ABSTRACT
Immediately after uplift, before surface (and also submarine) output points are targeted, fluids migrate under closed-system or near closed-system conditions, and may move up-dip (but still down-gradient) under artesian pressure within inception horizon voids. Where structure permits, flow concentrates within inception routes in anticlinal fold. zones, just as anticlines provide favoured migration routes and host accumulation of hydrocarbons and related water (itself a heretical concept a hundred years ago: Gries, 2002). For example, in Derbyshire (England), routes within buried anticlinal crests provide the favoured means for deep waters to reach thermal springs where inception horizons in fold crests are intersected by the land surface. More easily appreciated is the subsequent, open-system, situation. Gravitational drainage to surface outputs dominates, and many main drains follow plunging synclinal cores, even where fold limb dips are virtually imperceptible. This is displayed par excellence on Leck Fell in the western Dales, United Kingdom (Waltham, 1974). Two main drains are “superimposed”, separated by c. 130 m vertically, within the axial zone of a gentle syncline. Both are guided by inception horizons, the higher (Short Drop Cave) by the “Notts Pot Coal” and the lower (Lost Johns) by the “Porcellanous Bed” (Figure 1; Table 1). Dendritic tributaries join the main drains obliquely, down the dip of the inception horizons on the fold limbs (Figure 2). Analogues occur in adjacent systems such as Easegill Caverns, Pippikin Pot, Notts Pot, and Ireby Fell Cavern.
