BY W. N. BENSON, W. S. DVS , AND W. R. BROWNE. 301 



l)eils autl mere conglomerates rests at preseut upon a rapid survey only. It will 

 be necessary to establish and apply critically discriminative criteria before definite 

 conclusions concerning these beds may be obtr.incd. 



'Hie Werrie Volcanic Series. 



This consists cf an immense mass of basaltic rocks, which are now probably 

 over two or three thousand feet thick near Warragundi, and must originally have 

 been much more extensive. Invading these is an extensive series of siUs and 

 dykes described below The lavas are chiefly very decomposed basalts, of which 

 the petrological examination is very diiticult. No fresh examples have been ob- 

 tained, though the nature of the rock may be fairly well determined in a speci- 

 *men from the bottom of a deep well near the head of Anstey's Creek. The rocks 

 are very vesicular, the vesicles being either empty or filled with zeolites, calcite, 

 chlorite, or a form of silica. Here and there there is evidence that the mass is 

 composed of many flows of small size. In the banks of creeks the irregular out- 

 lines of the chilled margins of slaggy flows may be seen. 



On the summit of a hill in portion 110, Parish of Werrie (west of the 

 area mapped), at the highest point of the Werrie lavas so far as is yet known, 

 slaggy and ropy lava is found deeply weathered and of red brown colour. It is 

 not, however, a true basalt. 



Warragundi, ur Terriljle Mountain,* and the group of hills around it probably 

 formed the centre of the ancient volcanic activity. In all probability the original 

 volcanoes were dissected and reduced in Permo-Carboniferous times, and covered 

 with Glossopteris-hearing sandstones, of which a remnant still occurs near Werris 

 Creek. This covering being stripped off by subsequent erosion, perhaps in com- 

 paratively recent times, renewed dissection has cut deep into the core of the old 

 volcano. Probably there is no finer examjilc in Australia of a dissected volcanic 

 complex than is afforded by these liills, the detailed examination of which will 

 form a most fascinating study. The writer has been able to spend only three 

 days among these hills, and has therefore merely indicated on the map, Plate xvii., 

 rouighly the area in which the gTeatest variety of rocks is to be found, classing 

 the whole as the Warragundi complex. A few notes, ho'wever, may be given to 

 indicate the nature of this complex. The basaltic rocks are in one place associ- 

 ated with rhyolite, possibly a flow. They have been broken through by large 

 masses of trachytie or felsitic agglomerate, the largest of which forms Warra- 

 gundi itself, and adjacent to these are more basic agglomerates. In addition, 

 there is a varied and extensive series of intrusive rocks, which form dykes, sills 

 or sheets, or less regularly shaped masses, the rocks of which may be termed 

 provisionally felsites or granophyres and keratophyres, porphyrites of several 

 types, and dolerites. These are clearly related to the intrasive rocks, dykes and 

 sheets in the Carboniferous sediments, as will appear more clearly after a con- 

 sideration of the latter rocks. It will suflRee at present to point out that the 

 dykes in the sediments tend to radiate out from about Warragundi. From this 

 centre two bundles of dykes pass outwards, the one extending to the east, form- 

 ing the ridge at the head of Anstey's Creek, and extending for a considerable dis- 

 tance through the Kuttung rocks; the other bundle strikes to the south-west and 

 bends round almost to a southerly direction on crossing Werrie's Creek, and being 

 resistant to erosion the dykes have determined the yiresenee of the creseentie 



' See footnote p. 292. 



