Cretaceous strata were penetrated at only three of the five sites and indicate shifting depocenters and progressive condensation toward the seaward margin (Fig. F9).
The thick package of upper Albian through lower Cenomanian clay- and silt-rich sediments present at Sites 1052 and 1050 completely pinch out at seaward Site 1049, where the lower Albian is directly overlain by the Maastrichtian. The upper Aptian and lower Albian record at Site 1049, albeit relatively compact, provides a cycle-tuned time scale for this interval and a duplicate record of lower Albian polarity Subchron M"-2r".
The basal sediments overlying the major Late Cretaceous unconformity are progressively older toward the seaward margin: the early portion of Maastrichtian polarity Chron C31r is identified at landward Site 1052 and a sliver of mid-Campanian polarity Chron C33n is identified at Sites 1050 and 1049. Latest Campanian polarity Chron C32r was not recognized at any site. The Campanian/Maastrichtian boundary interval (polarity Chron C32n and its reversed-polarity subchron) is resolved only at Site 1050.
The Maastrichtian succession, which is relatively complete and expanded at Site 1052, is heavily distorted by condensation or hiatuses in the seaward sites. Early Maastrichtian polarity Chrons C31r and C31n are equivalent to nearly 120 m at Site 1052, but span only between 10 and 30 m at Site 1050, and are a depositional hiatus at Site 1049. Polarity zones corresponding to late Maastrichtian polarity Chron C30n and early Chron C29r also thin seaward but are partially preserved at all three sites. In contrast to the general tendency of seaward condensation, only Site 1049 has preserved an intact record of the K/T boundary impact event within polarity Chron C29r.
Paleocene strata were penetrated at four sites. The Maastrichtian pattern of seaward condensation was probably maintained, but apparently the upper Paleocene record at landward Site 1050 was later removed by middle Eocene erosion (Fig. F9).
The thickness of the Danian progressively thins from Site 1052 (135 m) through Sites 1051 and 1050 (~70 m) to Site 1049 (~25 m). There was a major mid-Danian episode of condensation or hiatus across the margin, as indicated by the absence or relative thinness of polarity Chrons C29n and C28r at all sites. Cycle stratigraphy through polarity Chrons C27r and C27n indicates that these chrons encompass 1.45 m.y. and that the total duration of the Danian stage should be shortened by ~0.35 m.y. to span from 65.5 to 61.85 Ma (Röhl et al., 2001).
The Selandian stage is approximately equivalent to the long reversed-polarity Chron C26r (Fig. F2) (Berggren et al., 1995). This interval is only significant at Site 1050 in the outer portion of the margin, where it spans ~50 m. At both the most landward (Site 1052) and most seaward (Site 1049) sites, only a thin sliver (<5 m) of the Selandian may be present. At landward Site 1052, this remaining Selandian sediment is directly overlain by the mid-Lutetian of the middle Eocene, and we postulate that this major unconformity was created by an episode of middle Eocene erosion that stripped away a significant thickness of upper Paleocene sediments in the landward portion of this margin. The reduced thickness of polarity Chron C26r at Site 1049 seems to be associated with a general pronounced condensation of the upper Paleocene through lowermost Eocene interval, rather than a specific unconformity.
The pattern of relative thickness of the Thanetian strata across the margin mirrors the underlying Selandian. There is a progressive seaward thinning from Site 1051 through Site 1049.
Sediments of the Ypresian (lower Eocene) and Lutetian (lower middle Eocene) display a progressive seaward thinning at Sites 1051, 1050, and 1049 but are an erosional hiatus at landward Site 1052 (Fig. F9). Bartonian (upper middle Eocene) and younger sediments are not preserved at seaward Sites 1050 and 1049. Cessation of deposition occurred at Site 1052 during the middle Priabonian (upper Eocene) and at the most landward Site 1053 near the Eocene/Oligocene boundary.
All polarity chrons of the Ypresian are present at Sites 1051 (spanning 125 m) and 1050 (90 m). The Ypresian at seaward Site 1049 is partially condensed (35 m), with omission of late Ypresian polarity Chron C22r.
The basal Lutetian is represented by a hiatus across the margin, and there are indications of erosion of the uppermost Ypresian and differences of timing of resumption of sedimentation at the various sites. The termination of sedimentation below the hiatus is during polarity Chron C26r at Site 1052, early Chron C22n at Site 1051, earliest Chron C22n at Site 1050, and possibly the beginning of Chron C21r at Site 1049. Preservation of sedimentation resumed during polarity Chron C19r at Site 1052, latest C21r at Site 1051, late C21n at Site 1050, and early C20r at Site 1049. This irregular pattern and magnitude of the depositional hiatus suggests an early Lutetian (lasting until the latest Lutetian at landward Site 1052) episode of bottom-current erosion and prevention of sediment accumulation across the margin. This episode may have been an initial pulse of the western boundary current that would later terminate sedimentation in late Eocene.
Above this basal Lutetian hiatus, the thickness pattern of individual polarity zones (e.g., polarity zones corresponding to Chrons C20r and C20n) display the typical seaward thinning. Middle Lutetian polarity Chrons C20r and C20n encompass 170 m at Site 1051, 110 m at Site 1050, and only 30 m at Site 1049.
The end of the Lutetian (end of polarity Chron C19n) is the termination of preserved sedimentation at seaward Sites 1050 and 1049. This end Lutetian event is also reflected as a minor hardground in the cored sediments of Site 1052.
The package of Bartonian sedimentation at Sites 1052 and 1051 appears to record all polarity chrons and the major polarity subchrons (e.g., C17n.1r and C17n.2r). Site 1053 did not yield an unambiguous magnetostratigraphy in this interval. The total thickness of the Bartonian is nearly identical (120 m) at both Site 1052 and 1051, although individual polarity zones indicate slight differences in accumulation patterns during this interval.
There is a progressive landward termination of sedimentation through the Priabonian, with the end of accumulation occurring during polarity Chron C16r at Site 1051, latest Chron C16n or early Chron C15r at Site 1052, and either latest Chron C15r or C13r at Site 1053. No Oligocene or younger sediments have accumulated on this margin swept by the western boundary current system.