Marine and ice-core records show that the Earth has experienced a succession of glacials and interglacials during the Quaternary (last ~2.6 million years), although it is often difficult to correlate fragmentary terrestrial records with specific cycles. Aminostratigraphy is a method potentially able to link terrestrial sequences to the marine isotope stages (MIS) of the deep-sea record 1,2 . We have used new methods of extraction and analysis of amino acids, preserved within the calcitic opercula of the freshwater gastropod Bithynia, to provide the most comprehensive dataset for the British Pleistocene based on a single dating technique. A total of 470 opercula from 74 sites spanning the entire Quaternary are ranked in order of relative age based on the extent of protein degradation, using aspartic acid (Asx), glutamic acid (Glx), serine (Ser), alanine (Ala) and valine (Val). This new aminostratigraphy is consistent with the stratigraphical relations of stratotypes, sites with independent geochronology, biostratigraphy and terrace stratigraphy [3][4][5][6] . The method corroborates the existence of four interglacial stages between the Anglian (MIS 12) and the Holocene in the terrestrial succession. It establishes human occupation of Britain in most interglacial stages after MIS 15, but supports the notion of human absence during the Last Interglacial (MIS 5e) 7 . Suspicions that the treeless 'optimum of the Upton Warren interstadial' at Isleworth pre-dates MIS 3 are confirmed. This new aminostratigraphy provides a robust framework against which climatic, biostratigraphical and archaeological models can be tested.Despite the importance of the terrestrial record for climate models, the difficulties of assigning specific sedimentary sequences to individual climate cycles restricts the use of these data in climate modelling. The British Quaternary is exceptional for the number of who used the extent of racemization in the amino acid L-isoleucine (to its diastereomer D-alloisoleucine, yielding an A/I value) in non-marine mollusc shells to build an aminostratigraphy of terrestrial sequences that could be linked to the marine oxygen isotope stratigraphy. Following debate concerning certain correlations, we developed a revised method of extraction and analysis 9 . Shells of freshwater gastropods (Bithynia and Valvata) from many of the original sites 10 have been re-analysed, confirming much of the A/I stratigraphy. However, it emerged that within-site and within-stage variability increases in shells from older sites. This variability probably results from diagenetic alteration of the biomineral carbonate from aragonite to the more thermodynamically stable calcite 10,11 .Our new method has five significant revisions, three of which reduced within-site variability. First, inter-species variation was minimised by analysing only a single genus of freshwater gastropod (Bithynia). Second, variability in amino acid concentration and D/L values was significantly lowered when samples were crushed to ≤ 500 μm and exposed ...

Aminostratigraphies of Quaternary non-marine deposits in Europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs. The value of analysing multiple amino acids from the opercula of the freshwater gastropod Bithynia, which are composed of calcite, has been demonstrated. The protocol used for the isolation of intra-crystalline proteins from shells has been applied to these calcitic opercula, which have been shown to more closely approximate a closed system for indigenous protein residues. Original amino acids are even preserved in bithyniid opercula from the Eocene, showing persistence of indigenous organics for over 30 million years. Geochronological data from opercula are superior to those from shells in two respects: first, in showing less natural variability, and second, in the far better preservation of the intra-crystalline proteins, possibly resulting from the greater stability of calcite. These features allow greater temporal resolution and an extension of the dating range beyond the early Middle Pleistocene. Here we provide full details of the analyses for 480 samples from 100 horizons (75 sites), ranging from Late Pliocene to modern. These show that the dating technique is applicable to the entire Quaternary. Data are provided from all the stratotypes from British stages to have yielded opercula, which are shown to be clearly separable using this revised method. Further checks on the data are provided by reference to other type-sites for different stages (including some not formally defined). Additional tests are provided by sites with independent geochronology, or which can be associated with a terrace stratigraphy or biostratigraphy. This new aminostratigraphy for the non-marine Quaternary deposits of southern Britain provides a framework for understanding the regional geological and archaeological record. Comparison with reference to sites yielding independent geochronology, in combination with other lines of evidence, allows tentative correlation with the marine oxygen isotope record.

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In order to obtain a better understanding of the infilling of the Saalian glacial basins during the Eemian, particularly following the recent research in the Amsterdam Basin (Terminal borehole), it was necessary to re-investigate the type locality of the Eemian at Amersfoort. Both published and unpublished data from various biota (diatoms, foraminifers, molluscs, ostracods, pollen) provide new information on the changing sedimentary environments during the Eemian. Although the organic and clastic sediments of the infilling represent nearly all the pollen zones, the sedimentary sequence at Amersfoort is discontinuous: four breaks at least are recognised at the type locality.The successive sedimentary environments and the breaks in the record are linked with the transgression of the Eemian sea, the topographic position at the margin of an ice-pushed ridge, and the changes in hydrodynamic conditions. Local conditions, such as a sandy sea bed, shallow water and a reduced water exchange near the North Sea margin, influenced the salinity of the basin. Rib counts of Cerastoderma edule shells indicate a higher salinity at the end of the Taxus (E4b) and the beginning of the Carpinus (E5) zones than that present in the modern North Sea. Local conditions were responsible for the higher salinity following the climate optimum.During the Abies phase (the later part of regional pollen zone E5), the sea level had already fallen. The change from eu-trophic peat growth (with Alnus and Salix) to an oligotrophic Ericaceae/Sphagnum community at the end of the Eemian resulted from the change from a marine to a fresh-water environment, probably coherent with a deterioration of the climate.

The marine molluscan faunas from different temperate stages of the Pleistocene of the North Sea vary enormously both in terms of species richness and in the diversity of their biogeographical composition. The marine assemblages from the Middle Tiglian, Eemian and Holocene have all yielded c. 100 species or more, including many with southern or ‘Lusitanian’ affinities. It is thought that during these stages the Strait of Dover was open, allowing entry of these southern taxa into the southern North Sea. Conversely, the temperate stages from the Late Tiglian up to and including the Holsteinian have yielded relatively impoverished faunas (no more than about 40 species) virtually lacking any of the southern elements. During these stages it would appear that the Strait of Dover was closed, so preventing the spread of marine molluscs into the North Sea. Examination of the history of fluvial molluscs (particularly prosobranchs and larger bivalves) on either side of the English Channel supports this interpretation. Fluvial provinciality is recognized during the stages when Britain is thought to have become an island. Non-provinciality, pointing to fluvial exchange, occurs during the other stages.