特涝(Turloughs)和天坑:与众不同的漏斗

TURLOUGHS AND TIANKENGS:DISTINCTIVE DOLINE FORMS

天坑是塌陷漏斗类型中非常极端的一员,并且其关键问题在于是否存在与众不同的“天坑作用”,即是否存在纯粹的形态上的差别。在漏斗类型对应的另一端,爱尔兰的特涝群是指那些宽阔的封闭洼地,这些洼地为季节性湖泊。天坑和特涝与波立谷的区别在于天坑和特涝具有较小的体量,而波立谷具有更为平缓的周壁边坡,再者它们的形成过程也有差异。特别是,特涝仅发现于冰川沉积的区域且至少部分是冰川喀斯特形态,而波立谷出现在许多气候带并且位置通常被证明受地质结构的影响。特涝已被欧盟认可为具有特色植物组合的一种特殊的喀斯特形态,虽然除爱尔兰外,这个术语没有被广泛使用。很明显,天坑也存在同样的问题,即大多数天坑分布于中国,以其巨大的体量和特殊的形成过程与塌陷漏斗区别开来。是否将“特涝”和“天坑”列入喀斯特地貌学词汇之列仍存在争论。

Tiankengs lie at one extreme of the collapse doline spectrum, and a key question is whether there is a distinctive ＇tiankeng process＇ or whether the distinction is purely morphological. At the opposite end of the doline spectrum, the turloughs of Ireland are broad closed depressions with seasonal lakes. They may be differentiated from poljes by their smaller dimensions, gentler surrounding slopes and processes of formation. In particular, turloughs are only found in areas where there are glacial deposits and are, at least in part, glaciokarstic landforms whereas poljes occur in many climatic zones and their locations frequently demonstrate a structural influence. Turloughs have been recognised by the European Union as special karst landforms with a distinctive vegetation assemblage, although the term is not widely used because, with one exception, they are confined to Ireland. There are clear parallels with ＂tiankeng＂ the majority of which are in China and which are distinguished from collapse dolines by their large size, and special processes of formation. It is argued that the terms ＂turlough＂ and ＂tiankeng＂ should both become established in the karst geomorphology lexicon.