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Localities are grouped geographically and numbered sequentially. Details for each are given in Appendix 1. Key to abbreviations: Palyno, palynofloral record across the putative boundary; Sub-dm, sample intervals of one decimeter or less; Ir ppb, iridium anomaly present; Clayst, boundary claystone layer present; Sh qtz, shocked minerals present; Pmag, magnetostratigraphic data available; Isoage, isotopic age data available; I< vert, Maastrichtian vertebrate fauna below; T vert, Paleocene vertebrate fauna above; I< flora, Maastrichtian megaflora below; T flora, Paleocene megaflora above; F spike, fern-spore abundance anomaly present. Features Sub-dm, Ir ppb, Clayst, and Sh qtz are triple-weighted because of their critical importance in identifying the K-T boundary. A TOTAL score of less than 10 indicates that the section probably is invalid for analysis of the record of plants at the K-T boundary. Note: The sections at El Kef (stratotype for the K-T boundary), Campo, Kawaruppu, Seymour Island, and Mid-Waipara River are marine sections for which data on terrestrial palynomorphs are available.

elements: (1) physical evidence of an impact based on a distinctive sedimentary layer, typically less than 1.5 cm thick, containing some combination of an anomalous concentration of iridium, shock-metamorphosed minerals, and spherules or tektites; (2) occurrence of the physical evidence within a zone of reversed magnetic polarity correlating to polarity subchron C29r; and (3) a larger biostratigraphic context both in terms of associated terrestrial biota and in relation to a time-correlative marine biota.

We have tabulated published terrestrial, plant-bearing, K-T boundary sections and have noted which attributes characterize each section (Table 2.1 and Appendix). By assigning scores for the presence of specific attributes at each section, we are able to assess the relative quality of the sections on a scale from 1 (least complete) to 20 (most complete). By this assessment, we recognize 100 terrestrial K-T boundary sections and 5 more in marine environments for which data on plant fossils are available. The majority (85) are located in North America (Figure 2.3).

Although scoring terrestrial K-T boundary sections may seem somewhat arbitrary, it provides a quick means of measuring the distribution and quality of terrestrial K-T boundary sections around the globe. Because of their critical importance in pinpointing the K-T boundary, we have given triple-weighting to certain attributes that are linked with high-resolution study or that define the impactite layer itself. These include subdecimeter sample resolution, the presence of a boundary claystone layer, existence of an iridium anomaly, and presence of shock-metamorphosed minerals.

The K-T sections in Table 2.1 are numbered sequentially, and these numbers will apply to the sections throughout the remainder of this book and will be used to identify localities on maps and figures.

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