Note the problematic age constel- lation of sample HBSL Such a relationship can be explained by non-monotonic cooling involving a rapid thermal overprint. The three single grain ages could only be modeled together assuming an U-depleted outer core for grain He A, B, C, D indicate the general thermal history, fault related thermal overprint, timing of temperature equilibrium and the post tectonic common thermal history see Figure 2.

In contrast, the majority of good 0. Fission Track Resultsa E-Long. Fission track ages are reported as central ages. Central FT age, 1s: A conjugated set of SW Sri Lanka. Faults are coated with Mn rich calcite fault data, and from the correlation between sample altitudes Figure 6, sample HBSL Joints and fractures show and distance of the sample location to the continental margin mainly a NE-SW trend Figure 5. In contrast, samples from MTL of Such a pattern could imply downwearing of a secondary mountain range or basin inversion followed by localized 5.

The timing of rock cooling in SW Sri Lanka coevals with phases of intracontinental rifting and the age of 5. Most undeformed base- nental break-up history when erosion along the evolving rift ment samples have significantly older FT ages than the fault shoulders and continental margins occurred. The eroded samples Figure 7. Mainly four basins may examined crustal section Figures 2 and 8, path A.

It refers represent suitable sedimentary sinks: Here, coarse to medium lasting erosional response to major geological processes. Gravity studies suggest a maximum thickness of 1. Cooling rates of this time span vary between 0. Other possibilities are the 0. Depending on the degree of thermal overprint apatite FT ages may vary between ca. A, B, C, D indicate the general thermal history, fault related thermal overprint, timing of temperature equilibrium and the post tectonic common thermal his- tory see Figure 2.

These natural uncertainties exclude present northern continental margin of northern Mozambique. Instead, results of every sample the Permian — Jurassic Figure 1a. Both basins contain con- have to be evaluated individually. We point out the fact that tinental sediments of late Jurassic to Early Cretaceous age thermochronological data do not necessarily refer to a which can reach an offshore thickness of several kilometers distinctive, generic fault age.

Dating of faulting activity [e. Seismic data suggest older on the base of thermochronological data has to consider Karoo-aged sediments in the deeper parts of the basins.

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However, faults have not been samples. The fault samples represent reheating events of dated and reactivation of older faults could not be distin- different degree e.

We defined the thermal ]. Depending on lithology, mode and depth of fault- ated fault samples reach a temperature equilibrium with the ing, and fluid availability, thermal conditions range from surrounding rock represented by the t-T histories of the mild hydrothermal activity to magmatic injection and fric- corresponding unfaulted samples e. The different degree of thermal HBSL In brackets data which were used as a temporal constraint.

Main composition of fault coating was analyzed by Raman spectroscopy or by visual inspection. Sigma 3 is the direction of extension calculated by fault kinematic data see Figure 5. The timing largely overlaps with the ages of the rock Figures 3d—3f. Cauvery basins Figure 1c. Furthermore, Mesozoic — [43] Paleostress directions were determined from four Ma igneous activity at the continental margins of central localities, all characterized by varying fault directions Gondwana and in Sri Lanka is likely responsible for fluid- Figures 1 and 5 and Table 3.

The dominant directions of fault interaction during this deformation stage. We relate this three localities could be related to a distinctive thermal faulting phase to the initial crustal extension between East overprint OC06—07, OC13, OC23—26 , and a conjugated Antarctica and Sri Lanka Figure 10 which triggered the fault set was dated in one locality OC70— Paleostress data indicate a continuous N-S exten- paleostress dating. The new data help constraining timing cooling path of sample HBSL Paleo-reconstructions and sedimentological evidences.

Faulting Madagascar [Storey et al. Sample HBSL was affected by a A contemporaneous cooling step is observed by apatite FT second low-temperature thermal stage but temperatures of data on the continental margin of western India [e.

It corresponds to the again. Paleo- reconstructions are taken from Desa et al.

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Arrows indicate the paleo-orientation of crustal extension based on rotated paleostress data see Figure 5. The timing of faulting processes on low ground near the western coast of Sri Lanka. Requirements for successful fault dating are: Alterna- the thermochronological record, ii faulting should post- tively, brittle deformation may have occurred subsequent to date general exhumation, and iii post tectonic cooling lateral erosion and would then be restricted to the surface must not exceed the thermal sensitivity of the applied level.

However, shape, orientation and location of the methods. Southern Escarpment Figure 1b , together with the ther- [53] The low-temperature thermochronological data of Sri mochronological data show that post-Gondwana faulting Lanka suggest two main exhumation stages at — Ma also exerts major control on the landscape of Sri Lanka. Break-up related tectonics has a significant control lithosphere. Instead, our data suggest that most of the sam- on the present-day landscape of Sri Lanka.

Nevertheless, the intensely jointed [54] Acknowledgments. Kumar for the preparation of the zircon ] confirm younger brittle deformation undetected by FT samples and Y. Qu for his help with the Raman spectroscopy. The qual- low-temperature thermochronology. Geo- minations using fault slip data, J.

Razakamanana , From oro- Campanile, D. Implications car , a multi-thermochronometer approach, Gondwana Res.

Hamana , Carslaw, H. Evidence for Oxford Univ. Chandra mochronometry data, Rev.

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Thermochronology - Wikipedia

Carlson , Variability of Cooray, P. Extrapolation to geological Ceylon , pp. Kehelpannala , A layered basic intru- along the San Gabriel fault, California: Evidence from fission-track ther- sion, deformed and metamorphosed in granulite facies of the Sri Lanka base- mochronology, Geology, 31, —, doi: Williams , Age of metamorphism in the high- Desa, M. Ramprasad , Seafloor spreading grade rocks of Sri Lanka, J. Kaul , Evolution of east coast doi: India, 73, De Wit, M. Fachmann , Phanerozoic history of the Mahanadi annurev. Bons , Mechanisms of fluid flow and Ehlers, T.

Geofluids, 1, —, doi: Acs , Easy handling of tectonic data: Graser , Phanerozoic tions and solubilities of fracture-sealing minerals, Tectonophysics, , upper crustal tectono-thermal development of basement rocks from 1—26, doi: An integrated fission-track and structural study, Parry, W.

Murphy Tectonophysics, , 61—86, doi: Belle , Mesozoic tectono-stratigraphic evo- Possible identification of thermally overprinted crustal segments? Joseph , 40 and R. An example from northern Mozambique, Tectonics, 30, granulite terrain, Tectonophysics, , —, doi: General behavior Ramsey, J. Res, B2 , Geology, vol. Laslett , Statistical models for mixed fis- Redfield, T. Gabrielsen sion track ages, Nucl. Constraints from new apatite fission track Gleadow, A. What are the real data, Phys. Earth, Parts A—C, , — Sahu , Tight reassembly of Glotzbach, C.

Frisch, and Gondwana exposes Phanerozoic shears in Africa as global tectonic C. Abdula , Development of the Mozambique and Laslett , Thermal annealing of fission tracks in apatite 1. A quali- Ruvuma sedimentary basins, offshore Mozambique, Sediment. Hurford , Neogene structural evolution of the Sierra San Felipe, Baja , Denudation history of the continental margin of western penin- California: Evidence for proto-gulf transtension in the Gulf Exten- sular India since the early Mesozoic - reconciling apatite fission-track sional Province?

Dating Methods

Schubert , Geodynamics. Application of 00 Continuum Physics to Geological Problems, pp. With some knowledge of the subsurface thermal structure, these dates are translated into depths and times at which that particular sample was at the mineral's closure temperature.

If the rock is today at the surface, this process gives the exhumation rate of the rock. Reviews in Mineralogy and Geochemistry. From Wikipedia, the free encyclopedia. References [ edit ] Reiners, P. This geochronology article is a stub. You can help Wikipedia by expanding it. Retrieved from " https: Radiometric dating Geochronology stubs Tectonics stubs.