23. on the ASHPRINOTON VOLCANIC S~Rn~S of SOUTH DEVON

Home , Ashprington, Dartington, Stoke Gabriel

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ON THE 2kSHPRINGTON VOLCANIC SERIES OF SOUTH DEVON. 369

23. On the ASHPRINOTON VOLCANIC S~Rn~S of SOUTH DEVON. By the late ARTHUR Crrx~te~a~OW~E, Esq., M.A., F.G.S.* (Read May 8, 1889.) (Communicated by Prof. k. GEIKIE, LL.D., F.R.S., F.G.S.)

INTRODUCTIOn'. TaERE exists in South Devon an extensive series of igneous and quasi-igneous rocks occupying a considerable area, mainly east of the River Avon, which have as yet received scarcely more than passing notice, and the study of which is attended with much perplexity Sir Henry De la Bechet noticed the u trappean rocks south-west of Paignton, which are included in our subject, and spoke of them as interposed between the Yalberton limestone and that of Watton, which forms the western termination of the Berry Head mass. The relations of the igneous rocks to the Devonian limestones will be considered de hove as we proceed. Dr. Hell + mentions the rocks of this series in the neighbourhood of Totnes, Ashprington, &c., as "thick slates, in which much vo!- canic matter is disseminated." He observes that "volcanic rocks are frequent," and that " beds which are light-coloured often yield a red soil." This was written with reference to rocks which occupy the ground between Harberton and the Dart. Though we might reasonably take exception to the term " slates " as not strictly ap- plicable to any portion of these rocks with which we are acquainted, yet as it is quite certain that Dr. Hell well appreciated the im- portance of the group, and as no spot could be pointed out where they attain a greater development than [at] Ashprington and its neighbourhood, the provisional term " Ashprington volcanic series" has been here retained. Many patches and lines of " greenstone" were laid down by De la Beche within the tract of country to be described; but these represent only a very small fraction of the actual spread of the rocks, which occupy on the east of the Avon a large part of Dipt- tbrd, Harberton, Totnes, Ashprington, Cornworthy, and Dittisham parishes, and on the east of the Dart, Berry Pomeroy, Stoke Gabriel, and Churston Ferrers. On the west of the Avon they range through North Hewish and Ugborough towards the Yealmpton and Plymouth district, but are * [The MS. of this paper was found by Mrs. Champernowne among her husband's papers after his death, and was handed over to me. I believe it to have been intended as an instalment of a general description of the Devonian rocks of the Totnes district, which, at my request, he had agreed to prepare. Though incomplete and evidently the first rough draft, it possesses much interest as an expression of some of the latest views of one of tbe most careful geologists who ever studied the rocks of Devonshire. The map to which reference is made is the 1-inch Ordnance Survey Sheet, no. 22, which was coloured after an original geological survey by the author. This work was presented by him to the Geological Survey, and it will be embodied in the new edition of the Survey Map (no. 22) now in preparation.--A. GEIKZ~.] 72. r Rep. Geol. CornwaU, Devon, and West Somerset, 1839, p. Quart. Journ. Geol. See. 1868, voh xxiv. p. 434. Q.J.G.S. No. 179, 2E Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

370 THE LATE MR. A. CHAMPERNOWNE ON THE

less expanded than on the east of that river, partaking of the narrow folds into which the country is thrown immediately south of the granite. To the north of the parallel of Paignton and Brent they nowhere occupy a large continuous area ; nevertheless various tufts seen in the Dartington, Kingskerswell, and Ogwell districts ought probably to be placed in the same category from their relations to Devonian limestones, although not attaining the development that the series exhibits on the banks of the Dart. Lavas, frequently amygdaloidal and vesicular, or even scoriaceous, but at other times very compact or aphanitic, constitute a great part of this series. They are either altered porphyrites, or basalts, or both. Tuff-beds are largely intermingled with them, all these rocks being highly basic in character. It is possible that some beds of purely detrital origin may be here and there interbedded (if not doubled in), but, so long as we have only the imperfect one-inch maps, they are too insignificant to be shown on paper. Some reddish schists, for ex- ample, are met with in a road descending from Weston within a mile east of Totnes to the head of the valley leading down to Fleet Mill. The lavas, where freshest, are usually of a blackish-green colour, often porphyritic in structure, from the presence of crystals of felspar, which sometimes in hand specimens appear as dark as the ground- mass. These harder rocks appear to run in lines, and have even been represented as dykes on the map, as, for instance, at Sharpham on the Dart, but they dip with the rocks among which they occur, and even pass into them. It is true they form projecting bosses by the river-bank, but it would be impossible to trace them away from the foreshore. I believe they are not dykes, but are simply intercalated, and I know of no single instance of a line of hard rock cutting across the strike. Sometimes the lavas become flaggy, breaking into irregular, long, wedge-like flags, weathering brown or purplish near the surface, and even splitting up into a shaly substance, from which, nevertheless, a perfect passage can be traced into the compact, dark rock used for road-metal; and these facts can be observed in one and the same quarry, as, for instance, in a quarry by the roadside on Totnes Down Hill. A mass of this rock at " Red Hill" or Pheasant's I-Jill quarry, Totnes, where it rests on limestone, as further to be described, is weathered brown on one side, but abruptly changes its colour to a deep red on the other, where I noticed a knob of limestone, immediately under the "trap," coated with a thin film of hmmatite. In a plantation above Sharpham Lodge, near Totnes, the rock is amygdaloidal, as often happens, the cavities being filled with a yellow powder, which appears to be pure limonite, and is doubtless a product of decomposition. At Broomborough quarry, also near Totnes, there occurs a singular rock, evidently included in this series, of a dull purplish and brownish colour, in which patches and strings of a greenish, felstone- like substance resembling porcellanite are included, with amygda- Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

ASHPRINGTON VOLCANIC SERIES OF SOUTH DEVON. 371 loidal kernels interspersed. At a small quarry above Allabeer on the right bank of the Dart and elsewhere some purplish and yellowish flecked shales are seen, the paler patches having a steatitic aspect. Again, the lavas are often highly calcareous, probably from sub- sequent infiltration, and as they are both aphanitic and sometimes flaggy, as above mentioned, they appear (without always assigning definite names, such as " porphyrite " or " basalt," to rocks which are so highly altered) to correspond to descriptions of "slaty calc- aphanites," even leading towards "' schalsteins." Of the fact of such alteration, the microscope leaves no room for doubt. The felspars are blurred, as if changing to saussurite, like the felspars in the Lizard gabbros ; or they exhibit a veined appearance. Some unaltered augite is usually present, as also a plentiful sprinkhng of magnetite or ilmenite ; but owing to the extent of alteration the thinnest sections let very little light pass. Nowhere do true grits appear to form any part of this series ; it is somewhat perplexing that the purple grits of Cockington, Beacon Hill, and Windmill Hill, which support the Triassic rocks of Paignton, do not apparently extend across the Dart between Totnes and Sharpham, as the same beds do south of Greenway and Ditti- sham. However, with the exception of a narrow strip which appears to be thrown down by a fault, and some beds at Langcombe Farm, they certainly form no feature south-west of a line extendi~g from Langcombe Cross to Stoke Gabriel. There are some signs of a N.W. and S.E. fracture bearing south-easterly for many miles, and its existence between the south-west of Ash and Stoke Gabriel was mentioned by Dr. Hell. If these strips really belong to the slaty beds at the base of the Cockington grits, then they overlie the volcanic series, and are thrown down by faults sensibly at right angles to the one just named, but they disappear before reaching the Dart. Were it not that the greenish aphanitic rocks can be actually observed passing to a deep red, the outlines of the felspars being still traceable, one might be inclined to regard all the soft, raddled, earthy-looking rocks as tufts; but for the reason just stated we could not safely do so. The quantity of magnetite or ilmenite which appears in every section I have had cut would furnish a ready source for any degree of peroxidation ; some sections, when seen by refiected light, show these specks turned brown, and when this destructive process is carried far enough, all distinctive cha- racters of the rock are lost. These decomposed rocks generally yield freely to the knife, differing in this respect altogether from grits of Devonian age. Iron-ores, both h~ematite and limonite, are occasionally found among the red rocks, as we might naturall}" expect, but their mode of occurrence is apparently so capricious that they have never been profitably worked ibr any length of time. I am indebted to ])r. Pridham for information on this point. In Cornworthy parish, on each side of the lane leading north-east from the village to Tuekenhay 2E2 Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

372 THE LATE ~R. A. CHAMPERNOWNE ON THE

Creek, there are some very old excavations which I have noticed myself, but could not then understand them. They were doubtless worked for iron long before the memory of man. "The tradition of the inhabitants carries them back to Roman times. In one of these Dr. Pridham discovered a specimen of Orthoceras, or perhaps Acti- noceras, with the siphuncle inflated between the septa and striated internally, a Cardi~tm-like bivalve, and a small specimen of Stro- matopora, all converted into h~ematite, besides some fibrous specimens of the same. On Mr. Studdy's land (Waddeton Court*) on the other side of the Dart, and also near Stoke Gabriel, limonite has been found.

]{ELATIONS WlTII D~-0NIAN LI~tESTOSES AND SLAT]~S. The Northern Limits. :Respecting the age of the rocks, of which so very inadequate a sketch has just been given, we find much that is suggestive and much that is very perplexing, even after their outlines have been laid down on the map, on account of their irregular mode of occurrence. In examining the principal sections in some detail, we will begin with the east bank of the Dart at Totnes. The " Red Hill" quarry has been already mentioned : Mr. Godwin-Austen noticed this quarry as showing trap resting on faulted Devonian limestone and slatet ; whatever appearance the quarry may have presented when he ex- amined it, it is now perfectly clear that the step-like surface of the limestone is not due to step faults, but that it has been eroded into small crags of the height of * * * to * * * feet on the outcrop side, the intervening hollows having been filled in by the " trap," which forms all the upper part of the quarry. The limestone beds below dip E.-S. at * * * Interesting as this section is, we must not too readily assume that, because of the disturbance and erosion of the limestone, a geo- logically vast space of time necessarily separates the two rocks, as that must depend upon what can be learned respecting the upper surfaces of the overlying mass, whether, in fact, we can find them dipping beneath higher members of the Devonian series. Tracing the line between the limestone and superincumbent rocks, we find it extending nearly to Truestreet, where it is shifted further to the south-east by a N.W.-S.E. fault passing Weston with upcast on the east. For the details of this broken bit of ground I must refer to the map. Thence the upper rocks continue to Langcombe Cross. The great N.W.-S.E. fault from Gatcombe to Stoke Gabriel here cuts them off; they cannot be traced further to the north-east in their line of strike. So far there have been signs of discordant relations, but perhaps not greater than we might expect to find in a reef district, supposing it to have been also the arena of contemporaneous volcanic outbursts. 9Watton Court on the Ordnance Map. t Trans. Geol. Soc. 2ud series, vol. vi. pl. xlii. fig. 4. Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

ASHPRINGTON VOLCANIC SERIES 0F SOUTH DEVON. 373

Beyond the great fault a coarse tuff is found at Ash, thrown on the east against some beds of coarse dolomite, which contain clear quartz and lie nearly horizontally. This tuff consists chiefly of red slaty- looking patches, decomposed felspar crystals, and grains of quartz. A precisely similar rock resting on limestone occurs near Watton ~Waddeton~ village, and beds of like constitution, but not red, are interstratified with bluish slaty shales over the Dartington limestone, being well exposed in the Ashburton railway-cutting, also overlying the limestone of Bulley Barton, and south of the limestone of Clennon ]_-Iill near Goodrington, where it would appear that they rest on an uneven surface. These belong to a characteristic type not specially mentioned in the first part; they are never amygdaloidal, and cannot have flowed, but seem to correspond to the :Nassau "porphyritic schalstein " so-called. The next exposure east of Ash occurs in the lane leading from Higher Yalberton to Windmill Hill, but it throws no clear light on the relations. Fine-grained flaky tufts forming the floor of the lane appear to dip east, and just before reaching the purple grits of the high ground some hard aphanite protrudes. No junctions are risible here. On the east of Higher Yalberton the limestone forms a narrow crest broken by two faults, but otherwise continuous with that of Clennon Hill over Goodrington Marshes, where it abruptly ceases on its strike, but can be followed across the narrow gorge on the south as far as the Brixham highroad near Crabb's Park. Here for a few chains it is in contact with the mass e• towards Watton village, which has the volcanic rocks dipping against it on the west. Clennon :gill is bounded on the east by a fault bearing N.N.E. through Paignton, which is very conspicuous from its shift- ing the Triassic boundary nearly half a mile to the south from the east end of Primley Hill. It passes just east of Crabb's Park, throwing down slaty shales and grits, and after bringing limestone against limestone, as mentioned (a point of minimum " throw "), sets on again with an opposite throw ibllowing the line of the Watton road, and comes out on the bank of the Dart, a short distance west of the Watton boat-house, bringing down the raddled volcanic rocks on the west against grey and purplish slates that dip under the Watton limestone, the dips at the junction being widely divergent. To complete this bit of ground, we recross north-west from the Watton and Paignton road to Higher Yalberton, and find all the intervening ground to consist of the trappean rocks, the narrow crest of limestone east of that place clearly dipping south under it. The north side of this crest is much more obscure in its relations than the south, and the same remark applies to that of Clennon Hill. Dr. l-loll considered it to be "doubled under " higher rocks "with inverted dip "% I do not feel satisfied on this point. A patch of limestone shown on the old map south of Goodring4on marshes must be expunged, as the ground consists of slates and grits. There are other faults shown on the map, but not described. OT. cit. p. 431. Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

374 THE LATE MR. A. CHAMPER!ffOWNE ON THE

The next patch of volcanic rocks brings us to the coast of Torbay. It lies east of Goodrington, forming the " Sugar-loaf" hill, of less elevation than the limesWne plateau to the south. A hard aphanitie rock protrudes for a short distance along the top, but does not reach the railway-cutting close to the cliff, where it is flanked by tufts. This patch throws off some beds of iron-shot limestone to the north, dipping north and exposed in the cutting. The face of Saltern Cove is a N. and S. line of fault, which has shifted the iron-shot limestone on the foreshore south of its exposure in the railway- cutting, and the Triassic outlier of the North Cove at Saltern, south of that at ]~Iilepost, 223. The fault continues to the south at Broad- sands, throwing down a strip of Triassic sand-rock that dips east, and again forming the face of the cliff. The above-named limestone is undoubtedly on a higher horizon than the great mass of Goodrington :Hill, Brixham, and Berry :Head. It abounds in corals--Farosites cervicornis, Edw. & H., Alveol~'tes, sp., Cyatl~ophylh~m cvespitos~rn, Goldf., and simple tbrms, Stromatopora, Crinoids, and more rarely Acevvularia (sp.). The layers are parted by a red clay. At the foot of the cliff in the main cove the tuff exposed is identical with a piece of Schalstein from Weilburg, h~assau, in my collection. The beds succeeding the iron-shot limestone consist of purple marly shale, and include the interesting fauna identical with tha~ of Budesheim worked out l~y Mr. Lee *. :Higher still, immediately under the Trias, they are more slaty and are interstratified with purple grits. Therefore eliminating the faults and disturbances, [owing to] which cause the beds [are much contorted, so that they] hang nearly vertically towards the north-west, bhe relations are as follows$ :--

Section nea~" Goo~b'i~gtcn. 6. Triassic conglomerate. 5. Hard red grits and slates. 4. Purple and blotched marly shales (Go~i(ttiles, Ilactrites, Cardiola retro- striata, &c.). 3. Iron-shot limestone bands (very fossiliferous). 2. Sehalstein : and aphanite nucleus ? not reaching the cutting. 1. Chief Devonian limestone. Following the Belgian and German classification, 3, 4, and 5 would certainly be considered Upper Devonian+~. Much of the red colour may be due to percolation through the Trias ; but, the beds may contain the sources of peroxidation in themselves, as has been proved in the case of the ]avas. In the railway- and road-cutting adjoining the Naval Hospitalw we have again the beds IN'o. 5 well exposed and dipping northerly, and, after an interval of level ground, Geol. Mag. 1877, p. 1U0. r [The drawing intended to accompany this deecription has not been found among Mr. Champernowne's papers.--A. G.] The tracing-out of calcareous horizons in South Devon, corresponding with 3, must remain for another communication. w ~Tow a private residence. Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

ASI~PRINGTON VOLCANIC SERIES OF SOUTH DEVON. 375 the Trias escarpment of Roundham Head follows. In fact wherever the base of the Paignton Trias is found, the under]ring rock is the same* (Cockington " old red"), only to the east of the Paignton •.:N.E. fault this forms low depressed ground, instead of' rising into bold features like Windmill Hill and Westerland Beacon. Thus, when once in INo. 5 we have reached a clear horizon, [the beds of] which throughout South Devon, including the Staddon Point and Pieklecombe grits in Plymouth Sound, are t~ee from igneous intercalations ; they are done with. Accordingly the chief problem consists ill satisfactorily piecing together the Berry-Park slat), shales, the igneous mass(~s, and the limestones No. 1. As to the first, which extend through Little ]:[empston into the Dartington trough, it is improbable that they are represented by 3, 4, or 5 (which, for practical purposes, may be considered one group). Apart from colours, they are utterly unlike them, and descending from Windmill ]:jill to the Yalberton limestones, not a vestige of the Berry-Park slates is to be seen, only the strip of tufts as described. This would appear to point to an unconfbrmity perhaps between 2 and 3, and it must be confessed that the appearances in the railway-cutting would favour this hypothesis. In the remaining part of this paper we shall hope to throw some light upon these relations. 77~e ,b'outhern Limits. These commence at Sharkham Point on the east, but the igneous series is not conspicuously developed until we pass the Torquay and Dartmouth road, when we find Brim ]:jill above Galmpton Mill and nearly the whole of Greenway Hill to consist of them; con- $inuing by Dittisham they extend to East Cornworthy, where the), are shifted to the north by a fault. From the bank of the Dart, near a barn marked on the map, a good boundary runs right along the village of Cornworthy, by Priory Gate, following the bottom of the Washburton valley to Middle Washburton, beyond which I have not yet satisfactorily followed itt. This last trace separates dark-coloured lavas on the north as exposed at many points in ground which is often deep red (due to causes already explained) from [the J bluish-grey slaty shales which overlie them on the south side. At the south end of Mudstone beach a very clear passage can be seen from the grey shales into lhe superincumbent limestone, and at Sharkham Point the limestone beds are vertical, and parallel with them is a sheet of compact greenstone, forming the point of the headland. I spoke of this as intrusive, but have since seen reason to doubt the correctness of this opinion. At a short distance west a steep

Dr. Hell, op. cgt. p. 434. t [On Mr. Champernowne's map the boundary is shown to be shifted about a quarter of a mile to ~r by fault at Middle ~Vashburton, and carried on for mile on south side of ttigher Washburton Houses.--A. G.] Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

376 THE LATE MR. A. CHAMPERNOWNE ON THE climb through the brushwood shows one a detached patch of limestone, which certainly appears to double back upon itself. It is possible that this may after all be only a lenticular patch, as it is difficult to get close to it. But be this as it may, a fuller know- ledge of the mapping proves me to have been in error in suggesting that the contorted grits of Southdown Cliff were older beds than the limestones, rolled up. We now take the principal points of interest from Sharkham Point (where we have a base) to the limestone, unseen in the Good- rington section. At Higher Brixham the outcrop of the limestone makes a marked feature at the back of the church, and at Upton lane, at the foot of the ascent, red grits at once come on, which must here rest directly on the limestone without even the igneous rocks between. With a quarry near Laywell House the Higher Brixham limestone terminates ; but as the beds dip north-east at low angles it is clear that it is not thinning out on its strike at this precise spot, but dips away from a fault, which throws down the country on the west, and surface-stones prove the ]avas to be represented near the foot of the hill at Churston Mill. If this termination is not a fault, there is no escape from the alternative that the red grits must cover up the continuation of this limestone by a great unconformity. I believe the fault to be the explanation. Beyond Lupton House the relations are most perplexing. There is no evidence of the presence of the igneous rocks along the Dartmouth road from the boundary of the Churston limestone, and instead of them we find grey slates extending for a mile and half, and the purple grits, which at Higher Brixham rest directly on limestone, are not en- countered until past Lupton Higher Lodge, near the track leading to Higher Lupton (in a field N.E.), a small quarry showing them dipping S.E. at ~ ~ ~ De la Beche's arrow-dip west(15~ ~) near Churston Station is correct. The grey slates for the first half-mile from the limestone boundary, although not immediately exposed, slope when seen towards the north with the fall of the ground ; but after the bearing of the road changes they appear to have arched over, as they dip steadily E. of S. in the direction of the road. This is near the third milestone from Dartmouth. The question arises on what horizon these slates are. It seems to be the general opinion that the soft grey slates on the south side of Galmpton Creek are the continuation of the Mudstone Slates; they are much like them, and, if so, they must be older than the bulk of the limestone, which dips towards them near the boundary, no junction being seen. Now, however, we have a dividing horizon south of Galmpton, inasmuch as the lavas begin to form a well- marked feature (a small patch occurring east of the railway extending to Greenway Ferry, Ewhile3 near the top of Greenway Hill, in a wooded escarpment, I collected a specimen identical with the :Nassau amygdaloidal schalstein). They overhe the grey slates at Galmpton Creek; they constitute Brim Hill, and dip S.E. 17 ~ at the mouth of the Greenway Tunnel. Continuing the section, we Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

ASHPRINGTON VOLCANIC SERIES OF SOUTH DEVON. 377 have bluish flaggy slates of the type of the Berry-Park slates over the lavas, &c., striking parallel with them in the lane leading to Greenway Farm. They continue beyond the farm to the wood, where the purple grits appear across the river, and strike down by the south side of Marlpool. Dr. Holl has continued the section from here to Kingswear, along the railway. Some grey slates with a few calcareous seams line the north side of this inlet, and rising from below them a great mass of lavas and tufts, with some very hard rock, forms the ledges, until we round Greenway Quay and reach their base. Along the bank from here to near Galmpton ]ilill some beds of dark limestone and buff-coloured shale extend. They are exceedingly rich in corals, the prominent forms being A~veo- lite,. (com+pressa?, Edw. & ]=[.), large specimens of Cyathophyll~+m dam~wniense, Phil., and others. Cystiphyllum vesiculosum, Goldf., also a specimen of Hallia occurred, Ethe latterJ with a quantity of Aulo- pora hanging about it. From the bend at the mill to the head of the creek the mudstone-like beds complete the tour of this ground. We may now review the facts that have been adduced, and try to get at their general meaning. In the first place, from what has been said, it will be seen that we regard the mass of these igneous rocks as truly intercalated in the Devonian deposits, and consequently that the facts observable at Redhill quarry and other spots near Totnes are only cases of contemporaneous disturbance and erosion of a quite subordinate character. 5Iore depends, however, upon how we understand the limits of the larger limestone masses. It must be admitted that the evidence on this subject is not so clear as one might wish. I quite agree with Dr. Holl, speaking of the Totnes district, that the limestones have, on the whole, been " dislocated from the slates, so that their boundaries are virtually lines of fault." The country, indeed, is shattered by faults. Although it is often difficult to distinguish the slates below the limestone from those above, yet with experience one can dctect a difference in the Berry- Park slates fi'om those which clearly dip under the Dartington, Berry-Pomeroy, &e. limestones*. But why should there not also be slates neither exactly above nor bclow the limestone, but re- placing it? so that De l+a Beche's words would also be true, viz., that " the geological continuation of certain limestone appears to consist of slate." DiscussioN. The P~ESlDE~'T said that the thanks of the Society were especially due to Dr. Geikie for having rescued this paper from oblivion. Dr. G~.I~IE, after alluding to the melancholy interest attaching to the paper, said that he had himself urged the Author to formulate his ideas upon the structure of the country. The present communication, however, was all that was found among his papers, in

* 2~OTE.--A specimen in my collection of Kramenzel-schiefer, from Adorf, Waldeck, strongly suggests comparison with the coarser beds of the Berry- ]?ark slates. Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

378 THE LATE 3t'R. A. CHAMPERNOWI~E ON THE

a condition for publication. :But it is imperfect, and no materials remained from which it could be completed ; still it was too valuable a piece of work to leave unpublished. There were two principal points in this last work of Mr. Cham- pernowne :--(1) the non-intrusive character of the beds in question ; (2) their geological horizon, regarding which, though, owing to the faulted nature of the country, it is rather obscure, 5ft. Champer- nowne's surmises may turn out to be correct. There was no allu- sion in the paper to the compression aud shearing the rocks had undergone, to which he (Dr. Geikie) attributed much of the schistose structure both of the sedimentary and igneous rocks of the region. The flaky beds of which the .(uthor speaks can be traced into the more massive rocks. The flattening-out of the amygdaloids was a striking proof of this mechanical deformation. Mr. RU~T.EY referred to the general soundness of Mr. Champer- nowne's conclusions; there were some interesting points in con- nexion with these lavas. He had himself noticed important differences in the volcanic beds on the east and those on the west side of Dartmoor respectively. On the east they were mostly porphyrites, on the west schistose lavas and basalts, the schistose beds being very characteristic of the Brent-Tor district, of which he considered the Saltash lavas were a continuation. No perfectly satisfactory. explanation of the causes of this schistose character had yet been given. He had not hitherto observed any mechanical deformation of the amygdaloids in the schistose lavas, such as those of Churl- hanger, and this, he thought, militated against the assumption that the schistose stz~cture was due to shearing. He referred to the boundary between the Carboniferous and Devonian as having been drawn along belts of igneous rock, which were, in point of fact, repetitions of the same bed. He referred to the new line of raihvay as likely to throw some light upon the district west of Dartmoor. Dr. HATC~ spoke of the rocks from Ashprington as tufts and diabases, mostly aphanitic, but sometimes porphyritic. They were not very suitable for microscopic examination, owing to their ad- vanced stage of decomposition, the felspars being turbid, the augibe having mostly passed into chlorite, the ilmenite into leucoxene, and there being an abundance of calcite. Where at all fresh there were traces of ophitic structure. In some cases the amygdaloidal rocks showed traces of shearing. The tufts closely resembled the " Schal- steins" of Nassau and the Hartz. Mr. WOR~ said that the volcanic series had occupied much of his attention, and that practically the rocks under discussion were similar to those in the neighbourhood of Plymouth. He differed from Mr. Champernowne's conclusion a~ to their horizons, especially as regards the Plymouth district. He was of opinion that they underlie the Plymouth Limestone, and that on this horizon may be traced the beginnings of a coral reef. He referred to the new line on the west side of Dartmoor, and to the light it was calculated to throw upon the geology of the district, especially in reference to the volcanic rocks. Alterations Downloaded from http://jgslegacy.lyellcollection.org/ at Nanyang Technological University on June 15, 2016

ASHPRIN6TON VOLCANIC SERIES OF SOUTH DEVON. 379 in some of the lavas were so gradual that one can hardly see where they begin or end. There were also intruded volcanic rocks of a similar character. Referring to the errors in tho mapping of the boundary between the Carboniferous and Devonian of this region, he asserted that the town of Tavistock is actuaUy on the Carboni- ferous, and yet that by a complex series of foldings the Devonian is brought up north and south of it. He spoke of trap dividing a series of " Schalstein "beds ; elsewhere two distinct lava-flows might be noticed, one above the other. Mr. W. W. BEAV~O~T criticized some of Dr. Hatch's remarks with reference to the alleged traces of shearing in the vesicular lavas, based partly upon the assumption that shearing would destroy the continuity of the cavities ; and Dr. HA~c~ pointed out that, accordifig t~ his view, the cavities having been filled at the time that the shearing took place, they must be regarded as solid bodies.