Dating of Sediments by physics methods Electron Paramagnetic Resonance (EPR) in the region of Iguape – Cananéia, Brazil.

Dating of sediments was used by physics method in this work, in the physics methods the radioactivity is present, but usually it is method based on the storage of energy of radiation in the solid, in which will be employed. In the present work, Icapara sediment dating was used Electron Paramagnetic Resonance (EPR) method, in this technique the energy absorption occurs when the frequency of the incident wave is in resonance with the energy difference made by the magnetic field between the parallel and antiparallel directions to this field with the irradiated sample that creates defects in its structure. In the state of S˜ao Paulo, in the region of Iguape on the southeast coast, it is a place called Icapara, a large sand terrace that was formed due to sea level fluctation that ocorred more than 130 thousand years ago. A sample was taken from a point about 9 meters above the current control of the sea. An age of about 38,000 ±12,000 and 46,000 ± 7,000 years were obtained (EPR) to correlate with the Quaternary period and will be presented to the data obtained.

The Stages of Debris Flow Activity During the Quaternary in the Xiaojiang River Basin, China

This study aimed to predict the laws and trends of modern debris flow by examining the activity cycle of debris flow during the Quaternary and its relationship with environmental change. The timing of the debris flow activity period was determined using sediment dating data based on typical debris flow deposition profiles selected from various terraces in the Xiaojiang River Basin, China. The relationships between debris flow and environmental change were compared and analyzed using neotectonic history, the deep-sea oxygen isotope δ18O curve, and the loess paleosol series. The results showed that the debris flow activities in the Xiaojiang River Basin could divided into eight activity cycles, namely 11.42 Ma, 0.985 Ma, 0.562–0.52 Ma, 0.218 Ma, 0.137 Ma, 14 Ka, 0.73 Ka, and since 3 Ka. The activity cycle of debris flow deposition coincided with the neotectonically active period. Neotectonic movement has controlled the cycle of large debris flow deposition in the Xiaojiang River Basin since the Quaternary. The sedimentary activity of debris flow was not completely consistent with a warm and humid climate, and the sedimentation activity of debris flow was the result of the combined effects of tectonic movement and climate change.

Residual Hole Concentration in Recombination Centres after Bleaching

Trapped charge dating method using electron spin resonance (ESR) of quartz is progressively used for sediment dating. ESR signals can be used for accurate age estimation only when these signals are zeroed by sunlight exposure before the layer creation or when one knows their ESR residual level (the part of the signal that is not bleached). It is well known that the ESR signal related to the Al-hole centres in quartz used for sediment dating has a significant residual signal. From the point of view of luminescence models, as a hole trap, the Al-hole centre is considered as a recombination centre in quartz. Recently, it was demonstrated experimentally that the ESR signal of the Al-hole centre is dependent on the total dose absorbed by the quartz sample in the past. The same effect was confirmed by simulations of the charge transport processes for a model including two recombination centres. Here, the dependence of residual hole concentration (RHC) in the recombination centres on the total dose absorbed by a sample in the past is studied in detail by computer simulations for a wide range of model parameters. The impact that the various relations of centre parameters have on the dependence of the residual as a function of dose is investigated and the implications for the dating practice are discussed.