41. At St . Ou�n's Bay the metamorphosis of greywacke has made hornblende-hornfels. 42. The Burnie or Oonah Formation with Greywacke is possibly from the Tonian period, dated around. 43. Greywacke pebble beaches can be seen forming a layer in Waitemata sandstone cliffs on Motutapu Island.44. The hemispherical voids and pits result from the selective dissolution of carbonate concretions within the greywacke . 45. Sedimentary rocks, most notably the Greywacke -Shale Formation, constitute the bulk of Laurie Island. 46. The Dundas Element lowest level starts with the Oonah Formation with greywacke , dolomite and basic volcanics. 47. Situated within the greywacke zone, they are also regarded as part of the Northern Limestone Alps. 48. Sandstone / greywacke ridges rise to between 300-370m altitude on each side of the valley floor. 49. The Rhine and the slate and greywacke weathered soils function as a heat storage to prevent large temperature fluctuations. 50. Malen�k is a rugged highland composed of culm greywacke , sandstones and shales, Devonian limestones and Miocene sediments.
