The Quaternary deposits at Hoxne, Suffolk

Abstract

The geology and palaeobotany of Quaternary deposits at Hoxne, Suffolk, have been investigated. It is shown that immediately after the ice which laid down the Lowestoft Till had retreated a lake basin was formed in the till. In the basin a series of interglacial lacustrine sediments was deposited, first clay-mud and later detritus mud. Reworking of these sediments under a periglacial climate with a fluctuating lake water level resulted in the deposition of alternating layers of silt, drift mud and brecciated clay-mud. After this, clay, sand and gravel were deposited in the lake by solifluxion under periglacial conditions. The lake basin as a topographical feature was then entirely obliterated, and clay, sand and till were deposited unconformably on the lake sediments. This till was formed during the Gipping Glaciation. After the retreat of the ice of this glaciation, the present valleys were excavated, and later to a small extent filled by fluvial deposits. Finally, aeolian sand, which now forms the surface deposit in the area, was deposited under periglacial conditions and, probably at the same time, a cryoturbation phase occurred. Macroscopic plant remains and pollen diagrams from the lacustrine interglacial sediments are described. They give evidence of the vegetational and climatic history of the interglacial period between the Lowestoft and Gipping Glaciations. Four major vegetational stages are distinguished; they are named the Late-Glacial, Early-Temperate, Late-Temperate and Early-Glacial stages. The Late-Glacial stage was characterized by Hippophaë scrub, the Early-Temperate stage by the development and persistence of mixed-oak forest, the Late-Temperate stage by the beginning of the replacement of the mixed-oak forest species by Carpinus and conifers, including Picea and Abies , and the Early-Glacial stage by the presence of park-tundra with scattered forest. There was a rapid climatic amelioration at the very beginning of the interglacial period, which led to a climatic optimum in the middle of the Early-Temperate stage. After that time there was a progressive deterioration of the climate, which resulted in the periglacial conditions under which the uppermost sediments of the lake were laid down. A phase of deforestation in the Early-Temperate stage and its relation to the Lower Palaeolithic (Acheulian) artifacts found during the investigations are described; they may be associated. The stratigraphical positions of those artifacts found recently and of those found by previous investigators at Hoxne are also described. The molluscan and mammalian faunas of the deposits and the glacial erratics from the covering till are described in Appendices. The stratigraphy demonstrated here differs from that previously found at Hoxne in showing that there is one interglacial temperate horizon, undivided by a cold phase, whereas previously two temperate horizons separated by a cold phase had been described. The origin of this difference is explained. A comparison of these Quaternary deposits is made with those elsewhere in Britain, in Ireland and on the continent. It is concluded that the Hoxne Interglacial is of Great (Elster/Saale, Mindel/Riss) Interglacial age.