GEOLOGY OF MARLBOROUGH.

Marlborough Express, Volume III, Issue 100, 8 February 1868, Page 5

GEOLOGY OF MARLBOROUGH.

Hector’s abstract report, on the,pro#-ess of the geologicaLsuiwey rffoHew during 1866-7;‘J«'®he work-is ißnafoate&hy a number of diagrams- showiug the sections of various ! localities, ' among i the Clarence Eiyer, ithe ;;•!limestone broken through by the river-y^Amurißluff; one mile south of-Amuri Bluff; • TuaMarina - Valley’between Blenheim and PiCton ;:the liooker-pn ,'the . George .®iyer- to, Hait^u iu (7 :: mile?)> ri.l/'. y.-insh'l fcii* }*! ,KOeKf!CfV j

coal outcrop at Motanau Creek ; submerged forest near Conway River; the sea near Waiau-ua River and limestone gorge, Conway River, two sections; and the Awatere Valley near the sea. As the contents of the work must be interesting to the inhabitants of the' province, we have made the following extracts: — MARLBOROUGH AND EASTERN NELSON. In November last Mr. Buchanan was instructed to proceed to the Kaikoura Mountains and the East Coast of the Province of Marlborough, for the purpose of collecting specimens of fossils, rocks, and plants, from those portions of this district which have hitherto received hardly any attention from observers. After an expedition extending over nine weeks, in the course of which he ascended the Lookers-on or seaward Kaikouras, and examined the valleys and coast line as far south as Motunau, in the Province of Canterbury; he returned with a large number of valuable specimens which are deposited in the Museum.

From an examination of these specimens I find the following formations to be represented in this district:— * 1. Post Tertiary, sands and gravels, forming terraces along the courses of the rivers, and fringing the coast. . Occasionally these gravels cover ancient forests, which, in some cases, are shown by sections on the sea coast to be submerged below the present sea level. 2. Pliocene.—(A.) Newer great terrace drift formation. (B.) Older blue clays of marine origin containing abundant fossil remains of mollusca and cetaceans, many of the former being of species still living in the neighbouring seas. 3. Miocene. — (A.) Bed and white crag limestone, fossiliferous. (B.) Clay marls and green sands. These are marine formations, characterised by a proportion of fossils, mostly of forms now extinct. (C.) In certain districts the above are underlaid by the brown coal formation. 4. Cretaceo-Tertiary—-(A.) Chalk marls, evidently of marine origin, but containing few fossils. These marls pass into pure chalk, and even crystalline limestones in some cases. (B.) Ferruginous clays, with septaria, containing upper secondary fossils (the Amuri beds). (C.) Sandstone and grit with plants, representing the West. Coast Coal Fields, are present probably at Motunau. 5. Lower Secondary. —lndurated green and brown sandstone and shales (corresponding to the Richmond series near Nelson). These form lower ranges, flanking the Kaikouras ; no fossils were obtained, but the marked lithological character of the beds leave no doubt as to their presence. 6. Schistose rocks of various ages, from the Maitai slates to the foliated mica schist. 7. Hornblendic rocks, associated with serpentine bands.. Mr. Bucbauan’s notes are as follows. He says:—

In communicating the following notes, I must premise that many of the names of rocks and rock formations are to be considered as provisional, until the collections have been examined at the Museum.

The long continuance of wet weather prevented much time being taken up with Botanical collecting, and more attention was paid to working out geological sections wherever it could be done, and the purpose of the following notes ■is to explain, the sections and accompanying map.

The geology of Marlborough appears to be very simple. ; To the East of the Wairau Yalley and South to the Conway Eiver there will be found a great development of palaeozoic diorite schists rising like islands from the marine tertiaries along the coast. South of-the Conway Eiver, passing through Nelson into Canterbury, the brown coal formation begins to appear, between the old schists and the .marine tertiaries, adding more interest to the study of the district. The sequence of the different, formations is shown in vertical section No,, 1. *’ I. —-PRIMARY ROCKS. The diorite and clay schists, which form the higher land of the district, occupy the greater part of the surface area.- The strike of these rocks is generally N.W., with a westerly dip of about 75 deg., but near Squally Point the strike is N.E., with a westerly dip of 80 deg. In Taylor’s Pass again, where there is apparently an anticlinal line of fault, they dip both to the S.W. and S.E. 75 deg., and: also in the valley between Blenheim and Picton there is another anti-clinal line of , fault, with the dip at the' Blenheim^nd-^.and S.E. 45 deg., whilst at the Picton end the dip is S.W. and; S;E. :60_deg.: to ;75 deg. ; in this case, and probably also in Taylor’s Pass the faiilt is much" wider at one hnd than at the dtheri T~~ . • To the South *of the Wairau Yalley, the greater part of these older- rocks are dioritic sandstones and slates alternating ; : but in some localities, as,,the vicinity of Blarich Cheek on the Eiver, a variety of rocks are found, ; as serpen’tihe, and""green 1 fine specimens' of f f; hornblend-e.* Higher, up the .Awatere, a of variegated diorite intersects Mount Mouat, taking in the 1 “whole of thd‘Stephen Moun-

tains, then crossing the Awatere, probablytaking in the highest Kaikouras, it trends southwards. This band never crosses the Clarence Biver to the East, but to determine its exact boundaries would require a long period of good weather. , f i Both on the Awatere and in Taylor’s Pass a highly feruginous rock is found in abundance, of which specimens have been collected. It is reported that Dr. Haast found copper on Blarich Creek at the time Dr. Hochstetter was in the country, but he lost the specimen, and wrote to Mr. M'llae, urging him to look for more, which he did, but found none, and the creek was also searched carefully by me without success. Several reports of coal having been found at different places being given, the localities were examined, but the supposed coal always proved to be a black shale, which, # when exposed to the weather, crumbles down into a substance like coal dross (serpentinous shale). The older rock formation to the North of the Wairau Yalley appears to be different altogether from that to the South, as'laminated slates prevail, having fine veins of quartz ramifying through their mass. A very puzzling formation is found between the dioritic schists and the marine tertiaries. This is a soft but tough blue marlstone, having the same strike and dip as the older rocks, and always forming a series of low rounded hills which bear a strong resemblance to the hills of the older tertiaries, intermingling so much with them that they are difficult to distinguish at a distance. In many cases also the marine tertiaries rest on these marl hills in such a way as almost to make it impossible to distinguish the line of junction. At many parts of the coast this soft blue marl forms reefs-of-a- very durable -nature, the- aetienof the waves having less degrading power on-them than-on the harder-limestone or primary rocks.* Earthquake Rents.

Along the course of the Awatere River where the marine tertiaries rest on the slates, the water from rains rushing down the steep slopes of these hard primary spurs, impinges at the line of junction on the gravels and sandstones of the softer tertiaries, producing a series of transverse troughs which are called earthquake rents. These troughs or watercourses are always shallowest on the bulge of the spur, deepening by the accumulation of water as they lengthen their course. . . These so-called earthquake rents are found on other rivers than the. Awatere, wherever the tertiaries rest on steep hard rocks, _and though there may" be oh the" Awatere Yalley and other places true earthquake faults, as hereafter mentioned, these rents are certainly fissures produced by the action of water. Anticlinal Goast Line of Fault.

From near Cape Campbell south to the "Waiau River a great anticlinal fault can be traced, as shown on the accompanying map. Before the deposition of the brown coal and marine tertiary formations, this upheaval tilted the primary rocks to a considerable angle on both sides of the line East and "West.; Near Squally Point and at Amuri Bluff they have an easterly dip of 80 deg. ; in other places it isj westerly, the general dip jof the inland ranges. On the tilted primary rocks the coal l and older marine tertiaries were deposited, but before the deposition of the newer tertiary terraces another upheaval took place on; the same line, producing on the former a dip from 15 deg. to 45 deg. East and West. Brol- - the same line takes a curve froriv near the Halidon hills, proceeding through Taylor's Pass (which is an anticlinal valley,) and thence across the- Wairau Valley, passing up the Tuamarina 1 ValleyL which is another line of fault, to Picton. [These two valleys may, however,- be distinct lines of fault from that of the coast line. J The coast and older marine tertiaries on the East Coast; show the : opposite dips of this antielinal line in* inorVplaces than the primary rocks, j Beginning at Cape Campbell, the dip as far as -the""TFre| River is 25 deg. to 30 deg. easterly, between Flag's River and Kekerahgu, dip 15 deg.| to 45 deg. Westerly; Clarence River,' | dip 30 deg. to 45 degs. westerly j Ainuri Bluff, dip 25 degs. easterly; niouth of thi3 Conway River, dip 30 !degs.-Vesferly ; j KaikouraPeninsula, dip]4s' deg. -easterly;; betweenthe Conway and "Waiau rivers, dip 20 deg. • westerly ; and probably a reef at sea nearMotunau dips westerly. & j n.—bbown; coal fobmatiqit. This formation rests uncomformably on the primary schists. , Assuming {the exist-, ence of' extensiye jdevel valleys, much swampy ground, and a luxuriant hregetation during the formation, there is np reason to _ suppose. a-wanner' climate tptan-tne present, as tne°climate! of. New Zealand is auite

capable of producing a most luxuriant vegetation under circumstances of abundant moisture; in fact, cold is, in my opinion, more favorable to the production of coal material than heat, if the latter is excessive, as it is derived chiefly from the growth of bogs and the lower class of cryptogamic plants which thrive best with a low temperature. Nothing could be more favorable to the production of this material than the great swampy valleys which must have existed before the deposition of the marine tertiaries, —though no doubt, on the soil produced from the decayed vegetation of the lower class of plants, flowering shrubs and trees also flourished; but there is abundant evidence that the different coal seams must have been formed under a gradual sinking of the land, interstratifying them with clays. The easterly coal formation of the Province of Marlborough is very small, it crops out at places along the coast with a dip to the East, but it hardly appears inland at all, except at the Amuri Bluff, where a few yards of coal may be found. The evidence is pretty conclusive that a large coal formation exists under the sea along the coast between Cape Campbell and Bank’s Peninsula, or if these brown coals are only found in small isolated basins, several may exist along this line. Amuri Bluff is the most northerly point where the coal sandstone actually shows on land. It rises beneath the limestone with a dip of 25 deg. S.E., and for two miles South it only shows a line rising along the beach above high-water. This sandstone is fossiliferous, containing Vermetus Dentalium, Peaten, angular jointed stalks like Encrinites and Cidarite ' spines. —CoaHs said to have been found in a creek ’at Amuri Bluff, but it never can be of much -importance,* as the —formation crops out within half-a-mile of the coast, or perhaps somewhat more, at a point immediately behind the Bluff. One mile South of the Bluff, the fossiliferous sandstone is tilted up sufficiently to produce a dip of 80 deg. East. It has at this place been thrust up through septaria clays, and at the line of junction the clay beds have the same dip as the sandstone, as shown in the , sections of the Amuri Bluff.

If, as reported, petroleum rises to the surface at sea, one mile off Squally Point, it is probably further , evidence of. coal seams existing under water along: the coast. The presence of submerged coal seams along the coast is a strong argument in the existence of a former line of valleys to -the-East-of- the-presentTandrduring-the-de-position of the marine tertiaries, to be afterwards noticed: “

Between the Conway and the Waiau rivers, all to the East of the anticlinal fault is now under water, and the newer tertiary terraces rest on the primitive rocks of the coast range. These terraces are here in some places over TOO feet high, in their scarps of sand and gravel. 'Whether coal may be found to the West of the coast range, in the Waiau basin, will be difficult to say from the unbroken nature of the hills and the thick covering of newer tertiary' gravels. Boulders of a soft sandstone are seen on the low hills between Cheviot Station and the Hurunui River, but. whether these hills are themselves sandstone, cannot be seen. This sandstone may, very probably, be that above the limestone, as it did not appear to have fossils, in which case it may have no connection with the coal, as these .older textiaries often rest in* this dis.tnct oU the primitive rocks. ; / -r, l! 'There is a strong probability from the swampy nature of the Waiau basin in former times, that lignite seams rest above the older perhaps at a,, considerable depth'; but it is only to the "South of the Hurunui River that the brown coal formation assumes. any .importance r !At the Motunau Creek the beds extend,’-four miles from the sea. Coal is also reported to have" been found at Stpnyhurst,, and,’such may probably be the case,’ but' the Motunau basin is entirely cut off from any that may be there.by a ridge,of prixnary.hills; On one of the branches, of the.. Motunau Creek, close to the base of, therßlack Hills, an outcrop of the. coal is seen r in t the. bed of the crepk; it dips tpjjo deg. On sinbingh hole the '.scam -was; proved to be three' feet thick ;' the hole was sunk one foot further .intp’-' a“w^^h-^3^ : but imperfect tools anything further being, seam lower down the 'cfpel^dssuperior coal, burning with a :cje|g ; §righ^ : flame,., and easily jignited ;. it well adapted, fhf the

• This coal bail beihg" eiamided' jn? th f e Laboratory of the Geological Department gave the following results:—Common Brown. Coal of the same character as that at Kowhai and Big Ben mines; powder black; ash .red; coke unchanged ;• water 18*15*;* fixed carbon 40*37 ; hydro carbon 36*11; ash 5*37.

(To he concluded in our next.)