646 ME. W. H. HAEDAKER 01!^ A JOSSIL-BEAEINa HOEIZON^ [DgC. I9I2, 



(2) Divisions, Lithoiogy, and Sequence of the 

 Hams tead- Quarry Series. 



The following ascending succession in the Quarry Series is 

 observed : — 



A^. The Colliery-Sandstone Sub-group (20 feet). — Imme- 

 diately east of Hamstead Colliery we meet with about 20 feet of soft 

 sandstones and marls ; they are not, however, well exposed in the 

 neighbourhood. Surface-indications point to the absence from them 

 of pebbly beds, but to the presence of a considerable portion of 

 marl. 



B^. The Gravel-pit Sandstone and Conglomerate Sub- 

 group (40 feet). — A rather harder band of calcareous sandstones — 

 some of them conglomeratic — succeeds. The pebbles are princi- 

 pally Carboniferous Limestone and chert. In thickness these cal- 

 careous sandstones, with thek included pebbly layers, are estimated 

 to measure about 40 feet. They are exposed in the gravel-pit at 

 the southern end of the main street of Hamstead village, and may 

 therefore be called the Gravel-pit Sandstone Sub-group. In the 

 quarry itself about 6 feet of fine conglomerate with small frag- 

 ments of yellow and brownish-red Mountain Limestone and chert 

 is well shown. The same group of sandstone rocks has been 

 bored through by Messrs. Turner & Hadley in the New Quarry 

 farther east, where it forms the floor of the principal seam of marl, 

 now worked for brick-making. A thickness of 36 feet of hard 

 calcareous sandstones, some of them pebbly, was met with in a 

 boring in the floor of the quarry. 



B^. The New-Quarry Marl Sub-group (25 feet). — All the 

 members of this succeeding group are well exposed in the face of 

 the New Quarry. At the base are 6 to 13 feet of marl, with 

 lenticular beds of sandstone. In these sandy layers, some of the 

 fossils to be described later were found. A sandstone of freestone 

 type, apparently unfossiliferous, appears above the marly beds. 

 The thickness of this sandstone varies considerably, but it is, on the 

 average, about 10 feet at the southern end of the quarry. At the 

 northern end of the quarry this bed dies out by passing laterally 

 into marl, which is replaced at a slightly higher horizon by another 

 seam of sandstone that thickens northwards. Above these sand- 

 stones the strata, as will be seen in fig. 2 (p. 645), are very variable. 

 In the northern part they consist of thinly-bedded marly sandstones, 

 which disappear southwards in a number of tongues of sandstone, 

 wedging into the marls there found. Still farther south, these 

 sandy marls are cut off with a local unconformity by beds of len- 

 ticular sandstone containing a few thin beds of marl. Most of the 

 fossils obtained from the quarry were derived from these thinly- 

 bedded sandy layers. In thickness these average 10 feet. 



