Volcanic rocks and surfaces as indicators of landform age

The Astrolabe Agglomerate, a unit of volcanic rocks consisting mainly of pyroclastics with a few lavas at the top, is used to estimate the former extent of a landsurface of low relief in eastern P.N.G. The pyroclastics are of flow origin, but consist mainly of large rounded and subrounded clasts with only small amounts of fine matrix. Basalt from one of the lava flows overlying the agglomerate has a K/Ar age of 5.7 million years. Since the Astrolabe Agglomerate was deposited it has been slightly warped and deeply dissected. Erosion on agglomerate surfaces has been at a minimum rate of 10 mm/1000 years, while scarp retreat has taken place at about 1000 mm/1000 years. The Sogeri Plateau is the largest remnant of a once much larger erosion surface that may have extended over much of the Owen Stanley Ranges

Agglomerate · Basalt · Caldera · Clastic rock · Erosion · Geochemistry · Geomorphology · Landform · Lava · Plateau (mathematics · Pyroclastic rock · Structural basin · Volcanic rock · Volcano · Geological and Geophysical Studies · Geology · Geology and Paleoclimatology Research · Pacific and Southeast Asian Studies · Paleontology