Evaluation of the four potential Cretaceous-Paleogene (K-Pg) boundaries in the Nanxiong Basin based on evidences from volcanic activity and paleoclimatic evolution

Abstract

Determining the location of the Cretaceous-Paleogene (K-Pg) boundary in terrestrial strata is highly significant for studying the evolution of terrestrial ecosystems at the end of the Cretaceous (especially the extinction of non-avian dinosaurs). At present, research on terrestrial K-Pg boundaries worldwide is concentrated in the middle and high latitudes, such as North America and Northeast China. Although many studies have also been carried out in the Nanxiong Basin, located at low latitudes (which has become the standard for dividing and comparing the continental K-Pg stratigraphy in China), many researchers have proposed four possible boundaries from different perspectives. Therefore, the exact location remains to be determined. In this study, the total mercury (Hg) content, environmental magnetism, geochemistry, and other parameters for the samples collected near the four boundaries were determined and compared with existing records. Results indicated that: 1) The total Hg content significantly increased in the upper part of the Zhenshui Formation and Pingling part of the Shanghu Formation with sharp fluctuations. As per latest dating results of Deccan Traps, the significantly high Hg value was attributed to the Deccan Traps eruption. Boundary 1 was located in the middle of the Hg anomaly interval, which was consistent with the relationship between the global K-Pg boundary and time of volcanic eruption. 2) The reconstructed paleoclimate evolution curve revealed that the red sediments in the basin recorded the late Maastrichtian warming event (66.2 Ma). Regarding the relationship between the four boundaries and this warming event, only boundary 1 was found to be closest to the real K-Pg boundary of the Nanxiong Basin.

Full text

Evaluation of the four potential Cretaceous-Paleogene (K-Pg) boundaries in the Nanxiong Basin based on
evidences from volcanic activity and paleoclimatic evolution
Mengting ZHAO1, Mingming MA1, Mei HE 1, Yudan QIU1 and Xiuming LIU1
Citation: SCIENCE CHINA Earth Sciences ; doi: 10.1007/s11430-020-9736-0
View online: https://engine.scichina.com/doi/10.1007/s11430-020-9736-0
Published by the Science China Press
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•RESEARCH PAPER•https://doi.org/10.1007/s11430-020-9736-0
...........................................................................................................
Evaluation of the four potential Cretaceous-Paleogene (K-Pg)
boundaries in the Nanxiong Basin based on evidences from
volcanic activity and paleoclimatic evolution
Mengting ZHAO1, Mingming MA2,3*, Mei HE1, Yudan QIU1& Xiuming LIU2,3,4
1School of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China;
2Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education, Fujian Normal University, Fuzhou 350007,
China;
3Key Laboratory for Subtropical Mountain Ecology, Fujian Normal University, Fuzhou 350007, China;
4Department of Environment and Geography, Macquarie University, Sydney NSW 2109, Australia
Received October 19, 2020; revised January 9, 2021; accepted February 2, 2021; published online March 3, 2021
Abstract Determining the location of the Cretaceous-Paleogene (K-Pg) boundary in terrestrial strata is highly significant for
studying the evolution of terrestrial ecosystems at the end of the Cretaceous (especially the extinction of non-avian dinosaurs). At
present, research on terrestrial K-Pg boundaries worldwide is concentrated in the middle and high latitudes, such as North
America and Northeast China. Although many studies have also been carried out in the Nanxiong Basin, located at low latitudes
(which has become the standard for dividing and comparing the continental K-Pg stratigraphy in China), many researchers have
proposed four possible boundaries from different perspectives. Therefore, the exact location remains to be determined. In this
study, the total mercury (Hg) content, environmental magnetism, geochemistry, and other parameters for the samples collected
near the four boundaries were determined and compared with existing records. Results indicated that: 1) The total Hg content
significantly increased in the upper part of the Zhenshui Formation and Pingling part of the Shanghu Formation with sharp
fluctuations. As per latest dating results of Deccan Traps, the significantly high Hg value was attributed to the Deccan Traps
eruption. Boundary 1 was located in the middle of the Hg anomaly interval, which was consistent with the relationship between
the global K-Pg boundary and time of volcanic eruption. 2) The reconstructed paleoclimate evolution curve revealed that the red
sediments in the basin recorded the late Maastrichtian warming event (66.2 Ma). Regarding the relationship between the four
boundaries and this warming event, only boundary 1 was found to be closest to the real K-Pg boundary of the Nanxiong Basin.
Keywords Nanxiong Basin, K-Pg boundary, total Hg content, late Maastrichtian warming event
Citation: Zhao M, Ma M, He M, Qiu Y, Liu X. 2021. Evaluation of the four potential Cretaceous-Paleogene (K-Pg) boundaries in the Nanxiong Basin based on
evidences from volcanic activity and paleoclimatic evolution. Science China Earth Sciences, 64, https://doi.org/10.1007/s11430-020-9736-0
1. Introduction
The Cretaceous-Paleogene (K-Pg) boundary was accom-
panied by Deccan volcanism, impact of asteroids, and a
significant global mass extinction event (Schulte et al., 2010;
Renne et al., 2013). The most famous extinction event has
been that of the non-avian dinosaurs, making the study of
paleoclimate and palaeontology near K-Pg boundary an
important research topic globally. At present, the Global
Stratotype Section and Point (GSSP) of the K-Pg boundary is
the El Kef section located in Tunisia (Molina et al., 2006),
which represents a typical marine deposit. The establishment
of this GSSP has not been able to explain many phenomenon
in the terrestrial biosphere, such as the extinction of non-
© Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature 2021 earth.scichina.com link.springer.com
SCIENCE CHINA
Earth Sciences
* Corresponding author (email: mamingming159@163.com)
https://engine.scichina.com/doi/10.1007/s11430-020-9736-0

avian dinosaurs and recovery of mammals, thus, making the
establishment of a “terrestrial stratotype” necessary (Li W T
et al., 2010). Most K-Pg boundaries established in the con-
tinental sediments are located in North America. Many K-Pg
continental sedimentary basins are situated in China (Li X H
et al., 2013), including the Songliao (Wu et al., 2009;Wan et
al., 2013;Wang et al., 2013;Wang, 2013), Jiayin (Sun,
2014), and Nanxiong basins (Zhao et al., 2002,2009;Clyde
et al., 2010;Li G et al., 2010;Zhang et al., 2013;Wang et al.,
2015), which provide materials for the study of terrestrial K-
Pg boundary and paleoclimate evolution. Researchers have
proposed several K-Pg standard profiles for the different
regions of China, such as the Songliao (Li S et al., 2013;Wan
et al., 2013), Jiayin (Sun, 2014), Nanxiong (Erben et al.,
1995;Tong et al., 2002,2013;Ling et al., 2005;Clyde et al.,
2010;Zhang and Li, 2015;Zhao et al., 2017), Jianghan (Li et
al., 2014), and Luanchuan-Tantou basins (Jiang et al., 2011).
However, the exact location of the K-Pg boundary in each
profile remains debatable due to two reasons (Xi et al.,
2019). First, no other typical pollen assemblage changes,
similar to those found in North America, have been found
(Liu et al., 2009), and second, the K-Pg boundary established
by different proxies have also been different (such as the
Nanxiong Basin). Therefore, further studies are needed to
clarify the location of the K-Pg boundary in the terrestrial
basins of China.
The Nanxiong Basin (Figure 1) located in Southeast China
preserves the continuous Upper Cretaceous-Early Palaeo-
cene red and purple mudstone-sandstone. The Datang profile
of the basin is regarded as the standard for dividing and
comparing the non-marine K-Pg strata in China. Many stu-
dies have been conducted on strata, palaeontology, non-avian
Figure 1 Schematic diagram of the Nanxiong Basin. (a) Location of the Nanxiong Basin; (b) stratum in the Nanxiong Basin (from Dafeng Formation to
Guchengcun Formation (modified from Li G et al., 2010); (c) Datang profile sampling route; (d) stratigraphy of the Datang profile (modified from Zhang et
al., 2006). 1–4 represent the four potential K-Pg boundaries.
2Zhao M, et al. Sci China Earth Sci
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dinosaur extinction, and the K-Pg boundary (Zhang, 1984;
Erben et al., 1995;Zhang et al., 2013;Zhao et al., 2017).
Furthermore, four K-Pg boundaries have been proposed
based on various evidences (Figure 1d). 1) The grey-yellow
bottom conglomerate at the bottom of the Shanghu Forma-
tion (i.e. Chinese-German Datang section (CGD) 162.5 m
proposed by Zhao et al. (1991) or between the 43/42 layers of
the Datang profile proposed by Zhang et al. (2006)), which is
based on the extinction of non-avian dinosaurs, emergence of
mammals, palaeomagnetism, and negative drift of δ13C
(Tong et al., 2002,2013;Clyde et al., 2010). 2) The upper
portion of the Pingling part of the Shanghu Formation (i.e.
CGD 231 m proposed by Zhao et al. (1991) or between the
49/48 layers of the Datang profile proposed by Zhang et al.
(2006)), which is based on the emergence of large mammal
bemalambda fossils and assemblage of non-marine gastro-
pod fossils (Yu et al., 1990;Zhang and Ling, 2004;Ling et
al., 2005). 3) The boundary of the Pingling and Xiahui parts
of the Shanghu Formation (i.e. CGD 250 m proposed by
Zhao et al. (1991) or between the 53/52 layers of the Datang
profile proposed by Zhang et al. (2006)), which is based on
the assemblage characteristics of ostracod fossils (Zhang,
1984,1992) and comprehensive characteristics of pa-
laeontology (Zhang and Li, 2015). 4) An interval of 21 m in
the lower portion of the upper part of the Zhenshui Forma-
tion (i.e. CGD 57–78 m proposed by Zhao et al. (1991) or
30–32 layers of the Datang section proposed by Zhang et al.
(2006)), which is based on the changes in pollen assemblages
(Erben et al., 1995;Stets et al., 1996;Buck et al., 2004;Zhao
et al., 2017).
Therefore, although Datang is regarded as the standard
profile for dividing and comparing the non-marine K-Pg
strata in China, its real K-Pg boundary position remains to be
further determined. Based on previous studies, mercury (Hg)
content, which is a promising proxy for ancient volcanic
activity, and paleoclimatic evolution were reconstructed in
this study to evaluate the four K-Pg boundaries.
2. Geological setting and methods
2.1 Geological setting
The Nanxiong Basin (25°03'–25°16' N, 114°08'–114°40' E),
with a modern average rainfall of 1555 mm and an average
annual temperature of 19.6°C, is located in Southeast China,
mostly in the Guangdong Province (Figure 1a, Li G et al.,
2010). The basin is elongated along its axis and is located
between the Zhuguang and Qingzhang granites (Shu et al.,
2004). The axis, which has a northwest inclination of 10–
20°, is oriented north-east to south-west (Figure 1b). The
continuous successions of red fluvial-lacustrine clastic that
stretches from the Upper Cretaceous to the Lower Palaeo-
cene are preserved in the basin (Zhang et al., 2013). In ad-
dition to granite, some Cambrian-Jurassic strata also exist
around the basin. The stratum in the basin, with a maximum
thickness of more than 7 km, is sufficiently exposed. Based
on stratigraphic sediments, the basin was divided into two
groups and nine formations, namely Nanxiong (Changba,
Jiangtou, Yuanpu, Dafeng, Zhutian, and Zhenshui forma-
tions) and Luofozhai groups (Shanghu, Nongshan, and Gu-
chengcun formations). The Nanxiong Group, with the
dinosaur and dinosaur egg fossils, represented the Upper
Cretaceous strata, and the Luofozhai Group, with mamma-
lian fossils, represented the Palaeocene strata (Zhang et al.,
2013). In the basin, the conglomerate and coarse-grained
sandstones were found to be similar to those of the adjacent
strata. In addition, pebbles in the basin were relatively
coarse, sharp edged, and poorly sorted, implying that the
sediment in the basin was a near-source accumulation (Shu et
al., 2004), and the provenance remained similar throughout
Late Cretaceous to Early Palaeocene (Yan et al., 2007).
Since the 1920s and 1930s, palaeontology, stratigraphy,
geochronology, and palaeoclimatology studies have been
conducted on this basin (Zhao et al., 1991,2002,2017;
Zhang et al., 2000,2006,2013;Yan et al., 2007;Clyde et al.,
2010;Li G et al., 2010;Zhang and Li, 2015;Zhao and Yan,
2000). Several profiles have been investigated in the basin.
Among these, the Datang profile (Figure 1c and d), with
clear stratigraphic succession and abundant fossils, was the
most systematically investigated. Many researchers have
analysed the Datang profile and found that it is a continuous
deposition with integrated contact (Zhao and Yan, 2000;
Zhang et al., 2006,2013;Tong et al., 2013), which was also
confirmed by our reconstructed paleoclimatic record (please
see Figure 3). In this study, the division scheme proposed by
Zhang et al. (2006) was adopted. The profile, with a total
length of 2300 m and a vertical thickness of 700 m (Zhang et
al., 2006), started at Yangmeikeng and ended at Nilongkeng
(Figure 1c). The profile was mainly composed of silty
mudstone and muddy siltstone with sandstone and con-
glomerate interbeds. The Datang profile consisted of three
formations: Shanghu Formation (287.3 m), Zhenshui For-
mation (294.9 m), and the upper part of the Zhutian For-
mation (104.6 m). The lithological characteristics and
sediment thickness of each formation were as follows (Table
1,Zhang et al., 2006,2013):
2.2 Method
Samples collected from the Datang profile were naturally
dried in the laboratory and subsequently gently ground to
disaggregate the grains. Mercury concentration was de-
termined using a Hydra-C mercury vapourmeter (Leeman
Labs Inc, USA) with a detection limit of 2 ppb (1 ppb=1 ng/g),
and a cold atomic absorption spectrometer. The measure-
ments were based on the direct thermal evaporation of Hg
3
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from the solid samples (800°C for 180 s). One sample was
measured repeatedly for every five samples to ensure the
stabilisation and accuracy of the data. Measurements were
conducted at the Nanjing Institute of Geography and Lim-
nology, Chinese Academy of Sciences.
Representative samples were selected for total organic
carbon (TOC) testing. First, the samples (800–1000 mg)
were placed in 50 mL beakers, with 1 mol/L HCl (3–4 drops)
added to each beaker to make the hydrochloric acid fully
react with the samples. Second, the samples were rinsed with
deionized water until the pH became neutral and subse-
quently dried in an oven at 40°C. Last, TOC was determined
using a soil carbon and nitrogen analyser (Elementar Vario
EL III, Germany).
Based on the Hg test, samples near the four boundaries of
the Datang profile were selected to measure magnetic sus-
ceptibility (χ), saturation isothermal remanence magnetisa-
tion (SIRM), and elemental composition. Samples were
packed into small non-magnetic plastic boxes (8 cm3). χwas
measured using a Bartington MS2-B meter at 470 Hz and
subsequently normalised by mass. SIRM was conducted in a
field of 1 T using a Molspin 1 T pulse magnetiser and
measured by a Minispin spinner magnetometer.
Elemental composition was determined by X-ray fluores-
cence analysis using a PANalytical Epsilon 3-XLE spectro-
meter and the major elements were expressed as oxides. The
chemical index of alteration (CIA-mol) was calculated as
CIA = [Al2O3/(Al2O3+CaO*+Na2O+K2O)]×100% (Nesbitt
and Young, 1982), where CaO* represents CaO associated
with the silicate fraction of the sample. In this study, non-
silicate minerals were not removed by acid leaching, there-
fore, correction method proposed by McLennan et al. (1993)
was used. χ, SIRM, geochemical elements, and TOC tests
were conducted at the Key Laboratory of Humid Sub-tro-
pical Eco-geographical Process of Ministry of Education,
Fujian Normal University.
3. Results
The total Hg content was between 1.69 and 15.58 ppb, lower
than many marine K-Pg profiles (Sial et al., 2013,2016;Font
et al., 2016,2018;Keller et al., 2018), this was probably due
to the arid and oxic deposition conditions. Mercury content
in the Zhutian Formation and lower part of the Zhenshui
Formation was found to be relatively low, which subse-
quently increased from the upper part of the Zhenshui For-
mation to the Pingling part of the Shanghu Formation,
exhibiting sharp fluctuations, and again decreased in the
Xiahui part of the Shanghu Formation (Figure 2c). Further-
more, four significant Hg peaks were observed. The first
peak occurred in the upper part of the Zhenshui Formation,
the initial Hg anomaly area, which coincided with boundary
4; the second peak was approximately located at the
boundary of the Zhenshui and Shanghu formations, the
middle of the Hg anomaly zone and close to boundary 1; the
third peak was observed in the Pingling part of the Shanghu
Formation, between boundaries 1 and 2; the fourth peak was
located at the bottom of the Xiahui part of the Shanghu
Formation, between boundaries 2 and 3, near the end of the
Hg anomaly area (Figure 2a and 2c).
TOC values were found to be significantly low, with most
values being less than 0.1% (Figure 2b), which was con-
sistent with previous studies (Yan et al., 2007). TOC ex-
hibited higher values in the Zhutian Formation, lower part of
the Zhenshui Formation, and Xiahui part of the Shanghu
Formation, and lower values in the upper part of the Zhen-
shui Formation, and Pingling part of the Shanghu Formation,
indicating a slightly negative correlation between TOC and
Hg (Figure 2b and 2c).
χwas found to mostly range from 5×10–8 to 10×
10–8 m3kg–1 and exhibited varying trends between different
formations (Figure 3a). The changes observed in χin the
Zhenshui Formation were divided into three stages: 66.6 to
66.4 Ma, subsequently decreasing to 66.3 Ma and then in-
creasing to 66.2 Ma, and again decreasing to 66 Ma. χvalues
in the Shanghu Formation were relatively higher than those
of the Zhenshui Formation, with two values found to be
approximately 65.7 Ma, corresponding to the two positive
shifts of δ18Ocarb and two negative shifts of δ13Ccarb (Figure 3b
and 3c, Clyde et al., 2010;Wang, 2012).
4. Discussion
Generally, five identification criteria exist for K-Pg. (1) The
Table 1 Lithological characteristics and sediment thickness of each formation in the Datang profile (modified from Zhang et al., 2006,2013)
Formation Thickness (m) Lithology Sediment
Shanghu Xiahui part 199 Dark-purple, brown-red muddy siltstone and silty mudstone with conglom-
erated sandstone and mudstone interbeds, and enriched in calcareous
concretions
Fine
clastic deposits
Pingling part 88.3
Zhenshui Upper part 164.8 Greyish purple sandstone and conglomerate with brown-red sandstone and
silty mudstone interbeds Coarse clastic deposits
Lower part 130.1
Zhutian 104.6 Purple-red, brown-red muddy siltstone with fine sandstone interbeds, the
sandstone contains a small amount of conglomerate
Fine
clastic deposits
4Zhao M, et al. Sci China Earth Sci
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extinction of planktonic foraminifera; (2) the evolution of the
first Danian species; (3) δ13C negative shift; (4) Iridium
anomaly; and (5) K-Pg clay and red layer (Keller et al.,
2018). Without biological basis, the latter three criteria
cannot be used as the standard for K-Pg identification
(Keller, 2011). The former two criteria focus on marine se-
diments. In terrestrial profiles, such as the ones in North
America, pollen is regarded as a crucial criterion for K-Pg
identification (Liu et al., 2009). Based on the research carried
out in North America, Erben et al. (1995) proposed that
changes in the pollen assemblage were found in CGD
57–78 m of the CGY-CGD section proposed by Zhao et al.
(1991) (boundary 4, Figure 3). However, other attempts to
find any changes in the pollen assemblage near boundary 4
failed due to the low number of pollens found in the samples
(Liu et al., 2009). In addition, the paleoclimate of the Nan-
xiong Basin (arid and semi-arid) and North America (humid)
were found to be different. Such different paleoclimatic
conditions lead to different vegetation types and preservation
conditions. Therefore, it has been considered that pollen in
the Nanxiong Basin cannot be directly compared to that in
North America, this should be considered when using pollen
data for identifying K-Pg in the Nanxiong Basin (Liu et al.,
2009;Li et al., 2014).
Recently, Clyde et al. (2010) confirmed the feasibility of
boundary 1 using evidences, such as the significant negative
shift of δ13C, position of the palaeomagnetic chron C29r,
extinction of non-avian dinosaurs, and evolution of Danian
mammals. However, Zhao et al. (2017) proposed that the
paleomagnetic results of the study profile were controversial
and required further study; thus, Zhao et al. continued to
persist in the pollen K-Pg boundary (boundary 4). Therefore,
boundaries 1 and 4 were found to be the potential candidates
for the K-Pg boundary. Although new evidences were sup-
plied, it remained impossible to determine which boundary
was closed to the real K-Pg. In addition to conventional
standards, new and innovative evidences should be proposed
to resolve this issue.
Mercury, as the only volatile metal in nature, is often
discharged into the atmosphere through volcanic activity
(Pyle and Mather, 2003;Zambardi et al., 2009). The re-
sidence time of Hg in the atmosphere is 0.5–2 years, which
ensures its global distribution while also being quickly de-
posited in terrestrial or marine sediments (Pyle and Mather,
2003;Witt et al., 2008;Bagnato et al., 2011). It has also been
successfully used as a tracer for reconstructing ancient vol-
canic activity (Grasby et al., 2015,2019;Shen et al., 2019a).
In recent years, an increasing number of studies have used
Hg to link mass extinction events with volcanic activities in
the large igneous provinces (e.g. Shen et al., 2019a,2019b,
2019c). Many studies have reported significant Hg spikes
near the K-Pg boundary of marine profiles, which was at-
tributed to the Deccan Traps volcanism (Silva et al., 2013;
Sial et al., 2013,2014;Font et al., 2016,2018;Keller et al.,
2018,2020). The latest high-precision chronology showed
that the Deccan Traps erupted less than 1 million years ago
Figure 2 Lithology (a), TOC (b), and total Hg content (c) of the Datang profile, the purple dash lines represent boundaries 1, 2, and 3, while the purple bar
represents boundary 4; (d) Hg content curve corrected by the paleomagnetic chronology provided by Clyde et al. (2010); (e) U-Pb age of the Deccan Traps
reported by Schoene et al. (2019), and the grey line represents the K-Pg boundary; (f) 40Ar-39Ar age of the Deccan Traps reported by Sprain et al. (2019), the
red thickness of the line represent higher eruption.
5
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(66.3–65.5 Ma, U-Pb, Schoene et al., 2019; 66.413–65.422
Ma, 40Ar-39Ar, Sprain et al., 2019,Figure 2), with the erup-
tion process crossing the K-Pg boundary, which implies that
Hg can be possibly used to reveal the K-Pg boundary in the
study area.
In previous studies, Hg was found to be attached to certain
substances, such as organic matter, sulphides, and clay mi-
nerals (Sial et al., 2013;Font et al., 2016;Grasby et al., 2019;
Shen et al., 2019d,2020). TOC estimated in this study was
found to be mostly below 0.1% (Figure 2b), which was lower
than the lowest value of TOC used for Hg/TOC correction
(0.2%, Grasby et al., 2019; 0.1%, Shen et al., 2019a). Fur-
thermore, it was found to be negatively correlated with the
Hg content (Figure 2b and 2c), indicating that organic matter
was not a carrier of Hg. In addition, the layers with high Hg
content contained both coarse clastic deposits (the upper part
of the Zhenshui Formation) and fine clastic deposits (the
Pingling part of the Shanghu Formation). Furthermore, no
correlation was found between Hg, Al, and Ti (Figure 4),
indicating that Hg was not carried by clay minerals or runoff.
Therefore, Hg in this study was most likely directly de-
posited from the atmosphere without being attached to a
specific substance, thus, reflecting the change in the Hg
content in the atmosphere emitted by volcanic activity. The
Hg anomalies lasted approximately 0.8 Ma (66.4–65.6 Ma,
Figure 2d), which should have been caused by the large
igneous province. Two periods of volcanic activity were
found in the Nanxiong Basin. One was 96±1 Ma of the basalt
age in the central part of the Zhutian Formation (Shu et al.,
2004), and the other was 60 Ma in the volcanic ash layer
discovered in the central part of the Nongshan Formation
(Tong et al., 2013). These two ages did not match with the
age of the Hg anomaly interval. The volcanic activity in
South China was concentrated during the Early Cretaceous.
No large igneous provinces were discovered during the Late
Cretaceous (Li et al., 2019). Therefore, Hg anomaly in the
Datang profile was caused by the volcanic activity in other
parts of the world. The greatest volcanic activity during the
Late Cretaceous-Early Palaeocene was found to be that of the
Deccan Traps, with the Hg anomaly roughly coinciding with
the eruptive time of the Deccan Traps (Figure 2d, 2e, and 2f).
Therefore, the Hg anomaly in the Nanxiong Basin can be
attributed to the Deccan Traps volcanic activity.
The chronologies of Schoene et al. (2019) and Sprain et al.
(2019) showed that K-Pg was approximately in the middle of
the Deccan Traps volcanic eruption (Figure 2e and 2f). Only
boundary 1 of the four possible K-Pg boundaries was located
in the middle of the Hg anomaly area, which corresponded to
the middle of the Deccan Traps eruption (Figure 2c).
Boundaries 2, 3, and 4 were found to be close to the end, out,
and at the beginning of the Hg anomaly intervals, respec-
tively (Figure 2c). Therefore, from the perspective of the Hg
record, boundary 1 was closer to the global K-Pg boundary
than the other three possible boundaries.
The δ18O of pedogenic carbonate was mainly controlled by
the δ18O of atmospheric precipitation, temperature, and
evaporation (Cerling et al., 1989;Cerling and Quade, 1993;
Quade et al., 2007). Many geological records have revealed
that the δ18O of pedogenic carbonate can be used as an ef-
ficient proxy to reflect paleotemperature (Gao et al., 2015).
The δ18Ocarb of the studied profile (Figure 3b) was found to
be consistent with the marine records (Figure 3d and 3e),
indicating that δ18Ocarb was mainly controlled by temperature
fluctuations. In addition, χ(Figure 3a) and δ18Ocarb both
showed similar trends to marine records (Figure 3), further
confirming their global paleoclimatic significances. Ma et al.
(2018) found that the main magnetic mineral within the
Datang profile was hematite, the concentration of which
controlled the variations in χ. They further proposed a
“pedogenic-plus hypothesis” to explain the mechanism by
which χcould be used as a reliable proxy for paleoclimatic
reconstruction, which implies that the magnetic minerals
(e.g., magnetite and maghemite) formed during pedogenic
Figure 3 (a) χcurve; (b) δ18Ocarb curve (data from Clyde et al., 2010;
Wang, 2012); (c) δ13Ccarb curve (data from Clyde et al., 2010;Wang, 2012);
(d) δ18Obenthic curve from the Pacific Ocean Ocean Drilling Program 1209
(Westerhold et al., 2011); (e) δ18O curve from the Elles section (Tunisia,
Thibault et al., 2015). Purple dash lines represent boundaries 1, 2, and 3,
while the purple bar represents boundary 4. LMWE and Dan-C2 refer to the
late Maastrichtian warming and Dan-C2 warming events.
6Zhao M, et al. Sci China Earth Sci
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processes were completely transformed to hematite by low-
temperature oxidation and chemical weathering under hot
and arid/semi-arid conditions. Moreover, the stronger the
pedogenic processes, the more hematite was generated, and
the higher the χvalues. In general, χand SIRM have been
determined by the phase and content of the magnetic mi-
nerals (Thompson and Oldfield, 1986), whereas the CIA can
be used to indicate the strength of weathering and pedo-
genesis (Nesbitt and Young, 1982,1984). The A-CN-K
(Al2O3-CaO*+Na2O-K2O) ternary diagram (Figure 5) was
drawn to predict the trend of continental chemical weath-
ering (Nesbitt et al., 1980). The early, middle, and late stages
of weathering were characterised by the depletion of Ca and
Na, depletion in K, and removal of Si, respectively. On the
A-CN-K ternary diagram, most data points are parallel to the
A-CN line, suggesting early stages of weathering of the se-
diments, which has not been affected by K-metasomatism
and metamorphism. The corresponding CIA was found to be
approximately 65–80, suggesting an intermediate chemical
weathering intensity. The samples were along the continental
weathering trend, suggesting that the provenance of the
Datang profile remained stable and sufficiently mixed
(Taylor and McLennan, 1985). The rare earth element values
of the Datang profile also suggested that the provenance of
the Datang profile remained stable and sufficiently well (Ma
et al., 2018). Furthermore, positive correlations were found
between χand SIRM/CIA (Figure 6), further confirming the
hypothesis that the change in χwas controlled by the content
of hematite generated in the process of weathering and by
pedogenic processes, thus, providing more evidence for the
reliability of χas an effective paleoclimatic proxy for the
study area.
Many paleoclimatic reconstruction studies have found that
a warming event occurred at the end of the Maastrichtian
period (late Maastrichtian warming event (LMWE), 66.2
Figure 4 Scatter plot of Hg versus major oxides (elements).
Figure 5 A-CN-K ternary diagram of the Datang profile.
7
Zhao M, et al. Sci China Earth Sci
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Ma) (Li and Keller, 1998;Abramovich et al., 2003;Nordt et
al., 2003;Wilf et al., 2003;Thibault and Gardin, 2010;
Woelders et al., 2017,2018;Hull et al., 2020), which was
attributed to the greenhouse effect from CO2emitted from
the Deccan Traps volcanism (Li and Keller, 1998;Nordt et
al., 2003;Wilf et al., 2003;Thibault et al., 2015;Woelders et
al., 2018). After this warming event, the global paleoclimate
pre-K-Pg boundary experienced significant cooling. Figure 3
shows the detailed paleoclimatic evolution process near the
four boundaries of the study area. At 66.2 Ma, χshowed high
values, corresponding to a positive shift of δ18Ocarb and a
negative shift of δ13Ccarb, indicating a significant climate
warming event (i.e. LMWE). Afterwards, χdecreased to 66
Ma and δ18Ocarb showed a negative shift, indicating rapid
cooling. These details can be compared with the δ18O records
of the Elles section, Tunisia (Thibault et al., 2015,Figure 3e).
Comparing the four possible K-Pg boundaries with the de-
tailed paleoclimatic evolution, especially their relation with
the LMWE, it was found that boundary 1 was consistent with
the global record, while boundary 4 was located before the
LMWE. χexhibited double peaks near boundary 2, while
δ13Ccarb also showed two negative shifts, corresponding to the
Dan-C2 event (Quillévéré et al., 2008;Coccioni et al., 2010,
Figure 3). Boundary 3 was found to be located after the Dan-
C2 event. Therefore, from the perspective of paleoclimatic
records, boundary 1 was closer to the global K-Pg boundary
than the other three possible boundaries.
5. Conclusion
New evidences from the Hg and paleoclimatic evolution
records were provided in this study, which aimed to evaluate
the four potential K-Pg boundaries in the Nanxiong Basin.
The following conclusions were obtained.
(1) The total Hg content exhibited high values in the upper
part of the Zhenshui Formation and Pingling part of the
Shanghu Formation with evident fluctuations, which can be
attributed to the Deccan Traps volcanic activity. Using the
latest high-precision eruptive chronology of the Deccan
Traps, only the location of boundary 1 was found to be
consistent to the relationship between the K-Pg boundary
and volcanic activity.
(2) LMWE was recorded in the Nanxiong Basin using χ,
δ18Ocarb, and δ13Ccarb. Boundary 1 was found to be located
after the LMWE, and a short and rapid cooling event was
recorded between boundary 1 and LMWE, consistent with
the records obtained from other regions worldwide.
Generally, boundary 1 was found to be closer to the global
K-Pg boundary than the other three possible boundaries, as
confirmed by the evidences from volcanic activity and pa-
leoclimatic evolution.
Acknowledgements We thank the two anonymous reviewers for their
constructive suggestions. The authors would also like to thank Professor
Enlou Zhang and Associate Professor Yuxin Zhu (Nanjing Institute of
Geography and Limnology, Chinese Academy of Sciences) for their gener-
ous support and assistance in mercury concentration measurements. This
research was supported by the National Natural Science Foundation of
China (Grant Nos. 41602185 and 41772180), the International Geoscience
Programme (IGCP 679), and the Innovation Research Team Fund of Fujian
Normal University (Grant No. IRTL1705).
References
Abramovich S, Keller G, Stüben D, Berner Z. 2003. Characterization of
late Campanian and Maastrichtian planktonic foraminiferal depth ha-
bitats and vital activities based on stable isotopes. Palaeogeogr Pa-
laeoclimatol Palaeoecol, 202: 1–29
Bagnato E, Aiuppa A, Parello F, Allard P, Shinohara H, Liuzzo M, Giudice
G. 2011. New clues on the contribution of Earth’s volcanism to the
global mercury cycle. Bull Volcanol, 73: 497–510
Buck B J, Hanson A D, Hengst R A, Shu-sheng H. 2004. “Tertiary Di-
nosaurs” in the Nanxiong Basin, Southern China, Are Reworked from
the Cretaceous. J Geol, 112: 111–118
Cerling T E, Quade J, Wang Y, Bowman J R. 1989. Carbon isotopes in
soils and palaeosols as ecology and palaeoecology indicators. Nature,
341: 138–139
Cerling T E, Quade J. 1993. Stable carbon isotopes in soil carbonates. In:
Swart P K, Lohmann K C, McKenzie J, Savin S, eds. Climate Change in
Figure 6 (a) Scatter plot of χand SIRM; (b) scatter plot of χand CIA.
8Zhao M, et al. Sci China Earth Sci
https://engine.scichina.com/doi/10.1007/s11430-020-9736-0

Continental Isotopic Records. Washington DC: American Geophysical
Union
Clyde W C, Ting S, Snell K E, Bowen G J, Tong Y, Koch P L, Li Q, Wang
Y. 2010. New paleomagnetic and stable-isotope results from the Nan-
xiong Basin, China: Implications for the K/T boundary and the timing
of Paleocene mammalian turnover. J Geol, 118: 131–143
Coccioni R, Frontalini F, Bancalà G, Fornaciari E, Jovane L, Sprovieri M.
2010. The Dan-C2 hyperthermal event at Gubbio (Italy): Global im-
plications, environmental effects, and cause(s). Earth Planet Sci Lett,
297: 298–305
Erben H K, Ashraf A R, Bohm H, Hambach U, Krumsiek K, Stets J, Thein
J, Wurster P. 1995. Die Kreide/Tertiar-Grenze im Nanxiong-Becken
(Kontinentalfazies, Sudostchina). Erdwissenschaftliche Forschung, 32:
1–245
Font E, Adatte T, Sial A N, Drude de Lacerda L, Keller G, Punekar J. 2016.
Mercury anomaly, Deccan volcanism, and the end-Cretaceous mass
extinction. Geology, 44: 171–174
Font E, Adatte T, Andrade M, Keller G, Mbabi Bitchong A, Carvallo C,
Ferreira J, Diogo Z, Mirão J. 2018. Deccan volcanism induced high-
stress environment during the Cretaceous-Paleogene transition at Zu-
maia, Spain: Evidence from magnetic, mineralogical and biostrati-
graphic records. Earth Planet Sci Lett, 484: 53–66
Gao Y, Ibarra D E, Wang C, Caves J K, Chamberlain C P, Graham S A, Wu
H. 2015. Mid-latitude terrestrial climate of East Asia linked to global
climate in the Late Cretaceous. Geology, 43: 287–290
Grasby S E, Beauchamp B, Bond D P G, Wignall P, Talavera C, Galloway J
M, Piepjohn K, Reinhardt L, Blomeier D. 2015. Progressive environ-
mental deterioration in northwestern Pangea leading to the latest Per-
mian extinction. Geol Soc Am Bull, 127: 1331–1347
Grasby S E, Them Ii T R, Chen Z, Yin R, Ardakani O H. 2019. Mercury as
a proxy for volcanic emissions in the geologic record. Earth-Sci Rev,
196: 102880
Hull P M, Bornemann A, Penman D E, Henehan M J, Norris R D, Wilson P
A, Blum P, Alegret L, Batenburg S J, Bown P R, Bralower T J,
Cournede C, Deutsch A, Donner B, Friedrich O, Jehle S, Kim H, Kroon
D, Lippert P C, Loroch D, Moebius I, Moriya K, Peppe D J, Ravizza G
E, Röhl U, Schueth J D, Sepúlveda J, Sexton P F, Sibert E C, Śliwińska
K K, Summons R E, Thomas E, Westerhold T, Whiteside J H, Yama-
guchi T, Zachos J C. 2020. On impact and volcanism across the Cre-
taceous-Paleogene boundary. Science, 367: 266–272
Jiang X J, Liu Y Q, Ji S A, Zhang X L, Xu L, Jia S H, Lü J C, Yuan C X, Li
M. 2011. Dinosaur-bearing strata and K/T boundary in the Luanchuan-
Tantou Basin of western Henan Province, China. Sci China Earth Sci,
54: 1149–1155
Keller G. 2011. Defining the Cretaceous-Tertiary boundary: A practical
guide and return to first principles. SEPM Spec Publ, 100: 23–42
Keller G, Mateo P, Punekar J, Khozyem H, Gertsch B, Spangenberg J,
Bitchong A M, Adatte T. 2018. Environmental changes during the
Cretaceous-Paleogene mass extinction and Paleocene-Eocene Thermal
Maximum: Implications for the Anthropocene. Gondwana Res, 56: 69–
89
Keller G, Mateo P, Monkenbusch J, Thibault N, Punekar J, Spangenberg J
E, Abramovich S, Ashckenazi-Polivoda S, Schoene B, Eddy M P,
Samperton K M, Khadri S F R, Adatte T. 2020. Mercury linked to
Deccan Traps volcanism, climate change and the end-Cretaceous mass
extinction. Glob Planet Change, 194: 103312
Li G, Hirano H, Batten D J, Wan X, Willems H, Zhang X. 2010. Bios-
tratigraphic significance of spinicaudatans from the Upper Cretaceous
Nanxiong Group in Guangdong, South China. Cretac Res, 31: 387–395
Li L, Keller G. 1998. Abrupt deep-sea warming at the end of the Cretac-
eous. Geology, 26: 995–998
Li S, Gao Q Q, Zhang Y Y, Qu H Y, Wang M Y, Wan X Q. 2013. Late late
Cretaceous-early Paleocene charophytes form the Songliao basin, North
China: SK1(N) core (in Chinese with English abstract). Acta Micro-
palaeontol Sin, 30: 1–16
Li W T, Liu G W, Braman D R, Cao W S, Chen Q B, Brinkman D. 2010. A
proposal to further investigate the Cretaceous-Paleogene boundary
section at Danyang Hubei Province (in Chinese with English abstract). J
Stratigr, 34: 187–206
Li W T, Liu G W, Braman D R, Li Y B, Cao W S, Brinkman D, Shen J,
Chen Q B. 2014. A potential stratotype for the regional lowermost stage
of the continental Paleocene in China. Sci China Earth Sci, 57: 1109–
1116
Li X, Xu W, Liu W, Zhou Y, Wang Y, Sun Y, Liu L. 2013. Climatic and
environmental indications of carbon and oxygen isotopes from the
Lower Cretaceous calcrete and lacustrine carbonates in Southeast and
Northwest China. Palaeogeogr Palaeoclimatol Palaeoecol, 385: 171–
189
Li X, Zhang C, Li Y, Wang Y, Liu L. 2019. Refined chronostratigraphy of
the late Mesozoic terrestrial strata in South China and its tectono-stra-
tigraphic evolution. Gondwana Res, 66: 143–167
Liu G W, Braman D R, Li W T, Brinkman D. 2009. Palynostratigraphic
charateristics of Cretaceous-Paleogene boundary of Western North
America and review on searching for Cretaceous-Paleogene boundary
in Eastern China (in Chinese with English abstract). J Stratigr, 33: 18–
34
Ling Q X, Zhang X Q, Lin J N. 2005. New advance in the study of the
Cretaceous and Paleogene strata of the Nanxiong Basin (in Chinese
with English abstract). J Stratigr, 29(Suppl): 596–601
Ma M, Liu X, Wang W. 2018. Palaeoclimate evolution across the Cre-
taceous-Palaeogene boundary in the Nanxiong Basin (SE China) re-
corded by red strata and its correlation with marine records. Clim Past,
14: 287–302
McLennan S M, Hemming S, McDaniel D K, Hanson G N. 1993. Processes
controlling the composition of clastic sediments. Spec Pap Geol Soc
Am, 284: 21–40
Molina J M, Vera J A, Aguado R. 2006. Reworked microcodium calcar-
enites interbedded in pelagic sedimentary rocks (Paleocene, Subbetic,
Southern Spain): Paleoenvironmental reconstruction. Spec Pap Geol
Soc Am, 416: 189–202
Nesbitt H W, Markovics G, price R C. 1980. Chemical processes affecting
alkalis and alkaline earths during continental weathering. Geochim
Cosmochim Acta, 44: 1659–1666
Nesbitt H W, Young G M. 1982. Early Proterozoic climates and plate
motions inferred from major element chemistry of lutites. Nature, 299:
715–717
Nesbitt H W, Young G M. 1984. Prediction of some weathering trends of
plutonic and volcanic rocks based on thermodynamic and kinetic con-
siderations. Geochim Cosmochim Acta, 48: 1523–1534
Nordt L, Atchley S, Dworkin S. 2003. Terrestrial evidence for two
greenhouse events in the Latest Cretaceous. GSA Today, 13: 4–9
Pyle D M, Mather T A. 2003. The importance of volcanic emissions for the
global atmospheric mercury cycle. Atmos Environ, 37: 5115–5124
Quade J, Rech J A, Latorre C, Betancourt J L, Gleeson E, Kalin M T K.
2007. Soils at the hyperarid margin: The isotopic composition of soil
carbonate from the Atacama Desert, Northern Chile. Geochim Cos-
mochim Acta, 71: 3772–3795
Quillévéré F, Norris R D, Kroon D, Wilson P A. 2008. Transient ocean
warming and shifts in carbon reservoirs during the early Danian. Earth
Planet Sci Lett, 265: 600–615
Renne P R, Deino A L, Hilgen F J, Kuiper K F, Mark D F, Mitchell W S,
Morgan L E, Mundil R, Smit J. 2013. Time scales of critical events
around the Cretaceous-Paleogene boundary. Science, 339: 684–687
Schoene B, Eddy M P, Samperton K M, Keller C B, Keller G, Adatte T,
Khadri S F R. 2019. U-Pb constraints on pulsed eruption of the Deccan
Traps across the end-Cretaceous mass extinction. Science, 363: 862–
866
Schulte P, Alegret L, Arenillas I, Arz J A, Barton P J, Bown P R, Bralower
T J, Christeson G L, Claeys P, Cockell C S, Collins G S, Deutsch A,
Goldin T J, Goto K, Grajales-Nishimura J M, Grieve R A F, Gulick S P
S, Johnson K R, Kiessling W, Koeberl C, Kring D A, Macleod K G,
Matsui T, Melosh J, Montanari A, Morgan J V, Neal C R, Norris R D,
Pierazzo E, Ravizza G, Rebolledo-Vieyra M, Reimold W U, Robin E,
Salge T, Speijer R P, Sweet A R, Urrutia-Fucugauchi J, Vajda V,
9
Zhao M, et al. Sci China Earth Sci
https://engine.scichina.com/doi/10.1007/s11430-020-9736-0

Whalen M T, Willumsen P S. 2010. Response–Cretaceous Extinctions.
Science, 328: 975–976
Shen J, Algeo T J, Planavsky N J, Yu J, Feng Q, Song H, Song H, Rowe H,
Zhou L, Chen J. 2019a. Mercury enrichments provide evidence of Early
Triassic volcanism following the end-Permian mass extinction. Earth-
Sci Rev, 195: 191–212
Shen J, Chen J, Algeo T J, Yuan S, Feng Q, Yu J, Zhou L, O’Connell B,
Planavsky N J. 2019b. Evidence for a prolonged Permian-Triassic ex-
tinction interval from global marine mercury records. Nat Commun, 10:
1563
Shen J, Yu J, Chen J, Algeo T J, Xu G, Feng Q, Shi X, Planavsky N J, Shu
W, Xie S. 2019c. Mercury evidence of intense volcanic effects on land
during the Permian-Triassic transition. Geology, 47: 1117–1121
Shen J, Algeo T J, Chen J, Planavsky N J, Feng Q, Yu J, Liu J. 2019d.
Mercury in marine Ordovician/Silurian boundary sections of South
China is sulfide-hosted and non-volcanic in origin. Earth Planet Sci
Lett, 511: 130–140
Shen J, Feng Q, Algeo T J, Liu J, Zhou C, Wei W, Liu J, Them Ii T R, Gill
B C, Chen J. 2020. Sedimentary host phases of mercury (Hg) and
implications for use of Hg as a volcanic proxy. Earth Planet Sci Lett,
543: 116333
Shu L, Deng P, Wang B, Tan Z, Yu X, Sun Y. 2004. Lithology,
kinematics and geochronology related to Late Mesozoic basin-mountain
evolution in the Nanxiong-Zhuguang area, South China. Sci China Ser
D-Earth Sci, 47: 673–688
Sial A N, Lacerda L D, Ferreira V P, Frei R, Marquillas R A, Barbosa J A,
Gaucher C, Windmöller C C, Pereira N S. 2013. Mercury as a proxy for
volcanic activity during extreme environmental turnover: The Cretac-
eous-Paleogene transition. Palaeogeogr Palaeoclimatol Palaeoecol, 387:
153–164
Sial A N, Chen J, Lacerda L D, Peralta S, Gaucher C, Frei R, Cirilli S,
Ferreira V P, Marquillas R A, Barbosa J A, Pereira N S, Belmino I K C.
2014. High-resolution Hg chemostratigraphy: A contribution to the
distinction of chemical fingerprints of the Deccan volcanism and Cre-
taceous-Paleogene Boundary impact event. Palaeogeogr Palaeoclimatol
Palaeoecol, 414: 98–115
Sial A N, Chen J, Lacerda L D, Frei R, Tewari V C, Pandit M K, Gaucher
C, Ferreira V P, Cirilli S, Peralta S, Korte C, Barbosa J A, Pereira N S.
2016. Mercury enrichment and Hg isotopes in Cretaceous-Paleogene
boundary successions: Links to volcanism and palaeoenvironmental
impacts. Cretac Res, 66: 60–81
Silva M V N, Sial A N, Barbosa J A, Ferreira V P, Neumann V H, De
Lacerda L D. 2013. Carbon isotopes, rare-earth elements and mercury
geochemistry across the K-T transition of the Paraíba Basin, north-
eastern Brazil. Geol Soc London Spec Publ, 382: 85–104
Sprain C J, Renne P R, Vanderkluysen L, Pande K, Self S, Mittal T. 2019.
The eruptive tempo of Deccan volcanism in relation to the Cretaceous-
Paleogene boundary. Science, 363: 866–870
Stets J, Ashraf A, Erben H K, Hahn G, Hambach U, Krumsiek K, Thein J,
Wurster P. 1996. The Cretaceous-Tertiary boundary in the Nanxiong
Basin (continental facies, southeast China). In: MacLeod N, Keller G,
eds. Cretaceous-Tertiary Mass Extinctions: Biotic and Environmental
Changes. New York: Norton. 349–371
Sun G. 2014. Late Cretaceous-Paleocene Biota, K-Pg Boundary and Di-
nosaur Extinction in Jiayin, Heilongjiang. Shanghai: Shanghai Scien-
tific and Technological Education Publishing House. 188
Taylor S R, McLennan S M. 1985. The Continental Crust: Its Composition
and Evolution. New York: Oxford. 312
Thibault N, Gardin S. 2010. The calcareous nannofossil response to the
end-Cretaceous warm event in the Tropical Pacific. Palaeogeogr Pa-
laeoclimatol Palaeoecol, 291: 239–252
Thibault N, Galbrun B, Gardin S, Minoletti F, Le Callonnec L. 2015. The
end-Cretaceous in the southwestern Tethys (Elles, Tunisia): Orbital
calibration of paleoenvironmental events before the mass extinction. Int
J Earth Sci-Geol Rundsch, 105: 771–795
Thompson R, Oldfield F. 1986. Environmental Magnetism. London: Allen
and Unwin. 227
Tong Y S, Li M Y, Li Q. 2002. The Cretaceous-Paleogene boundary in the
Nanxiong Basin, Guangdong Province (in Chinese with English ab-
stract). Geol Bull China, 21: 668–674
Tong Y S, Li Q, Wang Y Q. 2013. An introduction to recent advance in the
study of the continental early Paleogene stages in China (in Chinese
with English abstract). J Stratigr, 37: 428–440
Wan X, Zhao J, Scott R W, Wang P, Feng Z, Huang Q, Xi D. 2013. Late
Cretaceous stratigraphy, Songliao Basin, NE China: SK1 cores. Pa-
laeogeogr Palaeoclimatol Palaeoecol, 385: 31–43
Wang C, Feng Z, Zhang L, Huang Y, Cao K, Wang P, Zhao B. 2013.
Cretaceous paleogeography and paleoclimate and the setting of SKI
borehole sites in Songliao Basin, northeast China. Palaeogeogr Pa-
laeoclimatol Palaeoecol, 385: 17–30
Wang C. 2013. Environmental/climate change in the Cretaceous green-
house world: Records from Terrestrial scientific drilling of Songliao
Basin and adjacent areas of China. Palaeogeogr Palaeoclimatol Pa-
laeoecol, 385: 1–5
Wang Y. 2012. Paleoclimate changes of the late Cretaceous-early Paleocene
in the Nangxiong basin, South China. Masteral Dissertation. Nanjing:
Nanjing University
Wang Y, Li X H, Zhou Y, Liu L. 2015. Paleoclimate indication of terri-
genous clastic rock’s component during the late Cretaceous-early Pa-
leocene in the Nangxiong Basin (in Chinese with English abstract).
Acta Sedimentol Sin, 33: 116–123
Westerhold T, Röhl U, Donner B, McCarren H K, Zachos J C. 2011. A
complete high-resolution Paleocene benthic stable isotope record for the
central Pacific (ODP Site 1209). Paleoceanography, 26: PA2216
Wilf P, Johnson K R, Huber B T. 2003. Correlated terrestrial and marine
evidence for global climate changes before mass extinction at the
Cretaceous-Paleogene boundary. Proc Natl Acad Sci USA, 100: 599–
604
Witt M L I, Mather T A, Pyle D M, Aiuppa A, Bagnato E, Tsanev V I.
2008. Mercury and halogen emissions from Masaya and Telica volca-
noes, Nicaragua. J Geophys Res, 113: B06203
Woelders L, Vellekoop J, Kroon D, Smit J, Casadío S, Prámparo M B,
Dinarès-Turell J, Peterse F, Sluijs A, Lenaerts J T M, Speijer R P. 2017.
Latest Cretaceous climatic and environmental change in the South
Atlantic region. Paleoceanography, 32: 466–483
Woelders L, Vellekoop J, Weltje G J, de Nooijer L, Reichart G J, Peterse F,
Claeys P, Speijer R P. 2018. Robust multi-proxy data integration, using
late Cretaceous paleotemperature records as a case study. Earth Planet
Sci Lett, 500: 215–224
Wu H, Zhang S, Jiang G, Huang Q. 2009. The floating astronomical time
scale for the terrestrial Late Cretaceous Qingshankou Formation from
the Songliao Basin of Northeast China and its stratigraphic and paleo-
climate implications. Earth Planet Sci Lett, 278: 308–323
Xi D, Wan X, Li G, Li G. 2019. Cretaceous integrative stratigraphy and
timescale of China. Sci China Earth Sci, 62: 256–286
Yan Y, Xia B, Lin G, Cui X, Hu X, Yan P, Zhang F. 2007. Geochemistry of
the sedimentary rocks from the Nanxiong Basin, South China and im-
plications for provenance, paleoenvironment and paleoclimate at the K/
T boundary. Sediment Geol, 197: 127–140
Yu W, Gu H L, Zhang X Q. 1990. Assemblage sequence of late Cretaceous
and early Tertiary non-marine gastropods from Nanxiong Basin,
Guangdong (in Chinese with English abstract). Acta Palaeontol Sin, 29:
160–182
Zambardi T, Sonke J E, Toutain J P, Sortino F, Shinohara H. 2009. Mercury
emissions and stable isotopic compositions at Vulcano Island (Italy).
Earth Planet Sci Lett, 277: 236–243
Zhang X Q. 1984. Division and biota of the Luofozhai Group in Pingling
Section, Nanxiong Basin (in Chinese with English abstract). J Stratigr,
8: 239–254
Zhang X Q. 1992. A study on ostracod fauna of Shanghu Formation and
Cretaceous-Tertiary boundary in Nanxiong Basin, Guangdong (in
Chinese with English abstract). Acta Palaeontol Sin, 31: 678–702
Zhang X Q, Li S S, Li Y F. 2000. New progress in stratigraphic study of the
western area of Nabxiong Basin (in Chinese with English abstract).
10 Zhao M, et al. Sci China Earth Sci
https://engine.scichina.com/doi/10.1007/s11430-020-9736-0

Guangdong Geol, 15: 9–18
Zhang X Q, Ling Q X. 2004. Research status quo about the E/K boundary
in Nanxiong Basin. In: Dong W, ed. Proceedings of the Ninth Annual
Symposium of the Chinese Society of Vertebrate Paleontology. Beijing:
China Ocear Press. 35–42
Zhang X Q, Lin J N, Li G, Ling Q X. 2006. Non-marine Cretaceous-
Paleogene boundary section at Datang of Nanxiong, Northern Guang-
dong (in Chinese with English abstract). J Stratigr, 30: 327–340
Zhang X Q, Zhang X M, Hou M C, Li G, Li H M. 2013. Lithostratigraphic
subdivision of red beds in Nanxiong Basin, Guangdong, China (in
Chinese with English abstract). J Stratigr, 37: 57–67
Zhang X Q, Li G. 2015. Discussion on geological age of the Pingling
Member of Shanghu Formation in the Nanxiong Basin, Guangdong
province (in Chinese with English abstract). J Stratigr, 39: 74–80
Zhao Z K, Ye J, Li H M, Zhao Z H, Yan Z. 1991. Extinction of the
dinosaurs across the Cretaceous-Tertiary boundary in Nanxiong Basin,
Guangdong province (in Chinese with English abstract). Vertebrata
Palasiatica, 29: 1–12
Zhao Z, Yan Z. 2000. Stable isotopic studies of dinosaur eggshells from the
Nanxiong Basin, South China. Sci China Ser D-Earth Sci, 43: 84–92
Zhao Z, Mao X, Chai Z, Yang G, Kong P, Ebihara M, Zhao Z. 2002. A
possible causal relationship between extinction of dinosaurs and K/T
iridium enrichment in the Nanxiong Basin, South China: Evidence
from dinosaur eggshells.Palaeogeogr Palaeoclimatol Palaeoecol, 178:
1–17
Zhao Z, Mao X, Chai Z, Yang G, Zhang F, Yan Z. 2009. Geochemical
environmental changes and dinosaur extinction during the Cretaceous-
Paleogene (K/T) transition in the Nanxiong Basin, South China: Evi-
dence from dinosaur eggshells. Chin Sci Bull, 54: 201–209
Zhao Z K, Ye J, Wang Q. 2017. Dinosaur extinction and subsequent
mammalian recovery during the Cretaceous-Paleogene (K/Pg) transition
in the Nanxiong Basin. Chin Sci Bull, 62: 1869–1881
(Responsible editor: Maoyan ZHU)
11
Zhao M, et al. Sci China Earth Sci
https://engine.scichina.com/doi/10.1007/s11430-020-9736-0