|The Late Triassic and Early Jurassic was a critical time in Earth history, representing a fundamental end member of Earth System states. The continents were united in the supercontinent of Pangea, with recent proxy data indicating the initiation of the very high CO2 levels characteristic of the Early Mesozoic (Fig. 2.1). Although, all major groups of living terrestrial vertebrates evolved during the early Mesozoic, the Triassic-Jurassic boundary marked a mass extinction, perhaps of greater magnitude than that at the Cretaceous-Tertiary transition (Fig 2.2).|
|Figure 2.1 (right): Plot of pCO2 through the Phanerozoic, based on soil carbonate (based on Ekart et al., 1999) with the position of the three largest continental flood basalt events of the Phanerozoic shown.|
Either coincident with the Triassic-Jurassic mass extinction
or shortly thereafter, began what may have been the largest igneous event
in Earth history - the 6000 km diameter Central Atlantic Magmatic Province
(CAMP) event, which may also mark the initiation of the earliest Atlantic
Ocean seafloor (Fig. 2.3). These represent fundamental Earth System problems
requiring innovative approaches and high-resolution records for their analysis.
Fortunately, extension leading up to the break up of Pangea resulted in
the formation of the largest known rift province and associated basins,
the result of which is a spectacular sedimentary and igneous record of
Triassic-Jurassic tectonic, climatic, and biotic events with the interval
being represented virtually in many basins on all continents.
| Figure 2.2 (above): Extinction rate of "shelly"
through the Phanerozoic (based on Sepkoski, 1997) showing the same
continental flood basalt events as in Fig. 2.1.
| Figure 2.3 (above): Pangea with
superimposed Central Atlantic Magmatic
Province (adapted from Olsen, 1999).
|A high-resolution record of one of these basins, the
Newark rift basin of New York, New Jersey, and Pennsylvania, USA, has already
been recovered in nearly its entirety in 6700 m of core by the US National
Science Foundation funded Newark Basin Coring Project (NBCP) (Fig. 2.4).
Analysis of this record produced the longest continuous record of astronomical
climate forcing in the World, which in turn led to the development of an
astronomically tuned geomagnetic polarity time scale for the Late Triassic
and earliest Jurassic spanning roughly 31 million years (Olsen et al.,
1996; Kent et al., 1995; Olsen and Kent, 1996, 1999; Kent and Olsen, 2000a).
Subsequent studies have shown that this time scale can be used for high-resolution
correlation to other areas, hundreds to thousands of kilometers distant
(e.g. Kent and Olsen, 1997; Olsen and Kent, 2000b; Kent and Clemennson,
1996). The NBCP and related work demonstrates that it is possible to obtain
records equivalent in quality to those from the Neogene, but at a spatial
and temporal scale hitherto unavailable. This fine-scale temporal framework
should allow exploration of major events and processes at unprecedented
precision and scale.
It is within this exciting new context that the ICDP and
US NSF funded workshop was held to develop a community-based, prioritized
science plan including the identification of coring targets along a largely
pole to pole transect of Triassic-Early Jurassic Pangea. It is only with
continuous core that the extremely large magnitude global events and processes
can be examined at appropriate (large and small) levels of temporal and
|Figure 2.4 (left): Newark basin time scale: A, Rock Color; B, Formations (Bt., Boonton Fm.; Hm, Hook Mt. Basalt; To., Towaco Fm.; Pr., Preakness Basalt; Ft., Feltville Fm.; Om., Orange Mountain Basalt; Pc., Passaic Fm.; Lt., Lockatong Fm.; St., Stockton, Fm.); C, Filtered lake depth proxy (red) and rock color (green) showing the 404 ky lake-level cycles; D, Astronomically calibrated geomagnetic polarity sequence; E, Paleolatitude of the coring sites though time; F, Relative Ages; G, Numerical age based on astronomical calibration and radiometric ages from the basalts. Based on Kent and Olsen (1999) and Olsen and Kent (1999).|