Characteristics of a benchmark loess-paleosol profile in Northeast China

Authors: SUN, ZHONG-XIU - Shenyang Agricultural University; JIANG, YING-YING - Shenyang Agricultural University; WANG, QIU-BING - Shenyang Agricultural University; JIANG, ZHUO-DONG - Shenyang Agricultural University; Libohova, Zamir; Owens, Phillip

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2022
Publication Date: 6/7/2022
Citation: Sun, Z., Jiang, Y., Wang, Q., Jiang, Z., Libohova, Z., Owens, P.R. 2022. Characteristics of a benchmark loess-paleosol profile in Northeast China. Agronomy Journal. https://doi.org/10.3390/agronomy12061376.
DOI: https://doi.org/10.3390/agronomy12061376

Interpretive Summary: Deep sediment profiles can have signatures of past climates when the aerial deposition continues over time. In the paper, we evaluated a deep silty dust deposits that occured over millions of years to identify potential chemical signatures that could related to past climates. We analyzed the silty material and specifically focused on the magnetic minerals and the status of iron in the sediment. The iron will change forms depending on water status, temperature and time exposed to oxygen. We found that iron oxide amounts and mineral arrangement correlated well with magnetic susceptibility and other supporting information found in deep ocean cores. The record within the deep profile suggested there were cooler drier climates as well as warmer wetter climates throughout the past history of this landscape. Tools continue to be developed that help understand the climate and the impacts of climate on changes in soils.

Technical Abstract: The Chaoyang profile represents a rare multi-period, continuous and complete sequence of aeolian paleo-deposits with a stable sedimentary origin and multi-stage paleoclimatic cycles. Benchmark profiles including soil types at different pedogenic stages can be used for the recognition and classification of paleosols and paleoclimate reconstruction. The loess–paleosol sequence benchmark profile (LBP) is also helpful in comparing the results of paleoenvironment reconstruction from different ecological regions. In this study, a loess–paleosol profile derived from thick loess in Chaoyang city of Liaoning province, Northeast China, was investigated as a well-preserved LBP that included various paleosol types. To determine the nature and origin of the Chaoyang profile, the geographic, stratigraphic and morphological characteristics were described in the field. Bulk samples from 42 horizons were collected for chemical and physical analysis, and sub-sampling of 946 samples at 2 cm intervals from the surface to the bottom were taken to measure grain size distributions and magnetic susceptibility. Results showed that the 19.85 m thick loess–paleosol profile had been continuously deposited since 423 ka BP. The upper part (0–195 cm), or UPP, was predominantly of aeolian loess deposition origin but was mixed with water-reworked materials from a nearby secondary loess source. The middle part (195–228 cm), or MIP, was also indirectly affected by the water-reworking process through the leaching of materials from the overlying UPP. The lower part (228–1985 cm), or LOP, was characterized by four reddish stratigraphic layers interbedded with five yellowish ones, indicating several types of paleosols developed under different ecological environments. The multi-stage paleoclimatic cycles as evidenced by morphological and physical characteristics as well as age dating and magnetic susceptibility correlated well with the Lingtai section and LR04 benthic 18O. Because of these attributes, the Chaoyang profile can be deemed as a benchmark loess–paleosol profile for the recognition and classification of paleosols and paleoclimate reconstruction in Northeast China. The differences in morphological and physical properties between paleosols and loess suggest different soil fertility and agronomic properties and need further studies to assess their functionality with climate fluctuation.