Neogene paleoenvironments of north China

current as of 24-Feb-07

 

Late Miocene eolian red clay       deposits unconformably overlain by Plio-Pleistocene loess at Baode, Shanxi Province.

  

Evidence of recent mining activity...

 

 

 

Taking a break on the spoils heap of an old dragon bone mine.

 

Soil carbonate horizons in the Hipparion red clay at Baode.

 

   

A fossil cervid from the Lagrelius Collection showing mesowear characteristics of high cusp relief and sharp cusps, both indicative of a primarily browsing diet.

 

Overview  The late Neogene was a time of significant environmental change globally, and the sedimentary record in north China preserves this time period exceptionally well.  The classic Plio-Pleistocene loess deposits of the Chinese Loess Plateau comprise the 'famous' portion of this record, whereas the lesser known red earth deposits (aka Hipparion red clay) that conformably underlie the loess span a longer period of time (typically 7-8 Ma to 2.7 Ma, but locally extending back to ~22 Ma) and are geographically widespread as well.  The mode of deposition was primarily eolian, although local fluvial reworking is common.  Magnetostratigraphy is the primary basis for the geochronology of both the red clay and classical loess deposits.

 

Dragon Bones  The red clay was first studied in the early 20th century by European, American, and Chinese paleontologists in search of fossil mammals.  During this time, and to a lesser extent today, 'dragon bones' (fossil vertebrate bones and teeth) were mined for traditional medicinal uses.  The early expeditions capitalized on this system and amassed enormous collections of fossil material now housed around the world, and primarily at the Museum of Evolution in Uppsala, Sweden, The American Museum of Natural History in New York City, and the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing.  Following this time period, the red clay received little attention until the last two decades, when Chinese scientists and their foreign colleagues began to recognize the importance of the red clay as a high-resolution archive of Earth history.

 

Reoccupation  During 2004 and 2005, I participated in expeditions to the Hipparion red clay deposits at Baode, Shanxi Province, led by Mikael Fortelius (University of Helsinki) and Zhang Zhaoqun (IVPP, Chinese Academy of Sciences).  The primary goals of the fieldwork were to relocate some of the famous fossil localities worked during the last century, screenwash sediments for micromammals, and develop a geological and paleoenvironmental framework for the deposits and their fossil faunas.  We have been successful in these aspects and are now preparing the results for publication.

 

Sediment and stable isotope stratigraphy  A large portion of my own efforts during these expeditions was, along with Anu Kaakinen (University of Helsinki), to document and describe the detailed stratigraphy of the deposits.  We also collected several sequences of soil carbonates for stable isotope analysis.  Carbon isotopes allow us to deduce the relative contributions of C3 and C4 photosynthesizing biomass in the fossil ecosystems, which places constraints on the paleoclimate of the region, including monsoon history.  Oxygen isotopes yield additional clues about the past climates and environments.  Taken with stable isotope records from other places in the Loess Plateau, we have a very exciting story that we are now working on publishing.

  

 

Isotope ecology of fossil mammals  Another aspect of my research in north China is exploring the paleoecology of fossil mammals using stable isotopes, and, along with Mikael Fortelius, Jussi Eronen, and Liu Liping, tooth morphology including mesowear.  Our work has focused on the rich ungulate fauna, which includes fossil horses, rhinos, giraffids, deer, pigs, gazelles, and bovids.  In June 2005, Jussi and I traveled to the Museum of Evolution in Uppsala, Sweden, to sample this fossil material.  We sampled nearly 200 teeth in a multiple locality, multiple taxon sample design.  The results are in, and we have another exciting story, this one about niche partitioning, the relationship between behavior and morphology, and paleoenvironments in north China during the late Miocene.  We are in the process of preparing these results for publication as well.