21. Basement rock was formed during the Hercynian orogeny when a strong regional metamorphism affected the area.22. This isotope signature may be the effect of assimilation of deeper basement rocks during magma formation. 23. The islands are of volcanic origin with basement rocks forming between the late Cretaceous and early Eocene. 24. As such, the basement rock can become younger going closer to the edge of the continent. 25. Working on local Precambrian basement rocks , Sederholm instigated a igneous magma into metamorphic rocks at depth. 26. These basement rocks were created during the late Mesozoic era, long before the Itcha Range formed. 27. Lava from the western flank flowed over basement rocks and trachytes of the pre-explosive phase. 28. The Ravensthorpe region is underlain by basement rocks of the Albany-Fraser Orogen and Yilgarn Craton. 29. The area is composed of a well defined ridge of silicified brown sandstone overlaying the basement rock . 30. Typically, the temperature in those vast regions of the accessible crystalline basement rock increases with depth.
