Page 144 - Carbonate Sedimentology and Sequence Stratigraphy

CHAPTER 7: SEQUENCE STRATIGRAPHY OF THE T FACTORY 135

Site
1005
Site 0.2
400 1004
0.41
0.25
0.41
0.85
0.85
1.2
Site 1.44
1.72
1003 1.44
3.1
600 Site 0.25 1.72 3.6
Site
1007
1006 0.41 4.2
0.2 1.2 0.85
0.41 1.44 1.2
1.72
0.85 2.0 1.72
1.2 2.4 2.0
1.44 2.4
3.1
1.72 3.6 6.8
2.0 7.7
2.4 4.2 8.1
800 8.6
3.1
3.6
3.1
3.6 9.4
4.2
4.2
6.8
4.7 10.7
6.5 7.7 11.3
6.8 8.1 11.4
8.6
7.7
4.7 8.1
1000 8.6
11.8
11.9
5.6 9.4
6.5 9.4
6.8
10.7
10.7
7.7 11.4 11.3
11.4
8.1 11.3
8.6
11.8
1200 9.4 11.9 11.8
11.9
10.7
11.4
11.3
11.8
11.9
13.2
13.2
13.2 13.2
1400
13.2
13.6
13.6
Fig. 7.36.— Time lines correlated between ODP sites shown in Fig. 7.34. Age dating solely by tracing of seismic reflections yields
large uncertainties because time lines merge and diverge as sediment drifts thicken and thin. Consistent correlation in Fig. 7.34 was
achieved by adding ground truth from the boreholes to the seismic data. After Eberli, Swart, Malone et al. (1997), modified.
nite. Because of the different composition, highstand erratic. The borings are only 10 km apart yet their hiatuses
deposits on the slope are better cemented than the differ significantly in age and duration and the correlation
lowstand deposits. The result is a distinct impedance with seismic sequence boundaries is not obvious (Austin,
contrast at the sequence boundary with a hard, well- Schlager et al. 1986). One possible explanation is that cur-
cemented highstand layer overlain by a weakly ce- rent erosion is in step with sea level if the Gulf Stream is
mented lowstand layer. narrowly channeled, such as in the Florida Straits; on the
other hand, erosion is irregular if the Gulf Stream is free to
An unsettled question about sequence boundaries is
shown in Fig. 7.39. Whereas the record in the Florida Straits meander, such as on the Blake Plateau. Seismic data (Pinet
suggests that hiatuses form during lowstands of sea level, and Popenoe, 1985) indicate rather patchy erosion patterns
the record of two boreholes on the Blake Plateau is rather on Blake Plateau.