# Age model, biogenic opal contents and sedimentary U/Th for the last 150 ka at sites J1002 and J1007, Chilean Margin
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#               World Data Service for Paleoclimatology, Boulder
#                                   and
#                      NOAA Paleoclimatology Program
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# Template Version 4.0
# Encoding: UTF-8
# NOTE: Please cite original publication, NOAA Landing Page URL, dataset and publication DOIs (where available), and date accessed when using downloaded data.
# If there is no publication information, please cite investigator, study title, NOAA Landing Page URL, and date accessed.
#
# Description/Documentation lines begin with '#' followed by a space
# Data lines have no '#'
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# NOAA_Landing_Page: https://www.ncei.noaa.gov/access/paleo-search/study/36494
#   Landing_Page_Description: NOAA Landing Page of this file's parent study, which includes all study metadata.
#
# Study_Level_JSON_Metadata: https://www.ncei.noaa.gov/pub/data/metadata/published/paleo/json/noaa-ocean-36494.json
#   Study_Level_JSON_Description: JSON metadata of this data file's parent study, which includes all study metadata.
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# Data_Type: Paleoceanography
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# Dataset_DOI: 10.25921/4kpp-5998
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# Science_Keywords: Other Reconstruction
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# Resource_Links
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# Data_Download_Resource: https://www.ncei.noaa.gov/pub/data/paleo/contributions_by_author/li2022/li2022-expedition379t_j1002.txt
#   Data_Download_Description: NOAA Template File; J1002 G/B Data
#
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# Contribution_Date
#   Date: 2022-06-03
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# File_Last_Modified_Date
#   Date: 2025-05-28
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# Title
#   Study_Name: Age model, biogenic opal contents and sedimentary U/Th for the last 150 ka at sites J1002 and J1007, Chilean Margin
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# Investigators
#   Investigators: Li, Chen; Clementi, Vincent; Bova, Samantha; Rosenthal, Yair; Childress, Laurel ; Wright, James; Jian, Zhimin
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# Description_Notes_and_Keywords
#   Description: 
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# Publication
#   Authors: Li, C.; Clementi, V.J.; Bova, S.C.; Rosenthal, Y.; Childress, L.B.; Wright, J.D.; Jian, Z.; Expedition 379T Scientists
#   Published_Date_or_Year: 2022-09-01
#   Published_Title: The sediment green-blue color ratio as a proxy for biogenic silica productivity along the Chilean Margin
#   Journal_Name: Geochemistry, Geophysics, Geosystems
#   Volume: 23
#   Edition: 
#   Issue: 9
#   Pages: 
#   Report_Number: e2022GC010350
#   DOI: 10.1029/2022GC010350
#   Online_Resource: 
#   Full_Citation: 
#   Abstract: Sediment cores recently collected from the Chilean Margin during D/V JOIDES Resolution Expedition 379T (JR100) document variability in shipboard-generated records of the green/blue (G/B) ratio. These changes show a strong coherence with benthic foraminiferal d 18O, Antarctic ice core records, and sediment lithology (e.g., higher diatom abundances in greener sediment intervals), suggesting a climate-related control on the G/B. Here, we test the utility of G/B as a proxy for diatom productivity at Sites J1002 and J1007 by calibrating G/B to measured biogenic opal. Strong exponential correlations between measured opal% and the G/B were found at both sites. We use the empirical regressions to generate high-resolution records of opal contents (opal%) on the Chilean Margin. Higher productivity tends to result in more reducing sedimentary conditions. Redox-sensitive sedimentary U/Th generally co-varies with the reconstructed opal% at both sites, supporting the association between sediment color, sedimentary U/Th, and productivity. Lastly, we calculated opal mass accumulation rate (MAR) at Site J1007 over the last ~150,000 years. The G/B-derived opal MAR record from Site J1007 largely tracks existing records derived from traditional wet-alkaline digestion from the south and eastern equatorial Pacific (EEP) Ocean, with a common opal flux peak at ~50 ka suggesting that increased diatom productivity in the EEP was likely driven by enhanced nutrient supply from the Southern Ocean rather than dust inputs as previously suggested. Collectively, our results identify the G/B ratio as a useful tool with the potential to generate reliable, high-resolution paleoceanographic records that circumvent the traditionally laborious methodology.
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# Funding_Agency
#   Funding_Agency_Name: Ministry of Science and Technology of China
#   Grant: 2018YFE0202401
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# Funding_Agency
#   Funding_Agency_Name: US National Science Foundation
#   Grant: OCE-1756241
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# Funding_Agency
#   Funding_Agency_Name: Department of Energy's National Energy Technology Laboratory (NETL)
#   Grant: Methane Hydrates Fellowship Program
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# Site_Information
#   Site_Name: J1002
#   Location: Eastern Pacific Ocean
#   Northernmost_Latitude: -46.0716
#   Southernmost_Latitude: -46.0718
#   Easternmost_Longitude: -75.6869
#   Westernmost_Longitude: -75.6872
#   Elevation_m: 1534.85
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# Data_Collection
#   Collection_Name: Expedition_379T_J1002
#   First_Year: 83040
#   Last_Year: 300
#   Time_Unit: calendar year before present
#   Core_Length_m: 129.532
#   Parameter_Keywords: age control, physical properties, reconstruction
#   Notes: 
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# Chronology_Information 
#   Chronology: Radiocarbon
#   Chronology_Download_Resource: https://www.ncei.noaa.gov/pub/data/paleo/templates/noaa-wds-paleo-14c-terms.csv
#     Chronology_Download_Description: Radiocarbon terms and definitions.
#   Chronology_Notes: J1002 Chronology Table
#   Rejection_Rationale:
#   Reservoir_Method:
#   Calibration_Method:
#   Age_Model_Method:
#   Missing_Values: 
#   Chronology_Table:
# lab_code	depth_end_m	depth_start_m	material_dated	age_14C_BP1950	age_14C_1s_yr	date_type	age_calib_BP1950	age_calib_pos2s_BP1950	age_calib_neg2s_BP1950	calib_curve
# UCIAMS-240387	1.605	1.625	G. bulloides	4245	25	14C AMS	4838	4859	4815	IntCal20
# UCIAMS-240388	5.705	5.725	G. bulloides	10925	40	14C AMS	12802	12908	12752	IntCal20
# UCIAMS-240389	7.105	7.125	G. bulloides	13475	45	14C AMS	16244	16391	16058	IntCal20
# UCIAMS-240390	28.305	28.325	G. bulloides	20490	90	14C AMS	24705	24965	24292	IntCal20
# UCIAMS-240391	34.792	34.812	G. bulloides	23950	110	14C AMS	28043	28462	27790	IntCal20
# UCIAMS-240392	46.284	46.304	G. bulloides	26000	160	14C AMS	30207	30499	29995	IntCal20
# UCIAMS-240393	59.883	59.903	G. bulloides	34310	370	14C AMS	39513	40447	38322	IntCal20
# UCIAMS-240394	66.918	66.938	G. bulloides	44000	1600	14C AMS	46445	49790	44024	IntCal20
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# Variables
# PaST_Thesaurus_Download_Resource: https://www.ncei.noaa.gov/access/paleo-search/skos/past-thesaurus.rdf
#   PaST_Thesaurus_Download_Description: Paleoenvironmental Standard Terms (PaST) Thesaurus terms, definitions, and relationships in SKOS format.
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# Data variables follow that are preceded by "##" in columns one and two.
# Variables list, one per line, shortname-tab-var components: what, material, error, units, seasonality, data type, detail, method, C or N for Character or Numeric data)
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## Depth	depth,,,meter,,Paleoceanography,,,N,
## Age	age,,,calendar kiloyear before present,,Paleoceanography,,,N,
## G/B	green intensity/blue intensity,sediment,,dimensionless,,Paleoceanography,,,N,sedimentary green to blue ratio
## Opal%	biogenic silica,sediment,,percent,,Paleoceanography,,,N,
## Notes	notes,,,,,Paleoceanography,,,C,
## Site	sample identification,,,,,Paleoceanography,,,C,
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# Data:
# Data lines follow (have no #)
# Data line format - tab-delimited text, variable short name as header
# Missing_Values: -999
Depth	Age	G/B	Opal%	Notes	Site
0.105	0.3	1.232	4.36	-999	J1002
1.605	4.48	1.262	2.11	-999	J1002
2.905	7.24	1.224	2.87	-999	J1002
4.305	9.98	1.207	2.61	-999	J1002
5.705	12.84	1.139	1.69	-999	J1002
7.105	15.98	1.123	1.07	-999	J1002
36.192	28.35	1.018	0.63	-999	J1002
43.194	29.69	1.003	0.36	-999	J1002
59.883	39.6	1.114	0.91	-999	J1002
61.303	40.92	1.05	0.7	-999	J1002
64.113	43.55	1.088	0.81	-999	J1002
92.216	55.12	1.199	1.45	-999	J1002
104.965	67.8	1.04	0.62	Data_points_with_underestimated_opal_contents.	J1002
121.762	81.39	1.039	1.53	-999	J1002
124.482	83.04	1.12	1.04	-999	J1002