LAKE MICHIGAN CORE SAMPLE DATABASE

The following is a description of the relational databases that contain all measurements and samples from cores taken in 1988 and 1989 as part of the U.S. Geological Survey's Southern Lake Michigan Project.

Map of track lines and core locations

The primary database file is called LMSAMPLE; it contains all information related to the samples or measurements themselves. The first three fields in this database file are SAMPLE, SITE, and TYPE. All of the fields in each of the database files are described in detail later, but these fields are mentioned here because they are used to link the various database files.

Information related to the location, depth, and length of the cores is contained in the database file CORELOC. It is linked to LMSAMPLE by the common combined fields SITE and TYPE.

All measurements and analyses are contained in a series of database files called XXXX-RES, where XXXX is denotes the particular type of analysis. The XXXX-RES databases are linked to LMSAMPLE by the field SAMPLE.

The relations between the database files are shown diagramatically below, where "...." indicates additional fields that are described in detail later.

CORELOC: SITE TYPE ....

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LMSAMPLE: SAMPLE SITE TYPE ....

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XXX1-RES: SAMPLE .... .... ....

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XXX2-RES: SAMPLE .... .... ....

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XXX3-RES: SAMPLE .... .... ....

CORELOC

CORELOC contains the basic information on location, depth, and length of the cores it contains the following fields.

SITE: The site number of the coring station. Multiple cores were collected at each site.

TYPE: The type of core collected:

B, box core, Mini-Sutar type, sampled in 10 cm thin-walled tubes

G, gravity core, Woods Hole giant gravity corer, 10 cm diameter

P, piston core, modified Benthos type, 6.3 cm diameter

V, vibracore, Alpine type, 9 cm diameter

LATITUDE: Latitude in decimal degrees north.

LONGITUDE: Longitude in decimal degrees west.

DEPTH: Water depth in meters

LENGTH: Length of recovered core in cm

The combination of core SITE and core TYPE is unique and is used as the link to the LMSAMPLE database file

LMSAMPLE

LMSAMPLE is the main sample and measurement database. It is linked to CORELOC by the unique combination of core SITE and core TYPE. It contains all the basic data related to each sample or measurement. It is linked to the various analysis databases by the field SAMPLE. It contains the following fields:

SAMPLE: Sample number; every sample number is unique.

SITE: Core site number

TYPE: Type of core: B, box; G, gravity; P, piston; V, vibracore. See description of CORELOC for details.

TOP: Top of sampling interval, in cm.

BOT: Bottom of sampling interval, in cm. Same as TOP if sample is a point sample.

ANALYSIS: Type of analysis or measurement, as follows:

1. 18O-13C: Stable isotope measurements (18O and 13C) on biogenic carbonate. Results are stored in the database ISO-RES.

2. 210Pb: Lead-210 analyses. Results are stored in PB-RES.

3. AMS: AMS radiocarbon analyses. Results are stored in AMS-RES.

4. clay mins: Clay mineralogy. Results are stored in CLAY-RES.

5. geochem: Sulfur, sulfur isotope, carbon, phosphorus, and iron geochemistry. Results are stored in CHEM-RES.

6. mollusks: Mollusk abundances. Results are stored in MOLL-RES.

7. MS: Magnetic susceptibility measurements. Results are stored in MSR-RES and MSK-RES.

7. paleo: Paleontology (ostracodes, diatoms, and pollen). Because of poor preservation of diatoms and pollen, only ostracode results are reported, in OSTR-RES.

8. pmag: Paleomagnetic analyses. Results are stored in PMR-RES and PMK-RES.

9. rmag: Analyses of sediment magnetic properties. Results are stored in RMAG-RES.

10. texture: Grain-size analyses. Results are stored in TEX-RES.

11. water cont: Water content analyses. Results are stored in H2O-RES.

ANALYST: Last name of person who performed analysis (us = Colman et al.)

DATEOUT: Date sample submitted for analysis or date analysis begun.

DATEIN: Date results of analysis received.

COMMENT: Any comments about sample.

ANALYSIS RESULTS DATABASES (Skeletal)

The following databases contain the analytical results of the various types of measurements and analyses performed on core samples. Each database is linked to LMSAMPLE by its first field, SAMPLE, which is unique to each sample. [Each database should contain a description of the type of analyses, the methods used, and a description of each of the fields, including the units used. AMS-RES should serve as an example.]

AMS-RES: This database contains the results of accelerator-mass spectrometer (AMS) radiocarbon analyses. Carbonate samples were obtained by hand-picking 5 to 10 mg of ostracodes and small (< 2 mm diameter) mixed-species mollusk shells. Carbon dioxide was obtained by acidifying the shells with phosphoric acid in vacuo (Jones et al., 1989). For hand-picked carbon and total organic carbon samples, the sample was acidified with organic-free HCl and filtered through a nominal 1 m diameter pre-cleaned quartz-fiber filter. Reaction tubes were cleaned by soaking overnight in a chromerge solution, then roasted in air at 550 oC for two hours. The sediment and filter were added to the reaction tube along with 2 g of copper oxide and a 2-by-12 mm strip of silver foil. The tube was evacuated, flame sealed, and then heated in a muffle furnace at 550 oC for 5 hours.

Carbon dioxide from the shell and organic carbon samples was reduced to carbon monoxide over hot zinc and further reduced over hot iron to elemental graphite (Slota et al., 1987). The graphite targets were prepared at the Woods Hole Oceanographic Institution and analyzed at the National Accelerator Facility at the University of Arizona.

The database contains the following fields:

1. SAMPLE: Sample number, linked to LMSAMPLE.

2. AGE: Calculated age, in years B.P. (before 1950), corrected for 13C fractionation. A value of -2 indicates insufficient sample after hand picking; a value of -1 indicates insufficient sample during or after perparation to the CO2 stage.

3. ERROR: Analytical error (one sigma), in years.

4. MATERIAL: Code for analyzed material: CARB, biogenic carbonate (ostracodes or mollusks); TOC, total organic carbon; POM, hand-picked organic matter.

5. WHLABNO: Laboratory sample number at the Woods Hole Oceanographic Intitution's radiocarbon preparation laboratory.

6. AZLABNO: Laboratory sample number at the National Accelerator Facility at the University of Arizona.

CHEM-RES: This database contains the results of a variety of geochemical analyses, including different species of sulfur, iron, carbon, phosphorus, and sulfur isotopes.

.....

The database contains the following fields:

1. SAMPLE: Sample number, linked to LMSAMPLE.

2. SAV

3. S2

4. SO4

5. SORG

6. STOT(SUM)

7. STOT(MEASURED)

8. CTOT

9. CORG

10. CCARB

11. CR FE

12. AV FE

13. ELEM P

14. DEL-34SAV

15. DEL-34S2

16. DEL-34SORG

CLAY-RES: This database contains the results of clay mineral analyses. No results are available at the present time.

H2O-RES: This database contains the results of water content analyses. Measured volumes (ca. 3-5 cm3) of sediment were taken from the split core soon after the core was split, using a syringe as a small piston corer. Samples were weighed before and after dring at 60 oC overnight. Values that depend on volume (bulk density and grain-specific gravity) are potentially in error because of the difficulty in measuring volume accurately. Grain-specific gravity values of 2.5 to 2.7 suggest accurate volume values. Water content, which does not depend on volume, is more accurate than bulk density.

The database contains the following fields:

1. SAMPLE: Sample number, linked to LMSAMPLE.

2. PER_H2O: Water content, in weight percent

3. WET_SG: Wet specific gravity (bulk density), i.e. weight of solids and liquids divided by volume, in g/cm3.

4. DRY_SG: Dry specific gravity (bulk density), i.e. weight of solids only divided by volume, in g/cm3.

5. GSG: grain specific gravity (bulk density), i.e. weight of solids divided by volume of solids, in g/cm3.

ISO-RES: This database contains the results of stable carbon and oxygen isotopic analyses. Samples were prepared for stable-isotope analysis by selecting a few ostracode or mollusk shells from the samples prepared for paleontologic analyses and lightly crushing them in methanol. The samples were acidified with phosphoric acid in vacuo, and were analyzed on a VG Micromass 602D mass spectrometer following the procedures outlined by Keigwin (1979). All values are reported relative to the PDB standard.

MOLL-RES: This database contains the results of mollusk identifications and abundances. No results are available at the present time.

MSK-RES: This database contains results of whole-core magnetic susceptibility measurements. Magnetic susceptibility of the cores was measured by J.W. King at 3-cm intervals using a pass-through Bardington coil.

MSR-RES: This database contains results of whole-core magnetic susceptibility measurements. Magnetic susceptibility of the cores was measured by R.L. Reynolds at 3-cm intervals using a pass-through coil having a measurement field about 6 cm long. Susceptibility was measured at a frequency of 800 Hz in field of 0.1 mT using a commercial susceptibility meter having a sensitivity of about 1.0 x 10-7 emu/cm2 (1.3 x 10-6 volume SI).

OSTR-RES: This database contains the identifications and abundances of ostracodes in core samples. Ostracodes and mollusks were separated from the sediment and processed according to the following procedure. About 40 to 60 g of raw sediment from a core interval of 3 cm was frozen, placed in a beaker, weighed, and allowed to thaw. Once thawed, approximately 500 ml of boiling deionized water was added to the sediment followed by approximately 5 to 7 g of baking soda (NaHCO3). The sample was allowed to cool to room temperature, 5 to 7 grams of commercial Calgon (sodium hexametaphosphate, sodium carbonate, and soap) was added, and the sample was allowed to stand for at least one day to promote disaggregation. The sediment was then stirred and suspended in the beaker and slowly poured over stacked 100 (150 m ) and 230 (63 m ) mesh sieves under a gentle shower-type flow of hot tap water. Any remaining sediment was gently disaggregated, and the washed residue was then rinsed with deionized water. If the residue was low in organic matter it was transferred to paper towels for drying; if the residue was organic-rich it was freeze dried. Ostracode and mollusk shells were hand-picked from the dried residue.

PB-RES: This database contains the results of 210Pb analyses of the upper parts of selected cores.

PMK-RES: This database contains the results of paleomagnetic direction measurements made by John King at the University of Rhode Island.

PMR-RES: This database contains the results of paleomagnetic direction measurements made by Richard Reynolds at the U.S. Geological Survey.

RMAG-RES: This database contains the results of rock (sediment) magnetic properties measured by John King at the University of Rhode Island.

TEX-RES: This database contains the results of grain-size measurements on core samples. Samples were taken from the core tops, from continuous channel sampling of selected cores, and from other selected intervals; down-core grain-size samples were generally taken at continuous 3-cm intervals. The sand fraction was measured using standard sieving techniques and the silt and clay fraction were measured using a multi-aperture model TA-2 Coulter counter.