|
Polarity chron
|
Reversal
type |
Age
(Ma) |
Depth
(mbsf) |
Best estimate
|
Sedimentation rate
(m/m.y.) |
Comment
|
|
|---|---|---|---|---|---|---|---|
|
(mbsf)
|
(Core, section, interval)
|
||||||
| 0 | N | 0.000 | 0.00-0.00 | 0.00 | Top of Core 200-1223A-1H or higher |
|
* |
| C1n(o) |
R N |
0.780 | 0.11-0.17 | 0.14 | 200-1223A-1H-1, 14 cm | 0.18 |
|
| C1r.1n(t) |
NR |
0.990 | 0.77-0.81 | 0.79 | 200-1223A-1H-1, 79 cm | 3.10 |
|
| C1r.1n(o) |
RN |
1.070 | 1.20-1.26 | 1.23 | 200-1223A-1H-1, 123 cm | 5.50 |
|
| C2n(t) |
NR |
1.770 | 1.99-2.05 | 2.02 | 200-1223A-1H-2, 52 cm | 1.13 |
|
| C2n(o) |
RN |
1.950 | 6.87-7.50 | 7.19 | 200-1223A-1H-5, 119 cm | 28.69 | † |
| C2r.1n(t) |
NR |
2.140 | 15.02-15.04 | 15.03 | 200-1223A-3X-2, 85 cm | 41.29 | ‡ |
| C2r.1n(o) |
RN |
2.150 | 15.24-22.30 | 15.63 | 200-1223A-3X-2, 145 cm | 60.00 | ‡ |
| C2An.1n(t) |
NR |
2.581 |
|
|
Not observed |
|
** |
Notes: Ages for chrons are from Cande and Kent (1995). The suffixes (o) and (t) that are used for the chron names refer to the onset and termination of a polarity chron, respectively. NR: a reversal where the polarity of the field changed from normal to reversed. RN a reversal where the polarity of the field changed from reversed to normal. * = the mudline and possibly several centimeters of sediment may not have been recovered (see "Paleomagnetism"). † = the reversal is not observed as it occurs within a turbidite near the bottom of Section 200-1223A-1H-5, which is disturbed by drilling. ‡ = the short polarity interval is restricted to the bioturbated unit directly below the vitric tuff in Section 200-1223A-3X-2. A clear normal polarity direction is recorded after removal of the drilling overprint, but the direction trends toward a shallow or possibly negative inclination. This could indicate that a reversed component exists but is poorly resolved. The normal component would then be an overprint, perhaps of Brunhes age. Alternatively, the normal component is real, in which case the normal polarity subzone would likely be Chron C2r.1n. The base of this normal polarity subzone occurs somewhere between the base of the bioturbated sediment unit and the top of Core 200-1223A-4X. We have placed it arbitrarily at the base of Section 200-1223A-3X-2, which results in sedimentation rates consistent with the overlying interval. ** = the rocks from Cores 200-1223A-4X, 5X, and 6X all have reversed polarities, which are interpreted to be within Chron C2r.