ON THE PLANT-BEARING CHERTS AT RHYnIE, ABERDEENSHIRE. 209 



In October 1913, Mr. D. Tait, of the Geological Survey, at the 

 instance of the Assistant-Director, Dr. Flett, visited the area and made 

 several excavations with the view of fixing definitely the stratigraphical 

 position of these plant-bearing cherts. He proved their position within 

 the Old Red Sandstone ai-ea and about tvv'o hundred yards east of the 

 boundary fault, as laid down in the Geological Survey Map (Sheet 76). 

 The main locality is in the position of Ti'ench No. 1 of the accompanying 

 map (Fig. 1). His results are summarised in his report, which is 

 quoted in Dr. Mackie's paper communicated to the Edinburgh Geological 

 Society.' His conclusion was that these plant-bearing cherts belonged 

 to the Old Eed Sandstone. For reasons given in the paper referred to. 

 Dr. Mackie could not accept that conclusion, and the present investiga- 

 tion was undertaken with the view of determining the exact strati- 

 graphical position of the plant-bearing cherts. 



II. Investigations of the Committee. 



As the field of investigation lies almost wholly on agricultural land, 

 the trenches had to be covered up by the end of March 1916. The work 

 was much interrupted by unfavourable weather. Fortunately only a 

 small part of the work as originally planned was not can-ied out. 

 The Committee hope to be able to overtake the I'emainder in the late 

 autumn of this year or nearly next spring, with the aid of a grant from 

 the Royal Society. The work was conducted throughout under the 

 personal supervision of Mr. Tait, of the Geological Survey. 



The area of investigation lies to the west of the village of Muir of 

 Rhynie. About a quarter of a mile from the centre of the village, and 

 about'a hundred yards to the N.W. of the bridge of the Easaiche Burn 

 (see fig. 1), a small ditch between two fields occurs on the N.E. side of 

 the road. This ditch was made the datum line for measurement from 

 the road in a northern direction, while the road itself from the end of 

 the ditch was made the line of measurement in an east and west direc- 

 tion. As many blocks of the chert were found lying along the margins 

 of this ditch, it was cleared out and the I'ocks in place were exposed at a 

 distance of about fifty yards N.E. from the road. The chert band was 

 found in the ditch. A bed of clay was also found below it. The section 

 in the ditch remains as a record of the work of the Committee. 



A. Record of Evidence in the Trenches. 



The following are the records of the various trenches as drawn up 

 by Mr. Tait. Their positions are indicated on the accompanying map 

 (fig-1):- 



Trench No. 1. — In first field north of Easaiche Bridge, on south-east 

 side of path and ditch separating the two fields, and 178 feet north-east 

 of road. This trench is 38 feet long and about 3 feet wide. Its greatest 

 depth is 6j feet. The plant-bearing chert, which is about 8 feet in 

 thickness, projects upwards to within 6 inches of the surface of the 

 field and dips at an angle of 45° to the north. 



' ' The Rock Series of Craigbeg and Ord Hill, Rhynie, Aberdeenshire,' 

 Trans. Edin. Geol. Soc. vol. x. part 2, p. 223. 



1916 p 



