240+239Pu depositional signatures as a viable geochronological tool in the Amazon Basin

Depth profiles of dry bulk density (DBD) (g cm^-3) and mass accumulation rates (MAR) (g cm^-2year^-1) of the six sediment cores (PA2, PA9, PA10, RM, PP, PZC) studied in this work.

Depth (cm)	PA2		PA9		PA10		RM		PP		PZC
Depth (cm)	DBD	MAR	DBD	MAR	DBD	MAR	DBD	MAR	DBD	MAR	DBD	MAR
0–2	0.54	0.18	0.48	0.53	1.01	0.34	0.65	0.37	0.89	0.28	0.74	0.33
2–4	0.55	0.19	0.53	0.58	0.89	0.30	0.63	0.36	0.81	0.26	0.56	0.25
4–6	0.58	0.20	0.60	0.66	1.03	0.35	0.77	0.44	0.83	0.26	0.62	0.28
6–8	0.59	0.20	0.56	0.61	1.07	0.36	0.69	0.39	0.84	0.27	0.72	0.32
8–10	0.62	0.21	0.58	0.63	1.04	0.35	0.71	0.40	0.77	0.25	0.72	0.32
10–12	0.61	0.21	0.59	0.65	1.05	0.36	0.75	0.43	0.78	0.25	0.76	0.34
12–14	0.57	0.19	0.63	0.70	1.14	0.39	0.70	0.40	0.94	0.30	0.72	0.32
14–16	0.62	0.21	0.66	0.72	1.10	0.37	0.68	0.39	1.02	0.33	0.91	0.41
16–18	0.58	0.20	0.63	0.69	0.99	0.34	0.66	0.37	1.05	0.33	0.71	0.32
18–20	0.57	0.19	0.62	0.68	1.07	0.36	0.64	0.36	1.00	0.32	0.77	0.34
20–22	0.59	0.20	0.63	0.70	0.96	0.33	0.74	0.42	0.90	0.29	0.78	0.35
22–24	0.59	0.20	0.62	0.68	1.00	0.34	0.70	0.40	1.06	0.34	0.72	0.32
24–26	0.58	0.20	0.61	0.68	0.97	0.33	0.67	0.38	1.00	0.32	0.81	0.37
26–28	0.58	0.20	0.66	0.73	1.05	0.36	0.77	0.44	0.94	0.30	0.96	0.43
28–30	0.59	0.20	0.72	0.79	0.95	0.32	0.71	0.40	0.96	0.31	0.81	0.37
30–32	0.62	0.21	0.71	0.78	0.95	0.32	0.81	0.46	0.96	0.31	0.78	0.35
32–34	0.55	0.19	0.68	0.75	1.30	0.44	0.81	0.46	1.09	0.35	0.81	0.37
34–36	0.57	0.19	0.63	0.69	1.57	0.53	0.77	0.44	1.05	0.34	0.92	0.41
36–38	0.56	0.19	0.70	0.77	1.36	0.46	0.74	0.42	1.00	0.32	0.72	0.33
38–40	0.53	0.18	0.69	0.76	1.36	0.46	0.70	0.40	0.99	0.32	0.77	0.35
40–42	0.54	0.18	0.70	0.77	1.45	0.49	0.72	0.41	0.98	0.31	0.82	0.37
42–44	0.55	0.19	0.69	0.76	1.55	0.53	0.72	0.41	0.98	0.31	0.90	0.40
44–46	0.69	0.23	0.70	0.77	1.75	0.60	0.84	0.48	1.06	0.34	0.95	0.43
46–48	0.68	0.23	0.72	0.79	1.47	0.50	0.77	0.44	0.44	0.32	0.86	0.39
48–50	0.62	0.21	0.68	0.75	1.36	0.30	0.74	0.42	0.42	0.32	0.72	0.39
Average	0.59	0.20	0.64	0.70	1.18	0.39	0.72	0.41	0.91	0.31	0.78	0.35
Stand Dev	0.04	0.01	0.06	0.07	0.23	0.08	0.05	0.03	0.17	0.03	0.09	0.04

Table 2

Sediment accumulation rates (mm year^-1) and inventories (mBq cm^-2)based on the ²¹⁰Pb and ^239+240Pu sediment dating methods.

Study Site	²¹⁰Pb (mm year^-1)	²¹⁰Pb Bq cm^-2	^239+240Pu (mm year^-1)	^239+240Pu (mBq cm^-2)	Major River
PA2	2.7	6.5	2.4	4.9	Tapajos
PA9	18.6	7.0	10.2	1.0	Tapajos
PA10	8.2	53.6	2.3	0.5	Amazon
PP	6.2	22.4	3.4	2.7	Madeiras
PZC	5.8	3.1	4.2	2.0	Madeiras
RM	6.1	40.2	6.2	3.7	Madeiras

^239+240Pu, ²¹⁰Pb, ²²⁶Ra and ²¹⁰Pb_ex profiles from the six sediment cores in this work. The first occurrence of ^239+240Pu indicates ~1950 when these radionuclides were first introduced into the atmosphere. The ~1950 mark on the ²¹⁰Pb_ex profiles are based on the sediment accumulation rates dated through the Constant Initial Concentration (CIC) approach (Appleby and Oldfield, 1992). PP, PZC, RM, PA2, PA9, PA10 - study sites.

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DOI: https://doi.org/10.1515/geochr-2015-0068 | Journal eISSN: 1897-1695 | Journal ISSN: 1733-8387

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Language: English

Page range: 142 - 149

Submitted on: Jan 1, 2017

Accepted on: Apr 21, 2017

Published on: Jun 2, 2017

Published by: Sciendo

In partnership with: Paradigm Publishing Services

Keywords:

plutonium dating,

geochronology,

Amazon floodplain lakes,

sedimentation

Related subjects:

Geosciences,

Geosciences, other

© 2017 Luciana M Sanders, Kathryn H Taffs, Debra Stokes, Alex Enrich-Prast, Christian J Sanders, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Volume 44 (2017): Issue 1 (January 2017)

240+239Pu depositional signatures as a viable geochronological tool in the Amazon Basin

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Table 1

Table 2

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