The dominantly nonmarine Solent Group of the Hampshire Basin, southern England, spans the Late Eocene and earliest Oligocene. It contains a rich biota, including mammals and charophytes, but contains few fully marine, time-diagnostic intervals. Correlation with standard marine successions is provided here using bio-stratigraphically significant mammals and charophytes via interdigitation of strata with those containing marine zonal indicators or via magnetostratigraphy in other parts of Europe. This allows the re-identification of recently described normal polarity intervals in the Solent Group to magnetochrons C16n, 15n, 13r1n, and 13n, and improved calibration of the Solent Group to the geomagnetic polarity time scale (GPTS). Consistent with this calibration, interpreted Solent Group sea-level changes can be related to those recognized to be global in deep-marine successions in central Italy. The major sea-level fall associated with polar ice buildup at the Oligocene isotope event Oi-1 near the beginning of the Oligocene is shown to be represented in the Hamstead Member of the Bouldnor Formation by the falling stage systems tract followed by a major hiatus before the next maximum flooding surface. This hiatus encompasses the large European mammalian faunal turnover known as the “Grande Coupure.” Improved calibration to the GPTS allows better dating of climate proxies, such that recently described summer freshwater temperatures can be shown to track global fluctuations across the Eocene-Oligocene transition.

Abstract The most important onshore Paleogene deposits of Britain are the classic sequences of the London and Hampshire basins, SE England, which have been studied almost since the first interest in rocks and fossils developed in this country. Ostracods were identified and reported from these sequences relatively early (e.g. Jones 1854 ), following shortly after the key stratigraphical works of Joseph Prestwich published between 1846 and 1855, although not as early as continental workers recorded Cenozoic ostracods (e.g. Minster 1830). At the time of writing the authors are not aware of any significant published records of British Paleogene Ostracoda from outside the classic onshore sequences of SE England, and the present chapter primarily concerns that region. However, the occurrence of ostracods in offshore basins is briefly reviewed below.

Abstract Mammals from strata immediately underlying and overlying the Grande Coupure in the Hampshire Basin, UK, are described or reviewed. Precise superposed mammaliferous horizons are documented and the stratigraphy of older less precise records is assessed. The following species group taxa are described for the first time in the UK: Amphiperatherium minutum, A. exile, Peratherium cf. perrierense, Bransatoglis planus, Butseloglis micio, Theridomys bonduelli, Isoptychus margaritae, Pseudoltinomys cuvieri, Tetracus aff. nanus, Myxomygale cf. antiqua, Hyaenodon cf. dubius, Amphicynodon? sp., Plagiolophus major and Ronzotherium cf. romani . The main systematic innovations are as follows. The post-Grande Coupure record of Perather-ium cf. perrierense shows this species to range into the Oligocene, later than its supposed descendant P. cayluxi , with which it is tentatively concluded instead to have a sister relationship. Pre-Grande Coupure Glamys fordi represents the earliest record of the species; its morphology shows no increased similarity to its primitive sister species G. devoogdi , supporting the clado-genetic model for Glamys species. Intraspecific variation and the previously unknown upper fourth deciduous premolar are documented in the rodent Theridomys bonduelli , thanks to the discovery of the first substantial assemblage of the species. A first lower premolar is tentatively recognized for the mole Myxomygale , which if correctly associated suggests placement in the tribe Scaptonychini rather than Urotrichini, where it is usually classified. If the tentative identification to M. antiqua is correct, upper teeth are recorded for the first time in this species. An ulna is tentatively attributed to the oldest known mole Eotalpa . The occurrence of Leptadapis in the upper Hamstead Member is the first post-Grande Coupure adapid and the youngest member of the family Adapidae in Europe. The recent synonymy of Elomeryx porcinus with E. crispus is discounted and the former species resurrected. Diplopus is once more considered closely related to Elomeryx and returned from the Choeropotamidae to the Anthracotheriidae. In addition to the established dental differences, the subspecies Palaeotherium muehlbergi muehlbergi is shown to be distinguished from P. m. thaleri by having a shallower narial incision. The dimensions of Plagiolophus minor from the lower Hamstead Member imply a more complex pattern of relationships with its immediate relatives than the single-lineage model so far proposed. Plagiolophus major is distinguished from P. fraasi on proportional dimensions of M 3 and tentatively on crown height and position of the preorbital fossa. Implications for European Paleogene biostratigraphy are as follows. Reference level MP20 is difficult to identify without the terminal subspecies of Palaeotherium medium and P. curtum . The upper limit of the Palaeotherium curtumfrohnstettense–P . medium suevicum Biozone in the UK is raised to a position within the Hamstead Member. A significant and eventful timespan is concluded to be represented by the lowest European reference level above the Grande Coupure (MP21), which would be best resolved by conventional biostratigraphic subdivision. The distancing of Elomeryx crispus from E. porcinus means that the former may not be an early herald of the Grande Coupure.