* Corresponding author. Tel.: 0044-191-222-6440; fax: 0044-191-222- 5421. E-mail address: darrel.maddy@newcastle.ac.uk (D. Maddy). Quaternary Science Reviews 19 (2000) 1581}1588 Accelerated uplift resulting from Anglian glacioisostatic rebound in the Middle Thames Valley, UK?: evidence from the river terrace record D. Maddy*, D.R. Bridgland Department of Geography, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK Department of Geography, University of Durham, Durham, DH1 3LE, UK Abstract A relatively simple analysis of the terraces of the Middle Thames valley reveals a complex sequence of responses to late-Anglian (late Middle Pleistocene) drainage disruption. A decrease in the amounts of vertical incision separating the later post-Anglian terraces strongly suggests a major change in the rate of incision in the Middle Thames area in the post-Anglian. A late Anglian and early post-Anglian incision rate of 1.45 m ka was quickly replaced by incision at a rate of 0.089 m ka in the later post-Anglian period. The lower incision rate of the later post-Anglian compares favourably with previous estimates of regional uplift. Two plausible explanations for the enhanced incision in the late Anglian and early post-Anglian are recognized, one related to ponding of the river by Anglian ice and the other to glacio-isostatic rebound. In the latter case, the mismatch between expected and actual heights of late-Anglian deposits would suggest glacio-isostatic uplift of the order of 22}25 m.  2000 Elsevier Science Ltd. All rights reserved. 1. Introduction The river terrace sequence of the Middle Thames val- ley (Fig. 1) has attracted considerable interest in recent decades as it provides one of the most complete terres- trial records of Pleistocene environmental and climatic change in north west Europe (Green and McGregor, 1978, 1986; Gibbard, 1985; Whiteman and Rose, 1992; Bridgland, 1994). Most discussion concerning the development of this sequence has utilized, as a framework, lithostratigraphi- cal classi"cation of the terrace deposits (e.g. Hey, 1965; Gibbard, 1985; Bridgland, 1994). For dating the se- quence, limited information is available from biostratig- raphy (much less than in the neighbouring upper and lower Thames), together with `trace-fossila information from Palaeolithic artefacts. Geochronology for the Thames sequence is limited to a small number of radiocarbon age estimates (Gibbard, 1985), together with an aminostratigraphy (Bowen et al., 1989, 1995), the former restricted to late-Pleistocene deposits. Perhaps the most signi"cant marker within the sequence is pro- vided by deposits related to the Anglian glaciation. This glaciation was responsible for the diversion of the Thames into its present valley through London from a former, more northerly course (Gibbard, 1977, 1979; Bridgland and Gibbard, 1997; Fig. 2). It is generally agreed that this glaciation can be correlated with O Stage 12 of the deep sea record (Bowen et al., 1986), although some have questioned this assignment (Sum- bler, 1995). This paper uses the available dating evidence, together with the geomorphological and lithostratigraphical framework provided by the terraces themselves, to estab- lish a chronology for valley incision. 1.1. Controls on river terrace formation Progressive incision of the Thames in the post-Anglian is evident from the well-developed terrace staircase. Such progressive downcutting is believed here to result from sustained uplift thoughout this period (cf. Bridgland, 1994). This could result from the general plate-wide uplift suggested from other areas of northwest Europe (Cloetingh et al., 1990) but may also be in part the result of compensation in response to sediment loading in the North Sea Basin (Preece et al., 1990). Thus by deriving 0277-3791/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S 0 2 7 7 - 3 7 9 1 ( 9 9 ) 0 0 1 0 5 - 5