|
Polarity chron/subchron
|
Reversal type
|
Age
(Ma) |
Range
(mbsf) |
Best estimate (mbsf)
|
Best estimate core,
section, interval (cm) |
Measurement type
|
Range
(mbsf) |
Best estimate (mbsf)
|
Best estimate hole, core,
section, interval (cm) |
Measurement
type |
| C4r.2r-1 (o) |
R N |
8.651 |
|
|
|
|
404.81-404.88 | 404.85 | 1095B-34X-6, 5 | Discrete/Split-core |
| C4An (t) |
NR |
8.699 |
|
|
|
|
411.70-411.74 | 411.72 | 1095B-35X-4, 62 | Split-core |
| C4An (o) |
RN |
9.025 |
|
|
|
|
445.98-446.02 | 446.00 | 1095B-39X-1, 90 | Split-core |
| C4Ar.1n (t) |
NR |
9.230 |
|
|
|
|
460.70-461.04 | 460.87 | 1095B-40X-5, 7 | Split-core |
| C4Ar.1n (o) |
RN |
9.308 |
|
|
|
|
485.40-485.65 | 485.53 | Between 1095B-43X-2 and 43X-CC | Split-core |
| C4Ar.2n (t) |
NR |
9.580 |
|
|
|
|
504.74-522.88 | 520.50 | Between 1095B-46X-2 and 48X-1 | Split-core |
Notes: Ages for chrons are from Cande and Kent (1995). (o) = onset, (t) = termination of a polarity chron. 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 reversal boundary is the same as identified by Shipboard Scientific Party (1999a), but the location of the boundary has been adjusted slightly. † = identification of chron and reversal boundaries is speculative; therefore, these reversal boundaries are not used in the sedimentation rate plots. ‡ = the reversal boundary is identical to that given by Shipboard Scientific Party (1999a). Comments: (1) = depth to mudline in mbsf agrees to within 2 cm for the first core from Holes 1095A, 1095B, and 1095C. (2) = our interpretation places Chron C2n ~20 m higher in the section than that by Shipboard Scientific Party (1999a). (3) = the polarity subzone interpreted to represent Subchron C2r.1n is speculative. Rather than a geomagnetic origin, the subzone could be caused by coring disturbance at the top of Core 178-1095D-6H. We place the C2r.1n (t) reversal at the very top of Core 178-1095D-6H. This subchron was thought to be lost in a hiatus based on the interpretation of Shipboard Scientific Party (1999a). (4) = this reversal was interpreted to represent C2n (t) by Shipboard Scientific Party (1999a) and was thought to occur above a hiatus that removed reversals C2n (o) to C2An.1n (t). (5) = placing Subchron C2An.1n (o) at this locality produces a subchron (C2An.1r) that is short, with resulting sedimentation rates exceptionally slow relative to sedimentation rates above and below. (6) = average mcd depth taken from the best estimates from Holes 1095A and 1095D, which are 77.98 and 77.92 mcd. (7) = this reversal could be C2An.1n (o) instead of C2An.2n (o), in which case no Subchron C2An.2n appears to be recorded. (8) = average mcd depth taken from the best estimates for Holes 1095A and 1095B, which are 84.58 and 85.54 mcd. (9) = the reversal occurs within an interval that has some drilling disturbance. The best estimate for the location agrees with noisy discrete data. (10) = this is possibly a newly identified cryptochron, which we refer to as C3n.1r-1. (11) = Subchron C3n.3n was not previously identified by Shipboard Scientific Party (1999a). (12) = this poorly constrained reversal, C3n.4n (t), occurs somewhere within a broad zone of shallow inclinations. (13) = this is possibly a newly identified cryptochron, which we refer to as C3r-1. (14) = Subchron 3An.1n (o) is placed in the lower part of the coring gap (top of Core 178-1095B-16X) rather than the middle. (15) = reversals C4r.1n (t) and C4r.1n (o) possibly occur in a zone of shallow inclinations near 364 and 369 mcd, respectively. (16) = the transition zone for Subchron C4r.2r-1 (t) is from 393.94 to 394.48 mcd in discrete samples. This is a zone that is weakly magnetized. (17) = the transition zone for C4r.2r-1 (o) can only be limited to between Sections 178-1095B-34X-5 and 34X-6 in split-core data. (18) = the reversal C4Ar.2n (t) is arbitrarily placed near the top of Core 178-1095B-48X to better agree with logging estimate.