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Workshop Conclusions

Generalized Colorado Plateau section (Glen Canyon/Kaiparowits Plateau, based on
) with the cored sections recommended by the CPCP workshop participants, a generalized evaporation – precipitation (E-P) curve loosely based on climate sensitive facies, and some major geolofical and biological events (* actual boundary may or may not be present in rock section). See Figure 1 for core area abbreviations. Note that the relative thicknesses of various units are in general different than what is shown in the color section and not the same between different coring areas.

Given these overall goals, the workshop reached several conclusions that dictated the following conclusions.

  1. Early Triassic through Late Jurassic Formations Should be Cored: A key, initially unanticipated, conclusion of the workshop was the importance attached to spanning the full range of climatic milieus represented by these rocks, and thus the need to core the entire Triassic and Jurassic stratigraphic sequence including the Morrison Formation. Collectively, the group defined a three-tiered coring plan consisting of (1) three relatively thick (~1 km) synoptic intervals that together would yield an overlapping stratigraphic framework for the entire Jurassic and Triassic section, (2) two thin (<500 m) cored sections that would tie to critical outcrop areas or to expanded critical intervals, and (3) a number of shorter sections to address more specific problems or provide more regional coverage to the other five cores that are the nexus of the project.

  2. Superposition is Paramount: All breakout groups concluded that to evaluate the critical Early Mesozoic transitions it is necessary to see all Early Mesozoic units in clear superposition. In broad climatic terms, the five major stratigraphic units identified as major coring targets reflect, from oldest to youngest: arid (Moenkopi); humid to semiarid (Chinle); very arid (Glen Canyon and San Rafael); and return to semiarid and humid (Morrison) (above). Climate transitions have been explained in several ways, but most revolve around either a translation of the North American plate from equatorial to mid-latitudes through zonal climate belts (Dickinson, 2005; Kent and Muttoni, 2003; Kent and Tauxe, 2005), or large scale changes in the climate system involving changes in the non-zonal components of the climate system, particularly the monsoon (Kutzbach and Gallimore, 1989; Parrish, 1995; Rowe et al., 2007) or fluctuations in greenhouse gasses (CO2) (e.g., McElwain et al., 1999; Kürschner, 2001). That these hypotheses could be so fundamentally different and remain untested rests on the fact that the temporal evolution of major boundary conditions, most notably latitude, has not been resolved to a useful level of precision (see below). The clear test of these hypotheses involves the paleomagnetic determination of latitude with necessary empirically derived corrections (e.g., Tauxe and Kent, 2004; Tan et al. 2007) from all of the major units.

  3. Internal Time Calibration Needed: Correlation of the Plateau sequence is presently based on low-resolution and untested non-marine biostratigraphic approaches and does not provide clear biogeographic patterns or determination of the rates of biotic change in these very fossiliferous sequences. NONE of the major intervals of biotic change (e.g., Permo-Triassic; Triassic-Jurassic; or Toarcian) are located with precision in this succession. A combination of polarity stratigraphy along with geochronologic dates from ash deposits and dispersed grains will allow correlation with Triassic and Early Jurassic reference sections (e.g., Early Triassic composite sections from Central Europe (Szurlies, 2007), the astronomically calibrated polarity time scale from the Newark Supergroup basins (Kent and Olsen, 1999, in press; Olsen and Kent, 1999), St. Audrie’s Bay, UK (Hounslow et al., 2004; Kemp & Coe, 2007), the Germanic basin (Bachmann and Kozur, 2004), and fully marine Tethyan sections (e.g., Muttoni et al., 2004; Channell et al., 2003; Gallet et al., 2007), non-marine Jurassic to Early Cretaceous sequences of China (e.g., Feursich et al., 2002; Yao et al., 2003; Xu, 2005) and, possibly, the marine magnetic anomaly M-sequence (Sager et al., 1998) in the Middle and Late Jurassic succession to be cored.

  4. Minimize Hiatuses: Breakout groups recognized the significant unconformities in the sections and the likelihood that there are numerous smaller and cryptic hiatuses. Acquiring as much stratigraphic scope as possible through the more continuous units and testing any paleomagnetic reversal sequences across geography by designing stratigraphic overlap between cores will help address these concerns. The thickest sections, least likely to be affected by rampant hiatuses, are not confined to a single small area in the Colorado Plateau and adjacent areas because of lateral shifts in the basin’s depocenters. Several cores will be necessary to get the most favorable sections of each of the units. However, the thick sections proposed for coring are far from comparable surface outcrops and thus subsidiary sections more proximal to sources of the surface data must be cored as well. The goal is to provide a long enough section with unambiguous ties to the outcrop and sufficient stratigraphic scope to correlate with the main, long cores.

  5. Data Management Plan: A robust and effective data management/geoinformatics system, accessible through a CPCP Data Portal, will facilitate and support the science and provide the basis for education and outreach efforts. This will include coupling the drilling Information System (DIS) of the ICDP with SESAR (, EarthChem (, CoreWall (, and PaleoStrat (, a core-core hole-log integration system, and a novel digital framework of regional geology.

  6. Education and Outreach: Although not explicitly detailed at the meeting, the group recognized that an education and outreach program of the CPC will leverage the globally famous attributes of the Colorado Plateau and environs.