A direct approach to the analysis of systems with single, or commensurate delays is presented, and compared with other recently proposed methods. The finite polynomials arising in this direct method are shown to have useful sensitivity properties. Remarks are given concerning systems stable independent of delay.

The end-Devonian to mid-Mississippian time interval has long been known for its depauperate palaeontological record, especially for tetrapods. This interval encapsulates the time of increasing terrestriality among tetrapods, but only two Tournaisian localities previously produced tetrapod fossils. Here we describe five new Tournaisian tetrapods (Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis and Aytonerpeton microps) from two localities in their environmental context. A phylogenetic analysis retrieved three taxa as stem tetrapods, interspersed among Devonian and Carboniferous forms, and two as stem amphibians, suggesting a deep split among crown tetrapods. We also illustrate new tetrapod specimens from these and additional localities in the Scottish Borders region. The new taxa and specimens suggest that tetrapod diversification was well established by the Tournaisian. Sedimentary evidence indicates that the tetrapod fossils are usually associated with sandy siltstones overlying wetland palaeosols. Tetrapods were probably living on vegetated surfaces that were subsequently flooded. We show that atmospheric oxygen levels were stable across the Devonian/Carboniferous boundary, and did not inhibit the evolution of terrestriality. This wealth of tetrapods from Tournaisian localities highlights the potential for discoveries elsewhere.

No abstract

Devonian tetrapods (limbed vertebrates), known from an increasingly large number of localities, have been shown to be mainly aquatic with many primitive features. In contrast, the postDevonian record is marked by an Early Mississippian temporal gap ranging from the earliest Carboniferous (Tournaisian and early Viséan) to the mid-Viséan. By the mid-Viséan, tetrapods had become effectively terrestrial as attested by the presence of stem amniotes, developed an essentially modern aspect, and given rise to the crown group. Up to now, only two localities have yielded tetrapod specimens from the Tournaisian stage: one in Scotland with a single articulated skeleton and one in Nova Scotia with isolated bones, many of uncertain identity. We announce a series of discoveries of Tournaisian-age localities in Scotland that have yielded a wealth of new tetrapod and arthropod fossils. These include both terrestrial and aquatic forms and new taxa. We conclude that the gap in the fossil record has been an artifact of collection failure.Ballagan Formation | end-Devonian mass extinction | terrestriality | rhizodonts | lungfish

Stratigraphic and sedimentological fieldwork on the Falkland Islands confirms that they were originally part of South Africa. East and West Falkland have contrasting geological and deformation histories and are separated by the Falkland Sound fault, which marks a significant deformation edge to the Cape Fold Belt. The degree of structural deformation and metamorphism in West Falkland is substantially less than that of East Falkland, adjustments to differential shortening between the two islands being reflected by structures developed along the Falkland Sound fault. Prior to fragmentation of Gondwana the Falkland Platform and Maurice Ewing Bank were positioned in the Natal Valley, adjacent to the east coast of South Africa. This predrift reconstruction shows that the Falkland Islands have subsequently been rotated by 180 ø relative to South Africa and complements recent palaeomagnetic data. There was a complete overlap of the Maurice Ewing Bank and Falkland Platform to the exclusion of the Falkland Plateau Basin which is a small oceanic basin formed during the Jurassic fragmentation of Gondwana. Extension in this basin was accommodated by movements along the Aghulas Falkland Fracture Zone and the Gastre Fault System. Predrift restoration of these faults shows that Patagonia was positioned closer to both Africa and Antarctica. The Falkland Plateau Basin was an integral component of the West Gondwana Jurassic microplate system and provides an invaluable insight into the evolution of its western margin. At some time prior to the main opening of the South Atlantic, the Falkland Platform was rotated clockwise by 120 ø against the Agulhas Falkland Fracture Zone, such that the Falkland Islands were translated some 300 km to the south. The driving force for this rotation is not known but could possible have been initiated by periodic stress buildups in the Falkland Plateau Basin as the Gastre Fault System, within continental crust, became unable to accommodate the continuous dextral shear in the Agulhas Falkland Fracture Zone. The Falkland Islands represent an outboard extension of the Eastern Cape and are significant for understanding the paleogeography of both the Cape and Karoo supergroups. East Falkland is closely similar to South Africa in its geology, while West Falkland shows significant contrasts with both the Devonian and Permian successions being more proximal in character but still demonstrate the eastward continuation of the Cape and Karoo basins.

[1] Here we present combined radioisotopic dating (U-Pb zircon) and cyclostratigraphic analysis of the carbon isotope excursion at the Paleocene-Eocene (P-E) boundary in Spitsbergen to determine the numerical age of the boundary. Incorporating the total uncertainty from both radioisotopic and cyclostratigraphic data sets gives an age ranging from 55.728 to 55.964 Ma, within error of a recently proposed astronomical age of ∼55.93 Ma. Combined with the assumption that the Paleocene Epoch spans twenty-five 405 kyr cycles, our new age for the boundary suggests an age of ∼66 Ma for the Cretaceous-Paleogene boundary. Furthermore, our P-E boundary age is consistent with the hypothesis that the onset of the Paleocene-Eocene thermal maximum at the boundary occurred on the falling limb of a 405 kyr cycle, suggesting the event was initiated by a different mechanism to that which triggered the other early Eocene hyperthermals.

For the purposes of a high-resolution multi-disciplinary study of the Upper Jurassic Kimmeridge Clay Formation, two boreholes were drilled at Swanworth Quarry and one at Metherhills, south Dorset, UK. Together, the cores represent the first complete section through the entire formation close to the type section. We present graphic logs that record the stratigraphy of the cores, and outline the complementary geophysical and analytical data sets (gamma ray, magnetic susceptibility, total organic carbon, carbonate, δ13Corg). Of particular note are the new borehole data from the lowermost part of the formation which does not crop out in the type area. Detailed logs are available for download from the Kimmeridge Drilling Project web-site at http://kimmeridge.earth.ox.ac.uk/. Of further interest is a mid-eudoxus Zone positive shift in the δ13Corg record, a feature that is also registered in Tethyan carbonate successions, suggesting that it is a regional event and may therefore be useful for correlation. The lithostratigraphy of the cores has been precisely correlated with the nearby cliff section, which has also been examined and re-described. Magnetic-susceptibility and spectral gamma-ray measurements were made at a regular spacing through the succession, and facilitate core-to-exposure correlation. The strata of the exposure and core have been subdivided into four main mudrock lithological types: (a) medium-dark–dark-grey marl; (b) medium-dark–dark grey–greenish black shale; (c) dark-grey–olive-black laminated shale; (d) greyish-black–brownish-black mudstone. The sections also contain subordinate amounts of siltstone, limestone and dolostone. Comparison of the type section with the cores reveals slight lithological variation and notable thickness differences between the coeval strata. The proximity of the boreholes and different parts of the type section to the Purbeck–Isle of Wight Disturbance is proposed as a likely control on the thickness changes.

Important vertebrate faunas occur in fissure deposits of Late Triassic-Jurassic age in SW Britain. Although the faunas are well described, their age and palaeoenvironment remain poorly understood. One such fissure system was documented in detail during quarrying operations at Tytherington and has yielded in situ palynomorphs that add much information concerning its age and palaeoenvironment. Significantly, the Tytherington fauna is of the sauropsid type that has generally been dated as Norian or pre-Penarth Group transgression and was also regarded as representing a distinct upland fauna. The palynomorphs, which include a significant marine component, demonstrate that the Tytherington Triassic fissures are infilled with Late Triassic (Rhaetian) sediments that match specific levels in the Westbury Formation. In addition, many of the Tytherington solutional fissures probably formed during the Rhaetian and are consistent with a fluctuating saline to freshwater environment. There is no prima facie evidence of solutional formation and infilling of the reptilebearing deposits before the Rhaetian trangression. The fissure reptile fauna, which includes the early dinosaur Thecodontosaurus, inhabited a small fire-swept limestone island in the Rhaetian sea. The features of the herpetofauna are entirely consistent with this island model which has Quaternary analogues.