166 
Records of the Geological Survey of India. 
[vOL. XI. 
the representation of this great volcanic formation in Sind is far from improbable. 
The question as to whether the Ranikot trap belongs to the Deccan series may- 
now be answered in the affirmative. There is conclusive evidence that this rock 
is interstratified and not intrusive, for it occupies precisely the same position 
above the highest Gardita heawnonti beds, and below the base of the Ranikot 
group, for over 20 miles, and appears to be conformable with both, whilst not a 
single vertical dyke has been noticed in the country. The mineral character of 
the basalt is precisely that of a vei-y common form of the Deccan trap, whilst two 
mineral peculiarities—the occurrence of amygdala, suiTounded by green earth, 
and of cavities containing quartz crystals, with trihedral terminations—are both 
characteristic of the trap rocks of Western India. The geological position also 
at the base of the tertiary series con-esponds with that of the trap series in Cutch 
and Guzerat. 
It is clear, however, that the thin flows of basalt in Sind can only represent 
a portion of the great Deccan trap period, and the lower band in the cretaceous 
sandstones indicates that all the upper cretaceous beds between the two trap flows 
were, in all probability, contemporaneous in origin with the Deccan trap series. 
If now the age of the Gardita beaumonti beds has been rightly determined as upper 
cretaceous, the identification of the Sind representative beds confirms the views 
previously held by myself, but by no means generally accepted by my colleagues, ^ 
as to the cretaceous age of the lower portion, at all events, of the Deccan trap 
series. 
Banilcof group. —It was mentioned in a postscript to the previous paper in 
the Records 2 that the highly fossiliferous brown limestones seen north-west of 
Kotri and near Jhirak (Jhirk or Jermck) and Tatta must be classed with the 
Ranikot group, and not with the Khirthar. A list of fossils obtained from these 
brown limestones was given, ^ ffiit from this list two species must be removed, 
viz., Gardita heammnti and Nautilus lahecliei, the species thus identified (the 
identification is doubtful in the case of the Nautilus) being from the olive shales 
now classed as cretaceous. It was also noticed in the postscript that south of 
Ranikot there is distinct unconfoimity between the Khirthar limestone and the 
Ranikot group, the upper members of the latter being deficient in the Laki range, 
and there being at one place evidence of the lower group having been slightly 
disturbed and denuded before the deposition of the Khirthar limestone. The 
break between these two formations is, however, ju’obably not indicative of 
any great interval in time, for several of the Ranikot fossils pass upwards into 
•Oldham; Eec. G. .S. I., IV, p. 77; Wynne: Mem. G. S. I., IX, p. 48. I have lately had 
occasion to go over all the evidence again -n hen -n'riting a chiiptor on the Deccan traps for the 
Manual of Indian Geology, and it appears to me that the arguments in favonr of considering the 
traps tertiary are weaker than I at first supposed. Only one fact of any importance, so far as 1 know, 
has ever been adduced : the supposed identification of certain freshwater shells in the intertrappean 
beds of the Deccan with forms found in the lower eocene plastic clay of Belgium. Apart from the 
question, a very important one, whether freshwater shells afford trustworthy evidence of age, I 
greatly doubt the validity of the identification. 
2 Vol. IX, p. 21. 
^ 1. c., p. 14. 
