253 



NOTES ON THH GEOLOGY AND ARCH/COLOGY OF THE 

 CAYTHORPE AND LEADENHAM DISTRICT. 



IIi:XRV PRESTON. F.G.S., 



iiitiinin ; I'rrsiili-tit of tin' Lf)icolnslu'rf Nahiralists' ['nioii. 



The rock formations examined and described durins^- tiie visit 

 of tiie Lincolnshire Naturalists' Union to the Grantham district 

 in Aug-List 1902 consist of the Lincolnshire Limestone which 

 forms the Clifif Hill ; the Northampton Sands and the Upper 

 Lias Clay formini^- the western slope of the cliff escarpment, 

 and the Marlstone Rock-bed, which is here worked extensively 

 for Ironstone. Samples also were seen of the sandv and 

 micaceous clays of the Middle Lias underlying- the Marlstone. 

 The dip of the strata is mainly to the south-east, and the beds 



Fold in the Marlstone Rock near Hough Mill, Caythorpe, Lincolnshire. 



lie conformably upon each other, save in a case where the 

 Lincolnshire Limestone has a decided dip towards the west in 

 consequence of underground denudation. In this case some 

 spring's which issue on the western slope of the escarpment 

 have cut away the Northampton Sands and top beds of LIpper 

 Lias and let down the Limestone.''-' The Ironstone consisted 

 originally of ordinary Limestone, which subsequent depression 

 broug'ht in contact with subterranean water capable of depositing- 

 carbonate of iron. An uplift of the rock and denudation then 

 broug-ht these beds to the earth's surface, where carbonated 

 atmospheric water in the form of rain changed the soluble 

 carbonate into the insoluble oxide of iron, in which form it is 

 now worked. Folds and large fissure cracks occur in the 



^'" See Quart. Journ. Geol. Soc, \'ol. 59, 1903, pp. 29-32. 



1903 July I. 



