the Waikato Coal Measures concretions and hardpans was initiated and often largely completed in the methanogenic zone, within the upper 20 m of the sediment pile over a period possibly lasting 100–300 ka. Precipitation continued at a reduced rate to burial depths of 300 m or more when septarian cracking occurred in some siderite concretions and was healed by calcite vein cements that probably derived carbonate from the oxidation of methane ascending from the maturing coal seams directly below.Siderite precipitation in the concretions and hardpans of the overlying brackish-marine Glen Afton Claystone was completed in the topmost few metres of sediment, possibly a few 10 ka. Stable-isotope values near zero support a marine carbonate carbon source, suggested to be from remobilised shell material as evidenced by the common occurrence of shell casts in the formation and the high degree of Mg and Ca substitution in the siderites.The overlying marginal-marine to low-energy marine Rotowaro Siltstone contains calcite concretions precipitated from pore waters enriched in bicarbonate derived from the sulphate-reduction zone, largely within the upper 8 m of sediment, and possibly growing over a few 100 ka. Concretion development continued at a reduced rate to burial depths of several tens of metres and in some cases septarian cracks developed during the later stages of concretion growth. The precipitation of septarian vein calcites with more depleted δ18O values and more enriched δ13C signatures than central concretions cements, may be due to increasing burial temperatures, and the progressive introduction of carbonate sourced from shell dissolution.

Transfer zones in the southern Rio Grande rift

Despite recent interest in transfer zones in regions of continental extension, their detailed geometry and kinematics remain unclear. Four late Palaeogene and Neogene transfer zones within the southern Rio Grande rift, USA, are described, based on geological mapping at the scale of 1:24 000 and analysis of synrift stratigraphy. The Cutter Sag transfer zone is located between the overlapping tips of north-trending, west-dipping faults, and is characterized by a north-dipping structural ramp segmented by closely spaced, NE-trending normal faults. Similarly, the West Potrillo transfer zone occupies a position in the zone of overlap of north-trending, west-dipping faults, but the structural details of the transfer zone are largely hidden beneath Quaternary lava flows. However, isolated bedrock exposures outside the lava field, gravity data, and the alignment of cinder cones suggest that the West Potrillo transfer zone is a NW-dipping synclinal ramp cut by NE-trending fractures and/or faults. Positioned between north-trending, overlapping border faults that dip toward each other, the Cedar Hills transfer zone is a broad, north-trending arch whose summit collapsed into a graben along a series of north-trending normal faults. The Rincon transfer zone separates border faults that do not overlap and has a long history of faulting and sedimentation beginning in latest Oligocene and extending into the Quaternary. With the possible exception of reactivated early Tertiary compressional structures in the Rincon transfer zone, the transfer zones described here do not appear to be influenced by pre-rift zones of weakness. However, the Cutter Sag and West Potrillo transfer zones are preferred sites of basaltic volcanism, and the Cutter Sag.- Rincon, and Cedar Hill transfer zones influenced the location of the Plio-Pleistocene ancestral Rio Grande.

A latest Cretaceous hotspot and the southeasterly tilt of Britain

The southeasterly regional dip of England and Wales is usually ascribed to Miocene movements. Loss of up to 2 km of cover from northern England, shown by apatite fission track analysis, has been related to uplift and erosion induced by a mantle hotspot, but its effects were far more widespread than considered hitherto. Outcrop patterns throughout much of England, Wales and eastern Ireland can be related to a hotspot beneath the Irish Sea. Uplift occurred within the late Maastrichtian and erosion continued into the late Palaeogene. After post-Oligocene down-faulting of the Irish sea, the modern drainage was initiated on the eroded surface. Unconformities provide the best means of dating orogenic movements; in some localities the time interval between the youngest rocks preserved beneath the unconformity and the oldest preserved above may be small enough to enable the dating of fold movements to be determined with some precision. Thus in southeastern Britain the major E-W structures of the Hampshire Basin, the Weald and the London Basin can be dated as Miocene, as rocks of Oligocene age are involved in the folding in the Hampshire Basin and Pliocene sands rest in erosional pockets of the Chalk of SE England. Because fold movements tend to affect large areas of the crust at discrete intervals of time, the southeasterly tilt of Britain, evident from the fact that a NW-SE transect from Anglesey to London crosses outcrops of rocks getting progressively younger from the Precambrian of Anglesey to the Tertiary of the London Basin, has

Structure, kinematics and metamorphism in the Liguride Complex, southern Apennines, Italy

The Liguride Complex of south Italy is the remains of a Cretaceous-Paleogene accretionary wedge which was emplaced onto the African margin during Early Miocene time. Transport directions of thrust sheets and nappes in the internal zone are roughly towards the present-day northeast. Transport directions match well with the corresponding slip vectors derived from relative motion of the Calabria-Sardinia-Corsica block with respect to Africa (including Adria) during Late Eocene to Oligocene time. Deformation of the internal zone included extensive underthrusting followed by underplating of already lithified sediments, ophiolitic rocks and continental basement on to the base of an accretionary wedge down to depths in places exceeding 30 km. Overthickening by massive underplating caused Late Paleogene gravity-driven extension within the accretionary wedge. The contact between the lower ophiolitic nappe and the upper ophiolitic nappe is an extensional fault zone of this age. Transport directions during the gravity-driven deformation do not match plate derived slip vectors. It is inferred that the gravitational potential of the wedge dominated the kinematics of the Late Palaeogene extensional deformation.

Tertiary evolution of the Intra-Carpathian area: A model

The Outer Carpathian flysch nappes encircle an Intra-Carpathian domain which can be divided into two megatectonic units (North Pannonian and Tisza) mostly on the basis of contrasting Mesozoic and Palaeogene faciès development. We see two major kinematic problems to be solved: 1. (1) The present distribution of the Mesozoic and Palaeogene facies is mosaic-like, and some belts form exotic bodies within realms of Austroalpine affinity. 2. (2) Late Eocene palinspastic reconstruction of the Outer Carpathian flysch nappes suggest, that the entire Intra-Carpathian area must have been located several hundreds of kilometres to the south and to the west of its present position. Neogene extension can account for shortening in the external Carpathian nappes, but is unable to explain Mesozoic facies anomalies and offsets of Palaeogene formations. We suggest that evolution of the Intra-Carpathian area involved first Late Palaeogene-Early Miocene juxtaposition of the North-Pannonian and Tisza megatectonic units, accompanied by the closure of the external Carpathian flysch troughs; thereafter extension of this amalgamated unit occurred, which was compensated by thrusting of flysch nappes onto the European foreland and formation of molasse foredeeps. Eastward escape of the North-Pannonian unit from the Alpine collisional belt involved left lateral shear along the Pieniny Klippen belt and right lateral shear along the Mid-Hungarian zone. Parts of the Late Palaeogene basin and an Early Miocene volcanic edifice were dissected, offset and elongated by several 100 kms. The driving mechanism of the eastward escape of the Intra-Carpathian area can be related to the collision of Apulia and Europe and the subduction of the external Carpathian crust under the Pannonian units. The escape ceased gradually in the Early Miocene, when oblique collision between the North-Pannonian unit and European continent occurred. Neogene extension of the Pannonian region was an areal deformation. The extension at locally variable rate resulted in the break-up of the heterogenous floor of the Neogene basin. The driving mechanism of basin extension and contemporaneous compressional deformation of the external Carpathians is thought to be related to ongoing subduction, involving the marginal part of the attenuated European continental crust. Tectonic activity in the Carpathians and basin subsidence and volcanism shifted in time and in unison from the west toward the east-southeast.

The Cenozoic history of Antarctica and its global impact

The Antarctic continent and the peripheral ocean regions are the primary source of information on the Cenozoic cryosphere and events leading up to its development at least 36 million years ago. From a variety of data it is now apparent that the southern high latitudes have been subjected to a dynamic alternation of ice sheet expansion and decay through the late Palaeogene and Neogene. This history of climate change was accompanied by, and certainly strongly influenced by, significant vertical and horizontal lithosphere changes, including the evolution of major internal seaways and mountain ranges. The imprint of this record is preserved in the marine successions of the polar basins, in the world's bathyal and abyssal ocean basins and in the continental shelves of other continents, including those of the Northern Hemisphere. The Antarctic and extra-Antarctic terrestrial and marine data bases have developed separately in the past three decades and geospheric and biospheric information must now be integrated across latitudes. Future success in deciphering climate change depends on a better understanding of glacial–deglacial cycles from the point of view of both direct Antarctic and indirect or proxy extra-Antarctic data, through the complete temporal range of 107 to 103 years. Unfortunately, much of the high latitude record for the past 65 million years of earth history is presently veiled by thick ice sheets/ice shelves and deep and often ice-covered marine waters. Without the intensive application of the most advanced remote sampling equipment on the continent and in the Southern Ocean it will be difficult for this region to contribute significantly to global change and global climate programmes.