Swedish Triassic-Jurassic Late Triassic-Early Jurassic strata are present in southern Sweden (Scania), in the north-eastern part of the Danish-Polish basin. The sequence is important because it provides a link with the richly fossiliferous sections in Greenland and the classic Germanic basin to the south. The Swedish section represents the poorly known type of cyclical climates of the north temperate zone, different than those seen further south in Pangea. The sequence consists of red, gray and black, cyclical continental rocks and coal (Norling et al, 1993; Pienkowski, 1991). The dramatic floral transition that marks the Triassic-Jurassic boundary (Lund, 1977; Lundblad, 1959) is representative of the entire region from Northern Europe to Norway, Greenland, and Spitzbergen and its microstratigraphy and correlation with the boundary elsewhere needs to be examined. No complete cored section of these strata exists.
Germanic basin Key to all analyses of Pangean events and processes is correlation with the type Triassic in Germanic (Central European) basin. Presently, correlation is based entirely on bio- and sequence stratigraphy of the continental sections. There are a few marine intercalations within the Triassic part of the section and the early Jurassic is marine. Much of the Late Triassic section is cyclical and lacustrine, although the periodicity of that cyclicity is unknown. Paleomagnetic polarity stratigraphy would be critical to establish high-resolution correlation outside that area. Outcrops are generally poor, and although some paleomagnetic work has been done (e.g. Hahn et al., 1982) no significant fraction of the Late Triassic-Early Jurassic polarity sequence has been worked out. Preliminary inquires to a number of German colleagues have indicated that a complete core section through the critical portions of the Triassic-Jurassic section probably does not exist, and therefore should be recovered through scientific coring.
Fundy basin The Fundy basin is the largest single CAM basin with significant outcrop. Most of the section lies below the Bay of Fundy, however. The Triassic-Jurassic boundary is preserved in the cyclical, lacustrine upper Blomidon Fm., below the North Mountain Basalt (Fowell and Traverse, 1995). Work by Symonds et al. (1989) and us indicates that a high-resolution polarity stratigraphy can be recovered from these strata; however, outcropping strata have a very low sedimentation rate (based on the available biostratigraphy) and there are outcrop indications of small, but potentially confounding, unconformities. Lacustrine facies of Jurassic strata overlying the North Mountain Basalt is poorly represented in outcrop, but thickens greatly beneath the bay (Wade, et al., 1996). Based on the high frequency of evaporites and eolian strata, the Fundy basin sequence unquestionably lies in a far more arid setting than the southern CAM basins (Hubert and Mertz, 1984; Metz and Hubert, 1990; Olsen et al., 1989). Outcrop studies indicate significant differences in the mode of climatic cyclicity in this basin (Olsen, 1997) as well as the floral response to the Triassic Jurassic boundary (Fowell and Traverse, 1995); however, definitive analysis must await the recovery of higher sedimentation rate sections. These could be acquired by coring either on land or perhaps offshore in the Bay of Fundy by a joint program between ODP (or its successor), ICDP, and NSF (Continental Dynamics).
Moroccan basins These are landward representatives of salt basins, otherwise deeply buried on the North American and Moroccan continental margins. Preliminary work by us in one of these, the Argana basin (Fig. 1) shows that there is a recoverable polarity sequence, and has pinpointed the position of the Triassic-Jurassic boundary (Fowell, pers comm., 1996). Triassic and Early Jurassic strata are strongly cyclical (Smoot and Olsen, 1988), with a style appropriate for a basin intermediate between the Newark and Fundy basins in paleolatitude (Olsen, 1997). Like the Fundy basin, the exposed portions of the larger basins are up-dip edges of the tilted fault blocks, characterized by low sedimentation rates. In addition, the post-basalt section is very thin in the exposed basins, truncated by the post-rift unconformity. Coring would allow recovery of section around the Triassic-Jurassic boundary in areas of higher sedimentation rates, much better suited to detailed cyclo- and magnetostratigraphic investigations. Existing cores were drilled on salt structures and therefore have significantly deformed stratigraphy (Holser et al, 1988). They could however powerfully augment a well located, undisturbed section and allow for multiple lateral tests or cyclo- and magnetostratigraphy.
Hartford basin The Hartford basin has the best record of their late stages of CAM rift development, with sedimentation extending perhaps to the Toarcian (Cornet, 1977). It complements the already established Newark basin record, which together would provide a high-resolution Triassic and Early Jurassic cyclostratigraphic and geomagnetic polarity time scale, useful globally. The Hartford basin sequence ends with a thick fluvial interval which preserves a unique record of the closing phase of rift basin evolution important for testing quantitative rift models (Schlische and Olsen, 1990; Lambiase, 1990; Contreras et al., 1996). Previous work shows that the small exposed portions of the Hartford basin Jurassic section match the cyclostratigraphy of the Newark section (Fig. 4), and that there is a recoverable magnetic polarity record from Triassic as well as the Jurassic part of the sequence (Witte, 1991, plus unpublished data). Caliches from the Hartford basin have been successfully dated using U-Pb methods (Wang et al., 1996). With the existing U-Pb and 40Ar/39Ar dates from Early Jurassic igneous units, and correlation to the complete Newark basin record by polarity stratigraphy, radiometric as well as Milankovitch cycle calibration of sedimentation rates is thus possible. Cores would also allow a complete geochemical characterization of the lava flows (e.g. Philpotts and Reichenbach. 1985; Puffer, 1992; Tollo and Gottfried, 1992). Finally, although not strictly part of the Triassic-Jurassic theme of this project, most of the Jurassic section is covered by Pleistocene tills and varved clays of "Lake Hitchcock" - the basis of Antevs' classic varve chronology (Antevs , 1922; Ridge and Larsen, 1990; Verosub and Shumway, 1995). Were the basin to be cored, complete sections through the lake beds at several would be cored as a consequence, thus greatly adding to the value of this annual record of late Quaternary paleoclimate and global change studies. While obviously not a high priority in relation to the main goals of this project, it is value added with little or no additional expense.
Newark basin Thank's to the NBCP, extensive coring is not needed in the Newark basin; however, the region that has produced the World's best lithological and paleontological information on the continental Triassic-Jurassic boundary (Jacksonwald syncline), is characterized by spotty and ephemeral exposures (mostly due to house construction). Because of the high sedimentation rate, and exceptional development of the fossil-bearing lacustrine cycles, one or two short cores (ca. 500 m) through the Triassic-Jurassic boundary would add tremendously to our understanding of the boundary, and provide unweathered material for geochemical analysis.
Culpeper basin Preliminary investigation of the Triassic-Jurassic boundary in the Culpeper basin (Fowell, 1993; Weems, pers. comm.) shows that the development of lacustrine cycles around the Triassic-Jurassic boundary (Bull Run Fm.) is better than anywhere else. It is the southernmost basin in which the boundary has been positively identified, and has a sedimentation rate that is at least twice that seen in the highest sedimentation rate portions of the Newark basin (Jacksonwald syncline), and the rocks are richly fossiliferous, although very, very poorly exposed. Based on cores lower in the section (Fig. 4), the magnetic properties of the sedimentary rocks works as well as the Newark basin and the match between cyclostratigraphy and magnetic stratigraphy is excellent over a distance of 500 km. We have no doubt that the cores from the Culpeper basin Triassic-Jurassic boundary would successfully address the need for very high temporal resolution of the boundary as well as the climatic modes on either side of the boundary.
Richmond basin The Richmond basin does not contain strata of Early Jurassic age. However, the basin section is richly fossiliferous and spans a very poorly known part of the Late Triassic (early Late Carnian and Early Carnian). Despite having the highest concentration of drill holes of any of the eastern North American rifts (due to coal and hydrocarbon prospecting) its basic stratigraphy remains very poorly known. A modest coring project similar is design but smaller in scale to the NBCP would provide a template for the cyclo- and paleomagnetic stratigraphy of the earliest part of the Late Triassic and possibly late Middle Triassic.
Deep River Basin Despite having a very long history of coal and oil exploration, the basic stratigraphy of this poorly exposed basin remains very poorly understood. This is a significant problem because some of the richest vertebrate assemblages from the Norian tropics come from this basin (Durham subbasin). The recent TRIBI workshop outlined many of the critical aspects of this basin as well as possible modes of data acquisition.
South Georgia Rift - Clubhouse Crossroads Basalt Perhaps the largest gap in our understanding of the events around the Triassic-Jurassic boundary and the CAM igneous event is the relationship of the subsurface basalts of South Carolina and Georgia (Clubhouse Crossroads basalt) to the underlying rift sequences (South Georgia basin) and the seaward dipping reflectors (Fig. 1). Short, discontinuous cores taken for studies on the 1886 Charleston earthquake are intriguing, but do not answer the critical questions of age, timing, chemistry, and relation to the Triassic-Jurassic boundary, because of post-cooling alteration and apparently errors in core orientation (Phillips, 1983, pers. comm., 1986, 1996, Ragland, pers. comm. 1996). In addition, rift strata of the underlying South Georgia basin have cyclical lacustrine strata (D. Zeigler and B. Cornet, pers. comm., 1985), based on proprietary industry drilling. This sedimentary section comprises the southernmost of the CAM basins and should allow a look at equatorial climate cyclicity around the Triassic-Jurassic boundary. The only way do address these problems and opportunities is by continuously coring through the basalts into a significant thickness of relatively fine-grained sedimentary strata of the underlying rift basin sequence. Additionally a site could be picked to core from the Clubhouse Crossroads basalt into one of the possible feeder dikes. The site could be identified by tracing the aeromagnetic signature of the dikes to the basalt (e.g. Phillips, 1988, Figs. 1 & 2). An obvious, highly desirable, but very ambitious, related goal would be sampling the seaward dipping reflectors themselves, which might just be possible at their most landward extent (ca. 3-4 km, e.g. Holbook and Kelemen, 1993, Fig. 2).
OTHER BASINS Southern hemisphere basins, particularly in Argentina (e.g. Ischigualasto basin) and southern Africa (e.g. Karoo basin) are particularly interesting, we look forward to input on possible targets in these areas, as well as others.