Crustal subsidence

What can late Archaean sedimentary basins tell us about the early Earth system1 Sedimentary basins develop as a response to the interaction between sediment supply and crustal subsidence. In detail this reflects the complex interplay of tectonism, magmatism, eustasy and weathering rates, which are themselves a function of paleoclimate (Eriksson et al., 2001). In the late Archaean probably a number of these factors were different from the modern. For example there is evidence that climatic regimes were different and so it is likely that weathering rates and sediment supply were also different (Chapter 5, Section 5.3.2.1). In addition, many believe that the mantle was hotter at this time. If this is the case then tectonic processes and subsidence rates would also be different from those of modern sedimentary basins. 

The above-mentioned changes in paleogeography, volcanism, crustal movement (subsidence and uplift), and stress field clearly demonstrate that these features of back-arc volcanism in early-middle Miocene are quite different from those of Island arc volcanism in late Miocene to present. According to Yoshida and Yamada (2001), the age of change in volcanism from back-arc type to Island arc type in Northeast Honshu was 12.7 Ma and this age corresponds to the age of Kuroko formation. 

Tectonic processes, by contrast, can be simplified to two parameters. These are vertical uplift, which creates crustal source areas for weathering and erosion, and subsidence, which together with eustasy acts to control the accommodation space availaltle for accumulation of sediments (e.g., Sloss, 1962). 

According to Equation 14.1, the eustatic sea-level changes as well as the vertical crustal movements. The eustatic change is regarded constant over the whole area. Hupfer et al. (2003) propose a local eustatic rise of l.Omm/year for the last century within the western Baltic Sea. The vertical crustal movements show remarkable differences over the entire Baltic Sea area (Fig. 14.3), reflecting here the glacioisostatic adjustment (GIA). The center of uplift is in the Bothnian Bay, with a rate of about 9 mm/year. The coast of the southern Baltic Sea shows subsidence reflecting compensation currents in the upper mantle. 

Heat flow data provide important constraints on mantle models. For example, combined with the heat producing element content of crust and mantle rocks, and the physical properties of mantle minerals, they can be used to constrain the nature of thermal convection in the mantle. In addition, variations in the mantle contribution to crustal heat flow between the continents and oceans have been used to make inferences about the nature of the different types of mantle underlying continental crust and oceanic crust (Section 3.1.2 and Chapter 4, Section 4.3.1.2). Furthermore, heat flow data, combined with bathymetric measurements, rates of sea-floor subsidence, and the depth of seismic discontinuities are all a function of mantle temperature and can be used to estimate relative, lateral variations in mantle temperature (Anderson, 2000). 

Physical Crustal uplift and subsidence Solid-state deformation Erosion by water and wind Rock disaggregation by chemical and biological attack Solid-solution-gas reactions Dissolution, precipitation, cementation, corrosion... 

A sedimentary basin is a depression in the Earth s crust, usually the result of subsidence over a considerable period of time, forming a depositional site where a large thickness of sediment can accumulate. Lithospheric movement is involved (Fig. 3.24), resulting from thermal and tectonic (crustal plate movement) processes. There are three main causes ... 

Crustal thinning by extensional tectonics, causing fault-controlled subsidence (e.g. rift basins like the North Sea, and strike-slip basins as formed along the San Andreas fault zone). 

Howard KA, Foster DA (1996) Thermal and unroofing history of a thick, tilted Basin and Range crustal section, Tortilla Moimtains, Arizona. J Geophys Res 101 511-522 Hu S, O Sullivan PB, Raza A, Kohn BP (2001) Thermal history and tectonic subsidence of the Bohai Basin, northern China a Cenozoic rifted and local pull-apart basin. Phys Earth Planet Inti 126 231-245 Hughes JM, Cameron M, Crowley KD (1989) Stractural variations in natural F, OH, Cl apatites. Am Mineral 74 870-876... 

Fig. 15.6 The subduction of a lithospheric plate during the Mesozoic Era caused the eruption of felsic and mafic lavas in the Antarctic Peninsula and in Marie Byrd Land. The crust of Gondwana in the back-arc basin was stretched which caused block-faulting and subsidence of the Byrd Subglacial Basin. Crustal extension of the back-arc basin may also have caused rifts to form in the Ross orogen and in the overlying rocks of...

The drill site is located on the western edge of the Victoria Land Basin which extends to a depth of about 15 km below sea level and is filled with sedimentary and volcanic rocks on a basement of granitic gneisses. The sedimentary rocks are in large part of glacial origin. The Victoria Land Basin formed by crustal extension and subsidence related to the Cenozoic West Antarctic Rift (Section 15.5.5). 

The abrupt changes in depositional environments, styles and tectonic setting of Middle and Late Proterozoic rocks and their associated uranium deposits are significant evidence of extensive changes in supracrustal processes. Calc-alkaline volcanic and ophiolitic oceanic crustal suites are lacking in strata of this age. " Rock sequences are dominated by shallow marine to fluvial arenaceous clastic and carbonate sedimentary strata, and subaerial tholeiitic basalt and related shallow intrusions, all deposited in passively subsiding, rift-controlled basins. Oro-... 

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