L

Campanian

Kundur Formation

Upper avitan Formation

Taipinglinchang Formation

Santonian

Coniacian

Boguchan Formation

Yong'ancun Formation

Turonian

?

Cenomanian

Lower Zvitan Formation

Figure 8.9 Stratigraphic nomenclature for the Upper Cretaceous and Paleocene of Heilongjiang Province, northeastern China (column at right), showing correlations with the stratigraphically equivalent formations and members in the Russian Far East. The lower and upper contacts of the members of the revised Wuyun Formation are not defined lithostratigraphically (modified from Sun et al. 2002). Reprinted by permission.

Figure 8.9 Stratigraphic nomenclature for the Upper Cretaceous and Paleocene of Heilongjiang Province, northeastern China (column at right), showing correlations with the stratigraphically equivalent formations and members in the Russian Far East. The lower and upper contacts of the members of the revised Wuyun Formation are not defined lithostratigraphically (modified from Sun et al. 2002). Reprinted by permission.

biostratigraphy, the K-T boundary would appear to lie below the Wuyun Formation and above the Yuliangzi Formation, i.e. within the Furao Formation (Figure 8.9).

As noted, Liu (1983) had implied that the K-T boundary in Heilongjiang Province lies within the Furao Formation. Sun et al. (2002, 2004) proposed that the type area of the Furao Formation should be restudied because it may actually be composed of a lower part of latest Cretaceous age and an upper part of early Paleocene age. Sun et al. reasoned that the K-T boundary in the Heilongjiang area lies within an interval below the base of their Baishantou Member, in the uppermost part of the Furao Formation. In 2004, Dr. Sun Ge of the Research Center of Paleontology and Stratigraphy, Jilin University, Changchun, collected six samples for palynological analysis from the Baishantou Member, which he sent to one of us (DJN) for analysis. Results confirmed an early Paleocene age for the leaf bed that contains the Tiliaephyllum tsagajanicum assemblage, although microfossil recovery from that bed was poor. Two samples from lower in the section yielded good palynomorph assemblages of early Paleocene age. Unfortunately, three samples from the Furao Formation below the tuff bed were barren, and the possible Late Cretaceous age of that interval could not be verified. Thus, the exact position of the K-T boundary in Heilongjiang Province remained to be determined.

As of 2007, a search for the K-T boundary in northeastern China was under way using samples from two drill cores in the Furao Formation, the Xiaoheyan

2005 and 2006 cores from near Wuyun, Heilongjiang Province. Drilling of the cores was arranged by Sun Ge. Samples collected for palynology are under investigation by an international team including Rahman Ashraf of the Institut fur Geowissenschaften, Tübingen, Germany; Ian Harding, University of Southampton, England; Valentina Markevich of the Russian Academy of Sciences, Vladivostok; and one of us (DJN). Of particular interest are species of Aquilapollenites present in the samples, some of which are also found in western North America, and others that evidently are indigenous to northeastern China and adjacent areas in the Russian Far East. However, the stratigraphic ranges of species of Aquilapollenites and some others that are characteristic of the uppermost Maastrichtian of western North America are not definitively known in northeastern China and the Russian Far East. Recovery from the Xiaoheyan 2005 core was poor and unreliable in some intervals, which necessitated drilling of the Xiaoheyan 2006 core, from which recovery was nearly complete. Based on presence of pollen species in the lower parts of the Xiaoheyan 2006 core that are known to be Maastrichtian in North America, that interval appears to DJN to be Cretaceous in age. Based on stratigraphic ranges ofthose and some other species in the Russian Far East, Valentina Markevich also concluded (personal communication, 2007) that the lower part of the cored interval is Maastrichtian in age. A sample of uncertain stratigraphic position within the upper part of the Xiaoheyan 2005 core appeared to be of Danian age according to Markevich, but no samples from the upper part of the 2006 core yielded a similar assemblage. The investigations are continuing, but the results from the Xiaoheyan

2006 core, in which the goal was to locate the K-T boundary, verified the presence of the "K" in the lower part of the interval but not the "T" in the upper part.

The sections in northeastern China that include uppermost Cretaceous and lowermost Paleocene nonmarine rocks appear to hold much potential for future discoveries of direct relevance to plants and the K-T boundary. Although initial results from the Wuyun area in Heilongjiang Province were inconclusive, coring seems to be the best way to obtain samples for palynological analysis, because outcrops in the area are discontinuous at road cuts, in coal mines, or along the

Heilongjiang River. At the current state of knowledge, however, sites that rely solely on palynological data and that lack geochronologic, magnetostratigraphic, or geochemical data must be regarded at best as potential K-T boundary sections. At present, the resolution of the K-T boundary in this region is at the stage level (see Section 2.1).

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