The Geological History and Geology of Holt and Little Witley

There are essentially two features to the geology of Holt and Little Witley, the bedrock and superficial deposits. These features give the parishes their topographical form and influence the land use within them.

The bedrock throughout the two parishes dates to the end of the Permian and in to the Triassic geological periods. At the start of this period all the Earth's major land masses except portions of East Asia were collected into a single supercontinent known as Pangaea and the UK was situated near the equator. By the end of the Triassic the landmass had begun to break-up in to two supercontinents, Laurasia (Eurasia, including the UK, and North America) and Gondwana (South America, Africa, Antarctica, Australasia and India. By this time the UK had drifted in to a sub-tropical latitude.

The Late Permian

The Late Triassic

Throughout the period, climates in the zone occupied by the UK were generally hot, and conditions commonly arid. During the Triassic the polar regions were apparently moist and temperate, a climate suitable for reptile-like creatures, with no evidence of glaciation at or near either pole. Two types of bedrock laid down in these conditions form the bedrock of Holt and Little Witley; New Red Sandstones and Mercian Mudstones (formerly known as Keuper Marls).

The New Red Sandstone consists of beds of true red sandstones, mudrocks and evaporite strata laid down throughout the preceding Permian period (280 million years ago) to the beginning of the Triassic (240 million years ago). The sand grains are cemented together with the ferric iron oxide haematite (Fe2O3). The presence of haematite is evidence for a deposition in a desert environment, and gives the rocks the red color which they are named after. Plants and animals were thin-on-the-ground in the arid desert conditions hence the sandstone generally lacks fossils, although tracks of mammal like reptiles are sometimes found..

Holt and Little Witley in the late Permian

The Mercian Mudstones form deposits up to 1200m deep (in Cheshire) of predominantly red mudstones and siltstones laid down in rift-related basins during a period of regional subsidence. Following the Permian, Triassic rocks were deposited in the space created by the continued subsistence of the fault bounded Worcester basin.The mudstone was formed during the late Triassic Period (160-190 million years ago). It consists of clay-minerals with a large proportion of desert-blown quartz dust and minute crystals of dolomite. Some of the deposits were wind blown from eroding mountains to the south of the UK and some were deposited in shallow seas that occasionally inundated the land from south and east. These seas were fed by rivers originating in areas of wetter climate. There was a high rate of evaporation owing to the great heat. The evaporation of the sea water led to the deposition of a basal layer of rock salt in many areas, hence the salt deposits in nearby Droitwich.

The mudstones are not rich in fossils; the principal plants are cypress like conifers (Walchia, Voltzia) and a few calamites with such forms as horsetails (Equisetum spp.) and ferns. Fishes include lung fish (e.g. Ceratodus), sharks (e.g. Hybodus) and bony fish e.g. (Lepidotus). Giant amhibians are represented by the footprints of the Cheirotherium and the bones of Labyrinthodon, Mastodonsaurus and Capitosaurus. Among the reptiles are the early dinosaurs Hyperodapedon, Palaeosaurus and Plateosaurus, the crocodile like Belodon and the semi-aquatic sauropterygian Nothosaurus. The first fossil shrew-like mammals also make their appearance at this time.

Holt and Little Witley in the Triassic

In Holt and Little Witley the New Red Sandstone is visible in road cuttings near the Holt Fleet inn and in the village respectfully, and a number of small, mostly overgrown, quarries. The most obvious occurrence however is the older local buildings. Holt and Little Witley churches and Holt Castle are build almost entirely of the local stone, as are the abutments of Holt Fleet Bridge and at least the foundations of many of the local farm houses and farm buildings.

New Red Sandstone in Little Witley

Local examples of the use of the New Red Sandstone

The Mercian Mudstone is not visible as such, however its comparatively soft nature has lead to the cutting of the relatively deep and/or wide channels associated with the local brooks.

The bedrock has an impact on the surface soils. Freely draining slightly acid loamy soils are associated with the areas of New Red Sandstone. These soils tend to be of naturally low fertility, but with the input of fertilizers and irrigation can be very productive. They are easily worked and in Little Witley in particular are often used to grow horticultural crops.

Slightly acid loamy and clayey soils with impeded drainage and slowly permeable seasonally wet slightly acid but base-rich loamy and clayey soils are associated with the Mercian Mudstones in the two parishes. These soils have a naturally moderate to high fertility and are used to grow arable and grass crops; however their drainage characteristics can severely limit cultivation or their ability to carry livestock during the wet winter months.

In some places in the Holt there are, or were before quarrying, extensive areas of superficial deposits. These are fluvial (river based) deposits of Pleistocene age that form part of the Severn Valley Formation. The deposits actually take their name from the parish, being referred to as the Holt Heath Member (formerly known as the Third River Terrace). The basal deposits have a temperate fossil fauna believed to date from the Ipswichian interglacial, however most of the Holt Heath Member consists of outwash from an Irish Sea ice sheet which entered the Severn basin during the the Last Glacial Maximum or Late Devensian galication, some time after 20,000 years ago.

The Irish Sea Glacier at the time of its maximum extent

As with soils derived from the New Road Sandstone, soils associated with the fuvial deposits tend to be freely draining slightly acid and loamy, with naturally low fertility. Again they are often used to grow horticultural crops but can require considerable inputs of fertilizer and irrigation.