Early Mesozoic (?Triassic) Landscapes in Australia: Evidence, Argument, and Implications

Abstract

A B S T R A C TAustralia has strong claims to be known as the old continent. In addition to landscapes of later Cretaceous-early Tertiary derivation, remnants of early Mesozoic (Triassic-Jurassic) surfaces, which are part of the contemporary landscape, are also recognized. Being of etch type, they have two ages: one referring to the period of preparation by subsurface weathering and the other to their date of exposure. In many instances, exposure can be dated and the period of preparatory weathering closely inferred. Such old paleosurfaces are demonstrated on Kangaroo Island and are strongly implied in, for example, the Flinders, Gawler, and MacDonnell Ranges; in Arnhem Land and the Arcoona Plateaus; in many parts of the Eastern Uplands; and on several bornhardts in the Yilgarn and Gawler Cratons. They reinforce the suggestion that once in positive relief and shedding water, surfaces persist with little change for long periods. Such ancient features are incompatible with several well-known models of landscape evolution. The chronologies and events they imply extend our understanding of the landscape in the chronological context. They add to our knowledge of Earth's history.

Landscape age and soil fertility, climatic stability, and fire regime predictability: beyond the OCBIL framework

“…(4) Ancient Landscapes are also termed palaeosurfaces (e.g. Twidale 2000Twidale , 2003. Some have experienced extremely prolonged sub-aerial exposure and are pre-Cenozoic.…”

“…There are, however, undoubtedly places which have experienced prolonged tectonic quiescence, and which, due to the occurrence of a slowly eroding geological substrate, and sometimes in combination with relatively low precipitation, shows denudation rates slower than 10 m.Myrs -1 (sometimes as slow as 0.5-0.7 m.Myrs −1 ). Low denudation rates mean slow landscape rejuvenation and sub-aerial exposure of some palaeosurfaces (Gale 1992;Twidale 1997Twidale , 2000Twidale , 2003 suggest that these are of Proterozoic age. In harmony with the palaeo-climatic time dimension we therefore suggest a very conservative benchmark of 1.8 Mya (the Pliocene-Pleistocene boundary), and suggest that all landscapes older than 1.8 Myrs should be considered as old, while those older than 12-15 Myrs (pre-Langhian-Seravallian) should be called ancient (i.e.…”

“…Some old landscapes are found on palaeosurfaces being of extreme antiquity, some being pre-mid-Miocenic and even as old as pre-Cretaceous (e.g. Twidale 2000). However, less extreme ages (as young as 1.8 Myrs; see above) also qualify as OSLs and should have similar characteristics as measured by traits in their biota.…”

Pre‐Quaternary landscape inheritance in Australia

“…Twidale, 1976Twidale, , 2000Gale, 1992). However, while measured rates of long-term (10 5 -10 7 yr timescales) weathering (e.g.…”

Superfícies de erosão do setor centro-oriental da Bacia do Rio Paracatu, no Estado de Minas Gerais

“…Na aplicação prática desses modelos, diversos trabalhos foram desenvolvidos, entre os quais estão os de Fairbridge e Finkl (1978), Twidale (1988Twidale ( , 2000, Gale (1992). No Brasil, os estudos das superfícies de erosão couberam, outros, a De Martonne (1943), Freitas (1951a, King (1956), Barbosa (1959), Almeida (1951Almeida ( , 1964, Ab'Sáber (1949, Barbosa (1965), Varajão (1991), Valadão (1998), Vitte (1998) e Ferraz (2006.…”