52 



R.I. MACPHAIL AND P. GOLDBERG 











■^JV' 







' tJ& 

























.''."' . , . ; ' \ ••-■-- ■ ? .<i :i 









» -•. 









-:• ' ". ""' ./'. ,*-,-^<; " 4C* 

















i '•"• 1 









r- 



- 









MkJn^IH 









"HI 

















"■ 









j2g^ 







•*2 



n 





, 





^HP^ffiSnMflHfll^^BM^9 









■ 







^ 



^^^^^^HM 







■■■ --A 



■ 



Fig. 1 Field photo of Gough's Cave, Area 3. lower red silts, sample I. Note faint traces of bedding next to the sampling box (8 x 6.5 cm); cf. Fig. 2. 



At Gough's Cave, the basic sedimentary sequence has been modi- 

 fied by a number of post-depositional processes to produce different 

 micro-sedimentary fabrics. For example, the banded fabrics/link 

 capping features (Table 1 ) are the typical result of ice lensing 

 produced by alternate freezing and thawing ( Romans and Robertson, 



Fig. 2 Macrophotograph of whole thin section of sample I (cf . Fig. 1 ). 

 Shown here are interbedded beds of elutriated silts (Si) and clay (C). 

 Width of photo is 6.5 cm. 



1974; van Vliet-Lanoe, 1985, 1986). Extreme modification by 

 freezing and thawing results in the fragmentation and chaotic mixing 

 of the beds and link capping features, and infilling with impure clay 

 and silt (Macphail, 1999) (Fig. 4). 



Biological activity is also recorded at Gough's Cave, forming 

 channels and vughs through likely rooting and faunal burrowing. 

 Finally, in this sequence many of these voids have been coated with 

 dusty clay that implies renewed fluid transport vertically through the 

 sediments (see below). 



Sand Hole (Pleistocene to earliest Holocene) 



Here the sequence commences with the deposition of cave muds 

 (sample C) that accumulated in the base of the Sand Hole. These 

 muds are composed of clay with clasts of redeposited clay (Fig. 5) 

 and accumulated under conditions of low energy ponding. These 

 deposits have reticulate b-fabrics induced by minor shrinking and 

 swelling that reflect alternating periods of wetting and drying. It is 

 possible that these muds are the finest deposits within the cave 

 system, recording the end member of the upward fining sequence 

 present in the main chamber. It is likely that this red clay owes its 

 ultimate origin to the weathering of the Carboniferous Limestone, 

 and is a form of transported Beta B clay (Duchaufour, 1977). 



In the Sand Hole, the sequence continues with the 'Laminated 

 Stalagmite' and the 'Frog Earth' (Figs 6, 7). The laminated stalag- 

 mite is composed of cryoclastically produced fallen limestone clasts 

 and clay beds, which are both partially cemented by micrite originat- 

 ing from drip. These deposits are succeeded by muds containing 

 large numbers of frog bones that appear to be typical of early 

 Holocene faunas (Currant, NHM, pers. comm.). 



