SK9942 : View over fields on the edge of Wilsford Heath
taken 3 years ago, near to Wilsford, Lincolnshire, England
A band of hard Jurrasic limestone, the Lincolnshire Limestone, runs due south from the Humber towards Grantham, and forms an escarpment commonly known as the 'Lincoln Cliff'. It is a natural barrier to drainage only significantly breached by the River Witham at the 'Lincoln Gap'. A second gap at Ancaster has the small headwater of the River Slea.
However, this 'Ancaster Gap' may have been more significant during Pleistocene times, when it is thought to have carried a river draining much of the Midlands - a proto-Trent flowing west to east through the gap Link . Later glacial events caused this Trent drainage to divert north to the Lincoln Gap, and then further north again to the Trent's present route to the Humber.