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Environmental changes around the Jurassic/Cretaceous transition: New nannofossil, chemostratigraphic and stable isotope data from the Lókút section (Transdanubian Range, Hungary)

Article (PDF Available) inSedimentary Geology 360 · August 2017with348 Reads
DOI: 10.1016/j.sedgeo.2017.08.004
Jacek Grabowski at Państwowy Instytut Geologiczny
  • 26.87
  • Państwowy Instytut Geologiczny
János Haas at Eötvös Loránd University
  • 33.81
  • Eötvös Loránd University
Kristalina Stoykova at Bulgarian Academy of Sciences, Strashimir Dimitrov Institute for Geology
  • 22.87
  • Bulgarian Academy of Sciences, Strashimir Dimitrov Institute for Geology
Abstract
New biostratigraphical, chemical and stable isotope (C, O) data are presented from the Lókút section (Transdanubian Range, Hungary) representing a ca. 13 m thick continuous succession of Lower Tithonian–Lower Berriasian pelagic limestones. The study is conducted to verify timing of nannofossil events and major palaeoenvironmental changes at the Jurassic/Cretaceous transition including lithogenic input, palaeoredox and palaeoproductivity variations. Nannofossil zones from NJT 16b to NKT have been identified in the Lókút section and correlated with magnetostratigraphy, covering an interval from polarity zone M21r to M18r. The nannofossil Zone NJT 16b spans the interval from the upper part of M21r to lowermost part of M19n2n but its lower limit is poorly defined due to large diachronism in first occurrence (FO) of Nannoconus infans in various Tethyan sections. FOs of N. kamptneri minor and N. steinmannii minor are situated in the topmost part of the M19n2n and lowermost part of M19n1r magnetozones, respectively. They are located ca. 2–2.5 m above the J/K boundary defined as Intermedia/Alpina subzonal boundary, which falls within the lower half of magnetozone M19n2n. The position of first occurrences of these taxa is similar to that from the Puerto Escaño section (southern Spain) and slightly lower than in Italian sections (Southern Alps). Concentrations of chemical element proxies of terrigenous transport (Al, K, Rb, Th) decrease towards the top of the Lókút section, which suggests a decrease in input of terrigenous material and increasing carbonate productivity during the Early Tithonian and the Berriasian. Slight oxygen depletion at the sea bottom (decrease of Th/U ratio), and large increase in concentrations of productive elements (P, Ba, Ni, Cu) is observed upsection. Nutrients supply via upwelling seems to be the most likely explanation. Increase in phosphorus accumulation rate and a microfacies change from Saccocoma to calpionellid dominated took place in the polarity chron M19r, which apparently coincided with the worldwide Nannofossil Calcification Event, related to a bloom of strongly calcified calcareous nannoplankton taxa. Deposition in the Lókút area was probably affected by long-term climatic trends: aridization and warming. Decreasing δ¹³C values of bulk carbonates throughout the Tithonian and the Berriasian are interpreted as a result of a global trend of accelerated carbonate productivity supported by local factors such as increased upwelling intensity, and a possible change in the composition of carbonate mud.
Environmental changes around the Jurassic/Cretaceous transition:
New nannofossil, chemostratigraphic and stable isotope data from
the Lókút section (Transdanubian Range, Hungary)
J. Grabowski
a,
,J.Haas
b
, K. Stoykova
c
, H. Wierzbowski
a
,P.Brański
a
a
Polish Geological Institute National Research Institute, Rakowiecka 4, 00-975, Warszawa, Poland
b
MTA-ELTE Geological, Geophysical and Space Science Research Group, Eötvös Loránd University, Pázmány Sétány 1/c, Budapest 1117, Hungary
c
Geological Institute of the Bulgarian Academy of Sciences, Acad. G.Bonchev Str., Bl. 24, 1113, Soa, Bulgaria
abstractarticle info
Article history:
Received 4 May 2017
Received in revised form 8 August 2017
Accepted 14 August 2017
Available online 19 August 2017
Editor: Dr. B. Jones
New biostratigraphical, chemical and stable isotope (C, O) data are presented from the Lókút section
(Transdanubian Range, Hungary) representing a ca. 13 m thick continuous succession of Lower Tithonian
Lower Berriasian pelagic limestones. The study is conducted to verify timing of nannofossil events and major
palaeoenvironmental changes at the Jurassic/Cretaceous transition including lithogenic input, palaeoredox and
palaeoproductivity variations. Nannofossil zones from NJT 16b to NKT have been identied in the Lókút section
and correlated with magnetostratigraphy, covering an intervalfrom polarity zone M21r to M18r.The nannofossil
Zone NJT 16b spans the interval from the upper part of M21rto lowermost part of M19n2n but its lower limit is
poorly dened due to large diachronism in rstoccurrence (FO) of Nannoconus infansin various Tethyan sections.
FOs of N. kamptneri minor and N. steinmannii minor are situated in the topmost part of the M19n2nand lowermost
part of M19n1r magnetozones, respectively. They are located ca. 22.5 m above the J/K boundary dened as
Intermedia/Alpina subzonal boundary, which falls within the lower half of magnetozone M19n2n. The position
of rst occurrences of these taxa is similar to that from the Puerto Escaño section (southern Spain) and slightly
lower than in Italian sections (Southern Alps). Concentrations of chemical element proxies of terrigenous trans-
port (Al, K, Rb, Th) decrease towards the top of the Lókút section, which suggests a decrease in input of terrige-
nous material and increasing carbonate productivity during the Early Tithonian and the Berriasian. Slight oxygen
depletionat the sea bottom (decrease of Th/U ratio), and large increase in concentrations of productive elements
(P, Ba, Ni, Cu) is observed upsection.Nutrients supply via upwelling seems to be the most likely explanation. In-
crease in phosphorus accumulation rateand a microfacies changefrom Saccocoma to calpionelliddominated took
place in the polarity chron M19r, which apparently coincided with the worldwide Nannofossil Calcication
Event, related to a bloom of strongly calcied calcareous nannoplankton taxa. Deposition in the Lókút area was
probably affected by long-term climatic trends: aridization and warming. Decreasing δ
13
C values of bulk carbon-
ates throughout the Tithonian and the Berriasian are interpreted as a result of a global trend of accelerated car-
bonate productivity supported by local factors such as increased upwelling intensity, and a possible change in
the composition of carbonate mud.
© 2017 Elsevier B.V. All rights reserved.
Keywords:
Jurassic/Cretaceous boundary
Transdanubian range
Carbon and oxygene isotopes
Palaeoproductivity
Nannofossil stratigraphy
Magnetic susceptibility and lithogenic input
1. Introduction
The Jurassic/Cretaceous transition in the marine realm represents a
period of importantpalaeoenvironmental changes manifested bya
bloomofthe calcareous micro- and nannoplankton(e.g. Bralower et al.,
1989; Bornemann et al., 2003; Tremolada et al., 2006; Casellato, 2010),
sea-level variations (Hardenbol et al., 1998; Hallam, 2001; Haq, 2014)
and deposition of organic rich sediments over vast areas of external
shelves (Föllmi, 2012). Arid conditions prevailed in the Western Tethys
and neighbouring areas of central and northern Europe with decreased
chemical weathering rates (Abbink et al., 2001). A steady decrease
ofcarbonate δ
13
C values is interpreted either as indication of
oligotrophication of oceanic watersor as a result of increased burial of car-
bonate carbon(Weissert and Channell, 1989; Weissert et al., 1998; Price et
al., 2016; Celestino et al., 2017). Although robust palaeoclimatic and
palaeoceanographic models for the J/K transition have been constructed
(for review see e.g. Föllmi, 2012; Tennant et al., 2016), there is still insuf-
cient amount of data to evaluate synchronicity and global vs. regional
character of sedimentary events and processes (e.g. patterns of lithogenic
inux, productivity variations and anoxia) in particular regions and their
relation with eustasy, climatic changes and tectonic events (e.g.
Sedimentary Geology 360 (2017) 5472
Corresponding author.
E-mail address: jacek.grabowski@pgi.gov.pl (J. Grabowski).
http://dx.doi.org/10.1016/j.sedgeo.2017.08.004
0037-0738/© 2017 Elsevier B.V. All rights reserved.
Contents lists available at ScienceDirect
Sedimentary Geology
journal homepage: www.elsevier.com/locate/sedgeo
Strohmenger and Strasser, 1993; Adatte et al., 1996; Reháková, 2000;
Grabowski et al., 2013; Bover-Arnal and Strasser, 2013). Major
transgressiveregressive cycles in the Alpine Tethys are deduced from se-
quence stratigraphy analysis of sections in SE and E France (Strohmenger
and Strasser, 1993; Bover-Arnal and Strasser, 2013). Long-term climatic
trends (aridization during the TithonianEarly Berriasian and humidity
increase in the Late Berriasian) are also documented (Deconinck, 1993).
Reháková (2000) correlates calpionellid-dinoagellate events and breccia
horizons known from the Western Carpathians pelagic to hemipelagic
sections with eustatic sea-level changes. Grabowski et al. (2013) conrm
the presence and dating of these events by means of magnetic stratigra-
phy. However, many authors suggestthat long-term variations of clastic
inux might be additionally controlled by climate (Schnyder et al.,
2006) and regional tectonics (e.g. Neotethys closure, see e.g. Missoni
and Gawlick, 2011). Composition of nannofossil assemblages described
from ODP site 534 in Central Atlantic (Tremolada et al., 2006)andpelagic
sections from the Western Carpathians(Michalík et al., 2009, 2016) points
to climatic contrasts between the cooler Late Tithonian and the warmer
Berriasian, which is reected also in magnetic susceptibility and chemical
composition of sediments.
The aim of the curr ent study is to present a high-resolution record
of palaeoenvironmental changes across the Jurassic/Cretaceous
boundary in a chronostratigraphically well calibrated pelagic
section(Lókút, Transdanubian Range, Northern Hungary) using vari-
ous proxies: nannofossils, C and O isotopes, redox and productivity
sensitive elements. The nannooristic and geochemical trends are
compared to data from other Western Tethyan sections to evaluate
their palaeooceanographical and palaeoclimatic importance. The in-
terpretation is focused on the regional and global factors, controlling
the detrital input and surface water fertility within ca. 5 my time
span, between magnetic chrons M21r (Lower Tithonian) and M18r
(Lower Berriasian).
2. Geological setting
The studied section is located in a central part of the Bakony Moun-
tains (Fig. 1), which belong to the Transdanubian Range Unit. This
tectono-stratigraphic unit is, in turn, a part of the Alcapa Terrane; a
large composite structural megaunit including the Eastern Alps, the
Western Carpathians and the northwestern part of the basement of
the Pannonian Basin (Csontos and Vörös, 2004).
During an early stage of the Alpine plate tectonic cycle (Fig. 2a), the
Transdanubian Range was situated between the South Alpine and the
Austroalpine unit (Schmid et al., 1991; Haas et al., 1995; Vörös and
Galácz, 1998; Csontos and Vörös, 2004; Haas, 2012). Opening of the west-
ern basin of the Neotethys Ocean initiated in this region in the Middle Tri-
assic i.e. after continental rifting of Pangea. A new Penninic Ocean
(Alpine Tethys)basinbegantoopenintheEarlyJurassicinconnection
with the opening of the central Atlantic Ocean. As a result of this process
the Adriatic Spur (i.e. the Austroalpine, South Alpine and Transdanubian
Rage domains) separated from the European Plate. Closure of the
Neotethys Ocean began in the Middle Jurassic and led to onset of the
obduction of the oceanic basement onto the continental margins. During
the JurassicCretaceous transition and the Early Cretaceous the Adriatic
Spur was located between the expanding Penninic Ocean and the
compressing margin of the Neotethys Ocean (Frisch et al., 2011). In the
Late TithonianBerriasian a pelagic basin, which was in direct connection
with the Alpine Tethys, existed in the area of the Transdanubian Range.
Bathyal conditions prevailed in the western part of this basin located clos-
er to the Alpine Tethys whereas it eastern part became gradually
shallower (Fig. 2b). During the BerriasianBarremian, as a result of imbri-
cation of the Neotethys margin and obduction of the oceanic basement, a
submarine high (forebulge Tari, 1994; Fodor et al., 2013)developed,
which led to separation of the foreland-type Gerecse Basin in the eastern
part of the Transdanubian Range (Fig. 2c).
B
A
Fig. 1. Simplied pre-Cenozoic geological map of the Transdanubian Range Unit with indication of the most important Jurassic/Cretaceous boundary sections.
55J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
3. The Lókútsection
The Lókút section is exposed in an articial trench on the southern
slope of Lókút Hill, east from the Lókút village (geographical coordi-
nates: 47
o
1217N; 17
o
5256E). The strata dip gently to the north
(357°/20°). A total number of 79 beds was recorded in the section:
from 5to74(seeFig. 3).
A basal part of the studied section consists of pinkish, light red nod-
ular limestones of the Pálihálás Limestone Formation (Fig. 3,BedNo-5
to 7), rich in Saccocoma ossicles. The Pálihálás Formation was assigned
to the Kimmeridgian Lower Tithonian as based on ammonite fauna
(Vígh, 1984; Fözy et al., 2011). It is overlain by yellowish to white lime-
stones (Fig. 3, Bed No 8 to 50) containing calcareous tests of
calpionellids. Since the limestones are still nodular, mostly in a lower
part of this interval, and chert nodules occur in its upper part, the
discussed strata may be assigned to a transitional zone between the
Pálihálás and the Mogyorósdomb Formations. These beds are dated to
the Upper Tithonianlowermost Berriasian. The upper part of the
Lókút section (Fig. 3. Bed No 51 to 74) consists of white chertylimestone
of Maiolica-type, containing calpionellids, few radiolarians and aptychi,
and belongs to the Mogyorósdomb Limestone Formation.
Lókút section is well calibrated with microfossil stratigraphy and
magnetostratigraphy (Grabowski et al., 2010a,seealsoFig. 3). It em-
braces interval from the magnetozone M21r (upper part of Lower
Tithonian, Parastomiosphaera malmica Zone) to the M18r
(Calpionella alpina Subzone, Lower Berriasian). The Jurassic/Creta-
ceous boundary is located at 8.7 m of the section, in 37% of thickness
of the M19n2n magnetozone (Fig. 3). Sedimentation rate is rather
low, from 1 to 3 m/My in the Lower Tithonian to 57m/Myinthe
Lower Berriasian.
Based on biostratigraphic data, the Upper TithonianLower Berriasian
succession of the Lókút section can be precisely correlated with the corre-
sponding interval of the type section of the Mogyorósdomb Formation in
Sümeg, western Bakony (Fülöp, 1964; Haas et al., 1985,seeFig. 2bandc).
0102030km
Lókút
Sümeg
*
*
Tata
*
biogenic siliceous and
carbonate sediments
biogenic carbonate
sediments
condensed biogenic
carbonates
biogenic carbonates and
clastic deposits
overthrust
upwelling
SLT
Bakony Basin Gerecse Basin
internal external submarine high
Triassic formations
Jurassic formations
Bakony Basin
Gerecse
Basin
forebulge
foreland
C
B
Budapest
Iberia
LAURASIA
G
ONDWANA
N
EOTETHYS
Alpine Tethys
ACP
NCA
WC
SA
TR
DIN
deeper continental shelf & slope
oceanic basin with oceanic crust
shelf
obduction
zones of subsequent separation
land area
with
continental
crust
A
transform fault
Fig. 2. Palaeogeographic reconstructions for the Berriasian. A/Palaeoposition of the Transdanubian RangeUnit (after Frisch et al., 2011, modied). Abbreviations: ACPAdriatic carbonate
platform; DINDinarides; NCANorthern Calcareous Alps; SASouthern Alps; TRTransdanubian Range; WCWestern Carpathian units. B/depositional environments within the
Transdanubian Range Unit C/conceptional cross-section swi ng the structure of the Berriasian ba sins and the basic pattern of the sediment deposition and palaeo-oceanographic
conditions. Location of sections discussed in the text: SSümeg; LLókút; TTata.
56 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
Although basic lithological features are similar in both sections, there are
remarkable differences in microbiofacies. Biomicrite packstones with
large amount of calpionellids, Globochaete and usually only very few ra-
diolarians typically occur in the Lókút. On the contrary, large amount of
radiolarians along with the afore-mentioned components appear in
many layers of the Sümeg section (Haas et al., 1994). This difference
probably reects various palaeogeographic position of the both sections:
the Sümeg section represents succession of a deep, western part of the
sedimentary basin whereas the Lókút section records succession of the
transitional zone between the deeper and the shallower part of the
basin (Fig. 2c).
4. Methodology
For all investigations (nannofossils, isotopes and chemostratigraphy)
we used remaining rests of the drill cores collected for
magnetostratigraphy (Grabowski et al., 2010a). This approach enabled a
full integration of new results with existing calpionellid biostratigraphy
and magnetostratigraphy. Numbering of samples corresponds exactly to
the numbers of beds (see Fig. 3). For nannofossil study a total of 73
rock-chips samples have been processed and smear-slides have been pre-
pared as described in Bown and Young (1998). Examination was per-
formed on a Zeiss Axioskop 40 Pol polarizing light-microscope at 1000
1250× magnication, using immersion objective × 100. Digital images
were captured with a ProgRes®Capture Pro digital camera, using ProgRes
Capture Pro version 2.9. software. All images were taken in cross polarized
light (XPL), plane polarized light (PPL) or both (Plates I and II).
For the quantitative study, at least 200 elds of view were scanned
and logged for their nannofossil content. In addition, random traverses
of the smear-slide were scanned for rare species. All nannofossil speci-
mens were identied to the species level and then grouped at the generic
levelin5groups:Conusphaera,Polycostella,Watznaueria,Cyclagelosphaera
and Nannoconus. Estimate of nannofossil total abundance was performed
using the scale of Casellato (2010):
A (abundant): N11 specimens per eld of view (FOV);
C (common): 110 specimens per FOV;
F (few): 1 specimen every 110 FOV;
R (rare) 1 specimen every 11100 FOV.
Preservation of nannofossils was assessed adopting the commonly
used categories i,e, very poor (VP), poor (P), moderate (M)and good
(G; after Bown, 1992). In general, the preservation of the nannofossils
is poor to very poor along the whole section, except for a few samples
from the the lowest part of nodular limestones of the Pálihálás Fm
(see Supplementary File 1). The quantitative study of nannofossil spe-
cies is strongly affected by the preservation state. Signicant part of
the nannofossil skeletons (CaCO
3
) are in fact locked as building compo-
nents of the carbonatic rocks, being strongly recrystallized and diluted.
Therefore, the frequency of the registered nannofossil specimens
might not reect the true nannofossil assemblages.
For biostratigraphic purposes, the available biostratigraphic schemes
of Bralower et al. (1989),Bown and Cooper (1998) and Casellato (2010)
were considered. The latter was selected to apply for the Lókút section,
as the most appropriate for nannofossil record in this Tethys location.
The set of the studied smear slides is stored at the Department of
Geocollections, Geological Institute of the Bulgarian Academy of
Sciences.
Geochemical analyses of 32 samples from the Lókút section were car-
ried out at the Geochemical Laboratory of the Polish Geological Institute
National Research Institute in Warsaw. Major elements were analyzed
using XRF (Philips PW 2400 spectrometer), whereas trace elements con-
tents were determined by ICP-MS method (ELAN DRCII, Perkin
Fig. 3. Nannofossil Range Chart, againstcalpionellid and magnetic stratigraphy and lithologic log of the Lókút section.
57J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
Elmer).The analytical accuracy was 10% for major elements and 1020%
for trace elements.The enrichment or depletion in minor and trace ele-
ments was evaluated in samples studied relative to average shale value
(Li, 2000). Normalization is pronounced by enrichment factor (EF) calcu-
lated as follows: EF element X = (X/Al) sample/(X/Al) average shale. The
Pearsoncoefcient is used to express interactions between chemical
5 μm
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24 25
Plate I. 12. Conusphaeramexicana mexicana,sample Lo-2-1a, cross polarizedlight (XPL). 3Conusphaera mexicana mexicana, Lo 33, XPL. 46. Conusphaera mexicanamexicana,sampleLo
72, XPL. 7Conusphaera mexicana mexicana, sample Lo 74-1, XPL. 8Conusphaera mexicana minor, sample Lo 62, XPL. 910. Faviconus multicolumnatus, sample Lo 9c, XPL. 1113.
Polycostella beckmanni, sample Lo 9c, XPL. 1415. Polycostella beckmanni, sample Lo-5-1, XPL. 1617. Polycostella cf. senaria, sample Lo 74-1, XPL. 18 Hexalithus noeliae, sample Lo-2-
1a, XPL. 19 Hexalithus noeliae, sample Lo-5-1, XPL. 20 Cyclagelosphaera margerelii, sample Lo-5-1, XPL. 21 Cyclagelosphaera deandrei, sample Lo 72-2, XPL. 22 Cyclagelosphaera
deandrei, sample Lo 9c, XPL. 23 Cyclagelosphaeradeandrei, sample Lo 28-2a,XPL. 24 Watznaueria manivitae, sample Lo-5-1, XPL. 25 Zeugrhabdotus embergeri, sample Lo 28-2a, XPL.
58 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
components. Aluminium and phosphorus accumulation rates have been
calculatedusing the formula: element content (mg/g) × sedimentation
rate (cm/kyr) × rock density (g/cm
3
) (e.g. van de Schootbrugge et al.,
2003; Morales et al., 2013; Westermann et al., 2013). Density of
limestones was assumed as 2.5 g/cm
3
(op.cit.) while sedimentation rate
was calculated as based on magnetostratigraphic calibration
(Grabowski et al., 2010a).
Freshly broken surfaces of non-weathered 73 bulk carbonate rocks
derived from cores drilled for palaeomagnetic studies from the Lókút
section were sampled using a diamond micro-drill. Oxygen and carbon
isotope analyses of powdered bulk rock samples were performed using
a Gasbench II connected to a ThermoFischer Delta V Plus mass spec-
trometer at the GeoZentrum Nordbayern (Germany). Oxygen and car-
bon isotope values are reported in per mil relative to VPDB scale by
calibration to the accepted values of NBS19 and LSVEC references
(δ
13
Candδ
18
O values of + 1.95, and 2.20,aswellas46.6,
and 26.7, respectively). The reproducibility of the measurements
was monitored over the course of analyses by replicated analyses of
16 17 18 19 20
11 12 13 14 15
6 7 8 9 10
1 2 3 4 5
5 μm
Plate II. 12.Watznaueria communis,sampleLo9c,XPL.3Watznaueria c ommunis, sample Lo33, XPL. 4Watzna ueria britannica, sample Lo 72-2, XPL.5Polycostella beckmanni, sample
Lo 10, XPL.67. Nannoconus cf.kamptneri minor,sample Lo 62, plane polarized light(PPL, 6) and XPL (7). 8 Nannoconus cf. kamptneri minor, very poor preservation, sample Lo 59c, XPL.
910. Nannoconus cf. steinmannii minor, verypoor preservation, sampleLo 62, PPL and XPL. 1112. Nannoconus cf. steinmannii minor,sampleLo72-2,PPLandXPL.1314. N annoconus cf.
steinmannii minor, sample Lo 72-2, PPLand XPL. 15 Lithraphidites cf. carniolensis, sampleLo 28-2a, XPL. 16 Lithraphidites sp., sampleLo-2-1a, XPL. 1718. Nannoconus sp. indet., sample
Lo 72-2, PPL and XPL. 1920. Nannoconus cf. kamptneri minor, sample Lo 72-2, PPL and XPL.
59J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
laboratory standards Sol 2 (n= 13), and Erl 5 (n= 14) calibrated to
NBS19 and LSVEC. Reproducibility for δ
13
Candδ
18
O values was 0.03
and 0.06(±1σ) for Sol 2 as well as 0.05,and0.04(±1σ)forErl
5, respectively.
5. Results
5.1. Nannofossil biostratigraphy
The studied Tithonianlowermost Berriasian nannofossil assem-
blages show impoverishment towards the top of the section, along
with a change in the preservation state from good to moderate-poor
and very poor one. The upper part of the section is characterized by
the predominance of strongly etched and overgrown/recrystallized
specimens, a drop in species diversity, and a decrease in assemblage
abundance. A total of 25 species and subspecies, belonging to 9 genera
are identied. They are listed in Appendix 1. The stratigraphic position
of each sample studied is plotted respectively on the Range-chart (Fig.
3).
A most detailed biozonation scheme for the Tithonian-Lower
Berriasian interval is based upon nannoconid evolutionary bio-events
(Bralower et al., 1989; Casellato, 2010). The nannofossil events, docu-
mented in the present study, include the rst occurrences (FO) of
Nannoconnus infans, Nannoconus globulus minor, Nannoconus wintereri,
Nannoconus kamptneri minor and Nannoconus steinmannii minor. Due to
the extremely poor preservation and recrystallization, which hamper
precise taxonomical identication, the occurrence of the species marking
the base of NK-1 zone Nannoconus steinmannii steinmannii (and
Nannoconus kamptneri kamptneri) is ambiguous and therefore not satis-
factory documented/proved in Lókút. Zones and subzones NJT 16b, NJT
17a, NJT 17b and NKT are identied using the FO of Nannoconnus infans,
Nannoconus globulus minor, Nannoconus wintereri, Nannoconus kamptneri
minor and Nannoconus steinmannii minor, respectively.
5.1.1. NJT 16b Subzone
This subzone covers the lower-middle part of the section studied (0
7.66 m). The assignation of the sediments to this zone is based on the co-
occurrence of Nannoconus infans, Hexalithus noeliae, Polycostella
beckmanni and abundant Conusphaera mexicana minor in the lowermost
sample (-5). The nannofossil associations reach higher diversity and
abundance, within the rocks of Pálihálás Fm. It is worth noting that the
representatives of the genus Conusphaera (+Nannoconus) clearly domi-
nate associations in the lower part of the zone, whereas in the middle
and upper part there is a switch to Watznaueria (+Cyclagelosphaera)
dominated assemblages. In addition, rare and delicate-ornamented taxa
such as Hexalithus noeliae,H.geometricus,Faviconus multicolumnatus,
Lithraphidites carniolensis,Acadialithus spp. are recorded within this zone.
5.1.2. NJT 17a Subzone
T
hebaseofthesubzoneismarkedbytheFOofNannoconus
globulus minor in the sample 40. The subzone is documented in the
middle-upper part of the studied succession (7.9910.89 m). The
impoverishment of nannofossil associations impacts the overall spe-
cies. Nevertheless, the two main nannofossil groups are equally rep-
resented in the observed associations the group of the coccoliths
[Watznaueria (+Cyclagelosphaera)], and the group of the nannoliths
[Conusphaera (+ Nannoconus)].
5.1.3. NJT 17b Subzone
The base of the subzone is traced by the FO of Nannoconus sp. cf.
wintereri in sample 59, 10.89 m above the base of the section. The real
FO of the index-species is most likely affected by the nannofossil preser-
vation state discussed above, therefore the thickness of the subzone
may be slightly underestimated. The nannofossil associations of the
subzone reect the next turning point the recovery of domination of
ConusphaeraNannoconus in return for WatznaueriaCyclagelosphaera
one. Overall, the poor record embarrassed the more detailed biostrati-
graphic and palaeoenvironmental interpretations.
5.1.4. NKT Zone
The base of the zone is dened at the FO of Nannoconus steinmannii
minor. It is recorded in the sample 62, 11.30 m above the base. The zone
spans the uppermost 1.70 m of the section studied.Despite poor preser-
vation, the dominance of Conusphaera and Nannoconus in the associa-
tions is obvious. The FO of Nannoconus steinmannii minor in Lókút
roughly coincides with M19n2nr-M19n1r magnetic polarity chron
boundary.
The FO of Nannoconus steinmannii minor has been recently consid-
ered as reliable bio-event, largely detected across most of Tethyan loca-
tions (Bralower et al., 1989; Michalík et al., 2009, 2016; Casellato, 2010;
Lukeneder et al., 2010; Wimbledon et al., 2011, 2013; Svobodová and
Košt'ák, 2016; Hoedemaeker et al., 2016). Recently, it has been consid-
ered as a potential bioevent, marking the base of the Berriasian and
the JurassicCretaceous boundary (Wimbledon et al., 2011, 2013).
Unfortunately we were unable to document the bioevents, FO of
Nannoconus steinmannii steinmannii and Nannoconus kamptneri
kamptneri, tracing the base of NK-1 zone. Therefore this zone is not ev-
idenced in Lókút.
Table 1
Pearson correlation coefcient matrix (r) of the selected elements. Strong positive correlations with Al (rN0.81) are marked in bold.
Al Si Rb Fe Ni Th K Co Mg Na Cd U Zn Cu Pb P Ba Mn Sr
Si 0.99
Rb 0.96 0.97
Fe 0.91 0.91 0.92
Ni 0.89 0.87 0.88 0.83
Th 0.87 0.89 0.89 0.86 0.76
K 0.79 0.81 0.76 0.67 0.64 0.61
Co 0.78 0.76 0.78 0.70 0.91 0.61 0.51
Mg 0.77 0.79 0.79 0.82 0.63 0.73 0.71 0.45
Na 0.53 0.54 0.50 0.51 0.45 0.57 0.51 0.43 0.38
Cd 0.51 0.54 0.48 0.47 0.39 0.68 0.39 0.19 0.49 0.29
U 0.08 0.12 0.07 0.00 0.01 0.33 0.10 0.02 0.08 0.15 0.39
Zn 0.07 0.09 0.11 0.08 0.04 0.14 0.15 0.06 0.08 0.13 0.09 0.02
Cu 0.15 0.17 0.20 0.16 0.04 0.24 0.09 0.10 0.01 0.15 0.12 0.07 0.98
Pb 0.19 0.22 0.20 0.28 0.07 0.26 0.22 0.04 0.29 0.27 0.07 0.18 0.20 0.17
P0.19 0.21 0.13 0.28 0.11 0.16 0.31 0.03 0.27 0.19 0.19 0.26 0.10 0.08 0.11
Ba 0.29 0.31 0.31 0.51 0.14 0.32 0.29 0.05 0.50 0.13 0.26 0.05 0.22 0.22 0.55 0.51
Mn 0.36 0.40 0.32 0.17 0.24 0.31 0.48 0.19 0.31 0.20 0.57 0.32 0.22 0.18 0.18 0.07 0.10
Sr 0.56 0.60 0.58 0.66 0.43 0.68 0.52 0.34 0.58 0.43 0.63 0.28 0.20 0.26 0.31 0.52 0.65 0.37
Ca 0.92 0.93 0.91 0.84 0.81 0.85 0.75 0.65 0.78 0.44 0.55 0.12 0.10 0.19 0.03 0.10 0.26 0.44 0.52
60 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
5.2. Geochemistry
Correlation coefcients between 20 elements analyzed in the Lókút
section are presented in Table 1. Aluminium was accepted as a proxy
for terrestrial detrital input into the basin (see also vanderWeijdenet
al., 2006; Tribovillard et al., 2006; Grabowski et al., 2013).Al content is
strongly, and negatively correlated with Ca, which resides almost exclu-
sively in carbonate fraction. Other elements which can be used as proxies
for terrigenous fraction are Si, Rb, Fe, Ni and Th. These elements show very
strong positive correlation with Al (rN0.85)andtheshapesofalltheir
concentration curves are almost identical (Fig. 4).Concentrations of all
these elements decrease starting from spectacular maximum of lit hogenic
input in magnetozone M20r (middle part of Chitinoidella Zone, lower
part of NJT16b Zone). This eventreveals a characteristic shape with dou-
ble peak (Fig. 4). At the top of the section, in magnetozones M19n1r and
M19n1n, a small increase of lithogenic input is observed.
K, Co and Mg trends reveal still a good positive correlation with Al,
with linear correlation at values r higher than 0.7 (Table 1). Concentra-
tions of all the three elements follow the generaldecreasing trend, how-
ever shapes of particular curves differ in detail. The K curve shows only
one maximum in the Chitnoidella Zone(Fig. 4). Decreasing trend of the
Mg content is very gentle without any sharp maxima. Co curve is quite
similar to the reference Al curve, except its topmost part where a
pronouncedincrease in Co content is noted.
Only moderate correlation between both Na and Cd, and Al concen-
trations is observed (0.5 brb0.6), which results from partly authigenic
Fig. 4. Magnetic susceptibility (MS) and elements with very strong (rN0.86), strong (r= 0.77 to 0.79) a nd moderate (r= 0.51 to 0.53) correlation with Al.
61J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
origin of the former elements. Cd content curve revealsa subtle decreas-
ing trend towards the top of the section, while Na contentis almost con-
stant with only small second-order variations.U, Zn, Cu, P, Ba, Mn
concentrations reveal no correlation, or even slightly negative correla-
tions with Al. These elements are probable components of authigenic
minerals.Highest concentrations of U are observed in the lowermost
part of the section (M21r, below the lithogenic maximum, see Fig. 5).
Moderate, positive plateau of U concentration occurs also in the
magnetozone M19n2n, in the Jurassic/Cretaceous boundary interval.
Cu and Zn contents correlate perfectly with each other (r= 0.98) and
these elements show increased concentrations in the upper half of the
section (Fig. 6). Higher values of P and Ba contents are also observed
in the upper half of the section, above magnetozone M19r. Mn
concentration reveals a weak but considerable increase with maximum
values slightly above the J/K boundary (Fig. 6).
Sr contents are clearly negatively correlated with Al ones (Table 1).
Sr and Mn concentrations show also moderate positive correlation
with Ca contents (Table 1), therefore, they may be regarded as associat-
ed mostly with carbonate phases.
5.3. Oxygen and carbon isotoperatios of carbonate rocks
δ
18
O values of newly measured bulk carbonate samples vary be-
tween 3.5 and 0.1(mean1.5;Fig. 7) and show a scatter of ca.
0.5(occasionally up to 1.5) in neighbouring beds. A more or less
constant decrease in δ
18
O values is observed throughout the section
Fig. 5. Detrital input (Al), carbonate productivity (Ca) and redox proxies (U, Co and U enrichmentfactors, U/Th ratio).
Fig. 6. Detrital input (Al) and productive elements (Mn, P, Ba, Cu and Zn).
62 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
except for three outlier points characterized by abnormally low or high
values. δ
18
O values decrease gradually from ca. 1.0at the base of the
section (P.malmica Zone) to ca. 1.2in the middle part of the
Crassicollaria Zone. A more rapid decrease of the magnitude ca. 0.5
is observed in the upper part of the Crassicollaria Zone (Fig. 7). The
δ
18
O values decrease slightly higher, up to ca. 2.0at the top of the
section (the upper part of the Calpionella alpina Zone).
δ
13
C values of newly measured bulk carbonate samples vary be-
tween 0.4 and 1.7(mean 1.1;Fig. 7) and show a scatter of
0.2(occasionally up to 1.2) in neighbouring beds. A decrease of
δ
13
C values is observed throughout the lower and the middle part of
the section. The values decrease gradually from ca. 1.7at the base of
the section (P.malmica Zone) to ca. 1.3in the middle part of the
Crassicollaria Zone. A rapid decrease of magnitude of about 0.4is ob-
served in the upper part of the Crassicollaria Zone (Fig. 7). The δ
13
C
values oscillate about 0.9in the upper part of the Lókút section (in
the Calpionella alpina Zone) except for two beds characterized be anom-
alously low or high values. The newly measured bulk carbonates isotope
data are similar to the data published previously by Price et al. (2016)
from the same section. Slight differences, however, occur in the both
carbon isotope datasets as the bulk carbonate δ
13
C values presented
by Price et al. (2016) are in some intervals lower (up to 0.5) than
the newly obtained values (cf. Fig. 7).
δ
18
Oandδ
13
C values of newly measured bulk carbonates from the
Lókút section are positively and strongly correlated with each other
(R= 0.91; Fig. 8). δ
18
O values of bulk carbonates are negatively cor-
related (R=0.66) with Sr/Ca ratios of the rocks, which vary be-
tween 0.39 and 0.58 mmol/mol, and positively (R= 0.86) with
their Fe/Ca ratios, which vary between 2.65 and 6.73 mmol/mol
(Fig. 8). No statistically signicant correlation (R=0.21) is ob-
served between bulk rock δ
18
O values and Mn/Ca ratios, which oscil-
late between 0.38 and 0.98 mmol/mol (Fig. 8).
6. Interpretation and discussion
6.1. Calcareous nannofossil bioevents calibrated with magnetostratigraphy
and correlation with other J/K boundary sections
During the past decade (20072017), the investigations of Jurassic/
Cretaceous boundary sections usually integrated nannofossil biostratig-
raphy and magnetostratigraphy, accentuating at selected nannofossil
bioevents (mainly First Occurrences, FO). Casellato (2010) has pro-
duced a rst summary, where 26 nannofossil events from the Tethyan
sections of the Southern Alps and Apennines (Italy), and other areas
(DSDP Site 534, Western Carpathians) are calibrated against
magnetostratigraphic scale. Recently, similar data have been elaborated
for the Puerto Escano (Southern Spain, Svobodová and Košt'ák, 2016),
Le Chouet (South East France, Wimbledon et al., 2013), Nutzhof
(Lower Austria, Lukeneder et al., 2010), and Strapkova sections
(Slovakia, Michalík et al., 2016).
In general, the calcareous nannofossil data from the Lókút section,
calibrated against the magnetostratigraphy (Grabowski et al., 2010a)
are in good agreement with those from the other Tethyan localities.
Fig. 9 summarizes sixteen selected nannofossil events - FOs, calibrated
against magnetic polarity chrons (M22 to M17) in twelve Tethyan J/K
boundary sections.
The obtained data clearly show two separate groups of nannofosil
taxa: a rst, with rather scattered FOs, and a second, which displays
Fig. 7. Stratigraphy, magnetic susceptibility (MS), δ
18
Oandδ
13
C values of bulk carbonates fromthe Lókút section. New data blackdiamonds; data published by Price et al. (2016 ) grey
diamonds.
63J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
more or less consistent FOs' recordamongst different sections. The rep-
resentatives of the rst group include C. mexicana mexicana,Polycostella
beckmannii,Cy. argoensis,Hexalithus noeliae,Nannoconus infans. These
taxa clearly demonstrate a diachronism in their FO in the Tethyan do-
main, and therefore they could hardly be used for precise correlation.
The representatives of the second group include Nannoconus globulus
minor,Hexalithus geometricus,N. globulus globulus,N. wintereri,
Cruciellipsis cuvillieri,N. steinmannii minor and N. kamptneri minor.Over-
all, their FO falls within the long M19 magnetic polarity chron. Moreover,
the FO of the species Hexalithus geometricus looks as a fairly consistent
bio-event at the middle of M19n2n chron being of potentially high rele-
vance for detailed correlation. On the other hand, the FOs of commonly
used for biostratigraphic zonation N. steinmannii minor and N. kamptneri
minor are concentrated within upper parts of M19n and in M18r chrons.
Interestingly, next two biostratigraphic marker species, N. steinmannii
steinmannii and N. kamptneri kamptneri show relatively dispersed FO
within M19n1r - M17r chrons, which could be due to various reasons:
poor preservation, problematic bio-magnetostratigraphy calibrations or
simple diachroneity of appearance in different sections.
6.2. Geochemistry
It is documented from the distribution of lithogenic elements (Al, Si,
Rb, Fe, Ni, Th), that terrestrial input decreases throughout the Lower
TithonianLower Berriasian. One may argue that this trend reects in-
creasingrate of carbonate deposition. However, if aluminium accumula-
tion rate is calculated, the decreasing terrestrial input is still visible
across the majority of the Lókút section (Fig. 10). This suggests that
the transport of lithogenic elements towards the Lókút basin weakened
during the Tithonian and theBerriasian. EFs of lithogenic elements, such
as Si, Rb and K amount to ca. 1 (Table 2), which implies both, the ab-
sence of biogenic silica in the sediment and rather constant composition
of the terrigenous fraction. Nevertheless, small quasi-periodic variations
of relative contents of K and Th (Fig. 1) were found. They might be
interpreted either as a signal of uctuating riverine input (e.g.
Rodriguez-Tovar and Reolid, 2013; Aguado et al., 2016)orasanindica-
tor of changes in the weathering intensity (e.g. Deconinck et al., 2003;
Schnyder et al., 2006;Hesselbo et al., 2009). Unfortunately, it is not pos-
sible to discriminate between uvial and aeolian transport due to very
small quantities of Ti, and a lack of Zr data. Decreasing magnitude of
Th/K peaks andincreasing magnitude of EF K towards thetop of the sec-
tion (Fig. 10), might favour palaeoclimatic variations (aridization
trend). Small enrichment in Fe, Th and Co concentrations (1 bEFs
b5), along with only moderate enrichment inNi (3.4 bEF b11.5) is ob-
served, so these elements may be interpreted as occurring also in
authigenic phases. Very strong enrichments are observed, in turn, in
Na, Mg and Cd concentrations.EFs of these elements correlate very
well with each other and only slightly worse with Ca content (Table
2), thus they are probably related mostly to carbonate matrix
(Ishikawa and Ichikuni, 1984; Okumura and Kitano, 1986).
Trace metals U, V, Mo, Cr and Co are commonly used as redox prox-
ies (Tribovillard et al., 2006). In the Lókút section, only U and Co varia-
tions are determined while Mo, V and Cr are mostly below the
detection limit of chemical analyses. U/Th ratio is widely applied as in-
dicator of redox conditions (e.g. Jones and Manning, 1994; Powell et
al., 2003; Koptiková et al., 2010; Grabowski et al., 2013; Wójcik-Tabol
and Ślączka, 2015). The U/Th ratio decreases towards a minimum
value (0.110.12) in the lowermost part of the section (01.5 m lower-
most part of Chitinoidella Zone, M21r to lowermost M20r) and then a
stepwise increase of this ratio is observed upto ca. 0.4 in the Alpina Sub-
zone (above 10 m, M19n2n) (Fig. 5). The EF U curve roughly follows the
same trends, although the highest U EF is observed slightly lower, just
above the J/K boundary (9 m). Cobalt is relatively not enriched up to
9 m (with EF Co mostly below 1). In the upper part of the section EF
Co values increase to 1.52.5. Based on these data oxygen depleted con-
ditions can be interpreted as occurring from the, magnetozone M19n2n.
However, low concentrations of Mo, and only slight enrichments in U
and Co suggest dysoxic conditions only.
2.0
-3.0 -2.0 -1.0 0.0
1.0
0.0
19.0=R
δO[
18 ‰ VPDB]
[Cδ
31
]BDPV
8.0-2.1-0.2-
1.0
δO[
18 ‰ VPDB]
]lom/lomm[aC/nM
0.6
-1.8 -1.2 -0.6
0.5
0.4
δO[
18 ‰ VPDB]
]lom/lomm[aC/rS
-0.8-1.0-1.4-1.6-2.0-2.2
2
66.0=R
0.8
0.6
0.4
-1.8 -1.6 -1.4 -1.0 -0.6-2.2
12.0=R
8.0-2.1-0.2-
7.0
δO[
18 ‰ VPDB]
]lom/lomm[aC/eF
-1.8 -1.6 -1.4 -1.0 -0.6-2.2
6.0
5.0
4.0
3.0
2.0
68.0=R
Fig. 8. Plots of isotope valuesand elemental ratios of newly studied bulk carbonate samples from the Lókút section.
64 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
P, Ba, Ni, Cu, and Cd are regarded as palaeoproductivity indicators
(Tribovillard et al., 2006). Enrichment factors of these elements reveal a
good consistency throughout the section (Fig. 11 and Table 2). Relatively
low concentrations of the elements are observed in the lower part of the
section (L. dobeni Subzone, M21r to M20r magnetozone). From the bot-
tom of the M20n (Ch.boneti Subzone), the productivity proxies start to in-
crease and reach maximum values in the lower part of the Berriasian
(M19n2n, lower part of Alpina Subzone, above 8.8 m. Then
palaeoproductivity tends to stabilise or reveals even a gentle decreasing
trend. The phosphorus accumulationrate(PAR)isoftenusedasamea-
sure of total phosphorus ux controlling the palaeoproductivity, which
may, in turn, be correlated with continental weathering or upwelling in-
tensity (Föllmi, 1996; van de Schootbrugge et al., 2003; Charbonnier et al.,
2016). Spectacular rise of PAR in the Lókút section is observed (Fig. 12).
The rise is relatively slow and stepwise between the M21r and M19r,
from below 0.1 to 0.5 mg/cm
2
/ky. In the lowermost part to the M19n2n
its abrupt rise to 0.8 mg/cm
2
/ky is observed, which is followed by a gentle
decrease towards the middle part of the M19n2n. PAR reveals maximum
values of 1 mg/cm
2
/ky at the top of the section (the M19n1r to M18r).
The abrupt rise in PAR correlates with a general microfacies change
from Saccocoma to calpionellid dominated (Fig. 12).It apparently coin-
cides also with discernible shifts of δ
13
Candδ
18
Ocurvestowardsmore
negative values (Fig. 12), which might be interpreted as an effect of the
input of waters enriched in organic carbon and a warming trend (e.g.
Tremolada et al., 2006; Fözy et al., 2011; Price et al., 2016).Additionally,
PAR correlates almost exactly with Nannoconus abundance (Fig. 12).
Fig. 9. Callibration of selected nannofossil events (FOs) against magnetostratigraphy in 11 Tethyan sections (including Lókút).
65J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
This is surprising as Nannoconus has been usually interpreted as an oligo-
trophic taxon (e.g. Erba, 1994; Tremolada et al., 2006; Browning and
Watkins, 2008). However, our dataset is most probably the rst that inte-
grates nannofossil and geochemical data in the pelagic environment
within the TithonianLower Berriasian interval. Together with
Nannoconus, increasing frequency of Conusphaera and decline of
Watznaueria and Cyclagelosphaera are also observed above magnetozone
M19r (Fig. 13).
6.3. Diagenetic alteration ofδ
18
Oandδ
13
C ratios of bulk carbonates
δ
18
O values of marine carbonates can be affected by percolation of
diagenetic uids in post-depositional processes at much lower uid/
rock ratios than δ
13
C values (Banner and Hanson, 1990).δ
18
O values of
Mesozoic bulk carbonates are, hence, usually not interpreted as a
proxy for ancient seawater temperatures. A signicant positive correla-
tion between δ
18
Oandδ
13
C may indicate a diagenetic imprint on both
values as this phenomenon is observed in rocks affected strongly by
deep burial or meteoric diagenesis (cf. Jenkyns and Clayton, 1986;
Marshall, 1992; Padden et al., 2002; Jach et al., 2014).
The diagenetic processes affect not only the isotope ratios but also
chemical compositions of carbonate rocks. Minor and trace element dis-
placements during recrystallization of marine carbonates under burial
or meteoric diagenesis usually results in enrichments in manganese
and iron and a depletion in strontium (cf. Veizer, 1983; Banner and
Hanson, 1990). A negative correlation between δ
18
Ovaluesand
bothMn/Ca and Fe/Ca ratios as well as a positive correlation between
δ
18
O values and Sr/Ca ratios of diagenetically altered marine
carbonatesrocks is, therefore, often expected (cf. Brand and Veizer,
1980; Veizer, 1983). Studied rocks have intermediate Sr/Ca (between
0.39 and 0.58 mmol/mol), Fe/Ca (2.65 and 6.73 mmol/mol) and Mn/
Ca ratios (between 0.38 and 0.98 mmol/mol; Fig. 8), which deviate
from values predicted for JurassicCretaceous marine calcite fossils
(cf. Price and Mutterlose, 2004; McArthur et al., 2007; Fözy et al.,
2011; Dzyuba et al., 2013; Wierzbowski et al., 2016). This may indicate
diagenetic alteration of bulk rocks, however, iron is found to be associ-
ated mostlywith the detrital fraction (Fig. 4). In addition, a negative cor-
relation between bulk rock δ
18
OvaluesandSr/Caratios,apositive
correlation between δ
18
O values and Fe/Ca ratios, and a lack of statisti-
cally signicant correlation (R=0.21) between δ
18
O values and Mn/
Ca ratios do not point to signicant diagenetic alteration of the mea-
sured isotope values. Since δ
13
C values of bulk carbonates can be altered
solely by the percolation of high volumes of diagenetic uids(cf. Banner
and Hanson, 1990) there is, thus, no evidence for diagenetic alteration
of the carbon isotope composition of bulk carbonates from the Lókút
section. A few anomalous isotope values may be derived from micro-
fractured parts of the rocks lled with cements. Slightly lower δ
13
C
values of some samples measured previously by Price et al. (2016)
may be a result of sampling exposed parts of the rocks, which were af-
fected by minor diagenetic alteration.
6.4. Oxygen and carbon isotope compositions of bulk carbonates
Despite positive correlation between δ
18
Oandδ
13
C values of bulk car-
bonates the carbon isotope record of the Lókút section is interpreted as
representing a primary global oceanic signal (Price et al., 2016), which is
characterized by a long-term decline in δ
13
C values across the Jurassic
Cretaceous boundary. The decline is observed in both bulk carbonate
and belemnite carbon isotope records of various Tethyan and Boreal sec-
tions (cf. Weissert and Channell, 1989; Skourtsis-Coroneou and Solakius,
1999; Cecca et al., 2001; Padden et al., 2002; Tremolada et al., 2006;
Price and Rogov, 2009; Grabowski et al., 2010b; Nunn and Price, 2010;
Fig. 10. Normalized proxies of detrital input: aluminium accumulation rate, Th/K ratio and EF K.
66 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
Fözy et al., 2011; Žak et al., 2011; Jach et al., 2014; Michalík et al., 2016;
Price et al., 2016; Pszczółkowski et al., 2016) and considered as a conse-
quence of decreasing burial rates of marine organic matter and/or increas-
ing calcium carbonate productivity (Weissert and Channell, 1989;
Weissert et al., 1998; Price et al., 2016). In addition, the oxygen isotope re-
cord of the Lókút section showing increasingly more negative δ
18
Ovalues
towards the Lower Berriasian is similar to the belemnite and bulk carbon-
ate records of many Tethyan and Boreal sections (cf. Tremolada et al.,
2006; Price and Rogov, 2009; Grabowski et al., 2010b; Žak et al., 2011;
Price et al., 2016; Pszczółkowski et al., 2016). Therefore, it is claimed to re-
ect either a regional or global increase in the seawater temperatures or a
slight decrease in seawater salinities (cf. Föllmi, 2012; Price et al., 2016).
It is important to note that the stable isotope composition of marine
bulk carbonates may also be inuenced by changes in the origin and com-
position of carbonate mud (cf. Swart and Eberli, 2005; Wierzbowski,
2015). A notable change in lithology and microfacies is observed in the
Lókút section across the Tithonian (Fig. 12). The lower part of the studied
section consist of light red to pinkish limestones of the Pálihálás Forma-
tion, which are rich in Saccocoma ossicles, calcispheres and diversied as-
sociation of calcareous nannofossils. These rocks also contain carbonate
mud, fragments of molluscs and echinoderm debris, radiolarians, and fo-
raminifera (Haas et al., 1985). Studied strata pass gradually into white
cherty limestones of Maiolica-type of the Mogyorósdomb Formation,
which predominantly consist of nannoplankton, calpionellids,
Table 2
The enrichment factors (EF) of elements in the samples studied from the Lókút section.
Meter EF Cu EF Sr EF Cd EF Pb EF Zn EF P EF Mg EF Na EF Ni EF Mn EF Fe EF U EF Th EF Co EF K EF Si EF Rb EF Ba
0.12 22.17 45.52 73.90 6.37 14.32 27.02 8.91 6.34 4.23 0.99 1.57 2.43 1.93 0.74 0.63 0.67 0.52 0.32
0.62 105.08 45.67 89.01 6.27 38.72 20.10 10.33 6.34 4.74 1.15 1.87 1.49 1.76 0.74 0.79 0.64 0.50 0.26
1.15 47.27 53.91 63.82 8.54 20.15 21.05 9.32 6.34 4.64 1.93 2.09 1.31 1.51 0.85 0.47 0.62 0.49 0.27
1.4 24.31 31.28 37.92 5.59 12.28 20.01 5.75 3.67 3.44 1.09 1.43 0.76 1.46 0.77 0.37 0.58 0.46 0.20
1.76 44.59 28.30 35.10 18.40 18.67 11.06 5.79 3.83 4.66 1.00 1.52 0.62 1.25 1.14 0.43 0.55 0.42 0.17
2.15 80.09 43.23 41.91 9.90 29.88 14.16 8.48 4.59 3.73 1.47 1.62 1.05 1.08 0.66 0.64 0.58 0.42 0.21
2.63 54.70 33.59 40.50 5.77 23.22 18.74 7.20 4.02 4.28 1.03 1.47 0.95 1.12 0.82 0.80 0.59 0.46 0.21
3.05 74.72 49.99 49.43 8.52 30.27 21.85 9.94 6.22 4.22 1.72 1.80 1.33 1.61 0.73 0.84 0.62 0.55 0.30
3.35 83.62 82.54 69.88 12.90 35.77 31.10 13.66 9.09 5.49 3.14 2.46 1.61 1.75 0.76 0.68 0.63 0.63 0.40
3.61 81.92 62.82 59.00 13.38 35.57 27.42 10.57 6.07 5.47 2.22 2.23 1.19 1.79 0.85 0.50 0.65 0.64 0.33
4.27 123.12 100.74 116.68 16.01 51.59 49.10 18.29 8.80 7.00 3.53 2.85 2.59 2.41 0.88 0.27 0.66 0.63 0.51
4.55 99.01 75.48 86.75 17.96 41.09 42.37 12.79 9.09 6.22 3.22 3.00 2.41 2.11 0.80 0.45 0.56 0.59 0.37
5.03 70.43 77.82 74.70 11.06 32.72 38.76 13.37 8.18 5.78 3.14 2.57 1.34 1.75 0.65 0.68 0.62 0.67 0.36
5.39 149.88 108.05 104.33 52.13 61.77 41.47 16.51 9.84 6.46 4.46 3.19 2.54 1.79 0.88 0.61 0.66 0.63 0.51
5.91 63.43 72.13 63.34 10.07 28.75 34.43 12.18 7.47 4.87 2.34 2.11 1.76 1.63 0.72 0.37 0.59 0.47 0.36
6.13 219.26 175.52 152.42 21.49 86.64 75.67 28.74 20.91 10.31 6.37 4.93 3.69 3.05 1.88 1.04 0.76 0.87 0.77
6.41 117.37 83.88 70.94 38.41 46.21 36.08 13.10 7.53 4.52 2.48 2.17 1.72 1.44 0.53 0.83 0.62 0.51 0.39
6.92 171.89 101.62 96.26 80.82 65.40 54.56 15.48 11.00 6.65 3.44 2.46 1.94 1.46 1.06 0.55 0.62 0.59 0.77
7.27 143.54 88.77 68.73 10.18 55.31 65.93 12.83 7.53 5.85 2.27 2.07 2.46 1.55 0.98 0.63 0.60 0.58 0.53
7.99 180.45 114.98 104.69 11.27 71.47 69.69 15.23 10.45 6.74 3.44 2.74 2.57 2.16 0.56 0.58 0.61 0.61 0.63
8.49 151.28 112.13 127.15 14.62 60.74 59.76 15.34 12.30 6.46 4.05 2.75 3.62 2.61 0.67 0.61 0.63 0.57 0.67
8.85 300.84 183.58 138.56 18.37 131.27 88.11 25.40 18.82 10.31 8.26 4.19 5.54 3.19 1.58 1.04 0.69 0.76 1.24
9.35 162.74 117.48 104.69 9.42 65.15 68.53 14.48 10.45 7.57 4.78 2.46 2.39 2.08 1.31 0.29 0.59 0.62 0.74
9.63 199.32 139.25 107.38 41.98 76.57 68.03 15.88 13.07 7.48 4.84 2.62 3.46 2.77 0.98 0.65 0.70 0.56 0.95
9.96 326.70 190.28 141.08 15.95 119.33 66.91 23.09 15.21 11.49 6.10 3.36 3.92 2.14 1.27 0.95 0.61 0.64 1.04
10.37 207.66 166.27 123.64 11.19 82.13 76.55 18.51 14.47 7.42 4.90 3.03 2.84 1.60 0.34 1.20 0.68 0.56 0.88
10.77 193.02 173.27 136.43 12.53 74.05 58.21 19.54 14.47 7.16 5.03 2.84 2.84 1.49 0.34 0.80 0.58 0.48 0.92
11.15 131.60 165.29 140.69 673.79 56.55 98.08 19.54 12.87 8.95 4.11 3.03 3.32 2.03 1.21 0.40 0.63 0.67 1.04
11.45 188.94 179.64 120.09 37.62 74.39 85.52 20.05 17.42 8.87 5.16 3.08 3.08 1.73 1.17 0.87 0.66 0.65 0.93
11.82 103.22 104.65 65.98 59.34 42.51 56.27 11.78 8.96 7.92 3.44 2.11 2.05 1.25 2.00 0.50 0.60 0.63 0.59
12.03 162.42 159.57 122.73 693.42 66.26 59.24 17.19 13.44 9.03 4.18 2.64 2.64 1.78 1.44 0.74 0.58 0.65 1.22
12.52 161.85 132.87 83.14 10.65 60.16 73.21 15.88 11.76 7.38 3.98 2.93 2.69 1.47 2.30 0.65 0.67 0.72 0.76
Mean 132.70 103.13 90.97 61.37 53.40 49.34 14.54 10.02 6.54 3.42 2.54 2.32 1.84 0.99 0.65 0.63 0.59 0.59
Fig. 11. Detrital input (Al)vs. carbonate productivity (Ca) and productivity proxies (enrichment factors of Mn, P, Ba, Ni, Cd and Cu).
67J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
Fig. 12. Phosphorus accumulation rate and microfacies against relative Nannoconus abundance.
Fig. 13. Abundances and quantitative ratios of different nannofossil groups (Watznaueria,Cyclagelosphaera,Conusphaera and Nannoconus).
68 J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
radiolarians, and some other elements like calcispheres, mollusc shells,
aptychi, and echinoderm debris (Haas et al., 1985, 1994; Grabowski et
al., 2010a).
The observed microfacies change is likely a result of rapid evolution
of calcitic microplankton (cf. Haas et al., 1994; Bornemann et al., 2003)
and it is correlated with a decrease of magnetic susceptibility, and in-
crease in CaCO
3
content of the rocks (Fig. 7). The geochemical data
also point to increasing water fertility during the deposition of the
Lókút section (see also discussion in section 6.2). Higher fertility of wa-
ters, which were enriched in organic carbon, or increasing rates of pelag-
ic calcite particles, which are characterized by lower carbon isotope
enrichment factor than aragonite grains (cf. Romanek et al., 1992;
Swart and Eberli, 2005) may have contributed to the record of a step-
wise fall of δ
13
C values of the oceanic carbon pool. Therefore, not only
global isotope trends but also regional factors may be recorded in the
carbon isotope composition of bulk carbonates from the Lókút section.
7. Palaeoenvironmental interpretations
7.1. Variations of detrital input
Decrease of terrigenous input during the Tithonian and the Early
Berriasian in the Western Tethys is a well-known phenomenon.
Itisdocumented by magnetic susceptibility (MS) data from numerous
sections in the Carpathians: (Brodno Houša et al., 1999; Strapkova
Michalík et al., 2016;Pośrednie Grabowski et al., 2013); the Eastern
Alps (Lukeneder et al., 2010); the Sub-Betics (Pruner et al., 2010) and
the Apennines (Houša et al., 2004; Satolli et al., 2015).
Grabowski et al. (2013) suggest possible eustatic and/or
palaeoclimatic interpretation ofthe lithogenic input variations in the
Upper TithonianBerriasian of the Pośrednie III section(pelagic Križna
or Fatricsuccession of the Tatra Mts, Poland). Eustatic interpretation is
supported by the fact that MS (and terrigenous input) variations correlate
well with the transgressiveregressive cycles in the Tethyan domain
(Hardenbol et al., 1998).Bio- and magnetostratigraphically calibrated
MS peaks in the Upper Tithonian and the Upper Berriasian correspond
to regressive intervals, while profound MS minimum in the Lower
Berriasian is correlated with a sea-level rise. Second order MS variations
in the Pośrednie III section also correlate with sequence boundaries (Ti
4, Be 1 and Be 2), and important breccia occurrences in the Fatric area
(Reháková, 2000). The same interpretation has been applied to Upper
Berriasian interval of the Barlya section, Western Balkan, Bulgaria
(Grabowski et al., 2016). Both datasets from Poland and Bulgaria appar-
ently conrm the model of Ellwood et al. (1999) linking lowering of
sea-level with increased erosion, and elevated MS values, which are ob-
served even in sections located relatively far from the sea shore. Unfortu-
nately, the eustatic modelfails in the explanation of long term MS
decreasing trend in the Lókút section. The trend of decreasing sea-level
in the Tithonian, culminating in the regression peak in the magnetozone
M19r (Hardenbol et al., 1998) or close to the J/K boundary(Hallam, 2001;
Hesselbo, 2008; Price et al., 2016), should have been reected in a signif-
icant rise of MS values. In fact, a steady MS decrease accompanied by in-
creasing carbonate productivity is observed in this interval. The clastic
events reported by Reháková (2000) i.e. Hlbočevent (in Chitinoidella
Zone, M20n2n), and Zliechov event (just below the J/K boundary, in
Alpina Subzone, M19n2n), which are well documented in the Pośrednie
III section and reected in MS signal of the Strapkova section, Pieniny
Klippen Belt (Michalík et al., 2016) are not manifested in Lókút.
Alternatively, a long term decrease of MS might be interpreted
as result of aridization (Grabowski et al., 2013 and references therein).
The aridization trend in the Late TithonianEarly Berriasian is document-
ed by clay mineralogy and palynological data from the North Sea (Abbink
et al., 2001), Southern England (Hesselbo et al., 2009),Baltic area
(Šimkevičius et al., 2003), Russian Platform (Ruffell et al., 2002), SE
and EFrance(Deconinck, 1993; Bover-Arnal and Strasser, 2013),
Spain(Diéguez et al., 2009) and NAfrica(Schnyder et al., 2005). The
evaporitic successions occur in the J/K boundary beds in the English
Purbeck (Schnyder et al., 2006), and Central and SE Poland (Dziadzio et
al., 2004; Gutowski et al., 2005). This trend was most probably quite
widespread since it is noted also in the Central Asia (Zhang et al., 2014).
7.2. Palaeoredox, palaeoproductivity and possible palaeotemperature
changes
The increase of geochemical palaeoproductivity indicators (P, Ba
etc., PAR) towards the Berriasian is well documented in the Lókút sec-
tion. A peculiar feature of this section, especially in the Tithonian inter-
val, is a decoupling between δ
13
C trend and P burial rate (Fig. 12). This
situation is not typical since usually carbonate δ
13
C curves and PAR
are positively correlated (llmi, 1996). A similar case has been docu-
mented by van de Schootbrugge et al. (2003) from the Lower
Hauterivian of NW Tethyan margin in Swiss and French sections. Con-
trary to van de Schootbrugge et al. (2003) we do not see correlation be-
tween sea-level rise and decoupling between P and C cycles in the
Tithonian in Lókút. However, as in the case of Helvetic sections, the
decoupling trend is related to increasing carbonate sedimentation
(Fig. 5). Interestingly, decreasing rate of clastic components, increasing
carbonate productivity, and decreasing carbonate δ
13
C values are ob-
served in the Lókút section.
Increasing delivery of nutrients under decreasing detrital input, indi-
cates that these elements were not transported from nearby land areas.
Accordingly, upwelling is considered as the most likely mechanism for
nutrient transport in the Western Tethys (cf. Birkenmajer, 1986;
Golonka and Krobicki, 2001; Hotinski and Toggweiler, 2003; Rais et al.,
2007; De Wever et al., 2014). However, a long distance transport of nu-
trients in less-saline river plumes cannot be also excluded (cf.
Baumgartner, 2013). Indeed, palaeotopographic situation of the Lókút
section, on the elevation slope (Fig. 2) supports the upwelling explana-
tion. Last phases of synsedimentary tectonic movements (horst uplifts)
are documented in the Lower Tithonian (Vörös and Galácz, 1998;
Convert et al., 2006). A signicant enrichment in phosphorus is also re-
ported from the Berriasian of the Pieniny Klippen Belt (Golonka and
Krobicki, 2001). It has been attributed to upwelling controlled by uplift
of the Czorsztyn and other ridges as well as palaeowinds blowing parallel
to their axes. Enrichment in phosphorus is also observed in the Lower
Berriasian of the basinal Križna succession in the Tatra Mts (Grabowski
et al., 2013). Therefore, increase of relative phosphorus content in sedi-
ments across the Tithonian/Berriasian boundary might be a regional
phenomenon in the Western Tethys and upwelling might have taken
part in redistribution of that element (e.g. Baumgartner, 2013; Brunetti
et al., 2015). The upwelling might have caused an inow of waters
enriched in organic matter and additionally might have contributed to
increased burial of organic carbon.
Two contrasting palaeoenvironmental models might be proposed
for the Early Tithonian and Early Berriasian sedimentation at the
Lókút, respectively (Fig. 14). During the Early Tithonian, relatively high
inux of ne clay particles, and low carbonate production is
observed.Surface waters were inhabited mostly by Saccocomidae. Sedi-
mentation rate was very low, bottom water well oxidized and depleted
in nutrients (low values of PAR). Similar conditions are recently pro-
posed by Jach et al. (2012) for the Upper KimmeridgianLower
Tithonian Ammonitico Rosso facies in the pelagic basin of Križna unit
(Tatra Mts, Poland). During the Early Berriasian, the clastic inux de-
creased and was additionally diluted by increasing carbonate sedimen-
tation rate. Calpionellids became dominant constituent of the
microfacies. These processes coincide with aridization documented in
other sections (see last paragraph of Section 7.1). The surface water be-
came likely more eutrophic, which is manifested by high PAR and in-
crease of concentrations of other nutrients. Deterioration of bottom
water oxygenation took place. The lithological change occurring in the
studied section might be related to a major evolutionary event, called
Nannofossil Calcication Event(Bornemann et al., 2003) which took
69J. Grabowski et al. / Sedimentary Geology 360 (2017) 5472
place in the Late Tithonian, just before M19r chron. It is reected in a
microfacies change from Saccocoma to calpionellid dominated and a
shift of both bulk rock isotopic ratios (δ
18
O and δ
13
C) towards lower
values. Similar phenomena were found also in DSDP Site 534 in the Cen-
tral Atlantic (Tremolada et al., 2006). Therefore, we have a good reason
to assume that all the palaeoenvironmental changes in the
Transdanubian Range may have been related to signicant changes in
the climatic conditions (warming, and aridization) and an increasing
fertility of the surface seawater in this part of Tethyan realm. Interpreta-
tion of negative shift of bulk rock δ
18
O as an indicator of
palaeotemperature trend must be treated with some caution since it co-
incides with lithological or microfacial change. In DSDP site 534 the shift
correlates with a boundary between CatGap formation (red claystones)
and Blake Bahama Formation (pelagic limestones; Tremolada et al.,
2006) while in Lókút with already mentioned decline of Saccocoma fa-
cies. Tectonic reorganization of Bakony Basin might have been an addi-
tional factor, which resulted in the enhancement of upwelling intensity.
Some changes is nannoplankton assemblages at the J-K boundary of the
Lókút section, like increases in Conusphaera and Nannoconus percent-
ages, seem to reect a gradual rise in surface water fertility in the
Lókút basin (Fig. 13), although the eutrophication levelof surface waters
was probably not enough to affect the high carbonate productivity of
nano- and microplankton.
8. Conclusions
New micropalaeontological and geochemical data have been
presented from precisely bio- and magnetostrartigraphically dated sec-
tion of the TithonianLower Berriasian of the Lókút Hill (Transdanubian
Range, Hungary). Prominent variations in microfacies, microfossils, con-
centrations of chemical elements, as well as oxygen and carbon isotope
ratios are recorded within the section. They coincide with a gradual
transformation of lithofacies from the Lower Tithonian Ammonitico
Rosso-like formation (Pálihálás Formation) into the Lower Berriasian
Maiolica-type calpionellid limestone formation (Mogyorósdomb
Formation).
Decreasing concentration of detrital elements and decreasing δ
13
C
and δ
18
O values of bulk carbonates, as well as increasing calcium carbon-
ate content, and chemical indicators of oxygen depletion of bottom wa-
ters and palaeoproductivity are interpreted as a record of
palaeoenvironmental changes in the Lókút basin. They point to a decreas-
ing detrital input due to weakening ofcontinental weathering, increasing
surface water carbonate productivity, and increasing ux of nutrients
from upwelling. Similar variations are observed in many, coeval sections
of the Western Tethyan realm, therefore, most of the observed phenom-
ena are related to regional or global processes. Important
palaeoenvironmental events (increase of the PAR, decline of Saccocoma
microfacies and negative shifts of carbon and oxygen isotopic ratios)
are cumulated in the magnetozone M19r which coincides with the
Nannofossil Calcication Event(sensu Bornemann et al., 2003).
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.sedgeo.2017.08.004.
Acknowledgements
The investigations were nancially supported by the project
61.2301.1501.00.0 of the Polish Geological InstituteNational Research
Institute and grant K 113013 of the Hungarian National Science Fund
(OTKA). Special thanks are due to A. Teodorski (Warsaw University)
for technical assistance in evaluation of the geochemical data. This is a
contribution to the IGCP project 609 Climate-environmental deteriora-
tions during greenhouse phases: Causes and consequences of short-term
Cretaceous sea-level changes.
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Project
Better correlations in the late Tithonian - lower Berriasian, in both marine and non-marine facies, Fieldwork areas include Ukraine, France, Iraq, Tunisia, California, UK, and Italy
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