Fossil Mammals of Asia

Neogene Biostratigraphy and Chronology

Xiaoming Wang, Lawrence Flynn, Mikael Fortelius

• Publisher: Columbia University Press
• Year: 2013
• ISBN:
  9780231520829
• Topic: Scienze biologiche
• Subtopic: Evoluzione

Fossil Mammals of Asia, edited by and with contributions from world-renowned scholars, is the first major work devoted to the late Cenozoic (Neogene) mammalian biostratigraphy and geochronology of Asia. This volume employs cutting-edge biostratigraphic and geochemical dating methods to map the emergence of mammals across the continent. Written by specialists working in a variety of Asian regions, it uses data from many basins with spectacular fossil records to establish a groundbreaking geochronological framework for the evolution of land mammals.

Asia's violent tectonic history has resulted in some of the world's most varied topography, and its high mountain ranges and intense monsoon climates have spawned widely diverse environments over time. These geologic conditions profoundly influenced the evolution of Asian mammals and their migration into Europe, Africa, and North America. Focusing on amazing new fossil finds that have redefined Asia's role in mammalian evolution, this volume synthesizes information from a range of field studies on Asian mammals and biostratigraphy, helping to trace the histories and movements of extinct and extant mammals from various major groups and all northern continents, and providing geologists with a richer understanding of a variety of Asian terrains.

Part I

East Asia

Chapter 1

Neogene Land Mammal Stages/Ages of China

Toward the Goal to Establish an Asian Land Mammal Stage/Age Scheme

ZHAN-XIANG QIU, ZHU-DING QIU, TAO DENG, CHUAN-KUI LI, ZHAO-QUN ZHANG, BAN-YUE WANG, AND XIAOMING WANG

Led mainly by European and North American geologists, the domain of stratigraphy entered into a state of rapid development after World War II. Foremost among these developments were the discoveries, improvements, and widespread uses of new dating methods (age determination by isotopes, magnetostratigraphy, geochemistry, sequence stratigraphy, and tuning of astronomical cycles), which greatly increased the accuracy and precision of age estimates. Also instrumental in this rapid development was the publication of the International Stratigraphic Guide (ISG; Hedberg 1976; Salvador 1994) and the Revised Guidelines for the Establishment of Global Chronostratigraphic Standards (Remane et al. 1996), which clarified the basic principles and standardized terminologies and procedures. A direct reflection of these improvements is the establishment of the Global Standard Stratotype-Section and Point (GSSP) of the marine stages that is the foundation of the global standard geologic time scale. From 1972 to the present, GSSPs for about 60 of the 100 stages in the Phanerozoic Eonothem have been ratified and codified. This process is embodied in the publication of A Geologic Time Scale 2004 (Gradstein, Ogg, and Smith 2004).

Work on Neogene chronostratigraphy stands as one of the highlights of these developments. Of the eight Neogene stages (up to Piacenzian) in the Standard Global Chronostratigraphic (Geochronologic) Scale (SGCS), lower boundaries of six GSSPs have already been nailed, the boundary for another (Langhian) is all but settled, and only the lower boundary for the Burdigalian stage is still controversial. This progress especially benefits from studies, in the postwar period, of deep-sea drill cores and contained microfossils.

However, the fact remains that the importance of terrestrial stratigraphy and mammalian fossils did not gain sufficient recognition, nor did it gain an adequate expression in the International Stratigraphic Guides. Due to extremely large facies variation in terrestrial deposits and strong endemism, low abundance, and incompleteness of mammal fossil records, terrestrial stratigraphy differs greatly from invertebrate-based marine stratigraphy in methodology and working procedure. For lack of a uniform international standard, every continent, or even country, has established its own terrestrial stratigraphic system.

During the last three decades, progress has also been made in Chinese Neogene terrestrial stratigraphic studies. Most of the classic regions have been revisited, such as the Yushe and Baode areas in Shanxi, the Lantian area in Shaanxi, the Tunggur area in Inner Mongolia, and so on. New discoveries are made in well-exposed fossiliferous regions, such as Tongxin in Ningxia, eastern Nei Mongol (Inner Mongolia), the northern Junggar Basin in Xinjiang, the Linxia Basin in Gansu, the Qaidam Basin in Qinghai, and so on. Magnetostratigraphic work was also undertaken in several classic regions. Great gaps, however, still exist between China and its European and North American counterparts in terms of accumulation of fossils as well as such basic tasks as documentation of fossil occurrences and their biostratigraphic contexts.

This chapter is an attempt to reappraise the existing stages/ages in the Chinese Neogene in relation to the currently widely adopted approaches in terrestrial stratigraphy (Neogene Mammal unit [MN] and North American Land Mammal Age [NALMA]) and from the point of view of the International Stratigraphic Guides. We examine the principles, methods, and working procedures used for the establishment of Chinese stages/ages in the past. We propose a new Neogene chronostratigraphic framework that we consider more consistent with the reality of the state of research and conditions in China. This will provide a foundation for the establishment of a formal Chinese Regional Land Mammal Stage/Age system. Given that China possesses well-developed Neogene terrestrial strata that are richly endowed with fossil mammals, such a system should play a role in the establishment of a Centro-East Asian Land Mammal Stage/Age (CEALMS/A) scheme (Neogene System) in the future.

The numerical age data consistently used in this chapter are those based on the orbitally tuned calibrations for the Neogene, ATNTS2004 (Gradstein, Ogg, and Smith 2004).

For most of the definitions of stratigraphic terminology, we follow Woodburne (2004a:XI–XIV). Here, FHA (first historical appearance of Walsh) = first appearance datum (FAD), and LHA (last historical appearance of Walsh) = last appearance datum (LAD). For further explanations or alternative views, the readers are referred to articles by Walsh (1998, 2000).

REMARKS ON PRINCIPLES, METHODS, AND PROCEDURES

Different Approaches and Practices in Neogene Land Mammal Chronology and Stratigraphy

NALMA Scheme

Tedford (1970) systematically summarized in great detail the evolution of the North American terrestrial stratigraphic system based on fossil mammals. From the beginning of the last century, Osborn and Matthew (1909) organized the North American Cenozoic terrestrial strata into a series of “life zones” on the basis of lithological units containing representative mammalian genera. Although the system was limited by the knowledge then available and had no clearly defined boundaries, Tedford (1970:697) considered these “life zones” as “biostratigraphic units.” On the other hand, Matthew (1924) devised a series of “faunal zones” based on stage of evolution of the horses. Tedford noted that conceptually Matthew’s series is a temporal arrangement entirely different from a chronostratigraphic system, but did not explicitly refer it directly to a bio- or geochronologic system.

Toward the end of the 1930s, the temporal sequencing of the terrestrial Tertiary deposits of North America and the mammal faunas contained therein had become evident and widely accepted. However, its progression was “seriously hampered by the confusing use of identical terms for rock units and for the time units” (Wood et al. 1941:3). The purpose and goal of the Wood Committee, as mandated by the Vertebrate Section of the Paleontological Society, was very clear. It was “to present a provincial time scale for the North American Tertiary,” a system of “purely temporal significance” that will “cover all of Tertiary time,” and to propose “a standardized terminology of purely temporal significance” (Wood et al. 1941:1, 6). More than 300 significant rock and faunal units were analyzed. As a result, 18 mutually exclusive “North American Provincial Ages” (NAPA) were formally proposed. As stated by Wood et al. (1941:1), these NAPAs were established “based on North American mammal-bearing units, … defined in terms of precisely analyzed faunas and the related stratigraphy.” The fauna of each NAPA can be classified into four kinds: index fossils (confined within the NAPA), first appearances (at any point within the NAPA), last appearances (at any point within the NAPA), and characteristic fossils (common but not confined to the NAPA). In magnitude of time span, the NAPA was roughly equivalent to the Age in the European marine chronostratigraphy. As a replacement, Savage (1962) recommended the usage of “North American Land Mammal Age,” or NALMA, which is now unanimously accepted.

The strong conceptual intention to build a pure time scale based on stage-in-evolution of mammals, conflicted with ambiguous and sometimes mutually contradictory methodologies applied and diverged from the ideals of the ISG, which hampered the further development of the NALMA time scale. Commenting on Wood committee’s NALMA, Tedford (1970) pointed out that the conceptual underpinning of the Wood Committee proposal was divorced from their practices and that the two were self-contradictory. In practice, more than half of these “ages” were based on the time spans of specific rock units (Tedford thus called these ages “geochrons”). Even the names of these “ages” were taken from the rock units—for example, “the Arikareean Age equals the temporal span of the Arikaree Group.” Thus defined, these “ages” could not possibly cover the entire time span of the Tertiary Period, because of numerous gaps and hiatuses between them. These “ages” were neither biostratigraphic units, because of lack of detailed biostratigraphic analysis, nor geochronologic “ages,” which should be derived from established chronostratigraphic stages. Finally, Tedford came to the conclusion that these ages should be biochronologic units, “biochrons,” based on evolutionary stages of fossil mammals. Tedford also clearly noticed the fact that, although the NALMA “are useful in depicting gross region-wide faunal change” (Telford 1970:696), it is “impossible to define the exact temporal limits or boundaries of these units without arbitrary selection of criteria” (Telford 1970:701). For such criteria, first appearances of taxa, especially of exotic forms, were listed.

As a leading land mammal stratigrapher, M. O. Woodburne has published since the 1970s a series of papers with the aim of clarifying and remedying the ambiguities and misconceptions of the original NALMA scale (Woodburne 1977). We owe much to him in developing the modern role of mammal biochronology in defining biostratigraphy and chronostratigraphy within the general domain of stratigraphy.

In early years, some mammal paleontologists also attempted to establish formal stages in accordance with the international stratigraphic guidelines, as exemplified by Savage, who proposed the Cerrotejonian and Montediablan Stages in 1955. More recently, the Wasatchian, Clarkforkian, Whitneyan, and Orellan also have been called stages.

In spite of the shortcomings in its original version, the NALMA time scale has proved vital and useful in practice. The majority of North American mammal paleontologists show great sympathy for it and retain this scheme, refining it where possible. Since the middle of the past century, persisting efforts have been made by several generations of paleontologists to enhance the quality of the NALMA scheme. As a result, a carefully refined and comprehensive framework for the Neogene has been accomplished by groups of authoritative paleontologists in 1987, and updated in 2004 (Tedford et al. 1987; Tedford et al. 2004).

We take the Arikareean NALMA as an example to illustrate the principles and methodology adopted by Ted-ford and colleagues for the Neogene. The type of the Arikareean Age originally designated by Wood et al. (1941:11) was the “Arikaree Group of western Nebraska, Agate being the most typical locality, with the limits as defined by Schultz (1938), but including the Rosebud.” Originally, the Arikaree Group included, in ascending order, the Gering, Monroe Creek, and Harrison formations and was tentatively correlated with the Aquitanian Stage and the lower part of the Burdigalian Stage of the Miocene Epoch in the European time scale. Such a definition and correlation remained acceptable until the mid-1970s. Martin (1974) published a short article about some rodent fossils including two specimens of the earliest appearance of Plesiosminthus geringensis from UNSM Mo-19, Durnal locality of the Gering...

Table of contents

• Cover 
• Half title
• Title
• Copyright
• Dedication
• Contents 
• Introduction: Toward a Continental Asian Biostratigraphic and Geochronologic Framework
• Part I. East Asia
• Part II. South and Southeast Asia
• Part III. North and Central Asia
• Part IV. West Asia and Adjacent Regions
• Part V. Zoogeography and Paleoecology
• Plates
• List of Contributors
• Taxonomic Index
• General Index