Broom Hill Gravel

THE BROOM HILL GRAVEL, .

CREETING ST. MARY u r 0 T " Ü 1 W e r e v i s i t e d by Society on July 18th, 1953, when the Excursion Leader explained that in his opmion, the gravel was deposited later than the Chalky' Kimmendgic BoulderClay, named by Mr. D. F. W. B a d e n T W d l the Lowestoft Boulder Clay," and that it might be outwash gravel from the ice sheet which deposited that particular boulder clay laidl down by the melt water as the ice retreated. As the Upper Chalky Boulder Clay, the " Gipping Boulder C l a y ' of Baden-Powell, rests on this well-bedded gravel the eravel must necessarily be of intermediate age. One of the commonlst erratic (ice transported) rocks found in the gravel is BasaTt w S superficially resembles the " Toadstone'' of Derbyshire the presence of this rock suggests its use as a zone fossil ' Among the pits in the Lowestoft district visited during the progress of the Pit Survey, one at Oulton, Taylor's Grave! Pit was found to be excavated in a similar well-stratified gravel containing basalt erratics of the type found at Creetingg In this Pit however, the gravel rests on the Lowestoft Boulder Clay which in this area lies on the Corton Sand. Hitherto no boulder clay of this type had been observed at Creeting g interesting feature in Taylor's Pit is a large boulder of chalk twelve feet across which may be seen in the south side Th s boulder appears to be part of a mass of boulder clay which has

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A subsequent Visit to the Creeting Quarries resulted in the discovery of a limited patch of Lowestoft Boulder Clav in a small extension at the southern end of the large quarry This particular clay has every indication of having been exposed to weathenng influences and is undoubtedly a small remabder of a much greater mass which has been reduced by erosion and entirely removed over most of the Creeting district Lane Pit, Woodbridge, there is a similar gravel mL wh ch the basalt erratics are fewer, but like the Creeting deposit it .s capped with the Gipping Boulder Clay. In thii quarry the excavation has not yet been carried below the eravel so it has not been possible to ascertain what may be underneath. m S nlTr t a v i n g m U c h m a t e r i a l d e r i v e d from the Red Crag which forms the bed rock of the district. Derived W ^ T D ,8 n M ° C C U r i n S r a v c l s w e «t of the Ipswich Woodbridge Road, except possibly at Darmsden where it has in all probability come from the Red Crag outlier at Battisford

194

THE BROOM HILL GRAVEL

It is now apparent that Winkworth's Pit, situated between Rushmere and Woodbridge Roads and now filled in, and the derelict pit on the right of Playford Road, Rushmere, both belong to the Creeting gravel. In the latter the pale-coloured sand was formerly exposed under the gravel below the g^neral floor of the pit. Unfortunately no erratics were collected from these pits while they were being worked.

The establishment of the relationship of the Creeting gravel to the boulder clays, which are now proved to have been laid down by separate ice sheets, a fact which has hitherto been disputed, also proves the current bedded pale-coloured sand on which it rests to belong to the Corton Beds ; at least there can be no reasonable doubt that the sand occupies the same position in the geological sequence. It only remains for marine mollusca, similar to the scanty fossil shells which have occasionally been found in the Corton Sand, to be discovered for the removal of the last possible doubt; actually a few shells were discovered some years ago in a sand pit at Stowmarket but this was not learned until after the pit was disused.

The deep trenches excavated for sewers on the new Chantry Estate at Ipswich cut into a thick deposit of pale-coloured sand but in this area there are complications arising out of the presence of decalcified Crag sand. In the Valley Farm Pit, Sproughton, a considerable thickness of pale sand passes down into typical shelly Red Crag. The bedding merges definitely from the uncoloured unfossiliferous sand into normal crag. At rare intervals very delicate internal casts of univalves, such as turritella, have been exposed by wind erosion showing the pale sand must once have contained fossil shells.

A small excavation was made in the floor of the Creeting pit in order to discover what might be under the Corton Sand. The deposit rests on chalk from which the sand is separated by about twenty inches of stony material resembling the basement bed of the Red Crag which it may well be, since there is undoubted crag at Battisford at about the same level.

H.

E. P.

SPENCER.

THE NEW TELEPHONE EXCHANGE, IPSWICH Map reference 158448 ONE of the all-too-rare opportunities to learn something of geology within the boundaries of Ipswich has been afforded by a large excavation for the basement and foundations of the new telephone exchange building near Barrack Corner.