Hog Highland, Ipswich

40

RED CRAG DEER FROM TRIMLEY AND FELIXSTOWE

These specimens are of great importance in showing this genus of Cromer Forest Bed giant deer was living in East Anglia about half a million years earlier than has generally been supposed.

T h e y are also important in indicating, from their State of mineralisation, that the animals were living at the time of the deposition of the Crag beds, and are not derived as are the great majority of so-called Crag mammalian remains which were fossil millions of years before the Crag Sea invaded the land.

HOG HIGHLAND

:

B y HAROLD E . P . SPENCER,

IPSWICH F.G.S.

DĂźring the past year excavations have been carried out on the riverside face of Hog Highland, a spur of high ground which diverts the River Orwell from an easterly to a southerly course, for the purpose of obtaining Alling for the construction of the new Cliff Quay extension by the Ipswich Dock Commission. T h e work has resulted in the deepest section of a temporary character made in Suffolk other than in pits or quarries. T h e vertical height exposed is about seventy feet, of which the greater part consists of Eocene deposits.

At the top of the hill the plateau consists of Glacial gravel which, from the adjoining section made at the rear of the new Power Station, has been channelled and another gravel of a Cannon Shot type laid down. In this area the plateau graVels sometimes contain small erratic patches of Chalky Boulder Clay and there are limited areas of solifluction at the hillbrow. It is considered the gravel dips southward to a little above the Spring tide mark below the cliff at the northern end of Piper's Vale. T h e site is now obscured by the ash disposal area of the Power Station.

Unfossiliferous Red Crag Sand is next in the section, below which the Crag Basement Bed is of unusual character, consisting mainly of boulders of London Clay with a small admixture of sand and phosphatic nodules. T h e deposit contains very little flint and very few fossils of any kind. In the hill section behind the Power Station the base of the Crag is lower and its basement bed richer in " Coprolites" and fossils, such as much rolled London Clay Crustacea. At the north end of Piper's Vale the Red Crag extends down to the mean tide level where it is subjected to tidal erosion.

HOG HIGHLAND,

IPSWICH

41

T h e London Clay is thin in the Highland section and, except for a scattering of septaria, un-noteworthy.

It is usual to find at the base of the London Clay a thin bed of pebbles generally regarded as the local equivalent of the Oldhaven or Blackheath Beds which may occasionally yield a few teeth of sharks. In this section there is a considerable thickness of very dark laminated sand containing scattered pebbles, and in the lower part there are patches of rotted shells which, unfortunately, are much too fragile to collect. A few sharks' teeth of the same types as those found in the Oldhaven Pebble Bed have been secured. When dry the sand is grey ; the dark colour in the section is due to its being saturated with water. (At Bobbitshole a similar dark deposit was observed on a hill slope above the lake deposits in which no fossils other than lignite were seen.

Here the underlying Reading Clay was crushed by ice pressure and fĂźll of slickensides, while the upper beds, Oldhaven and London Clay, were tilted away from the Valley centre. While Professor Boswell was non-committal in his reference to these deposits in the Ipswich area*, there can be little doubt these sands truly represent the Oldhaven Bed in Suffolk and that the deposit was formerly much more extensive, the existing remnants being all that survived erosion before the deposition of the London Clay.) Where this Oldhaven sand rests on the Reading Bed below there are finger-sized holes bored into the clay, presumably by mollusca the shells of which have decomposed, filled with the darker upper deposit.

T h e lower part of the hill section consists mainly of Reading Sand with rafts of tough plastic mottled clay the base of which was not exposed. A boring was attempted to determine the thickness of the sand but this had to be abandoned at about five feet owing to the quantity of underground water, although the site was well above water level. While the sand of this deposit as a whole is relatively fine and compact with masses of incompletely Consolidated sandstone, below the general level of Cliff Quay, in the boring the sand became increasingly coarse and angular, a feature not previously observed in the district.

At the Power Station site where the foundations are all in red and greenish mottled clay the top of the Reading Beds is some twenty feet lower, sand being noted only once below the clay in a small hole. A noteworthy feature occurred along a trench running east to w e s t ; all the red mottlings to a depth of about thirty inches were drawn out into vertical lines, which, near the surface, bent over in an easterly direction. T h e upper part of this deposit was levelled by scraper or bulldozer working north and south. Where the upper part of the coloured clay had been acted on by the weather it had become an ochreous yellow, a feature also observed * 1927 Boswell, P. G . H .

T h e Geology of Ipswich (Mem. Geol. Survey).

42

HOG HIGHLAND,

IPSWICH

on the opposite side of the estuary in a trench near the L.N.E.Rly. Halifax Box (where much of the Reading Clay contained abundant and large nodules of " race ").

At no time has the Thanet Bed been exposed in any of the excavations for the construction work for the several stages of building ClifF Quay, but the Bull Head Bed was formerly exposed on the foreshore between tide marks before the quay was made.

Thanet Sands of a bright green colour were exposed during the building of the British Petroleum Company's Tank Farm about one quarter of a mile to the north. It has also been dredged from about twenty-five feet in the river bed a few miles downstream.

Recent dredging alongside the ClifF Quay extension has, for the most part, been in the chalk. Above the chalk is a rubble consisting of sand, clay and chalk with angular flints, with occasionally flints worked by Pre-historic man, one having been collected while the dredger was working.

This deposit very closely resembles the more chalky portions of the Upper Boulder Clay, (deposited during the last but one Glaciation) and sometimes contains above eighty per Cent of chalk. It is evidently from this rubble that the large boulders of Sarsen were brought up during the work which in places prevented the steel piles from being driven to their pre-determined depth. Between this Stratum and the mud and ooze there is a peaty deposit the upper part being interlaminated with sand. One of the dredger crew recovered a femur of the extinct giant ox Bos primigenius from this level which is presumably of post Glacial age.

COLLECTING IN SUFFOLK, JULY, 1956 For the third year in succession I have visited Suffolk towards the end of July. In 1956 I motored direct to Southwold on July 23rd where I joined Mr. E. J. Hare. Conditions were very promising with a warm south-west wind and a dark sky. As in the previous year, we decided to try the marshes near Walberswick which we reached by 9.30 p.m., and set up our mercury-vapour light. Insects soon started Coming freely. One of the first to arrive was a female of the Oak Eggar (Lasiocampa quercus Linn.), while a little later an even larger female of the Läppet (Gastropacha quercifolia Linn.). We were kept busy up tili 12.30 a.m., with a steady stream of visitors comprising up to 43 species of the macrolepidoptera. Of these among the marsh-loving insects noted were the Striped Wainscot (Leucania pudorina Schiff.), the Shore