Gilbert. — Geology of Waikato Heads District. 97 



Art. XIII. — Geology of the Waikato Heads District and the Kawa 



Unconformity. 



By M. J. Gilbert, M.Sc. (Rev. Brother Fergus), Sacred Heart College, 



Auckland. 



Communicated by J. A. Bartrum. 



[Read before the Auckland Institute, 15th December, 1920 ; received by Editor, 31st December, 



1920 ; issued separately, 27th June, 1921.] 



Plates XX, XXI. 



n, 



Contents. 

 Introduction. 



Previous Work in the District. 

 The Coastal Area between Manukau Entrance and Waikato River. 



The Area East of the Sand-dunes. 



A Suggestion of Origin of the Sand-dunes and of the Lignite-beds. 



Sub-recent Oscillations of Level : Origin of Manukau Harbour. 



Mutual Relations of the Areas North and South of the Waikato River : an 

 Hypothesis of Major Faulting. 

 The Area South of the Waikato. 



General Description. 



Drainage of the Southern Area. 



The Older-mass of the Southern Area. 



The Marine Fossiliferous Shales or Belemnite-beds. 



The Fossil -plant Beds. 



Age of the Older-mass. 



General History of the Coastal Area South of the Waikato River. 



Relation between the Mesozoic Older-mass and the Younger-mass (or Notocene) 

 Beds. 



The Younger-mass (or Notocene) Beds. 

 The Kawa Section. 



Order of Ascending Sequence. 



The Kawa Pumice-bed in Relation to the Waikato River. 

 Structural Plateau near the Coast. 

 Slipped Country above Waiwiri Beach. 

 Sinkholes. 

 Microscopic Characters of some of the Rocks : The Kawa Basalt ; Waitangi Bay 



Basalt ; Pakau Basalt ; Algal Limestone ; Glauconitic Limestone ; Marly 



Limestone ; Globigerina Limestone. 

 Summary and Conclusions. 



Introduction. 



The entrance to the Manukau Harbour and the lower part of the Waikato 

 River separate three notably distinct topographic and structural regions. 

 That to the north of the Manukau is characterized by a broad range of 

 hills of resistant rock, deeply dissected by streams. The middle area is 

 constituted by a line of ancient sand-dunes facing the ocean, and is con- 

 siderably worn by streams, moderately low country rising behind it to 

 the east. The third area, that south of the Waikato River, is a broad 

 minutely-dissected upland of more varied structure than the others, and 

 it, with the second or middle area, forms the subject of this paper. 



Previous Work in the District. 



Hochstetter (1867) in 1859 collected fossils from the Waikato South 

 Head, as well as from the plant-beds near Oruarangi Point, some four 



4 — Trans 



