
Global and Planetary Change 233 (2024) 104361

Available online 16 January 2024
0921-8181/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Integrated cyclostratigraphy of the Cau core (SE Spain) - A timescale for 
climate change during the early Aptian Anoxic Event (OAE 1a) and the 
late Aptian 

Rafael Martínez-Rodríguez a,b,*, Sietske J. Batenburg c, José M. Castro a, Ginés A. de Gea a, 
Luis M. Nieto a, Pedro A. Ruiz-Ortiz a, Stuart Robinson d 

a CEACTEMA and Geology Department, University of Jaén, Campus Universitario, 23071 Jaén, Spain 
b GEODESPAL Department (Geodynamics, Stratigraphy and Paleontology), Faculty of Geological Sciences, Complutense University, Madrid, C/ José Antonio Novais, 12, 
28040 Madrid, Spain 
c Facultat de Ciències de la Terra, Universitat de Barcelona, Martí i Franqués, 08028 Barcelona, Spain 
d Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK   

A R T I C L E  I N F O   

Editor: Dr. Alan Haywood  

Keywords: 
Cyclostratigraphy & astrochronology 
Aptian 
OAE 1a 
Time-series analysis 
Paleoclimatology 

A B S T R A C T   

We report a cyclostratigraphic study performed on the Cau core (Spain), which is considered an Aptian strati
graphic reference for global correlation and paleoenvironmental reconstruction. This investigation presents an 
astronomical timescale for the Aptian from the Ap2a to Ap14 carbon-isotope stages. Based on the evaluation of a 
multiproxy dataset from the Cau core, we recalibrate the age and duration of different biozones, bioevents, 
chemostratigraphic substages and horizons from the early and late Aptian, with special focus on the Selli Event, 
providing a new astronomical framework for Aptian climate. From the recognition of 14 long-eccentricity cycles, 
we propose a time span of 5.67 Ma from C-isotope segments Ap2a to the top of Ap14, and ages of 120.82 Ma for 
the onset of the nannoconid crisis, and 120.20 Ma for the onset of oceanic anoxic event (OAE) 1a. Calculations 
yield a duration of 1.47 Ma for OAE 1a. We estimate the age for the onset of the main non-radiogenic phase of the 
Os isotopes at 120.08 Ma, 120 ka after the onset of OAE 1a. The high-resolution data from the Cau core provide 
further insights in the temporal constraints of the OAE 1a and other Aptian paleoclimatic events. The onset of the 
main non-radiogenic excursion in Os isotopes occurring 120 ka after the onset of OAE 1a reinforces the theory of 
rapid destabilization of methane hydrates as the trigger of the anoxic event, that preceded the onset of large-scale 
volcanism.   

1. Introduction 

The Aptian-Turonian interval was characterized by intermittent 
super-greenhouse conditions and a warm climate, with an absence of ice 
sheets and weak latitudinal temperature gradients (Bodin et al., 2015; 
Föllmi, 2012; Friedrich et al., 2012; O'Brien et al., 2017). During the 
Aptian (121.4 to 113.2 Ma; Gradstein et al., 2020), temperatures and 
sea-levels oscillated, with a major rise in both during the early Aptian. 
Recurrent anoxic conditions in the Tethys Ocean and worldwide led to 
the deposition of several organic-rich beds, including the Selli, Noir, 
Fallot, and Jacob levels (e.g., Ando et al., 2017; Bréhéret, 1994, 1995; 
Caillaud et al., 2020, 2022; Ferry, 2017; Friedrich et al., 2003; Friès and 
Parize, 2003; Heimhofer et al., 2004, 2006; Herrle et al., 2003, 2004, 

2010; Rubino, 1989; Stein et al., 2011; Tribovillard, 1989; Tribovillard 
and Gorin, 1991; Westermann et al., 2013). One of the intensely studied 
Oceanic Anoxic Events (OAEs) is the early Aptian OAE (OAE 1a) (see 
Arthur et al., 1990; Erba et al., 1999, 2015; Méhay et al., 2009; Stein 
et al., 2011). The most distinct feature of this event is a negative 
excursion in carbon isotope values, followed by a pronounced positive 
excursion. The positive and negative shifts in δ13C have been observed 
worldwide and both in terrestrial and marine records (e.g., Ando et al., 
2008; Bralower et al., 1999; Castro et al., 2021; De Gea et al., 2003; 
Elkhazri et al., 2013; Gröcke et al., 1999; Heldt et al., 2008; Hu et al., 
2012; Kuhnt et al., 2011). Although OAE 1a has been extensively studied 
with many studies focused on environmental changes, the pacing of the 
event itself is poorly constrained, leading to uncertainty regarding the 

* Corresponding author at: CEACTEMA and Geology Department, University of Jaén, Campus Universitario, 23071 Jaén, Spain. 
E-mail addresses: rodrigue@ujaen.es, rafaelma@ucm.es (R. Martínez-Rodríguez).  

Contents lists available at ScienceDirect 

Global and Planetary Change 

journal homepage: www.elsevier.com/locate/gloplacha 

https://doi.org/10.1016/j.gloplacha.2024.104361 
Received 5 August 2022; Received in revised form 18 December 2023; Accepted 12 January 2024   

mailto:rodrigue@ujaen.es
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Global and Planetary Change 233 (2024) 104361

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causal mechanisms (Adloff et al., 2020). Although it is considered that 
OAE 1a was characterized by a major warming, there is some evidence 
that cooler intervals or “cold snaps” occurred during the event (e.g., 
Jenkyns, 2018). Three possibly global cooling episodes have been 
documented within OAE 1a through high-resolution studies. Cooling has 
been tentatively related to reduced atmospheric CO2 levels (Jenkyns, 
2018) possibly resulting from lessened volcanic activity in combination 
with an increase in global burial of organic matter (Gröcke et al., 1999; 
Skelton and Gili, 2012) and accelerated silicate weathering on the 
continents (Archer, 2011; Berner, 2004). 

Despite its rich sedimentary record of environmental change, a 
complete picture of climatic evolution during the Aptian is not available, 
because most successions cover only limited portions of the Aptian stage 
(Li et al., 2008; Lorenzen et al., 2013; Malinverno et al., 2010). In 
particular, the middle and late Aptian lack a sufficiently constrained 
chronology, limiting paleoclimatic studies. 

Unravelling the sequence of events leading to episodes of oceanic 
anoxia requires constraints on the tempo and mode of climate change by 
studies of well-dated sedimentary successions. The newly drilled Cau 
core in south-eastern Spain presents an exceptional archive of past 
environmental change during the early and late Aptian. The Cau Core is 
particularly suitable for the study of OAE 1a as it provides an expanded 
succession from a relatively shallow marine environment, in comparison 
to other deeper and/or condensed sections from the Tethyan domain. 
The objective of this work is to analyse and study the cyclostratigraphic 
data from the Cau core to establish a floating timescale for the Aptian 
stage, with particular interest in OAE 1a. 

1.1. Aptian timescale 

The Aptian is the third-longest stage in the Cretaceous, and the du
rations and timings of its main events are still under debate (Erba et al., 
2015). A duration for the Aptian stage of 13.4 Ma was suggested by an 
astrochronology from the Piobbico core which recovered 33.7 m of the 
Fucoid marls near Piobbico, central Italy (Huang et al., 2010). Scott 
(2014) sets a duration of the Aptian of about 12 Ma, while the duration 
estimates in the International Chronostratigraphic Chart (ICC - Cohen 
et al., 2013; v2023/04) and the GTS2020 (Gradstein et al., 2020) for the 
Aptian stage are 8.4 and 8.2 Ma, respectively. A study from the Umbria- 
Marche Basin (Italy) has proposed a shorter timespan for the Aptian of 
~7.2 Ma (Leandro et al., 2022), whereas other study from the Vocontian 
Basin (SE France) proposes a timespan of ~9.4 Ma (Charbonnier et al., 
2023). The former studies show the high variability in estimations of the 
duration of the Aptian stage. 

Concerning the Aptian boundaries and events, a proposal is under
way to define the base of the Aptian with a Global Boundary Stratotype 
Section and Point (GSSP) at the base of the Ap3/C3 carbon isotope 
segment, with the Cau section amongst the candidate localities (Castro, 
pers. comm.). Meanwhile, different definitions of the stage boundaries 
and differences in dating efforts result in a range of ages and durations 
suggested for the Aptian and OAE 1a. The base of the Aptian is set at 
~121.4 Ma in the ICC (Cohen et al., 2013; v2023/04)), and the GTS2020 
(Gradstein et al., 2020) provides an age of 121.4 ± 0.6 Ma for the Bar
remian/Aptian boundary (Zhang et al., 2021). This age is in close 
agreement with a published cyclostratigraphic calibration of the Bar
remian (Martinez et al., 2020), suggesting an age for the Barremian/ 
Aptian boundary of 121.40 ± 0.34 Ma, updated to 121.15 ± 0.31 Ma 
(Martinez et al., 2023). Charbonnier et al. (2023) proposed a duration of 
the Aptian Stage of 9.4 Ma and an age of 122.6 ± 0.3 Ma for the base of 
the Aptian. The top of the Aptian is set at ~113.0 Ma in the ICC (Cohen 
et al., 2013; v2023/04) and at 113.2 ± 0.3 Ma in the GTS2020 (Grad
stein et al., 2020), based on a U–Pb date of a basal Albian volcanic ash 
layer in north-west Germany (Selby et al., 2009). Several studies have 
focused on estimating the duration of OAE 1a in the early Aptian, 
including Li et al. (2008), Huang et al. (2010), Malinverno et al. (2010), 
Ogg and Huang, 2012 Scott (2014), Moullade et al. (2015), Scott (2016), 

Leandro et al. (2022), and Charbonnier et al. (2023) resulting in esti
mated durations ranging from 0.56 to 1.5 Ma. 

2. Geological setting and earlier work 

The Cau Core was drilled during 2015–2016 in the Cau section 
(Latitude: 38.70389◦N - Longitude: 0.00472◦W), located in the SE of 
Spain, in the province of Alicante. Four boreholes were drilled (Fig. 2) in 
the Cau hill to obtain an almost continuous record of the Almadich 
Formation (Fm) (Castro et al., 2019; Ruiz-Ortiz et al., 2016). The drilled 
materials of the core from the Cau hill have a mean dip angle of 200, but 
some sections display 100 of dip while others have 300, so a dip 
correction was applied over 5 m intervals. Hole D4 overlaps D3 by 15.4 
m, D3 and D2 overlap by 6.4 m, there is no overlap between D1 and D2, 
and a gap of 1 m has been assigned. For a more detailed report on the 
extraction, logging, biostratigraphy, and lithology of the core see Ruiz- 
Ortiz et al., (2016) and Castro et al. (2021). At Cau (SE Spain), hemi
pelagic marls with varying amounts of organic carbon were deposited in 
a tropical climate at a palaeolatitude of about 22.5◦N (Fig. 1A-B), on a 
margin that experienced extensional rifting as the Western Tethys was 
opening (Castro et al., 2019; De Gea et al., 2003; Naafs et al., 2016). 
Palaeographically, the area is in the Southern Iberian Palaeomargin 
(SIP) (Fig. 1B), which is currently positioned in the Prebetic (Betic 
External Zones) (Martín-Chivelet et al., 2019; Vera, 2001; Vera, 2004). 
The Aptian succession of the Almadich Fm at Cau is composed by marls, 
with intercalated beds of marly limestones less than one-meter thick 
(Fig. 3). Alternations between marls and limestones are more easily 
observed in the field than in the core. The materials represent the distal 
expression of a shallow carbonate ramp with hemipelagic sedimenta
tion. During OAE 1a, laterally equivalent shallow carbonate platform 
materials from the eastern sector of the Aptian Prebetic platform were 

Fig. 1. A. Palaeogeographic reconstruction (based on www.osdn.de; Hay et al., 
1999) for the Early Aptian (120 Ma) showing the location of the Cau section. B. 
Palaeogeography of the Iberian Plate during the Aptian (simplified from Masse 
et al., 1993). 

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  

http://www.osdn.de


Global and Planetary Change 233 (2024) 104361

3

drowned under a transgressive regime (Castro et al., 2008; Martínez- 
Rodríguez et al., 2018; P. W. Skelton et al., 2019). 

2.1. Biostratigraphy 

The record of the Cau Core begins in nannofossil Subzone NC6A 
(Fig. 2), with the nannofossil markers Hayesites irregularis, Nannoconus 
truittii and Conusphaera rothii found at the base of the core. Also recorded 
in the lowermost part of the core is the highest occurrence (HO) of 
Nannoconus steinmanii, which represents the “nannoconid crisis” event 
(Fig. 2). The identification of the nannoconid crisis and the absence of 
Leupoldina cabri allows us to situate the base of the core within the 
planktonic foraminifera biozone of Globigerinelloides blowi. The Cau Core 
ranges through the Aptian until the Paraticinella rohri zone, in the up
permost part of the NC7 zone. The biostratigraphic information provides 
a framework for a first order estimate of sedimentation rate variability 
across the cored interval (Table 1). 

Estimated sedimentation rates vary according to the ages applied by 
different authors, with the starkest difference for the planktic forami
nifera (Fig. 4, Table 1). The main difference in the sedimentation rate 
tendency from the two provided planktonic foraminifer zone age sets is 
found in the Hedbergella trocoidea zone, with estimated sedimentation 
rates of 10.00 cm/ka (using ages from Gradstein et al., 2020) and 4.17 
cm/ka (using ages from Malinverno et al., 2010) (Fig. 4, Table 1). This 
comes from differences in timespan for the H. troicoidea zone between 
the two chronologies, spanning 0.2 Ma in Gradstein et al., (2020) and 
0.48 Ma in Malinverno et al., (2010). However, this biozone only spans 
20.0 m of the 144.4 m long series. The Cau Core is biostratigraphically 
complete, yielding a weighted average sedimentation rate of 5.42 cm/ka 
(forams) and 2.45 cm/ka (ammonites) for the early Aptian, whereas for 
the late Aptian, the sedimentation rate is 0.98 cm/ka (forams) (Fig. 4). 
The sedimentation rate was generally higher in the early Aptian than in 
the late Aptian, due to a decrease in regional rifting activity (Castro 
et al., 2021). 

2.2. Chemostratigraphy and correlation 

Stable carbon-isotope ratios of bulk carbonates were analysed at a 
~30 cm resolution throughout the four individual cores to generate a 
composite record (Castro et al., 2021). Fig. 2 shows 755 values along the 
144.4 m composite of the Cau Core. To provide an Os-isotope record for 
the entire Cau section, 56 samples were collected, between the base and 
top of the Cau section (Fig. 2) (Martínez-Rodríguez et al., 2021). The 
composite record of the core has been constructed comparing the 
gamma ray signal between cores, correlating the δ13C data and faunal 
data from biostratigraphy. 

3. Materials and methods 

3.1. Natural gamma ray logging and magnetic susceptibility 

Gamma Ray levels were measured with a wireline QL40 sensor probe 
at a 3 cm spacing and reported as API (American Petroleum Institute) 

(caption on next column) 

Fig. 2. Bulk-carbonate carbon and oxygen isotope data from Cau composite 
core against depth, and the Cau outcrop section (from Naafs et al., 2016). CIE- 
Carbon Isotope Excursion; OAE 1a-Oceanic Anoxic Event 1a. Segments of δ13C 
chemostratigraphy (Ap2-Ap14) follow the nomenclature by Castro et al. (2021). 
Stratigraphic profile of Os isotope ratios from Martínez-Rodríguez et al., (2021). 
Facies description: (I) Dark grey massive facies, locally with faint lamination 
and scarce bioturbation. (II) Light grey bioturbated facies, the intensity of 
bioturbation is highly variable. (III) Dark grey undisturbed mudstones with 
planar lamination. (IV) Light to dark grey brecciated to nodular facies with 
chaotic organization and massive mudstone/wackestone texture irregularly 
interbedded with partially recrystallized limestone. (V) Grey to orange, 
weathered, recrystallized, or altered facies. 

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  


Global and Planetary Change 233 (2024) 104361

4

radioactivity units (Fig. 3). Magnetic Susceptibility (MS) was measured 
on the cut core-surface using a cylindrical Bartington MS2E core logging 
sensor device, with the BartSoft program. Measurements were per
formed manually at a 5 cm spacing under atmospheric conditions at 
25 ◦C temperature. Each point was measured three times and averaged 
to reduce errors, and reported in IU (instrumental units), although the 
lower part of the data from 144.4 to 110 m has been removed due to 
measurement errors. 

3.2. Carbonate content 

The Cau Core has been sampled with a standard spacing of 10 cm for 
powder samples, and 250 to 300 mg of each sample was reacted with 
5.3 M hydro-chloric acid. Emitted carbon dioxide was measured with an 
automatic calcimeter (DREAM Électronique SAS, Pessac, France) to 
determine the carbonate content. 

3.3. Sedimentary cyclicity 

To test for a potential orbital imprint on sedimentation at Cau, the 
high-resolution physical property and carbonate data were subjected to 
time series analyses. The program Redfit, designed to work with un
evenly spaced series (v3.8e; Schulz and Mudelsee, 2002), was used to 
generate power spectra from the original data. The spectrum of the 
detrended series was calculated using the multi-taper method (2π-MTM 
spectrum; Thomson, 1982; Thomson, 1990). 

Continuous wavelets transform, evolutive harmonic analysis and the 
Average Spectral Misfit (ASM) method (Meyers, 2019; Meyers and 
Sageman, 2007) were conducted using the Astrochron software package 
(v1.1; Meyers, 2019) in R⋅Studio (R Core Team, 2013), to investigate 
periodicities in the records. Scripts used in R, are available in Appendix 
C. Correlation coefficient (COCO) and evolutionary Correlation Coeffi
cient (eCOCO) analyses were performed in Acycle (v2.6; Li et al., 2019). 
The core logging data were also analysed visually, integrating the ob
servations with the facies lithology of the core, the biostratigraphic data 
and the stable isotope profiles to complement the spectral calculations. 

4. Results 

4.1. Sedimentary response 

The Cau Core presents an alternation of light and dark colored bands 
or levels, usually on a decimeter scale. Marl levels are darker in colour, 
in contrast to limestone levels that have lighter tones. The expression of 
rhythmic marls/limestones is the result of the multi-million-year record 
of hemipelagic deposition in the distal part of the Prebetic carbonate 
ramp. An image of a limestone-marl alternation is shown in Appendix B, 
which displays a portion of the core and a micro-X-ray fluorescence 
(μ-XRF) mapping image. The limestone is enriched in Ca, whereas the 
marly part is enriched in other elements such as Al, Si, Ti, S, K, Fe, Sr and 
Zr. The marls have higher gamma ray values, higher MS values and 
lower CaCO3 contents than the limestones (Fig. 3) (see also Figs. 1 and 3 
in Appendix B). 

4.2. Cyclicity 

Time series analyses performed with Redfit are presented against 
MTM spectra to compare the results (Fig. 5). The redfit analyses were 
conducted on the original raw data, without subtracting the mean and 
detrending, as a first test of the reliability of detected periodicities. For 
the MTM analyses, data were linearly interpolated, and trends in the 
signals were subtracted using the LOWESS smoothing method 

Table 1 
Identified biozones in the Cau Core, with base and top depths, corresponding 
estimated ages from Malinverno et al., (2012), Coccioni (2019), Gradstein et al. 
(2020), and resulting sedimentation rates.  

Foraminifera 
zones 

Depth 
(m) 

Ages from  
Gradstein 
et al., 2020 
(Ma) 

Sed. 
rate 
(cm/ 
kyr) 

Ages from  
Malinverno 
et al., 2010 & 
Coccioni, 2019* 
(Ma) 

Sed. 
Rate 
(cm/ 
kyr) 

G. blowii 

Base: 
144.4 

Base: 120.7 
24.9   

Top: 
119.5 

Top: 120.6 

L. cabri 

Base: 
119.5 Base: 120.6 

2.45 
Base: 120.80* 

2.37 Top: 
70.6 

Top: 118.6 Top: 118.74 

G. ferroelensis 

Base: 
70.6 

Base: 118.6 
0.53 

Base: 118.74 
0.67 

Top: 
63.2 Top: 118.2 Top: 117.64 

G. algerianus 

Base: 
63.2 Base: 118.2 

1.66 
Base: 117.64 

1.22 Top: 
40.0 

Top: 116.8 Top: 115.74 

H. trocoidea 

Base: 
40.0 

Base: 116.8 
10.00 

Base: 115.74 
4.17 

Top: 
20.0 Top: 116.6 Top: 115.26 

P. rohri 

Base: 
20.0 Base: 116.6 

0.83   
Top: 
0.0 

Top: 114.2   

Ammonites 
zone 

Depth (m) GTS2020 Age 
(Ma) 

Sedimentation rate (cm/ 
kyr) 

D. forbesi 
Base: 
144.4 

Base: 120.7 
8.57 

Top: 84.4 Top: 120.0 

D. deshayesi 
Base: 84.4 Base: 120.0 

0.50 Top: 79.9 Top: 119.1 

D. furcata Base: 79.9 Base: 119.1 4.00 
Top: 67.9 Top: 118.8 

E. martini Base: 67.9 Base: 118.8 1.31 
Top: 50.9 Top: 117.5  

Fig. 3. 3-m interval of core lithology, gamma ray, CaCO3 and MS. Three darker bands display higher values of gamma ray, MS, and lower values of calcium car
bonate. Clear lithologic intervals show the opposite behaviour in the physical and chemical data, showing minima in gamma ray, MS, and maxima in CaCO3. A 
complete image of proxies for the complete Cau Core can be found in Fig. 9 and in Appendix B (Fig. 1). 

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  


Global and Planetary Change 233 (2024) 104361

5

(Cleveland, 1979). Then, the 20% LOWESS trends were calculated on 
the instantaneous amplitudes of the signals, using the Hilbert transform. 
The residual signals were divided by the long-term signal of the 
instantaneous amplitude, and then standardized, so that both the 
average and variance of the series are stationary. This detrend procedure 
allows the elimination of the lowest frequencies while not impacting 
higher frequencies or creating spurious frequencies in the lowest part of 
the spectrum (Ait-Itto et al., 2023). The red-noise modeling was calcu
lated using the classic AR(1) method following Husson (2014). 

The CaCO3 content record reveals its main periodicities at 72, 10.28, 
and 0.35–0.37 m (above 99% confidence, Fig. 5A), in the redfit spectra. 
In the MTM spectra, 11.50, 0.80 and 0.36–0.37 m periodicities present a 
99.9% level of confidence, and 0.88, 0.47, 0.43 and 0.40 m are above 
99% (Fig. 5B). In the redfit spectra of the gamma-ray record, the main 
periodicities above 99% are at 35.93, 20.52, 13.1 and 5.76 m (Fig. 5C). 
In the MTM spectra, periodicities of 35.93 and 13.1 m are present a 
99.9% confidence, and a 5.76 m periodicity is detected is above 99% 
confidence (Fig. 5D). In the redfit spectra of MS, the periodicities above 
99% confidence are at 54.84 and 9.97 m (Fig. 5E). In the MTM spectra, 
the periodicities above 99.9% confidence are at 54.84 and 10.28 m, and 
a peak at 4.00–4.38 m reaches the 99% confidence level (Fig. 5F). 

4.3. ASM, COCO and eCOCO 

The ASM method is used to evaluate the main frequencies observed 
in the spectral analyses (>99% confidence) and to assess the data 
spectrum with an astronomical target spectrum for the Aptian (118 Ma), 
using the most stable components of eccentricity at 405-ka, 131-ka, 124- 
ka, 99-ka and 95-ka (see GTS2020 – chapter 4) and predicted orbital 
periods for obliquity (49.588-ka and 38.404-ka) and precession (22.156 
and 18.392) from Berger et al. (1992). The optimal sedimentation rate 
obtained using a range from 0.5 to 24.9 cm/ka (Table 1) for the Cau core 
is 2.377 cm/ka (Fig. 6). COCO analysis for the gamma ray record, for a 
range of sedimentation rates from 1.00 to 20.00 cm/ka, exhibits two 

main maxima of stable sediment accumulation rate, at 3.33 cm/ka and 
13.67 cm/ka (Fig. 6B), but the peak at 3.33 cm/ka exceeds the null 
hypothesis significance level (H0, no orbital forcing) by one order of 
magnitude. COCO analysis for the MS record (from 110 m to top), for a 
range of sedimentation rates from 0.5 to 10 cm/ka, exhibits a main 
maximum at 2.36 cm/ka (Fig. 6C) surpassing the null hypothesis sig
nificance level (H0, no orbital forcing). This MS result, although not for 
the complete record, are is in close agreement with the ASM result for 
the complete record (2.37 and 2.36 cm/ka respectively). The eCOCO 
results of the gamma ray record, tested for a range of 1.00 to 20.00 cm/ 
ka with a window of 17.5 m (Appendix C). The evolutionary null hy
pothesis (H0) significance level showed the lowest results by 1.5 to 3.0 
cm/ka (Fig. 6D), lower than 0.02. COCO and eCOCO analyses of the 
CaCO3 data resulted in similar outcomes (scripts in Appendix C) The 
COCO sedimentation rates are 3 and 11 cm/ka (Fig. 4 of Appendix B), 
but the eCOCO analysis indicates higher significance levels for lower 
sedimentation rates, roughly between 1 and 4 cm/ka (Fig. 5 of Appendix 
B). The target series used for both COCO and eCOCO is the La2004 as
tronomical solution (Laskar et al., 2004) at 118 Ma. 

5. Discussion 

The gamma ray and MS records mirror the CaCO3 data (Fig. 3) (see 
also Fig. 2 from Appendix B), likely reflecting variations in the terrige
nous input of clay leading to the deposition of marls, and in the supply of 
carbonate by marine productivity leading to the formation of 
limestones. 

The marls contain higher concentrations of detrital elements Al, Si 
and Fe, while the limestones possess a higher Ca content (Appendix B – 
Fig. 3). The driver of the observed sedimentary cyclicity may be varia
tions in the amount of run-off and weathering influencing the amount of 
clay input and carbonate productivity (Martinez et al., 2015; Moiroud 
et al., 2012). Climate variations forced by cyclic changes in the insola
tion pattern may have resulted in these alternations of limestones and 

Fig. 4. Range of ages (Ma) for the different biozones from the Cau Core, listed in Table 1. FAD = first appearance datum; LAD = last appearance datum. Triangles 
with apex up represent FADs. Diamonds represent LADs. Planktic foraminifera from GTS2020 (Gradstein et al., 2020); ammonite zones from GTS2020; planktic 
foraminifera from Malinverno et al., 2010, and Coccioni et al., 2019; and δ13C segments from Malinverno et al., 2010 are represented. In black dots, tie-points for the 
cyclostratigraphic model of this study. 

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  


Global and Planetary Change 233 (2024) 104361

6

marls. This may be driven by changes in seasonality, with a high 
amplitude of precession causing increased seasonality and stronger 
monsoon-like precipitation and increased run-off and clay input 
(Batenburg et al., 2016). The higher sedimentation rate in the lower 
Aptian (~4 cm/ka) compared to the upper Aptian (~1 cm/ka) indicates 
more presence of siliciclastics in the lower Aptian, and more presence of 
carbonate in the upper Aptian. 

According to independent biostratigraphic control and to spectral 
analyses, 405-ka periodicities may fall in the range of 8–13 m, with the 
Cau core encompassing 11 to 18 long eccentricity cycles. Periodicities 
above 99% confidence at 72, 54.84, 35.93, 21.93 and 20.52 m are too 
long to be evaluated in this study, and only the periodicity of 35.93 m 
found in the redfit and MTM spectra of gamma ray would represent the 
1.2-Ma periodicity. Gamma ray, CaCO3 and MS follow the lithological 
banding patterns, showing alternations on various spatial scales (Fig. 7). 
Collectively, the ratios of periodicities of 2.36 m: 0.95 m: 0.53 m is 
4.5:1.8:1, correspond to the hierarchy of the frequencies of the orbital 
parameters of short eccentricity, obliquity, and precession. The hierar
chy of cycles, with short alternations at a scale of 0.40 to 0.65 m, and 
longer periodicities of about 2–2.72, may correspond to the periodicities 
of precession and short eccentricity. The 10.50-m cycles, varying be
tween 11.50 and 13.1 m and 8.01–9.97 m may represent the 405-ka 
component of long eccentricity. The periodicities shorter than 10.50 m 
are detected in the lower Aptian, yielding sedimentation rates of 2.5–1.9 
cm/ka, that is in accordance with calculated sedimentation rates from 
ammonites (2.45 cm/ka) but differ from sedimentation rate calculated 
from foraminifera (5.42 cm/ka). The 11.50 and 13.1 m periodicities 
occur in the late Aptian, yielding a higher sedimentation rate of 3.1 cm/ 
ka. That differs more from calculated sedimentation rates from 
biostratigraphy of 0.98 cm/ka (forams) and 1.04 cm/ka (ammonites). 
Applying the ammonite sedimentation rate to the 7.7–10 m periodicity 
results in durations of 314–408 ka. 

5.1. Cyclostratigraphic interpretation 

Peaks at 5.76, 4.38 and 4.00 m in the spectral analyses of this study 
(Fig. 5) could be the result of an interference between long- and short- 
components of eccentricity (Liebrand et al., 2017), or may represent 
the 200-ka eccentricity component (e.g., Hilgen et al., 2020). Another 
interpretation for this cyclicity may be the presence of obliquity 
amplitude modulation with a duration of 173 ka. An obliquity-related 
signal can be amplified by internal climate feedback of the carbon 
cycle under different geographic and climate conditions, as reported by 
Huang et al. (2021). Short eccentricity (~100 ka) is represented by 
periodicities of 2.72, 2.43 and 1.99 m in the record. Short eccentricity 
displays a loss of power in the MS record upsection (Figs. 5E-F). 
Obliquity is represented by periodicities of 1.11, 1.05, 0.96, 0.92, 0.87, 
0.84 and 0.80 m, (Fig. 5). Precession is represented by periodicities of 
0.65, 0.50, 0.47, 0.44, 0.43, 0.42 and 0.40 m (Fig. 5). 

In the visual evaluation of the core and gamma ray and carbonate 
records, cycles of 0.80–1.1 m are observed, interpreted as obliquity 
cycles (Fig. 7). This variation in the length of this periodicity suggests a 
strong influence of variations in the tilt of Earth's axis on climate. The 
presence of obliquity fades in different intervals of the core, from 99.5 to 
82 m depth, from 56 to 48 m, from 27.5 to 19 m, and from 9 m depth to 
the top of the core. This attenuation in the sedimentary imprint is 
associated with more variability in seasonality. Although the largest 
obliquity insolation amplitude effect is found at higher latitudes, some 
studies have found a significant obliquity signal in tropical latitudes (e. 
g., Park and Oglesby, 1991). During maximum obliquity, stronger 
monsoons can occur (Tuenter et al., 2005), as there is potential for at
mospheric and oceanic currents to interplay between high and low lat
itudes, showing the interconnection of Earth's climatic system (Tuenter 
et al., 2003, 2005). The most significant influence of these remote 
mechanisms develops in the subtropics (20◦–30◦N) (Tuenter et al., 
2003), where our study area was located. 

Fig. 5. Redfit power spectra (using a Welch window and a segment of 1) and 
three 2π prolate tapers (2π-MTM) of CaCO3 (A-B), gamma ray (C–D) and 
magnetic susceptibility (E-F) for the whole interval. Periods are labelled in 
meters. Colour bands represent the ranges of astronomical parameters. The red 
band represents 405-ka eccentricity. Pink band: possible long obliquity modu
lation. Yellow band: 100-ka eccentricity. Green band: 40-ka obliquity. Blue 
band: 20-ka precession. (For interpretation of the references to colour in this 
figure legend, the reader is referred to the web version of this article.) 

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Global and Planetary Change 233 (2024) 104361

7

Short-eccentricity cycles (between 1.7 and 2.7 m wide) are observed 
in most of the record, except for the interval from 128 to 118.4 m 
(Fig. 7), where the record is dominated by obliquity-paced cycles. This 
part of the record corresponds to the onset of OAE 1a, with variable 
sedimentation rates and an increase in clastic input from the continent 
through intensification of weathering (Castro et al., 2021; Martínez- 
Rodríguez et al., 2021). The influence of obliquity-paced cycles can be 
observed intermittently from 104 to 89 m. The carbonate record shows a 
stronger influence of obliquity than of precession, likely because of 
lacking carbonate levels. Although the western Tethys was under gen
eral warm conditions during the OAE 1a, the climate was unstable 
(Bottini and Erba, 2018). The intermittent presence of obliquity through 
OAE 1a may be indicative of changes in the latitudinal temperature 
gradient, allowing obliquity to affect the patterns in the exchange of 
energy over lower latitudes, in a similar way as described in Gubbio, at a 
very similar paleolatitude (25◦N), in the Umbria-Marche basin (Sinne
sael et al., 2016). 

The presence of an obliquity imprint during the upper Aptian may be 
related to the long-lasting cooling in the western Tethys (O'Brien et al., 
2017) and in the proto North-Atlantic (McAnena et al., 2013). A global 
cooling would imply that the latitudinal temperature differences 
become bigger and that the climate zones shift more toward the equator. 
In such a regime, the paleolocation of Cau likely came under a 

subtropical climatic regime (instead of purely tropical), in which remote 
obliquity mechanisms can have a larger effect (Tuenter et al., 2003). 

This dominance of the obliquity periodicities over the precession 
cycles may have been affected by other factors. The probe used to 
measure gamma-ray is the QL40 GAM (see Martinez-Rodriguez, 2022), 
and the length of the sensor indicated by the manufacturer is 7.62 cm, 
considering an average lateral penetration adjacent to the hole of c. 20 
cm, using a sample distance of 3 cm. This produces a smoothing effect, 
due to the overlapping area between consecutive measurements (Thi
bault and Perdiou, 2018), that is ≈20% of the cone of influence (Fig. 8), 
acting as a lowpass filter, which decreases the high frequencies. The 
sampling distance of CaCO3 (10 cm), results in 4 to 6 points per pre
cession cycle (thickness of 30–50 cm), generating an underestimation of 
the amplitude (Herbert, 2009). Finally, bioturbation mixes the sediment 
and decreases the high frequencies, especially if the sedimentation rate 
is lower than ~3 cm/ka (Hinnov, 2018; Martinez, 2018; Pisias, 1983). 
This may have partially affected the record, given the mean sedimen
tation rate of 2.37 cm/ka (Fig. 6A, C), but specially below 65 m depth 
(Fig. 6D), corresponding to the lower Aptian. Collectively, these biases 
may explain the higher power of in the obliquity band rather than in the 
precession band. 

The paleolocation of Cau was within the humid and temperate sub
tropical paleoclimatic belt during the early Cretaceous. The dominance 

Fig. 6. A) ASM of the main frequencies detected in the gamma ray data over the complete record, performed in Astrochron. Frequencies analysed are above 99% 
confidence. Target orbital periodicities selected are components of eccentricity at 405-ka, 131-ka, 124-ka, 99-ka and 95-ka (in decreasing amplitude) and predicted 
orbital periods for obliquity (49.588-ka and 38.404-ka) and precession (22.156 and 18.392) for 118 Ma. The optimal sedimentation rate obtained using a range from 
0.5 to 24.9 cm/ka (Table 1) for the Cau core is 2.377 cm/ka. The Astrochron script used is available in Appendix C. B) Correlation coefficient for the gamma ray 
record, with tested sedimentation rates range from 1 to 20 cm/ka. C) Correlation coefficient for the magnetic susceptibility record (from 110 m depth to the top), with 
tested sedimentation rates ranging from 0.5 to 10 cm/ka. D) eCOCO analysis of the gamma ray record, showing the null hypothesis (H0) significance level. For both 
the COCO and eCOCO analyses, the number of Monte Carlo simulations is 2000. Parameters used are available in Appendix C. 

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Global and Planetary Change 233 (2024) 104361

8

Fig. 7. High-resolution data from the Cau Core. On the left: depth scale in meters, flanked by the composite image from the Cau drill holes, the data of gamma ray 
(API units) and CaCO3 content (%). Rhythmic banding patterns on different scales are represented by lines in different colours: orange bars indicate pairs of dark and 
light lithologies on a scale of 32–54 cm which are thought to represent the influence of precession; purple bars indicate variations on a scale of 61 cm to 1.1 m, 
thought to represent an obliquity influence; red arches delineate groupings of colour variations and oscillations in the data records on a scale of 1.7 to 2.7 m, and are 

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  


Global and Planetary Change 233 (2024) 104361

9

of temperate, humid subtropical and tropical savannah climate zones, 
representing a combined 70% of the total land area, would have resulted 
in higher Earth surface temperatures and reduced latitudinal gradients, 
thus, resulting in less climate variability (Burgener et al., 2023). Starting 
in the Aptian, a transition begins from a moderately-high CO2 green
house world to a high CO2 hothouse world in the Turonian, and as a 
consequence the Hardley cells begin to shrink during the Aptian 
(Hasegawa et al., 2012). This shrinking in Hardley cells and a southward 
shift of the equatorial humid belt from ~9◦ N in the Berriasian- 
Valanginian to 1◦ S in the Albian (Santos et al., 2022) influenced the 
climate of Cau in the long-term. Through the shrinking of the Hadley 
cell, Cau may have come under the influence of the Ferrel cell, with 
possible changes in oceanic circulation leading to changes in upwelling 
patterns and nutrient distribution. The southward shift of the Inter
tropical Convergence Zone (ITCZ) would result in decreased rainfall, 
thus leading to reduced riverine input of nutrients in the marine envi
ronment. Lower organic carbon production in the surface waters may 
result in decreased organic carbon burial rates. The long-term 
decreasing conditions in humid climate affecting marine productivity 
and organic carbon burial probably contributed to a less marked 

thought to represent the influence of short-eccentricity. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of 
this article.) 

Fig. 8. Cone of influence for the gamma-ray probe used in this study, with a 
theoretical adjacent influence of 20 cm, in a wireline logging diagram showing 
an overlap of two consecutive measurements taken at 3 cm steps. 

Fig. 9. Standardized CaCO3 (A) and gamma ray (B) datasets, with Taner-Hilbert filters centred on a frequency of 1 cycle/m (flow 0.75 and fhigh 1.25, roll-off rate of 
1024). MS: modulated signal (in red), IA: instantaneous amplitude (envelope – in blue). C–D) Lomb-periodograms of the Taner-Hilbert filters of the CaCO3 (C) and 
gamma ray (D) records. The most prominent frequencies are labelled in cycles/m. The upper and lower red dashed lines indicate a confidence levels of p < 0.01 and p 
< 0.05 in each periodogram, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  


Global and Planetary Change 233 (2024) 104361

10

modulation of the short eccentricity cycle in the upper Aptian record 
than in the lower Aptian (as shown in the MS record). 

To test for a modulator of the obliquity, Taner filters have been 
calculated, for periodicities between 1.33 and 0.80 m, that correspond to 
obliquity in the CaCO3 and gamma-ray records (Fig. 9A-B)A Hilbert 
transform was applied over the filter outputs, to calculate the instanta
neous amplitude. The simple periodograms of the filters are displayed in 
Fig. 9 (C–D), and they show frequencies of 0.18 and 0.16 cycles/m as the 
highest peaks. This indicates that the periodicity of 5.76 m (frequency of 
0.17 cycles/m), is possibly a long obliquity modulator, as previously 
described with a pacing of 173-ka in Huang et al. (2021). 

5.2. Chronology 

Although the La2010b solution (Laskar et al., 2011) is considered the 
best fit for geological data beyond 52 Ma (Westerhold et al., 2020), 
chaotic transitions are suspected in the upper Cretaceous (Ma et al., 
2017) and a phase-relationship has not been established. 

To calibrate the astronomical tuning for the complete record we have 
selected an anchor point at the boundary between the Ap11 and Ap12 
segments (Fig. 2), from a revised chronology of the upper Aptian (Ait- 
Itto et al., 2023). This point coincides with the base of the “Faisceau 
Nolan” (Herrle et al., 2004), which is nine 405-ka eccentricity cycles 
below the Aptian-Albian boundary, dated itself as 113.2 ± 0.4 Ma, as 
proposed in the Geologic Time Scale 2020. Consequently, the base of the 
Ap11-Ap12 boundary is dated at 116.8 ± 0.4 Ma. This point (40.2 m 
depth) is located immediately under the bioevent of the last appearance 
of G. algerianus in this study (40.0 m depth) and correlates with a lith
ologic bundle linking the MS data from Charbonnier et al. (2023) to the 

C-isotope stratigraphy from Herrle et al. (2004). 
Taner-Hilbert bandpass filters with a lower and higher frequency cut 

of 0.076 cycles/m and 0.125 cycles/m (roll-off rate: 1012) have been 
calculated for the CaCO3, gamma ray and MS data (Fig. 10). Ages are 
assigned considering a constant duration of 405 ka between consecutive 
peaks in the filter of the 405-ka eccentricity cycle and data were inter
polated linearly between tie points, thus assuming a constant sedimen
tation rate between two consecutive anchor points (Fig. 10) (Table 2). 
The error considered is the same as the floating age of the anchor point, 
400-ka or ± 0.4 Ma. The tie points to anchor the orbitally calibrated age 
model have been selected picking the middle point between filter 

Fig. 10. Normalized CaCO3 (A), gamma-ray (B) and MS (C) data (in grey), with Taner filters (red) centred on a frequency of 0.095 cycles/m, representing the 405-ka 
long eccentricity band. Tie-points for chronology represented by dashed purple lines. (For interpretation of the references to colour in this figure legend, the reader is 
referred to the web version of this article.) 

Table 2 
Tie-points for constructing the orbital age model. 
*Anchor point.  

Depth (m) Age (Ma) 

26.9 116.3 ± 0.4 
37.4 116.7 ± 0.4 
*40.2 *116.8 ± 0.4 
48.6 117.1 ± 0.4 
59.6 117.5 ± 0.4 
71.7 117.9 ± 0.4 
81.3 118.3 ± 0.4 
90.2 118.7 ± 0.4 
100.4 119.1 ± 0.4 
111.8 119.5 ± 0.4 
121.8 119.9 ± 0.4 
130.7 120.3 ± 0.4 
139.8 120.7 ± 0.4  

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Global and Planetary Change 233 (2024) 104361

11

extremes of CaCO3 and gamma ray, in order to distribute the error. 
The investigated section spans from 115.28 Ma to 120.95 Ma (5.67 

Ma), encompassing fourteen long eccentricity 405-ka cycles in total 
(Fig. 10). Spectral (MTM) and evolutionary spectral analyses by Fast 
Fourier transform (LAH), following Kodama and Hinnov (2014), have 
been conducted on the tuned CaCO3 and gamma ray data (Fig. 11D). 
Evolutive harmonic analysis in the time domain (Fig. 11C) shows that 
spectral power is concentrated in a band centered around a 434–400 ka 
periodicity (frequency of 2.5 cycles/Ma – Fig. 11A) in the CaCO3 record, 
which is a direct result of tuning to the periodicity of long eccentricity. 
In the gamma ray record, the spectral power in the long eccentricity 
band is less focused. The evolutionary analyses of both records display 
more power near the base and top of the core, from the base to 120.2 Ma, 
and from the top to 116.3 Ma, probably due to changes in sedimentation 
rate, and the introduction of additional incorrect frequencies due to zero 
padding introduced to cover the sliding window (1.2 Ma) at both ends. 
In the CaCO3 harmonic analysis (Fig. 11C) there is more power in the 
interval from 117.7 to 118.7 Ma, and transfer of power from the long to 
the short eccentricity band (111–90-71 ka) is observed. The long 
obliquity modulation is better observed in the CaCO3 record, both in the 
MTM (250–166 ka periodicities) and evolutive (242–200-181 ka peri
odicities) analyses (Figs. 11A-C). A series of prominent peaks above 99.9 
and 99% confidence can be observed in the MTM spectra of both the 
CaCO3 and gamma ray records (Fig. 11A-B) at 37–32 ka, possibly caused 

by an interference between obliquity and precession periodicities. 

5.3. Timescale, previous results, and implications 

Based on the high-resolution data from gamma ray, CaCO3 and MS 
from the Cau Core, we propose a new astronomically calibrated 

Fig. 11. Spectral analysis in the time domain, for the tuned data of CaCO3 (A) and the gamma ray (B). The upper panels represent the 2π-Multi-Taper Method (MTM) 
spectra. Evolutive spectrograms with window size of 1.2 Ma are represented in the lower panels (C-E). D displays the tuned data of gamma ray (orange) and CaCO3 
(blue). Significant periods are labelled in Ma and ka. Colour bands represent the different ranges of astronomical parameters. The red band represents 405-ka ec
centricity. Pink band: possible long obliquity modulation. Yellow band: 100-ka eccentricity. Green band: 40-ka obliquity. Blue band: 20-ka precession. (For inter
pretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 

Table 3.1 
Estimated age for the most prominent stratigraphic horizons present in this 
study.  

Horizon Depth (m) Age (Ma) 

NC - Nannoconid crisis 141.2 120.82 
Ap2a-Ap2b (Onset CIE) 133.7 120.53 
Ap2-Ap3 (OAE 1a onset) 125.4 120.20 
Ap3-Ap4 119.5 119.97 
Ap4-Ap5 (End CIE) 113.8 119.74 
Ap5-Ap6 91.7 118.87 
Ap6-Ap7 (OAE 1a end) 88.1 118.73 
Ap7-Ap8 76.1 118.26 
Ap8-Ap9 68.7 117.97 
Ap9-Ap10 63.0 117.74 
Ap10-Ap11 52.3 117.32 
Ap11-Ap12 40.4 116.85 
Ap12-Ap13 16.1 115.89 
Ap13-Ap14 7.6 115.55  

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Global and Planetary Change 233 (2024) 104361

12

chronology for the lower and middle Aptian of this intra-shelf basin site 
(Table 3.1). A comparison with other studied sections (Malinverno et al., 
2010, the Cismon APTICORE in N Italy; Beil et al., 2020, La Bédoule in S 
France; Steuber et al., 2022, Abu Dhabi; Leandro et al., 2022, the Poggio 
le Guaine core; Charbonnier et al., 2023, in the Vocontian basin) for the 
duration of Aptian events is provided in Tables 3.2 and 3.4. The resultant 
chronology of this study is older than the duration calculated by Leandro 
et al. (2022). The onset of the NC at Cau (Fig. 12) is 1.42 Ma older than 
the age calculated at Poggio le Guaine (Table 3.2). Regarding the 
calculated timespan of the biozones, the timespan for the G. ferreolensis 
and G. algerianus biozones is similar, with 0.3 and 0.23 Ma, and with 0.7 
and 0.85 Ma, respectively (Table 3.2), but the duration of the L. cabri 
zone is longer in this study (2.00 Ma) in comparison with the study from 
the Poggio le Guaine core (0.6 Ma) (Table 3.2). The biozone of 
G. algerianus is longer in the study from Leandro et al. (2022), with a 
time span of 2.2 Ma, in contrast to the 0.89 Ma calculated in this study 
(Table 3.2). 

The differences found amongst Aptian records means that we are still 
far from reaching a unified astronomical timescale (ATS) for the Aptian 
stage. Independent relative age methods such as biostratigraphy and 

stratigraphic control (such as δ13C chemostratigraphy), or absolute time 
methods (radio-isotopic dating), and differences in thickness/sedimen
tation rates between sections, as well as different hiatuses that could be 
present in the records, are a key factor when applying cyclostratigraphic 
studies, leading to different results. Regarding the different C-13 Aptian 
substages, the C3 stage (Ap notation in this study) calculated from the 
Cismon section is the shortest (46.7 ka), while the C3 stage calculated 
from the Vocontian Basin (Charbonnier et al., 2023) is the longest (485 
ka). The duration of the C3 stage in this study is 230 ka, which is closer 
to the duration calculated from Steuber et al. (2022) at Abu Dhabi, of 
104 ka (Table 3.4). The duration of segment C4 is similar in this study 
(230 ka) to the studies from Malinverno et al. (2010) (239 ka) and 
Charbonnier et al. (2023) (262 ka), whereas the C4 calculated from Abu 
Dhabi is shorter (40 ka) and the C4 duration calculated from La Bédoule 
is longer (388 ka, Table 3.4). The calculated timespan for the C5 
segment is 360 ka longer in this study (870 ka) than in the study from 
Malinverno et al. (2010) (510 ka) (Table 3.4). In contrast, the C6 
segment calculated from the Cismon section (349 ka) is 209 ka longer 
than in our calculations (140 ka) (Table 3.4). Segment C7 is much longer 
in the Cismon section, with a duration of 1590 ka, compared to this work 
(470 ka) (Table 3.4). Finally, the duration of OAE 1a calculated in this 
study (1470 ka, Fig. 12) agrees with the duration calculated from the 
Piobbico core (Huang et al., 2010), of 1400 ka. The duration estimates of 
OAE 1a from the Cismon and Poggio le Guaine cores are shorter with 
durations of 1110 and 920 ka respectively (Table 3.4). Recent data from 
the Vocontian Basin (Charbonnier et al., 2023) indicate an intermediate 
result of 1290 ka (Table 3.4). 

Diverse time estimates can be related primarily to the thickness 
differences of the OAE 1a interval and its segments between sections, 
which are more marked in the C3 segment (Table 3.4). OAE 1a was 
defined at the Cismon section (Menegatti et al., 1998), with a reduced 
thickness, and a probable presence of hiatuses (Beil et al., 2020). 
Expanded sections of OAE 1a were studied later, from the Vocontian 
basin (e.g., Lorenzen et al., 2013; Charbonnier et al., 2023) and the 
Southern Iberian Paleomargin (de Gea et al., 2003; Castro et al., 2019, 
2021), which provide a longer duration of the OAE 1a, doubtless due to a 
more complete record. Interestingly, the C6 segment has similar dura
tion from the thin Cismon section (Malinverno et al., 2010) and the 
expanded Vocontian Basin (Beil et al., 2020) (Table 3.4). This can be 
related to the global context of extensional tectonics that occurred 
during the Early Aptian. Extensional pulses provoked abrupt paleogeo
graphic changes in subsidence patterns, and therefore in sedimentation 
rates (e.g., Skelton et al., 2003; Martin-Chivelet et al., 2019). 

Regarding the Re–Os chemostratigraphy from the Cau core (Martí
nez-Rodríguez et al., 2021), the durations of the detected oceanic 
magmatic phases have been calculated (Table 3.3, Fig. 12), in absence of 
any cosmic dust or meteoritic material source, although this cannot be 
totally discarded. Before analysing these results, a consideration must be 
made, relating to the main emplacement of the Ontong-Java Plateau 
(OJP). The emplacement is reported in literature to have occurred at ca. 
123–121 Ma (Chambers et al., 2004), but a younger age for the 
emplacement of the Ontong-Java LIP has been proposed (Davidson 
et al., 2023), pointing to a connection of the OJP with OAE 1b, thus, 

Table 3.2 
Estimated timespan of bioevents from Leandro et al., (2022), and comparison 
with this study. *Top of the biostratigraphic zone.  

Biostratigraphic 
zones 

Age (Ma)* ( 
Leandro 
et al., 2022) 

Age* 
(Ma) 
(this 
study) 

Timespan 
(Myr) ( 
Leandro et al., 
2022) 

Timespan 
(Myr) (this 
study) 

H. trocoidea 114.5 116.00 0.7 0.85 
G. algerianus 115.2 116.85 2.2 0.89 
G. ferreolensis 117.4 117.74 0.3 0.23 
L. cabri 117.7 117.97 0.6 2.00 
G. blowii  119.97   
Onset of NC 119.4 120.82    

Fig. 12. Correlation of carbon (black line) and osmium (blue line) isotope 
values from the Cau section. The δ13C record is from Castro et al. (2021), the Osi 
record is from Martínez-Rodríguez et al. (2021), with available biostratigraphic 
data (left). The records of Cau are plotted against the age model derived from 
the independently established cyclostratigraphic interpretation of this section 
(this study). (For interpretation of the references to colour in this figure legend, 
the reader is referred to the web version of this article.) 

Table 3.3 
Estimated duration for the Re–Os isotope chemostratigraphy segments from 
Martínez-Rodríguez et al., (2021).  

Re–Os isotope chemostratigraphy segments (Cau Core – from  
Martínez-Rodríguez et al., 2021) 

Timespan (kyr) 

B2 Early HALIP?/Manihiki Plateaus pulses 310 
C1 HALIP? pre-massive magmatism 210 
C2 160 
D1 

HALIP? main volcanic phase 
220 

D2 570 
D3 740 
E Reduced HALIP? activity / Hikurangi plateau 1000  

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Global and Planetary Change 233 (2024) 104361

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leaving OAE 1a without an identified volcanic source, except for the 
High Arctic Large Igneous Province (HALIP) (Dockman et al., 2018). 
Besides, the studied samples from the OJP belong to the top ~200 m 
from the surface of the plateau, whereas the top 8–9 km of the 35 km 
thick megastructure are considered the eruptive portion (Isse et al., 
2021), so that, an older age for lower portions of the OJP cannot be 
discarded. Segment B2, that corresponds to the early magmatic pulses 
from the Manihiki plateau, spans 310 ka (Table 3.3). Segment C, that 
may correspond with the pre-massive HALIP activity, spans 370 ka 
(Table 3, Fig. 12). The beginning of the main Os negative isotopic 
excursion is dated at 120.42 Ma, 120 ka (duration of C2 segment) after 
the onset of OAE 1a. The possible main volcanic activity of the HALIP 
(segment D) is calculated to 1.53 Ma (from Table 3.3, Fig. 12). Segment 
E, corresponding to reduced activity from the HALIP/Hikurangi pla
teaus, presents a duration of 1 Ma (Table 3.3, Fig. 12). 

Regarding OAE 1a, some consensus has been reached on the duration 
of the event (920 ka – 1.1 Ma – 1.29–1.40 Ma - 1.47 Ma), yet more 
variability is found when assessing the different parts of the event. E.g., 
four different calculated durations for the negative excursion (C3/Ap3 
segment), 46.7, 104, 230 and 485 ka, yield a ten-fold difference between 
the Cismon section and the Vocontian Basin. At Cismon, the C3 segment 
is 0.26 m thick, whereas at La Bédoule, it is 6 m thick. This reveals that 
the character of the section, whether is condensed or expanded, can 
have an influence on the calculations. Leandro et al., (2022), based on 
their age estimate, suggest that the magmatic events from OJP and 
HALIP helped to trigger the oceanic anoxia recorded in the Selli Level 
(Polteau et al., 2016; Percival et al., 2021). On the one hand, the C3/Ap3 
negative excursion requires more carbon than just the mantle carbon 
(δ13C composition of − 6‰, Gales et al., 2020), and the Hg-cycle 
perturbation is smaller than for the OJP (Percival et al., 2021). On the 
other hand, our study calculates a 115 ka delay between the onset of the 
OAE 1 and the main phase of non-radiogenic Os, pointing to the release 
of methane hydrates (Adloff et al., 2020) as a potential trigger of the C3/ 
Ap3 segment. Methane hydrates are a suggested trigger for other OAEs, 
such as the Toarcian OAE (T-OAE), as they may explain negative δ13C 
excursions. The cyclic δ13C negative excursions found in the Cau core 
during the Ap2 segment also resemble those observed in the T-OAE 
(Kemp et al., 2005), pointing to an orbital control of the C-cycle influ
enced by short eccentricity. Finally, the broad positive δ13C excursion 
(C4/Ap4 segment) also presents considerable divergences in calculated 
timespans, up to x10 times, e.g., from 40 ka (Stauber et al., 2022) to 388 

ka (Beil et al., 2020), despite the C4 segment having a similar thickness 
in both sections (5.5 m thick in La Bédoule and 5.18 m thick in Abu 
Dhabi). Such different results underline the importance of the role that 
the selected cyclostratigraphic approach plays in these studies. 

The phasing between maxima in CaCO3 and minima in gamma-ray is 
roughly coincident from 20 m depth to the base of the core, so the 
reliability of the data can be considered as reasonably good from 20- 
depth until the base of the core, in the CaCO3 and gamma ray data. 
However, the MS signal is out of phase from 0 m until 70 m depth, so the 
MS data seems to be less reliable. Nevertheless, extremes of the filters 
are more in phase from 80 m depth, with a maximum gap of ~2 m 
(between 112 and 122 m depth), so the accuracy of data in the interval 
of the OAE 1a (88 m to 125 m depth) may present less error. 

6. Conclusions 

The influence of obliquity and eccentricity-modulated precession is 
reflected in a hierarchy of cycles revealed by time series analysis of 
physical property and elemental data. However, this chronology has less 
confidence in the uppermost and lowermost part of the record, where 
the cyclicity is not clear. Although the uncertainty near the base causes 
difficulty for anchoring the record, the durations suggested by the 
cyclicity during the interval of OAE 1a can be considered robust. The 
intermittent presence of obliquity through the record may indicate cold 
snaps or transient cooling episodes in which climatic zones shift 
equatorward. 

Data from this study provide ages of 120.95 Ma for the base of the 
Cau Core, and 115.28 Ma for the top of the Cau Core, with a time span of 
5.67 Ma, which implies a mean sedimentation rate of 2.53 cm/ka. This 
result is more consistent with the sedimentation rate of 2.38 cm/ka 
obtained from the ASM (Fig. 6A) and the 2.36 cm/ka obtained from the 
MS COCO (Fig. 6C), than with the COCO/eCOCO results (peak of 3.33 
cm/ka associated to a null hypthesis significance level lower than 0.001 
– Fig. 6B). The investigated interval has permitted the construction of a 
405-ka astronomically tuned age model. Based on the astronomical 
tuning, we have obtained a duration for OAE 1a of 1.47 Ma, an age for 
the NC of 120.82 Ma, and of 120.20 Ma for the onset of OAE 1a. The 
calculated age for the onset of the main non-radiogenic phase of Osi 
isotopes is 120.32 Ma, occurring 120 ka after the onset of OAE 1a. The 
duration of the main non-radiogenic phase of the Os-isotopes is calcu
lated as 1.53 Ma. As evident from different authors, there are still 

Table 3.4 
Estimated duration for the most prominent stratigraphic features present in this study and comparison with studies from Li et al., (2008), Malinverno et al. (2010), 
Huang et al. (2010), Scott, (2016), Beil et al. (2020), Steuber et al. (2022), Leandro et al. (2022), and Charbonnier et al. (2023).     

Carbon isotope segment duration 

Reference Location Section/core C3 
(kyr) 

C4 
(kyr) 

C5 
(kyr) 

C6 
(kyr) 

(C3-C6) OAE 1a 
(Myr) 

C7 
(kyr) 

This study (kyr) 

This study Prebetic zone Cau 230 230 870 140 1.47 470 Ap2b 330 
Charbonnier et al., 

2023 
Vocontian basin composite 485 262 296 247 1.29  

CIE (Ap2b- 
Ap3) 

560 

Leandro et al., 2022 Umbria Marche basin Poggio le Guaine     0.92  Ap8 290 
Steuber et al., 2022 Abu Dhabi offshore well 104 40     Ap9 230 
Beil et al., 2020 South Provence basin La Bédoule 434 388 281 315 1.418  Ap10 420 

Scott et al., 2016 
Umbria Marche basin 

Cismon 
Rotter Sattel 

80 160 210 110 0.56 990 

Ap11 470 
Ap12 960 

Carbonate platform 
Mexico 

Santa Rosa 
Canyon Ap13 340 

Moullade et al., 2015 South Provence basin composite     1.157 1695  
Scott, 2014 various composite     1.36   
Ogg and Huang, 2012 various composite     1.5   
Huang et al., 2010 Umbria Marche basin Piobbico     1.4   
Malinverno et al., 

2010 Umbria Marche basin Cismon 46.7 239 510 349 1.11 ± 0.11 1590 

Li et al., 2008 

Carbonate platform 
Mexico 
North Atlantic Ocean 
Umbria Marche basin 

Santa Rosa 
Canyon 
DSDP Site 398 
Cismon 

44  

27–41 

930 310 
1.28 
1–1.2 
1.27     330 570 330  

R. Martínez-Rodríguez et al.                                                                                                                                                                                                                  


Global and Planetary Change 233 (2024) 104361

14

substantial differences in the calculated ages and durations for the 
different intervals and horizons from the Aptian stage and for the 
different phases within OAE 1a. Furthermore, the danger of linking the 
OJP LIP with OAE 1a can lead to incorrect conclusions, pointing to a 
need to reevaluate causal relationships between igneous and sedimen
tary records, as in the lack of cosmogenic sources, to better understand 
major biosphere perturbations such as OAEs and LIPs. 

CRediT authorship contribution statement 

Rafael Martínez-Rodríguez: Conceptualization, Data curation, 
Formal analysis, Investigation, Methodology, Software, Supervision, 
Validation, Visualization, Writing – original draft, Writing – review & 
editing. Sietske J. Batenburg: Investigation, Methodology, Software, 
Supervision, Writing – review & editing. José M. Castro: Project 
administration, Resources, Supervision, Writing – review & editing. 
Ginés A. de Gea: Writing – review & editing, Supervision. Luis M. 
Nieto: Supervision, Writing – review & editing. Pedro A. Ruiz-Ortiz: 
Funding acquisition, Project administration, Writing – review & editing. 
Stuart Robinson: Funding acquisition, Writing – review & editing. 

Declaration of competing interest 

The authors declare that they have no known competing financial 
interests or personal relationships that could have appeared to influence 
the work reported in this paper. 

Data availability 

The data used and generated is attached in the file step. (as Appendix 
A) 

Acknowledgements 

We thank the anonymous reviewers for their careful reading of our 
manuscript and their many insightful comments and suggestions. The 
authors are very grateful for the constructive review of M. Martinez, 
which led to improvements of the final version of the manuscript. This 
work is the result of a research visit to the University of Oxford by the 
first author and is a contribution to his PhD thesis within the research 
group RNM-200 “Basin Analysis and Environmental Geology”. Pro
fessors J. M. Molina, M. L. Quijano and M. Reolid, members of the “Cau 
Core Project”, contributed with the sampling and analysis of the core. 
Drs. D. Gallego-Torres, J. M. Ramírez, C. López-Rodríguez and M. 
Rodrigo Gámiz participated in the sampling and description of the cores. 
Laboratory technicians I. Sanchis, J. Lechuga, A. Molero and A. 
Fernández are acknowledged for their help in sampling and processing 
samples from the core. Funding for this study was provided by project 
CGL2014-55274-P of the Spanish Ministry of Science and Technology, 
project 06.17.02.80.P1 of the University of Jaén and FEDER, a PhD- 
student scholarship and a stage grant from the University of Jaén 
(Spain) given to RMR. In loving memory of Professor Roque Aguado 
Merlo. 

Supplementary data 

Supplementary data to this article can be found online at https://doi. 
org/10.1016/j.gloplacha.2024.104361. 

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	Integrated cyclostratigraphy of the Cau core (SE Spain) - A timescale for climate change during the early Aptian Anoxic Eve ...
	1 Introduction
	1.1 Aptian timescale

	2 Geological setting and earlier work
	2.1 Biostratigraphy
	2.2 Chemostratigraphy and correlation

	3 Materials and methods
	3.1 Natural gamma ray logging and magnetic susceptibility
	3.2 Carbonate content
	3.3 Sedimentary cyclicity

	4 Results
	4.1 Sedimentary response
	4.2 Cyclicity
	4.3 ASM, COCO and eCOCO

	5 Discussion
	5.1 Cyclostratigraphic interpretation
	5.2 Chronology
	5.3 Timescale, previous results, and implications

	6 Conclusions
	CRediT authorship contribution statement
	Declaration of competing interest
	Data availability
	Acknowledgements
	Supplementary data
	References