Geology of the Poole-Bournemouth area: part of 1:50 000 Sheet 329 (Bournemouth)

This report summarises the results of the three phases of a three year project to investigate the geology of the Poole-Bournemouth area in Dorset, funded by the Department of the Environment

Geology of Sheets SY 99 NE and SE and parts of SY 99 NW and SW Corfe Mullen - Lytchett Minster, Dorset: part of 1:50 000 sheet 329 (Bournemouth)

Some 55 km² of the Corfe Mullen - Lytchett Minster area have been geologically surveyed at the 1:10,000 scale. As a result, the detailed stratigraphical sequence established in the Poole Formation during 1984 has been followed westwards; additionally, sand members within the London Clay have been recognized and mapped over a wide area. Gentle E-W flexures which are superimposed on the regional dip of l° SE, probably overlie faults of pre-Aptian age (mid-Cretaceous). Dinoflagellate floras collected from the clays of the Poole Formation and London Clay allow the various stratal units to be placed within the known dinoflagellate zonal sequence. Landslips developed on the clays of the Reading Formation, and solution-collapse hollows developed over the Chalk have been identified at a number of sites. Many of the clays of the London Clay and Poole Formation have been exploited for bricks, tiles and pottery, but most pits are now disused and mostly backfilled. In addition, extensive reclamation of low-lying ground and tidal flats has occurred. A map showing the extent and nature of the Made Ground is included. Summaries of grading data for sand samples collected in the field are presented graphically. River Terrace Deposits occur at various levels; except in the extreme south and north they have been either built over, or exploited, or are of too limited extent or thickness to form significant resources. An account of the hydrogeology of the district is included. The application of geophysical techniques, principally using the EM 31 and 34 to measure ground conductivity as an aid to geological mapping, is discussed in Appendix 1. A glossary of technical terms appears at the end of the report

Geology of Sheet SZ 19 (Hurn-Christchurch): part of 1:50 000 sheet 329 (Bournemouth)

The original geological survey of the area comprising sheet SZ 19 was made by H W Bristow and J Trimmer at the one-inch to one-mile scale (1:63 360) as parts of Old Sheets 15 and 16 published in 1856 and 1855 Series Geological respectively. The drift deposits were not represented on these maps. Clement Reid resurveyed the area on the six-inch to one-mile scale (1:10,560) in 1893, and his results were incorporated in New Series One-Inch Geological Sheet 329 (Bournemouth), published in 1895 in both Solid and Drift editions, and in the accompanying memoir (Reid, 1898). A second edition of this memoir was produced by H J 0 White, and was published in 1917. White re-examined much of the ground, but the published maps remained unaltered. In 1983 the Institute of Geological Sciences (now British Geological Survey) was commissioned by the Department of the Environment (contract PECD7/1/0103-149/82) to provide new 1:10,000 geological maps of the Poole-Bournemouth area. This contract comprises the survey of ten 1:10,000 sheets, and parts of four others, (Figure 1) over three years, to form a basis for the planning of urban and industrial development, and the safeguarding of mineral and water resources. During 1983, in the first phase of the contract, the four constituent quadrants of Sheet SZ 19 were mapped as follows, under the direction of R W Gallois, District Geologist: SZ 19 NW B J Williams; SZ 19 NE E C Freshney; SZ 19 SW E C Freshney; SZ 19 SE C R Bristow

Culm Basin

To the south of the Mississippian platform carbonate successions of South Wales (Chapter 5) and Bristol, Mendips and Somerset (Chapter 6), Carboniferous rocks predominantly occur within the strongly deformed Culm synclinorial belt of Southwest England. The Culm Basin has a broad graben architecture, with an inner graben (Central Devon Sub-basin) flanked by half-grabens (Bideford and Launceston subbasins) (Fig. 4.1; Leveridge & Hartley 2006; Waters et al. 2009). The Bideford Subbasin is bounded to the north by the Brushford Fault, the Central Devon Sub-basin by the Greencliff Fault and the Launceston Sub-basin by the Rusey Fault. To the north of the Brushford Fault is the Northern Margin of the Culm Basin. The Tavy Basin has limited development of Famennian to Tournaisian strata. The High separating the Tavy Basin and Launceston Sub-basin includes a Tournaisian to ?Visean succession (Yeolmbridge and Laneast Quartzite formations). Remnants of Carboniferous strata also occur in the South Devon Basin