Procedimientos de operación estándar (POE)

2.9.1 Banwell Bone Cave, Banwell, Somerset

Museum collections: NHM, SCM Structure o f the deposits

The faunal collections are from the highest chamber in the series o f

carboniferous limestone caves in Banwell Hill. The site was excavated by W. Beard from 1824 onwards, and opened to the public as a show cave. It appears likely that hundreds o f thousands o f mammalian specimens were originally present, many o f which were stacked in piles around the sides o f the cave. There are no published accounts o f the structure o f the deposits from this major period o f investigation,

although more recent 20* Century excavations indicate a homogeneous fauna despite some internal stratification (Currant 2000). The bones were contained in a mixture o f earth and stones proposed to derive fi*om outside the cave, and very few specimens were found in articulation. These two factors indicate that the deposits were

sporadically moved into the cave by secondary processes (Currant 2000). The reason for accumulation o f carcasses outside the cave entrance remains unclear. Faunas o f ‘Banwell type’ may relate to 01 Stage 4 (Currant & Jacobi 1997, 2001).

Palaeoenvrionmental evidence

The restricted mammalian fauna from Banwell Bone Cave indicates a period o f cold climate conditions. This is supported by the presence o f species such as R.

tarandus and Alopex lagopus (arctic fox).

2.9.2 W illm ent’s P it, Islew orth, M iddlesex Museum collections: NHM

Structure o f the deposits

The site occurs within the lowest (Kempton Park) terrace o f the Thames. The sequence (table 2.24) consists o f approximately 5m o f gravels, sands and organic silt clays and has been described by Coope & Angus (1975). The organic sediments, fi"om which B. priscus and R. tarandus have been recorded in situ, are interpreted as

representing a period o f quiet water conditions. Radiocarbon dating o f these deposits has been attempted, but results close to the limit o f the method were produced. The organic layers are overlain by high-energy fluvial deposits, which provide evidence o f cold climatic conditions. A significant proportion o f the machine-collected fauna may have accumulated in these horizons (Stuart 1982). The fauna is correlated with Banwell Cave (section 2.9.1) using biostratigraphy (Currant & Jacobi 1997, 2001).

Table 2.24: The stratigraphie sequence at Wiiments Pit, Isleworth, Middlesex (after Coope & Angus 1975; Kemey et al. 1982).

Bed Description Fauna + Palaeoenvironment

6 Brickearth + soil

5 Poorly-graded gravels Ice wedge casts 4 Stratified + current-bedded sands

and gravels Mammalia?

3 Sands + gravels with clay partings

2 Organic silty clay Mammalia, Coleoptera 1 Basal red gravel

Palaeoenvironmental evidence

Pollen collected from the organic deposits indicates treeless conditions and a herb-dominated community (Kemey et al. 1982). Species o f disturbed ground are also present. The beetle fauna supports the interpretation o f the vegetation provided by pollen evidence (Coope & Angus 1975). A vegetation o f recently exposed, poorly developed soils is indicated and no coleopteran taxa dependent on tree species are recorded. However, the beetle fauna suggests relatively temperate climatic conditions, with average July temperatures o f 17-18 °C and winter temperatures o f -2 - 1 °C (Coope & Angus 1975). Mollusca also support the existence o f a relatively temperate climate during the deposition o f the organic layers (Kemey et al. 1982).

The organic deposits may therefore record a short-lived interstadial period contained within a generally cold episode. The period o f warming may have been too short to allow immigration o f tree species from their southem réfugia. The existence o f such interstadial periods during 01 Stage 4 has been proposed from studies o f

speleothem growth in Stump Cross Cave (section 2.9.3) (Baker et al. 1996). Some o f the mammalian fauna certainly relates to the interstadial layers but it is possible that significant proportions came from the gravels and sands also, which were probably laid down under much colder periglacial conditions. The mammalian fauna is certainly characteristic o f a cold climatic period; species diversity is low and R. tarandus^ a species only recorded from cold stages o f the British Pleistocene, is present.

2.9.3 Stump Cross Cave, Pateley Bridge, North Yorkshire

Museum collections: NHM Stmcture o f the deposits

The limited mammalian fauna from this limestone cave site was recorded from within laminated fiowstones, which consist o f alternating calcite and mud layers (Sutcliffe et al. 1985). These deposits were underlain by current-bedded sands and gravels, and covered by more massive fiowstones. The lower beds are considered to represent alluvial deposits and stream flow, with the muddy layers o f the laminated fiowstones produced by periodic flooding o f the cave. The cave is thought to have acted as a trap for animals that entered and could not escape, so the high proportions o f wolverine remains are not considered to represent a breeding lair (Sutcliffe et al. 1985).

The Gulo gulo material has been dated to 83 ± 6 kyr B.P. by uranium-series methods

Palaeoenvironmental evidence

The low-diversity mammalian fauna indicates cold climatic conditions. Wolverines are adapted for living in environments including snow and extreme cold and occupy a modem range very similar to R. tarandus in the boreal forest and tundra (Sutcliffe et al. 1985). Periods o f speleothem growth inside the cave provide evidence o f interstadial conditions at the beginning o f 01 Stage 4 (Baker et al. 1996), and may date the fauna to this period also (Currant & Jacobi 1997, 2001).

2.9.4 Windy Knoll, Castleton, Derbyshire

Museum collections: MAN, NHM, SMG, TNH, UMZC Stmcture o f the deposits

Dawkins excavated at this site in the 19* Century. The yellow clay deposits containing mammalian remains appear to be associated with a swallow-hole formed by solution o f limestone. The bones were found collected in a limestone depression and can be considered to represent animals that fell into the hole or were carried there by the river or lake associated with the drainage feature (Dawkins 1877). Articulated skeletons were recorded. The fauna is o f ‘Banwell type’, which may indicate an 01 Stage 4 correlation.

Palaeoenvironmental evidence

The presence o f R. tarandus indicates a cold climatic period; no thermophilous or woodland indicators are present.

2.9.5 Windsor, Berkshire

Museum collections: BGS, MAN

Very little is known about this Pleistocene mammal site. It is mentioned by Dawkins (1875), who reports the discovery o f the fauna by Captain Luard in 1866 during the digging o f foundations for the cavalry barracks at Windsor. The bones are described as deriving from fluvial deposits o f the River Thames. Dawkins considered the site to be the same age as Windy Knoll (section 2.9.4), on the basis o f the

mammalian species recovered. This bio stratigraphie interpretation is still supported, with a characteristic bison-reindeer fauna represented.

2.9.6 Wretton, Norfolk

M useum collections: UMZC Structure o f the deposits

A complex sequence o f Ipswichian and Devensian terrace deposits o f the River Wissey are recorded at this site (Sparks & West 1970; West et al. 1974). Ipswichian interglacial units occur at the base o f the sequence, overlain by fluvatile sands and gravels containing periglacial structures. Within the sands and gravels are organic horizons containing plant, moUuscan and mammalian remains. These horizons have been formed in small channels and depressions formed by the melting o f ice mounds (W est et al. 1974). The organic sediments record a complex sequence o f environmental changes, but the majority o f the mammalian fauna appears to have been deposited during only one o f the identified vegetation sub-stages (see following discussion) (Stuart 1982). This interpretation is supported by the uniformity o f the fauna, despite the fact that very little o f the material was found in situ.

Palaeoenvironmental evidence

The mammalian fauna has been assigned to W retton herb sub-stage I, the earliest o f the Devensian organic beds (Stuart 1982). Pollen and plant macro fossils indicate that this period was characterised by a tundra-like grassland habitat, with a few shrubs and no trees present (West et al. 1974). Beetle remains from zones A and B o f herb sub-stage I support the results from plant studies, suggesting a vegetation o f open, marshy grassland.

Coleoptera can also provide information on palaeotemperature conditions. During the deposition o f the mammal fauna the beetle community is interpreted as representing cool but not arctic climates. The moUuscan fauna from this sub-stage contains an unusual mix o f temperate and cold climate species (West et al. 1974), this may result from the ability o f MoUusca to survive cold winters if summers are warm. Both Coleoptera and MoUusca indicate the existence o f a continental climate with strong seasonaUty. The palaeoenvironmental information from W retton supports the hypothesis that mammaUan faunas from 01 Stage 4 accumulated in periods when summer temperatures were relatively high, but winter conditions remained extremely severe. Open vegetation habitats developed, supporting large grazing animals e.g. B.