New Mexico Geological Society Downloaded from: https://nmgs.nmt.edu/publications/guidebooks/70 Revising Palynostratigraphic Concepts in the Raton Basin a Half-century after R.H. Tschudy’s Pioneering Work: A New Pollen Proxy for the Campanian-Maastrichtian Stage Boundary and Reevaluation of the Famous K-PG Fern-Spore Spik Keith Berry, Spencer G. Lucas, and Paul L. Sealey, 2019, pp. 67-72 in: Geology of the Raton-Clayton Area, Ramos, Frank; Zimmerer, Matthew J.; Zeigler, Kate; Ulmer-Scholle, Dana, New Mexico Geological Society 70th Annual Fall Field Conference Guidebook, 168 p. This is one of many related papers that were included in the 2019 NMGS Fall Field Conference Guidebook. Annual NMGS Fall Field Conference Guidebooks Every fall since 1950, the New Mexico Geological Society (NMGS) has held an annual Fall Field Conference that explores some region of New Mexico (or surrounding states). Always well attended, these conferences provide a guidebook to participants. 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TSCHUDY’S PIONEERING WORK: A NEW POLLEN PROXY FOR THE CAMPANIAN- MAASTRICHTIAN STAGE BOUNDARY AND A REEVALUATION OF THE FAMOUS K-PG FERN-SPORE SPIKE KEITH BERRY1, SPENCER G. LUCAS2 AND PAUL L. SEALEY2 1Science Department, Hoehne Re-3 School District, 19851 County Road 75.1, Hoehne, CO, 81046; [email protected]; 2New Mexico Museum of Natural History and Science, 1801 Mountain Road NW, Albuquerque, NM, 87104 ABSTRACT — R.H. Tschudy pioneered palynostratigraphy in the Raton Basin nearly a half-century ago and established two key precedents: (1) that the Campanian-Maastrichtian stage boundary should be placed at or near the first appearance datum (FAD) of Kurtzipites and (2) that the Cretaceous-Paleogene (K-Pg) boundary fern-spore spike signaled the comparatively rapid recovery of ferns following the K-Pg impact event. In light of new discoveries, revisions to these key concepts are proposed. First, correlation between the Raton Basin and the Rock Springs uplift in Wyoming indicates that the pollen proxy for the Campanian-Maastrichtian stage boundary should be moved lower, to within the uppermost part of the Trudopollis meekeri Zone (formally defined as an Interval Zone between the FAD of Aquilapollenites striatus and the LAD of T. meekeri). Second, the apparent association of Cyathidites spores with Anemia-like schizaeaceous foliage and Laevigatosporites spores with thelypteridaceous foliage in the Raton Basin suggests that it was not a general property of ferns, such as the ability to regenerate rapidly from short-lived spores or rhizomes in the soil spore bank, which conferred an advantage in the harsh, post-im- pact world of the earliest Danian. The long-term viability of modern Anemia, Lygodium, and Thelypteris spores contrasts with that of mod- ern cyatheaceous and Blechnum ferns (the taxa traditionally associated with the dominant fern spores at the K-Pg boundary), presumably accounting for the monotaxial nature of the two-phase fern-spore spike in the Raton Basin. Thus, spores of these ferns could have survived a decade-long impact winter, which has been suggested to have caused a mass-extinction event among dicot angiosperms. INTRODUCTION spore spike in the Raton Basin (Berry, 2019). Therefore, the objective of this study is two-fold: (1) to select a new pollen Beginning 45 years ago, R.H. Tschudy pioneered palynos- proxy for the Campanian-Maastrichtian stage boundary in the tratigraphy in the Raton Basin of northeastern New Mexico and Raton Basin and (2) to evaluate the implications of the discov- south-central Colorado. Here, he established two key prece- ery that the traditional familial affinities of the dominant fern dents that would later become widely recognized chronostrati- spores in the two-phase K-Pg boundary fern-spore spike in the graphic markers in both western North America and globally: Raton Basin, Cyathidites (Cyatheaceae) and Laevigatosporites (1) placement of the Campanian-Maastrichtian stage boundary (Blechnaceae), are likely incorrect. at the first appearance datum (FAD) of Kurtzipites (Tschudy, 1973) and (2) correlation between the abrupt disappearance of BRACKETING THE CAMPANIAN-MAASTRICTHIAN Cretaceous angiosperm pollen and an earliest Paleocene (Da- STAGE BOUNDARY USING POLLEN MARKERS: nian) fern-spore spike (Orth et al., 1981; Tschudy et al., 1984). CORRELATION BETWEEN THE ROCK SPRINGS The former concept would later be formalized by Nichols and UPLIFT, WYOMING, AND THE RATON BASIN Sweet (1993) in recognizing the Campanian-Maastrichtian stage boundary in western North America, whereas the latter Correlation between the Western Interior and the Global concept would later be applied globally (Vajda and Bercovici, Standard Stratotype Section and Point (GSSP) for the Campa- 2014). Since these pioneering studies, there have been two nian-Maastrichtian stage boundary places this boundary at the major advances in the biostratigraphy of the Raton Basin: (1) base of the Baculites baculus ammonite zone (Cobban et al., the discovery that the Campanian-Maastrichtian stage bound- 2006). Tschudy (1973) suggested the base of the B. baculus ary can be placed in the upper part of the Pierre Shale through- Zone was correlated with the FAD of the palynomorph Kurtz- out the Raton Basin (Sealey and Lucas, this volume) and (2) ipites trispissatus and, therefore, placed the Campanian-Maas- the discovery that Anemia-like schizaeaceous foliage and the- trichtian stage boundary near the top of the Vermejo Formation lypteridaceous foliage may have produced the dominant fern (Fig. 1A, B, C) in its type area in New Mexico (Nichols and spores in the two-phase Cretaceous-Paleogene (K-Pg) fern- Sweet, 1993; Nichols, 1994). However, the stage boundary is 68 BERRY, LUCAS AND SEALEY actually known to lie within the upper part of the Pierre Shale ary in this area as well (Fig. 2), and actually lies within the (Fig. 1A) in this region (Sealey and Lucas, this volume). There- lower part of Nichols’ (1994) Aquilapollenites striatus Interval fore, a new pollen marker for the stage boundary is required. Zone (Lynds and Slattery, 2017). The FAD of Aquilapollenites Within the Raton Basin, the uppermost part of the Trudo- striatus is within the highest unit of the Kaiparowits Formation pollis meekeri Zone encompasses the Campanian-Maastrich- in southern Utah (Miller et al., 2013), which has been dated tian stage boundary (Fig. 1A). Tschudy (1973) placed the top at 74.21±0.18 Ma (Roberts et al., 2005). Therefore, the up- of this zone slightly above the top of the Trinidad Sandstone permost part of the Trudopollis meekeri Zone, which is here (Fig. 1A), which, in the type area of the Vermejo Formation, defined formally as an Interval Zone between the FAD of A. contains the index inoceramid “Cataceramus” barabini (Sea- striatus and the LAD of T. meekeri (Fig. 2A), closely brackets ley and Lucas, this volume). “C.” barabini is a marker for the 72.1 Ma Campanian-Maastrichtian stage boundary (Figs. the Baculites eliasi-B. baculus Zones in the Western Interior 1, 2). For the purposes of this study and for correlation be- (Walaszczyk et al., 2001). Although Nichols (1994) described tween northern New Mexico and Wyoming where the FAD of T. meekeri as not extending into the lower Maastrichtian and Kurtzipites is much too high and the FAD of Wodehouseia is as being restricted to the late (but not latest) Campanian Aq- not a useful marker given the geographic restriction of this tax- uilapollenites quadrilobus Zone, the top of this zone is actual- on to areas further north (Stone, 1973; Tschudy, 1973; Sweet, ly found within the uppermost part of the Almond Formation 1994), the uppermost part of the T. meekeri Zone is selected as (Fig. 2A, B) at a stratigraphic position higher than the base of a new proxy for the stage boundary. This determination is con- the B. baculus Zone in the area of the Rock Springs Uplift, Wy- sistent with the informal conventions of other researchers, who oming (Fig. 2C; Gill et al., 1970; Stone, 1973; Lynds and Slat- previously used the LAD of T. meekeri as a provisional marker tery, 2017). Thus, the uppermost part of the T. meekeri Zone for the Campanian-Maastrichtian stage boundary in west-cen- also encompasses the Campanian-Maastrichtian stage bound- tral Alberta, Canada (Fanti and Catuneanu, 2009).