LAMPLUGH : NEARTH-MOVEMET IN NORTH-EAST YORKSHIRE. 393 
since Rhsetic times, and its present position shows the net result of 
all the movements. Its synclinal attitude, now interrupted toward 
the north by the superimposed anticline of the northern moorlands 
and by the Guisbrough trough, is the residue of the deeper s}Ticline 
before the Tertiary uplift. It will be noticed that the deepest part 
of the depression still coincides nearly with the tract in which the 
Oolitic sediments attained their maximum thickness.* 
Summary and Conclusion. 
To sum up the course of the events which we have traced with 
the help of the planes, we may recognise : — 
1. A horizontal floor throughout the north-eastern part of 
Yorkshire during the deposition of the Rhsetic beds. 
2. A subsidence during the period of the Lias, with a tilting of 
the floor downward to the north, so that at the close of the 
period it was over 1,000 feet lower in the north-east than in 
the south-west. 
3. A continuance of the same unequal subsidence during the 
period of the Lower Oolites, bringing the extreme difference 
of level up to 1600 feet. 
4. Toward the close of the period of the Middle Oolites the 
difference had increased to about 2100 feet. 
5. A further increase of the depression during the period of the 
Upper Oolites and until Upper Cretaceous times, but the 
amount not now directly ascertainable ; the maximum 
depth of the depression, however, was probably not less than 
2500 feet. 
6. A reversal of the process during the Tertiary epoch, with a 
relatively greater uplift of the country in the north than in 
the south, obscuring and partly obliterating the original 
arrangement. 
* Incidentally, the plotting of the Malton group of faults north of 
Acklam, from the data on the Geological Survey maps and sections, 
brings out the circumstance frequently to be observed in much-faulted 
districts, that the average inclination of the dominant folding-structures 
is hardly altered at all by the step-faults, the local effect of the faults 
being counteracted by a reduction, or reversal, of the dip in the blocks 
of strata between the faults. There is probably some complementary 
faulting on the northern slope of the hollow, where none is shown ; 
the presence of Kinameridge Clay at the surface above this slope is 
unfavourable for the detection of faults. 
