The Highland Boundary Fault : Reverse or Wrench Fault?
DETAILED work which I have done in the Loch Lomond area suggests a definite answer to the above problem which is of some importance since it concerns one of the major geological features of the British Isles. The direction in which the principal stress acted in the production of the fault can be approximately determined from the pattern of structures in the Lower Old Red Sandstone conglomerates, and this supports the contention put forward in stratigraphical accounts (summarized by J. G. C. Anderson1) that the Highland Boundary Fault is a reverse fault of Caledonian age and not a Proto-Armorican wrench fault as envisaged by E. M. Anderson2.
Record of fluid flow history through fractured conglomerates, Lower Old Red Sandstone of central Scotland
Synopsis Extensively fractured quartzite clasts in Lower Old Red Sandstone conglomerates adjacent to the Highland Boundary Fault Zone in central Scotland contain multiple populations of healed microfractures delimited by fluid inclusion planes. Microthermometric analysis indicates that the healing of microfractures oriented perpendicular to the trend of the Highland Boundary Fault Zone, which probably formed during Acadian overthrusting towards the SE along the fault zone in Middle Devonian times, involved moderate temperature (Th 102 to 238°C), low to moderate salinity (3 to 17 wt% NaCl eq.) aqueous fluids. The clasts also contain a second set of fluid inclusion planes oriented parallel to the Highland Boundary Fault Zone, which formed during extension associated with the intrusion of late Carboniferous quartz dolerite dykes. The healing of this set of microfractures involved low temperature (Th 58 to 155°C), low to moderate salinity (1 to 12 wt% NaCl eq.) aqueous fluids.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.