The Mariana Trench remarkable geological features on Earth.pptx
Dating aeolian sediments using ESR Ti-Li ISRP.pptx
1. Dating aeolian sediments
using Ti-Li center in quartz,
TL, OSL-SAR: Dama Branca
study.
LUCAS CARMO, SHIGUEO WATANABE, RAFAELA DE JESUS, JOSÉ F.CHUBACI
IPEN – UNIVERSITY OF SÃO PAULO
University of São Paulo
Ipen-SP
LACIFID
Institute of Physics
FAPESP
1
5. Sample collection
Sediments were collected using
PVC tubes at different heights
and depths from the positions
mentioned before (DB and
2DB)
The objective is to identify
different ages at different
heights and depths, evidencing
the different ages of sediment
establishment depending on its
relative position in a dune.
Trench 1 m x 1 m
Trench 1 m x 1 m
PVC tube 1 m length
Coupled PVC tubes (2 m)
Exemple of Sample Collection
Dune
5
9. Preparing samples for dating: Quartz
concentrate
Sediments wet sieved to retain grains of 150 – 90 μm
Samples were chemically washed using HCl 10% followed by H2O2 27%,
HF 48% for 40 min and HCl 10% aiming removal of carbonates, organic
material, feldspars as well as an outer layer of the quartz grains to
exclude the alpha radiation contribution, respectively.
Density separation using solution of Sodium Polytungstate at densities of
2,75 g/cm³ and 2,65 g/cm³ to remove heavy minerals and remaining
feldspars, respectively.
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10. Trapped Charge Dating of sediments
Based on radiation energy deposited in matter (quartz, in thiswork).
It can be splitted into two parts:
Accumulated Dose Measurement (DE): Measurement of absorbed dose
induced by natural radiation in sediment quartz grains (Gy)
Natural Dose Rate Measurement (DR): Measurement of Uranium, Thorium
and Potassium-40 concentrations in the sample environment. Natural Dose
Rate (Gy/year)
𝑨𝒈𝒆 =
𝑫𝑬
𝑫𝑹
10
12. OSL-SAR flowchart
Radiation
Preheat
Measurement
(L)
Radiation test
dose
Cut heat
Measurement
(T)
Regenerative
Loop
(variable dose)
Correction
Loop
(constant dose)
SAR
Protocol
L/T
signal
Dose (Gy)
Natural dose
Natural L/T
intensity
Calibration curve for
only one aliquot
16 aliquots of a particular sample are measured.
The final result of accumulated dose is calculated
using common or central age models
(Galbraith, et al., 1999).
L
T
13. OSL-SAR Results
De values were calculated using models proposed by
Galbraith, et al., (1990)
1600 1800 2000 2200 2400
0
2
4
6
8
10
12
Frequency
Equivalent Dose (mGy)
2DB10
De = 2070.53 ± 66.79 mGy
440 480 520 560 600 640
0
2
4
6
8
10
12
De = 541.85 ± 17.23 (mGy)
DB11
Frequency
Equivalent Dose (mGy)
1200 1400 1600 1800 2000 2200
0
2
4
6
8
10
12
Frequency
Equivalent Dose (mGy)
2DB11
De = 1647.04 ± 52.4 mGy
13
Samples the zero point (base)
14. OSL-SAR Results
0 10 20 30 40 50 60
0
2
4
6
8
Frequency
Equivalent Dose (mGy)
DB20
De = 36.88 ± 1.58 mGy
40 50 60 70 80 90
0
2
4
6
8
De = 67.09 ± 2.27 mGy
Frequency
Equivalent Dose (mGy)
DB30
50 60 70 80 90
0
2
4
6
8
10
De = 71.92 ± 2.36 Gy
Frequency
Equivalent Dose (mGy)
DB40
20 30 40 50 60 70 80
0
2
4
6
8
10
Frequency
Equivalent Dose (mGy)
2DB20
De = 52.07 ± 2.51 mGy
14
De values were calculated
using models proposed
by
Galbraith, et al., (1990)
Samples from upper positions
18. Conclusions
Dating aeolian sediments is useful to study dune mobility and stabilization
The OSL ages shown that samples from the dune’s base (2DB10, 2DB11 and
DB11) were always older due to better stabilization.
In the case of 2DB10 and 2DB11, both samples belong to the same mound,
but 2DB10 is deeper. The OSL age difference between them is 0.69 ± 0.04
kyears.
As the height increases, the younger is the sediment.
The studied dunes, accordingly to the presented results, are formed by a well-
established sediment at the base with a recent established sediment
mounted above. Evidencing its activity.
18
