Fig. 2.

Carbon-isotope (δ¹³C) profile for carbonates, spore/pollen ratio, and distribution of lycopsid microspores preserved in tetrads in the P-Tr transition sequence of southern Jamesonland, East Greenland. Assuming uniform sedimentation rates, 1 m of lower Wordie Creek Formation represents between 20 and 60 kyr (28). Although the conodont element Hindeodus parvus is the first unquestionable indication of earliest Triassic age, first occurrences of the bivalve Claraia approximate the P-Tr boundary. Small horizontal lines represent position of palynological samples. The sample gap is due to lack of accessible exposures. Relative abundance of the microspores is expressed as a percentage of the total spore/pollen assemblage content. The spore/pollen ratio represents the counted number of spores of lycopsids, ferns, and bryophytes, divided by the total number of counted identifiable spores and pollen grains [n = 80–380 per sample (standard count 200), tetrads representing four spores]. Successive ratios depict two-step vegetation development from closed gymnosperm woodland to open shrubland dominated by herbaceous lycopsids. A, Collapse phase; B, delayed-extinction phase (for details, see ref. 2).