# Midland Naturalist/Volume 01/Some New Features in the Geology of East Nottingham

Some New Features in the Geology of East Nottingham.
By J. SHIPMAN, Esq.
Any one who has seen the Government Geological Survey map of the Nottingham district (71 N.E.) will hardly fail to have noticed two white lines stretching across the north-east of Nottingham. Those white lines mark the course, or what the Government surveyors believed to be the course, of two important faults, or dislocations of the rocks. The white line nearest to Nottingham takes a straight course from Colwick Wood, in the south, to Patchitt's Park, in the north. The other white line describes a parabolic curve, starting from the top of Sneinton Dale, sweeping round by the Hunger Hills and disappearing about midway between Carrington and Sherwood. To the geologist faults are peculiarly interesting, and they sometimes account for a good deal of what is observed in the physical features of a district. They are the unwritten records of the motion, at some remote period in the past, of those natural agencies which we know are ever at work somewhere at great depths, producing oscillations of level in the earth's surface, But, apart from whatever may be the origin of faults, there are some physical features connected with the curved white line which, to say the least, have always been perplexing to those who have cared to pay much attention to local geology. There has hitherto been an air of mystery about it, and nobody was ever able to meet with if at any part of its course. Even Professor Hull speaks disappointedly, in his work on the "Triassic Rocks of the Midlands," at not being able to find the fault just where it was marked to cross Woodborough Road at the end of Red Lane. This fault has hitherto been an object of interest chiefly because if was abnormal for a fault receding at both ends from the fault forming the opposite side of the trough, to help to produce a downthrow of the rocks lying between. It will readily be understand, therefore, why the course this fault really took should be an object of solicitude for years to local geologists. Indeed, I very well remember learning some of my earliest lessons in field geology while trying to trace it; and it was while engaged in the same work in the early part of this year, on account of the unusual facilities afforded by excavations all ever that part of Nottingham, that I discovered such serious discrepancies in the Geological Survey's mapping as induced me to resurvey the north-east part of what formed the old borough—that is, the area lying between Mansfield Road, Great Alfred Street, and Coppice New Road, and the result is the map which I now bring before you. In compiling this map, I have necessarily had to fall back, to some extent, on my recollection of what was the geological character of some parts now built upon, and I have found these observations, begun in 1868, very useful in elucidating what would otherwise have been almost beyond reach. The task was far from being an easy one, however pleasant field geology may be. Even where the character of the strata was exposed by sections I found the Keuper, which forms the lower pert of the area, extremely difficult to deal with, both in the tracing of faults and in determining the boundary line between the Upper and Lower Keuper. Many spots, too—geologically hallowed ground, ground unusually prolific in interesting points—had to be ​visited again and again in order to obtain satisfactory results, chiefly owing to the uncertainty of building operations being begun. Then there was no map published that was on a scale large enough to admit of detailed observation s, so I enlarged one to a scale of one inch to 200 feet, which, divided into small handy sections for field use, I found to answer very well. For the levels, without which it would have been impossible for me to have constructed the horizontal sections to illustrate the character of the rocks below the surface, I am indebted to the kindness of Mr. Tarbottom, the borough engineer. No. 1 Section extends from the top of Dame Agues Street to a point on Blue Bell Hill, north-west to south-cast; No. 2, from Hawkridge Street, along Blue Bell Hill, to a point a few yards beyond Belle Vue House: and No. 3, from Great Alfred Street South, along the slope of Blue Bell Hill, to Bombay Street; each to a scale of 50 feet to an inch, and a maximum depth of 220 feet.
Turning now to the new map, perhaps the most striking feature is a broad, ribbon-like band of Keuper marl, shut in on each side by two parallel white lines, stretching across the map from the south-east to north-west. Those white lines are the equivalents of the straight and the curved faults respectively of the Government map, The fault nearest to Nottingham I have, for convenience, called No. 1 fault; the equivalent to the curved fault is No. 2. No. 1 fault, you will observe, has the effect of bringing down the Lower Keuper marl (f5) alongside the Bunter sandstone (f2) all along its course after leaving Blue Bell Hill, where the outcrop of the Keuper is on the south-west side of the fault. This fault strikes N.W., but before reaching Mapperley Read it seems to became deflected, bearing N.N.W., through Patchitt's Park, and joining No. 2 fault somewhere near the bottom of Red Lane, while only a minor dislocation is found taking the north-westerly course. Both faults throw down the Lower Keuper marl, the N.N.W. fault being well seen breaking through the east end of the sandstone cliff and bringing down the Lower Keuper twenty or thirty feet. Beyond No. 2 fault, that is on its north-east side, instead of the three-cornered inlier of Bunter (f2) which appears on the Government map, we have a double tongue of Bunter stretching up towards the Westminster Abbey, (as on the Government map,} on the one hand, and forming the valley at the foot of the Hunger Hills on the other—evidently the extremity of a broad offshoot up the St. Ann's Valley from the main area of Bunter to the south-west. We thus find that what the Geological Surveyors supposed to be a curved fault turns out to be a parallel fault to the straight one, striking about 55° west of north. This fault was exposed during the excavations for lowering Mapperley Road, near the reservoir, some years ago, then at the top of Dame Agnes Street, again half-way down that street, where it crosses obliquely, and may be traced passing down Martin Street and through the field where the St. Ann’s Flower Show is held, across the hills to Carlton Road, where it is again seen at the elbow turn, and also in a section off Crown Street, opposite. It appears to have a throw of about 95ft. in Dame Agnes Street, increasing slightly further south, throwing down the Upper Keuper alongside the Lower, and the latter level with the Bunter. When cut through in Dame Agnes Street this fault was found to hade to the south-east, just as we should expect, considering that it unites with No. 1 fault, which hades in the opposite direction, to let in a sort of broad wedge of clay rocks belonging to a higher level; and the space between the walls of the fault was filled with pebbles embedded in a crystalline calcareous red sandy matrix, associated with red marl and "skerry." Acting as a sort of connecting link between the two main faults, and shifting the boundary line of the Upper Keuper about four hundred feet, is a fault familiar enough to most of us on account of its being long exposed in the section of marl opposite ​Cranmer Quadrant, where it is seen bringing down the lower beds of the Upper Keuper alongside the markstones of the Lower Keuper. This fault strikes north 40° west, with a throw of apparently about 15ft; it is not again seen. It so mush resembles. No. 1 fault, as seen on Blue Bell Hill, that one can scarcely wonder that, in the absence of more complete data, the Survey should have regarded it as a continuation of the same fault. Reverting to No. 1 fault, it evidently forms quite a focus of small dislocations on Blue Bell Hill, varying in direction between west and north. One of these, bearing 10° north of west, and throwing down the Lower Keuper against Bunter about 10ft., produces the triangular patch of Bunter, just at the apex of which were a few feet of Lower Keuper capping the Bunter. When these beds were cut through during the formation of Turner Street, a remarkably interesting section of the conglomerate at the base oi the Lower Keuper was exposed. Unfortunately, however, it has since been removed for building purposes. Another fault, having a down throw of 6ft. 3in. on the east side, is traceable crossing Blue Bell Hill Road 12° west of north, and coming out in the cliff in Lower Bencon Street. The other minor dislocations marked on the new map, mostly parallel with this, all have a downthrow to the east, but they are of no further importance than to serve to show the general tendency of the down-throw of the faults on Blue Bell Hill, east of No. 1 fault. In fact I met with mere dislocations radiating from No. 1 fault than in any other part. I ought not to omit to mention that No. 1 fault is finely exposed in the section opposite the saw mills on the Blue Bell Hill Road. The Lower Keuper between Pease Hill Road and the Robin Hood's Chase is also much disturbed by faults. Two or three may be seen in the brick yard there, but others, having a downthrow to the north-east, probably exist; for, on the down-throw side of No. 1 fault at the junction of Cooper Street and Pease Hill Road, the Bunter was met with at a depth of 16 feet, while near the Chase, with a rise of ground of about (illegible text) feet, the Bunter was not reached till a depth of 54 feet of Lower Keuper had been passed through, and then only on the upthrow side of a fault which was found to cut through the well. Again, just where we might expect to find the lowest beds of the Keuper, namely, at the bottom of Dame Agnes Street, over 40 feet of water-stones have been pierced without reaching the Bunter. This, coupled with the fact that brickyards existed years age along the bottom of Blue Bell Hill on St. Ann's Road, leads me to infer the existence of a series of transverse faults running nearly parallel with that road, and letting in the higher beds of the Keuper.
While tracing the fault I have mentioned in the Beacon Street Cliff, I came across some very interesting geodes in the Lower Keuper sandstone beds. The geodes ramified in the thick beds of sandstone without any regard to the lamination; were lined with rhombohedral crystals of calcite, occasionally tinged with copper and a black mineral—probably manganese: and appeared to have been formed long after deposition and consolidation of the rock. The crystals were all rhombohedrons, except where the copper or the black substance was present, when they became double six-sided pyramids. These are the first crystals of calcite, as far as I know, that have been found in the Keuper—at least in this district. The geodes extended through about three feet of the marlstone, and were confined literally to the space of a few square yards. The calcareous matter appeared to have come from above, a thin lenticular band of it, about three feet long, being met with about five feet above where the geodes were found.
To be continued.
* ↑ Read before the Nottingham Naturalists' Society, Nov. 28th, 1877. The paper was illustrated with a geological map, sections, photographed sketches of the main faults, the site of the geodes, and of the conglomerate.
* ↑ This conglomerate is described at a later stage.
This work was published before January 1, 1930, and is in the public domain worldwide because the author died at least 100 years ago.
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