Stratigraphical Geology. 87 



Ireland," by Joseph Wright, f.g.s., also the Appendix to the 

 year 1884-85. 



The chalk has been much indurated by the basaltic flows 

 of Tertiary times. In some places, where in contact with 

 the sides of a basaltic dyke, it presents a crystalline structure, 

 and is often stained a light ochreous colour. 



The Tertiary Period. 



After the deposition of the Cretaceous rocks, our 

 district underwent a period of elevation. The bottom of 

 the Chalk sea was elevated and became dry land, subject to 

 sub-aerial denudation. Consequently, the upper surface of 

 the Chalk is found to have been weathered, the softer cal- 

 careous material has been washed away, leaving many flint 

 nodules embedded in an ochreous clay as an evidence of 

 the amount of denudation which the Chalk has been sub- 

 jected to before the outflows of basalt. This red ochreous 

 material might well be compared with beds of similar charac- 

 ter which occur in many parts of the country between the 

 various basalt flows. An excellent example may be seen 

 in the old chalk quarry at Whitehead, where the irregular 

 form of the upper surface of the Chalk seems to indicate 

 the sides of an old river valley. The flints are of a deep 

 red colour, induced by the heat of the thick, deep lava flow. 

 The only fossils recorded from this band are redeposited 

 Chalk fossils. Over this old land surface numerous sheets 

 of basic lavas were outpoured in early Tertiary times. 

 During the periods of quiet, between the successive out- 

 flows of igneous material, the surface of the lava flow was 

 subjected to denudation, a scanty soil was formed, vegeta- 

 tion got* a footing, only to be submerged in the next flow. 

 Remains of such vegetation are to be found in a well- 

 defined band forming the division between the lower and 

 the upper basalts. The band consists of volcanic tuffs, 

 clays, conglomerates, thin lignites, and pisolitic iron ore. 

 At Ballypallidy this seam has yielded abundant remains of 

 plants — Finns, Sa/ix, Populus, Acer, Quercus, etc. At Ballin- 

 toy lignites are found. 



Mr. Starkie Cardner considers these remains indicate the 

 same horizon as the Bournemouth beds; that is, they belong 

 to the middle Eocene period. 



