Citation:

PANGAEA.948709

Name: Iceberg-Rafted Debris data from South Atlantic for study of Antarctic Ice Sheet stability over last ~500 kyrs
Published: 2022-09-21
License: https://creativecommons.org/licenses/by-sa/4.0/
Keywords: Antarctic ice sheet stability; iceberg rafted debris; ODP 177-1090; ODP TN0576-PC4

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Abstract:

This database contains the data resulting from a study of Antarctic Ice Sheet history, over the last ~500 thousand years. Iceberg-rafted debris (IRD), considered as an indicator of the presence of a continental ice sheet in the source area, is counted and analyzed in relation to the other components of the studied size fraction. The study materials are derived from two cores raised from a deep-water marine site in the southeastern Atlantic Ocean: the piston core TN057-6-PC4 and the associated drill core from the Ocean Drilling Program (ODP) Leg 177 Site 1090 (177-1090). Because the top portion of the 177-1090 drill core was apparently disturbed by the drilling, the piston core TN057-6-PC4 has been used to represent the most recent part of the record. The site is located at ~43 deg S, 9 deg E, about 2/3 of the way from the Antarctic coast to South Africa. The location from which both cores were raised is on the southern slope of the Agulhas Ridge, on the northern edge of the Agulhas Basin, in the southeastern Atlantic Ocean.

The initial cleaning and preparation of samples from these cores was carried out by Kathryn Venz and David Hodell (UF). The methods used here to examine the IRD are those described by Allen and Warnke (1991, doi:10.2973/odp.proc.sr.114.118.1991), Stanton (1997), and Murphy et al. (2002, doi:10.1016/S0031-0182(01)00495-3). The samples were first weighed, then separated by sieving into four size fractions: <150 microns, 150-250 microns, 250 microns to 2 mm, and >2 mm. The medium to coarse sand size fraction (250 microns to 2 mm) was utilized for our study. Within this, a split of about 1000 grains was obtained; the grains in this split were counted. Grains that were counted within categories that included: quartz, feldspar, mafic minerals, lithic fragments, volcanic lithics, volcanic ash, diatoms, planktic forams, benthic forams, radiolarians, and 'other'. The counts of quartz, feldspar, mafic minerals and lithic non-volcanic fragments were then summed as IRD. Following the suggestion of Murphy et al. (2002), the final step of this stage was a brief overview of the non-counted portion of the 250 micron to 2 mm size fraction, primarily to look for 'background rafting'. Background rafting refers to the presence of IRD in the non-counted portion (i.e., outside of the counted split) of the size fraction. For this study, a note was made of the presence or absence only of any IRD clasts in the non-counted portion.

Keyword(s):

Antarctic ice sheet stability; iceberg rafted debris; ODP 177-1090; ODP TN0576-PC4

Related to:

Teitler, Lora; Warnke, Detlef A; Venz, Kathryn A; Hodell, David A; Becquey, Sabine; Gersonde, Rainer; Teitler, Winston (2010): Determination of Antarctic Ice Sheet stability over the last ∼500 ka through a study of iceberg-rafted debris. Paleoceanography, 25(1), https://doi.org/10.1029/2008PA001691

Further details:

Stanton, Cathy (1997): History of ice rafted debris at ODP Leg 162, Site 982, in the North Atlantic for the past 2 million years [thesis]. California State University, Hayward, Hayward, CA

Project(s):

Ocean Drilling Program (ODP)

Coverage:

Median Latitude: -42.913533 * Median Longitude: 8.799900 * South-bound Latitude: -42.913700 * West-bound Longitude: 8.600000 * North-bound Latitude: -42.913300 * East-bound Longitude: 8.900000

Date/Time Start: 1997-12-26T15:22:00 * Date/Time End: 1997-12-30T00:55:00

Minimum DEPTH, sediment/rock: 0.030 m * Maximum DEPTH, sediment/rock: 17.010 m

Event(s):

177-1090B * Latitude: -42.913700 * Longitude: 8.899700 * Date/Time Start: 1997-12-26T15:22:00 * Date/Time End: 1997-12-28T14:55:00 * Elevation: -3699.4 m * Penetration: 397.5 m * Recovery: 373.23 m * Location: South Atlantic Ocean * Campaign: * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 43 cores; 397.5 m cored; 0 m drilled; 93.9 % recovery

177-1090D * Latitude: -42.913600 * Longitude: 8.900000 * Date/Time Start: 1997-12-28T23:25:00 * Date/Time End: 1997-12-30T00:55:00 * Elevation: -3702.1 m * Penetration: 225.9 m * Recovery: 213.64 m * Location: South Atlantic Ocean * Campaign: * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 24 cores; 225.9 m cored; 0 m drilled; 94.6 % recovery

TN057-6-PC4 * Latitude: -42.913300 * Longitude: 8.600000 * Elevation Start: -3751.0 m * Elevation End: -3701.6 m * Recovery: 12.76 m * Method/Device: Piston corer (PC)

Parameter(s):

#	Name	Short Name	Unit	Principal Investigator	Method/Device	Comment
1	Event label	Event		Teitler, Lora
2	Sample code/label	Sample label		Teitler, Lora	DSDP/ODP/IODP sample designation
3	Section	Sect		Teitler, Lora
4	Depth, section	Depth sect	cm	Teitler, Lora
5	DEPTH, sediment/rock	Depth sed	m	Teitler, Lora	IODP Depth Scale Terminology	Geocode – mbsf
6	Size fraction 2-0.250 mm, coarser sand	2000-250 µm	g	Teitler, Lora
7	Number of subsamples	Subsamples	#	Teitler, Lora		# of splits of size fraction to obtain a split of ~1000 grains
8	Quartz	Qz	#	Teitler, Lora	Counted
9	Feldspar	Fsp	#	Teitler, Lora	Counted
10	Mafic minerals	Mafic min	#	Teitler, Lora	Counted
11	Lithic grains	Lithic	#	Teitler, Lora	Counted	Non-volcanic lithics other than Qz, Fsp, or Mafic
12	Lithic grains, volcanic	Lithic volc	#	Teitler, Lora	Counted
13	Tephra or volcanic ash	Tephra	#	Teitler, Lora	Counted
14	Diatoms	Diatoms	#	Teitler, Lora	Counted
15	Foraminifera, planktic	Foram plankt	#	Teitler, Lora	Counted
16	Foraminifera, benthic	Foram benth	#	Teitler, Lora	Counted
17	Radiolarians	Rad	#	Teitler, Lora	Counted
18	Grains, other	grains other	#	Teitler, Lora	Counted
19	Grains, counted/analyzed	Grains	#	Teitler, Lora	Calculated	Total grains count (in split)
20	Garnets, presence/absence	Garnets presence		Teitler, Lora		Presence of garnets (yes=1, no=0)
21	Dictyocoryne profunda, presence/absence	D. profunda presence		Teitler, Lora		Presence of D. profunda (yes=0.8, no=0)
22	Sample comment	Sample comment		Teitler, Lora
23	Iceberg rafted debris grains, total, in subsample	TIRD grains subsample	#	Teitler, Lora	Calculated	TIRD{split} = Qz + Fsp + Mafic + Lithic counts
24	Iceberg rafted debris index	IRD index		Teitler, Lora	Calculated	defined as a percent: IRDI = [TIRD{split} / (TIRD{split} + Foram plankt{split})] × 100
25	AGE	Age	ka BP	Teitler, Lora	Adopted from Hodell et al. (2000); Venz and Hodell (2002)	Geocode
26	Sedimentation rate	SR	cm/ka	Teitler, Lora	Calculated	SedRate = depth increment (sample, in cm)/age increment (sample, kyr)
27	Iceberg rafted debris grains/total grains ratio	IRD/tot grains		Teitler, Lora	Calculated	IRD Ratio = TIRD{split} / Grains tot{split}
28	Accumulation rate, mass	MAR	mg/cm²/ka	Teitler, Lora	Calculated	MAR = SedRate × Dry Bulk Density (DBD). Note: because we did not have measured DBDs for our samples, in order to calculate MARs we used an average DBD of 0.8 g/cm³ (or, 800 mg/cm³)
29	Accumulation rate, apparent mass	AMAR	mg/cm²/ka	Teitler, Lora	Calculated	AMAR = MAR × IRD ratio
30	Sample, dry mass	Samp dm	g	Teitler, Lora	Calculated
31	Iceberg rafted debris, grains, per dry mass	IRD grains/dm	#/g	Teitler, Lora	Calculated	Total IRD {size fraction} = TIRD {split} × (2 raised to the power of #splits)
32	Iceberg rafted debris, mass, minimum	IRD m min	mg	Teitler, Lora	Calculated	IRD min wt = IRD Ratio × Szfrac M × 1000
33	Iceberg rafted debris, mass, per dry mass	IRD/dm	mg/g	Teitler, Lora	Calculated	IRD mg/g = IRD min wt / Samp dM
34	Fragmentation	Fragm	%	Teitler, Lora	Adopted from Hodell et al., 2001	TN057-6-PC4 only
35	Radiolarians	Rad	%	Teitler, Lora	Calculated	Radiolarians / Total grains count {split} × 100
36	Foraminifera	Foram	%	Teitler, Lora	Calculated	(Foram plankt + Foram benth) / Total grains count {split} × 100
37	Volcanic grains, total, in subsample	Volc grains tot subsample	#	Teitler, Lora	Calculated	Volc lithics + Tephra

License:

Creative Commons Attribution-ShareAlike 4.0 International (CC-BY-SA-4.0)

Status:

Curation Level: Enhanced curation (CurationLevelC)

Size:

12810 data points

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