Geology

The geology and topography of Wold Newton are based on the massive chalk deposits of the Cretaceous Period (145 to 65 million years ago) and the subsequent glaciation during the coolest period of the current ice age.  (N.B. An ice age is a time when there is ice present on the surface of the Earth all year round, so we are in one now!  Ice ages contain glacial periods, when it is particularly cold, and interglacial periods, like now, when it is relatively warm.)

The vast layer of chalk, from which the Lincolnshire Wolds were formed, was laid down during the Cretaceous Period when Wold Newton would have been 100 to 500 meters below sea level.  The high sea level of the period was caused by an unusually active period of ocean spreading.  When new Oceanic Plate is created, at mid-ocean ridges, it is hot and has a lower density, and is thus buoyant.  As Oceanic Plate spreads away from the mid-ocean ridge it cools, becomes denser and thus less buoyant.  Hence, the oceans are shallowest at the mid-ocean ridges and deepest where they meet Continental Plate.  During the Cretaceous period, there was an unusually high rate of creation of Oceanic Plate leading to shallow oceans.  This displaced sea water onto the Continents creating vast shallow seas, perfect for the deposition of calcite or limestone .  The high level of volcanic activity involved in the high level of ocean spreading, led to an increased level of carbon dioxide in the atmosphere and thereby caused a relatively warm climate.  So, the vast shallow seas were warm, perfect conditions for Cocolithophores, a type of algae with microscopic calcite skeletons called Cocoliths.  When the Cocolithophores died, their bodies sank and their skeletons piled up to make chalk.

Within the chalk, there are layers of tabular and nodular flint, a form of the mineral quartz.  The origins of these silicate deposits remain somewhat mysterious.  The most widely supported hypothesis is that during low temperature lithification of the chalk, the siliceous material dissolved and flowed into holes made by burrowing molluscs, where it solidified.

The topography of Wold Newton and the Lincolnshire Wolds was created by the sequence of glaciation and melting during two ice incursions of the last glacial period.  The details of this are hidden away in the academic paper below, but the essence is that the Wold Newton valley was a conduit for melt water which flowed down to East Ravendale and then into West Ravendale where a narrow gorge is cut through to the edge of the Wolds, joining water coming from Thorseway via Croxby Ponds.

At Petterhills, there was a proglacial lake in which silts were laid down.  Proglacial lakes are formed during the retreat of glaciers, when the valley may be blocked by ice dams or moraines, trapping water.  The clay silts laid down were used briefly in the 18th and 19th centuries for making bricks.  The wood on the south side of Petterhills Pond used to be called Osier Holt, presumably because willows were grown there, taking advantage of the wet ground.

The most interesting geological feature in Wold Newton is a "marker unit" of stratigraphic value, recorded by the British Geological Survey, which can be found in the chalk pit at the west end of the Valley.  The marker unit is known as the Wootton Marls.  Marl is lime-rich mud stone and this one is grey in colour and about 1cm thick.  It commonly splits to form a double layer with localised areas of a marl complex up to 2cm thick.  Separating the upper and lower Wootton Marls is white chalk, containing discrete nodular flints up to 40cm thick.
 
The picture and slideshow below is of a number of fossils scratched out of the ground by rabbits, badgers and foxes in the grass field on the east side of the village.





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