Betzler et al. Progress in Earth and Planetary Science (2018) 5:5
DOI 10.1186/s40645-018-0165-x

Progress in Earth andPlanetary Science

RESEARCH ARTICLE

Open Access

Refinement of Miocene sea level andmonsoon events from the sedimentaryarchive of the Maldives (Indian Ocean)
C. Betzler1* , G. P. Eberli2, T. Lüdmann1, J. Reolid1, D. Kroon3, J. J. G. Reijmer4, P. K. Swart2, J. Wright5, J. R. Young6,
C. Alvarez-Zarikian7, M. Alonso-García8,9, O. M. Bialik10, C. L. Blättler11, J. A. Guo12, S. Haffen13, S. Horozal14,
M. Inoue15, L. Jovane16, L. Lanci17, J. C. Laya18, A. L. Hui Mee2, M. Nakakuni19, B. N. Nath20, K. Niino21,
L. M. Petruny22, S. D. Pratiwi23, A. L. Slagle24, C. R. Sloss25, X. Su26 and Z. Yao27,28

Abstract
International Ocean Discovery Program (IODP) Expedition 359 cored sediments from eight borehole locations in the
carbonate platform of the Maldives in the Indian Ocean. The expedition set out to unravel the timing of Neogene
climate changes, in particular the evolution of the South Asian monsoon and fluctuations of the sea level. The
timing of these changes are assessed by dating resultant sedimentary alterations that mark stratigraphic turning
points in the Neogene Maldives platform system. The first four turning points during the early and middle Miocene
are related to sea-level changes. These are reliably recorded in the stratigraphy of the carbonate sequences inwhich sequence boundaries provide the ages of the sea-level lowstand. Phases of aggradational platform growth
give precise age brackets of long-term sea-level high stands during the early Miocene and the early to middle
Miocene Climate Optimum that is dated here between 17 to 15.1 Ma. The subsequent middle Miocene coolingcoincident with the eastern Antarctic ice sheet expansion resulted in a long-term lowering of sea level that isreflected by a progradational platform growth. The change in platform architecture from aggradation to progradation
marks this turning point at 15.1 Ma.
An abrupt change in sedimentation pattern is recognized across the entire archipelago at a sequence boundary dated
as 12.9–13 Ma. At this turning point, the platform sedimentation switched to a current-controlled mode when the
monsoon-wind-driven circulation started in the Indian Ocean. The similar age of the onset of drift deposition frommonsoon-wind-driven circulation across the entire archipelago indicates an abrupt onset of monsoon winds in the
Indian Ocean. Ten unconformities dissect the drift sequences, attesting changes in current strength or direction thatare likely caused by the combined product of changes in the monsoon-wind intensity and sea level fluctuations in thelast 13 Ma. A major shift in the drift packages is dated with 3.8 Ma that coincides with the end of stepwise platformdrowning and a reduction of the oxygen minimum zone in the Inner Sea.
The strata of the Maldives platform provides a detailed record of the extrinsic controlling factors on carbonate platform
growth through time. This potential of carbonate platforms for dating the Neogene climate and current changes
has been exploited in other platforms drilled by the Ocean Drilling Program. For example, Great Bahama Bank,
the Queensland Plateau, and the platforms on the Marion Plateau show similar histories with sediment architectures
driven by sea level in their early history (early to middle Miocene) replaced by current-driven drowning or partial
drowning during their later history (Late Miocene). In all three platform systems, the influence of currents on
sedimentations is reported between 11 and 13 Ma.
Keywords: Carbonate platform, Icehouse world, Sea level, Ocean circulation, Neogene, Indian Ocean* Correspondence: christian.betzler@uni-hamburg.de
1
Institute for Geology, CEN, University of Hamburg, Bundesstrasse 55, 20146
Hamburg, Germany
Full list of author information is available at the end of the article© The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Introduction
The Neogene is a time of major changes in climate, sealevel change, and ocean currents (Flower and Kennett
1994, Zachos et al. 2001). In regard to climate, the middle Miocene experienced a warm period known as the
Miocene Climate Optimum (MCO) which was followed
by a general cooling that culminated in the onset ofnorthern hemisphere glaciation at about 2.8 Ma. Sea
level reaches a high during the MCO with subsequent
lower sea level and higher amplitudes of sea level fluctuations (Miller et al. 2005, 2011). The modern global circulation system established in the Miocene and is still
active today (Poore et al. 2006; Wright and Miller 1996).
The South Asian Monsoon (SAM), one of the most intense modern climatic elements, developed during the
Miocene (Betzler et al. 2016a). An increase of sediment
flux into the Indian Ocean occurred around 11 Ma (Rea
1992; Zheng et al. 2004), and a peak in the sedimentation rates of the Indus Fan took place between 16 and
10 Ma (Clift et al. 2008). In addition, the onset of
monsoonal-triggered marine upwelling at ~ 8.5 Ma indicates a strengthening of the monsoon system at this time
(Kroon et al. 1991). The Maldives archipelago contains
the sedimentary record of all these paleo sea-level, climatic, and oceanographic changes. The biostratigraphically dated cores drilled at various locations of theplatform-basin system offer the opportunity to datethese changes with high precision.
The Miocene sea-level changes are recorded in thearchitecture of carbonate platforms of the archipelagothat has been imaged in a variety of seismic data sets
(Purdy and Bertram 1993; Aubert and Droxler 1996;
Belopolsky and Droxler 2004a, 2004b; Betzler et al.
2009, 2013a; Lüdmann et al. 2013). The response to the
middle MCO and its high sea level, for example, is documented by aggrading carbonate platform growth, while
the subsequent cooling and lowering of sea level resultsin platform progradation and no aggradation (Betzler et
al. 2009). The modern SAM is an atmospheric circulation pattern with reversing winds during the winter andthe summer monsoon. This atmospheric circulation produces an annual reversing current system in the Indian
Ocean (Tomczak and Godfrey 2003). These currents
transport sediments into the Inner Sea of the Maldivesand deposited in thick drift deposits. These drifts in the
Inner Sea are a formidable record of the onset and variations of the monsoon winds (Betzler et al. 2016a).
The timing of paleoclimatic and paleoceanographic
changes can be recorded geochemically, such as in theδ18O values of benthic foraminifer tests, and also physically, in the sediments themselves. A common approachto assess timing of temperature and size of Earth’s cryosphere is constructing stacks and compilations of
δ18Obenthic values (Lisiecki and Raymo 2005; Cramer etPage 2 of 18

al. 2009; Zachos et al. 2001, De Vleeschouwer et al.
2017). The stable oxygen isotope records are powerfulproxies to monitor trends but also to record highfrequency changes caused by orbital forcing (Lisiecki
and Raymo 2005; Bell et al. 2015; De Vleeschouwer et al.
2017). However, this proxy record may be less accurate
in defining the exact time when an environment ispushed over a threshold that could produce lastingchanges in the climate system. For example, it is difficult
to pinpoint on the oxygen isotope curve the answers toquestions such as: when in the Middle MCO did rates ofsea level change increase so drastically that coral systems
had to adjust, or when did the strengthening of themonsoon winds trigger changes in the oceanic circulation pattern. In contrast, in the sedimentary record,high-frequency changes driven by orbital forcing are
muted, but major turning points and thresholds are
expressed precisely because deposition is generally
driven by one dominating factor that overrides othervariables.
The Maldives archipelago contains the sedimentary
record of Neogene climate changes in the carbonate sediments of the atolls and the deep Inner Sea. The
Maldives carbonate edifice is a carbonate platform witha twofold configuration of atoll growth and deposition ofcontourites and drifts in areas just some kilometersapart (Betzler et al. 2009, 2013a, 2013b; Lüdmann et al.
2013). Sea-level changes and ocean current interacted
during the evolution of the carbonate platforms, andone or the other factor determined the major changeovers in the platform evolution. Unconformities markthese points, and these unconformities can be recognized on seismic data throughout the archipelago. Cores
retrieved during IODP Expedition 359 enable us to datethese unconformities and provide the exact timing
within the resolution of biostratigraphy of these major
turning points. Previous works established that the currents established abruptly, in response to the onset of the
Indian Monsoon around 12.9 Ma (Betzler et al. 2016a).
This paper describes the correlation of the seismic datawith the sediment cores and their lithology and discusses
the turning points in these seismic and sedimentary records in the light of the global changes during the Neogene. Furthermore, the sedimentary architecture of theMaldives and timing of changes therein can be comparedto other carbonate platforms in the Caribbean and theCoral Sea within the context of global climate change.

Geological and oceanographic setting of theMaldives
Modern morphology and oceanographic setting

The chain of the Maldives archipelago in the central
equatorial Indian Ocean is an isolated tropical carbonate
platform edifice constituting the central and largest part

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

of the Chagos-Laccadive Ridge, located southwest ofIndia (Fig. 1a). A north- to south-oriented double row ofatolls encloses up to 550 m deep Inner Sea of theMaldives (Fig. 1b). Inter-atoll channels that deepen towards the Indian Ocean separate the atolls (Fig. 1b, c).
The modern archipelago comprises about 1200 smaller
atolls that lie near or slightly above the sea surface. The
oceanward margins of the Maldives archipelago are generally steeply inclined, with dips of 20°–30° to 2000 m
water depth. On the Inner Sea side, terraced atoll slopes
have the same dip angles but reach water depths of only
150 m, where the gradient rapidly declines (Betzler et al.
2016a; Fürstenau et al. 2010). Sediment-drift bodies surround the atolls in the Inner Sea (Betzler et al. 2009,2013a, 2013b, 2016a, 2016b; Lüdmann et al. 2013). The
seasonally reversing Indian monsoon system influences
the oceanographic and depositional processes (Tomczak
and Godfrey 2003). Southwestern winds prevail during

Page 3 of 18

Northern Hemisphere summer (April–November) whilenortheastern winds prevail during winter (December–March). These winds generate ocean currents that are
directed westward in the winter and eastward in thesummer. Inter-seasonally, a band of Indian Ocean equatorial westerlies are established, enforcing strong
eastward-flowing surface currents with velocities up to
1.3 m/s. Currents reach water depths of more than
200 m with only slightly reduced velocities (Tomczak
and Godfrey 2003). Within the modern atolls’ passages,
currents can reach velocities of up to 2 m/s.
Evolution of the Maldives

The Maldives archipelago comprises an approximately
3 km thick shallow water and hemipelagic carbonate succession (Aubert and Droxler 1992; Purdy and Betram
1993) (Fig. 1d) that formed on a lower Paleogene (60–50 Ma) volcanic basement (Duncan and Hargraves 1990).

Fig. 1 a, b Location of the Maldives archipelago in the Indian Ocean. The rectangles labeled B and C in (a) and (b) outline the detailed views
shown in (b) and (c), respectively. c Merged multibeam imagery and satellite photography of the atolls in the area studied (from Betzler et al. 2016a).
Stippled white line indicates position of seismic cross section shown in (d). Satellite imagery and seafloor imagery from www.worldwind.arc.nasa.gov andwww.geomapapp.org. d Schematic cross section through the Maldives carbonate edifice with projected location of industry wells ARI1 and NMA1 as
well as the locations of IODP sites. These were strategically positioned to core the most relevant intervals of the Neogene carbonate platform succession.
The drift facies encompass all current-controlled sediments of the Maldives carbonate platform (sheeted drifts and drift fans, submarine dunes)Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

During the early Eocene, carbonate production was established, when flat-topped carbonate banks originatedon topographic highs created by the volcanic basement.
During the late Oligocene, bank margins typically had
elevated rims that separated bank-interior areas fromthe open ocean. During the early Miocene, carbonate
production became restricted to narrow bands at therespective most oceanward areas, forming the double
row of platforms. During the Miocene, platform margins prograded towards the Inner Sea, as recognized indifferent versions of seismic reflection data, irrespectiveof seismic resolution (Purdy and Bertram 1993; Aubertand Droxler 1996; Belopolsky and Droxler 2004a,
2004b; Betzler et al. 2009, 2013a; Lüdmann et al. 2013).
Coincident with the partial drowning of the Maldivescarbonate bank, drift deposits occupied the Inner Sea
and the flanks of the atolls (Betzler et al. 2009, 2013a,
2013b, 2016a, 2016b, Lüdmann et al. 2013). The current
control on the platform evolution continues until today
and can be linked to the Indian Monsoon circulation(Betzler et al. 2016a). Since the inception of the currents,
two additional drowning steps have affected theMaldives (Betzler et al. 2009, 2013a). Flat-topped andatoll-shaped banks are interpreted to have drowned
quickly, whereas mound-shaped banks are interpreted tohave undergone sequential drowning under elevated nutrient fluxes (Betzler et al. 2009), similar to banks described by Zampetti et al. (2004) offshore Malaysia.

Methods/Experimental
The data consist of two main packages: (1) a set of seismic data from various vintages (Betzler et al. 2013a,
2013b, Lüdmann et al. 2013) and (2) the coring and logging data collected during IODP Expedition 359 (Betzler

Page 4 of 18

et al. 2017). The vertical resolution of the seismic data isapproximately 4–6 m, depending on depth. In addition,
published low- to medium-resolution industrial reflection seismic lines shot for Elf in 1973–1974 (Purdy andBertram 1993; Aubert and Droxler 1996) and for Shellin 1989–1990 (Belopolsky and Droxler 2004a, 2004b)
were used for regional context and initial sequence analysis. Interpretation and visualization was performed ontime-migrated data in the time domain using the software package Petrel (Schlumberger). All seismic data
were tied to the seafloor topography computed from themultibeam data acquired during the site survey.
During Expedition 359, eight sites were drilled along two
transects in the Kardiva Channel in the Inner Sea of theMaldives (Figs. 1, 2, 3, 4, and 5). Core retrieval, handlingand all on board measurements including downhole logging are described in detail in the methods section of the
Expedition 359 Proceedings Volume (Betzler et al. 2017).
The age assignments of the successions drilled rely on
calcareous nannoplankton and planktonic foraminiferal
events (Table 1). For the calcareous nannoplankton, thestandard zonal scheme of Martini (1971) was adopted as a
general frame of reference. However, for age models andinter-site calibration, individual events were used according to their reliability and ease of recognition irrespectiveof whether they formed part of the standard zonation. The
compilations of Backman et al. (2012) and Raffi et al.
(2006) were used to provide additional information on thereliability, definition, and timing of events. For the planktic foraminifers, see Betzler et al. (2017).
The core to seismic correlation relies on an accurate P
wave velocity model for time-depth conversion. Twocheckshot surveys were performed at dedicated logging
holes (U1467E and U1471E). At Site U1467, theFig. 2 Seismic line across the Maldives Inner Sea (for location of line see Fig. 1c) with line drawing showing the platform sequence boundaries(PS) and the drift sequence boundaries (DS). Ages of selected horizons are given. For a complete overview of sequence boundary ages see
Table 2. Numbers 1–6 refer to the turning points of the platform evolution discussed in the text

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Page 5 of 18

Fig. 3 Seismic lines with locations of IODP Exp. 359 sites and positions of sequence boundaries. Platform deposits and drift deposits are seismicallywell-resolved and are based upon their differing geometries, with a convex down shape characteristic of the platform clinoforms and a convex up
shape characteristic of the drift deposits. Note that the position of Site U1472 is projected onto the seismic line

waveforms of the recorded shots were of high quality
with a high signal-to-noise ratio, and consequently, firstarrival times were easy to pick (Fig. 5). The velocity inthe oldest drift sequences (DS1–DS3) reaches 2600–
3000 m/s. At sites where logging operations could not
be fully conducted, the time-depth conversion relies on
fixed points provided by the cored formation, such as
for example the contact between the indurated Oligocene shallow water limestone and the overlying chalky
deposits (Oligocene/Miocene sequence boundary).

Results and interpretation
Seismic stratigraphy

The seismic and core data set covers the inner part of
the Maldivian archipelago (Fig. 1). Two transects of sitesaligned along two 2D seismic lines in this area cover the
Neogene succession of the Inner Sea of the Maldives(Fig. 3). Here, previous work identified a drowned carbonate bank with drift deposits adjacent and overlying thedrowned platform (Aubert and Droxler 1996, Belopolsky
and Droxler 2004a, 2004b; Betzler et al. 2009, 2013a;
Lüdmann et al. 2013).
Prior to the drilling of eight sites in the Inner Sea ofthe Maldives during Expedition 359, a preliminary sequence analysis had been performed on the seismic data

(Betzler et al. 2013a, 2013b; Lüdmann et al. 2013) (Fig. 3),
amending previous work of Belopolsky and Droxler(2004a, 2004b). Erosional truncations and onlap geometries were applied to define sequence boundaries, and 22
sequences were differentiated. Lower-bounding sequenceboundaries and overlying correlative seismic sequenceswere labeled as platform sequence boundaries 1 to 11(PS1–PS11) and platform sequence 1 to 11 (ps1–ps11) inthe drowned Neogene carbonate bank, and as drift sequence boundary 1 to 10 (DS1–DS10) and drift sequences
1 to 10 (ds1–ds10) in the drift deposits (Figs. 2, 3) fromolder to younger age, respectively. The ages of these sequence boundaries are here examined and refined using
the shipboard biostratigraphy.
Several of these sequence boundaries delimit stratigraphic packages with distinct growth characteristics.
These boundaries are marked as “turning points” inFig. 2. The lowermost boundary, horizon O/M, is traceable as a distinct seismic reflection throughout the data
coverage and was placed into the Late Oligocene inprevious works (Aubert and Droxler 1996; Belopolsky
and Droxler 2004a, 2004b). This horizon has been identified as a drowning unconformity terminating the
growth of carbonate banks several 10s of kilometers inwidth, and is the first turning point in the investigatedstrata.

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Page 6 of 18

Fig. 4 Sequence stratigraphic correlation of IODP Expedition 359 sites along the northern transect of wells in the Maldives (see Fig. 1 for locations).
HSGR: downhole gamma ray log; NGR: gamma ray counts on wholeround cores. See text for details. M mudstone, W wackestone, P packstone, G
grainstone, F/R floatstone/rudstone. Carbonate mineralogy: blue: aragonite, green: high Mg calcite, gray: low Mg calcite, red: dolomite

Shallow water sedimentation eventually resumed on
the drowned edifice during the latest Oligocene and
Early Miocene. The banks with widths of ca. 5 km were
therefore much narrower than the Oligocene precursor
edifices and were characterized by a low relief from thebank top to the basin (Figs. 1 and 2). Furthermore, noreefs can be differentiated in seismic data (Aubert andDroxler 1996). Subsequently, a shallow-water succession
developed in which 11 seismic sequences are recognized(Betzler et al. 2013a; Fig. 2). The sequence boundary PS1
is the second turning point and corresponds to the baseof a stratigraphic package with a ramp depositional profile, which steepens through time in sequences ps 2, 3,
and 4, until a platform with a steep rim forms sequence
ps4 (Fig. 2). Ramp sequences ps2 and 3 aggrade, and sequence ps4 progrades on the eastern rim of carbonate
platform and thereby widened it eastward to around 7–
8 km (Fig. 2). The same pattern is recognized elsewherein the Maldives edifice where the seaward progradationis less in the carbonate banks located on the eastern partof the Inner Sea when compared to the western carbonate banks (Aubert and Droxler 1992, 1996).
Progradation is halted in sequence ps5 and changes toa pronounced aggradation in seismic sequences ps6 andps7. Sequence boundary PS5 marks this transition and isdefined as third turning point (Fig. 2). At the same time,a backstepping of the outer platform margins facing theopen Indian Ocean occurred (Betzler et al. 2009, 2013a).
Aggradation changes back into progradation at SB PS8,
which is the fourth turning point. Progradation continues in the next three sequences but terminates withsequence ps 11. The end of the progradation marks themost pronounced turning point 5 in the sedimentation
pattern, which corresponds to sequence boundary DS1.
At this turning point in the upper middle Miocene(Fig. 2), large-scale lobate clinoform bodies are deposited by currents in the Inner Sea representing the onsetof current-controlled deposition (Betzler et al. 2013a;
Lüdmann et al. 2013). The currents themselves are
driven by the monsoon winds that start at 12.9–13 Ma(Betzler et al. 2016a). These drift bodies are funneledthrough passages where some platforms had drowned,
while remaining banks and atolls continued to grow(Betzler et al. 2009, 2013a). These atolls are characterized by aggrading margins (Betzler et al. 2009, 2016b)
with the exception of the current-protected flanks facing towards the Inner Sea, where some margins show
progradation (Belopolsky and Droxler 2004a, 2004b,
Betzler et al. 2013a, 2013b). Lobes are fed by easterly
currents and reworked by a current system flowing

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Page 7 of 18

Fig. 5 Sequence stratigraphic correlation of IODP sites along the southern transect of wells in the Maldives (see Fig. 1 for locations). HSGR: downhole
gamma ray log; NGR: gamma ray counts on whole cores. See text for details. Inset to the left shows the time-depth curves for Sites U1467 and U1471
with VSP check shot stations. M mudstone, W wackestone, P packstone, G grainstone, F/R floatstone/rudstone. Carbonate mineralogy: blue: aragonite,
green: high Mg calcite, gray: low Mg calcite, red: dolomite

obliquely or normally to this main stream (Betzler et al.
2013a). This current pattern filled the Inner Sea fromwest to east (Lüdmann et al. 2013). Starting with seismic sequence ds6, the opening of a southern gateway
introduced northward flow of bottom water into theInner Sea, leading to deposition of giant elongateddrifts at the eastern flank of the basin, filling it fromeast to west (Lüdmann et al. 2013).
The last turning point in the platform evolution, turning point 6 at DS8, is the end of an episode which wascharacterized by several steps of partial carbonate platform drowning. This process is documented in the studies done by Betzler et al. (2009, 2013a) and Lüdmann etal. (2013).
The sedimentary record

In the following paragraph, the facies of five different environments that were recovered in the cores are described.
They consist of (1) shallow-water carbonate platform, (2)carbonate platform slope, and (3) basin, (4) pelagic chalk,and (5) carbonate drift. With an overall core recovery rateof 57%, a reasonable core to seismic correlation can be

performed and the seismic sequence boundaries can bepositioned in the cores (Figs. 4 and 5, Table 2).
Shallow-water platform facies

Shallow-water carbonate platform facies were recoveredfrom the upper Oligocene (Site U1468) and the middle
Miocene (Sites U1465, U1469, and U1470) (Figs. 4 and 5).
Shallow water deposits consist of packstone to rudstone
with red algae, large benthic foraminifers, and corals(Fig. 6a).
Outer platform and platform slope facies

Distal carbonate platform slope deposits make up morethan 500 m at Site U1466 and more than 250 m at Site
U1468. Slopes pertain to the Miocene carbonate platform and form clinoform geometries. Outer platform
and slope deposits consist of an alternation of decametric thick intervals of lithified fine- to medium-grained
packstone and wackestone with discrete chert layers.
Contacts between distinct intervals are gradational andconsist of changes in bioturbation intensity and sediment color from grayish brown to light brownish gray

0.44

2.39

58

9.83
10.46

FO Neogloboquadrina acostaensis

LO Paragloborotalia mayeri

8.79

587

533

407

341

305

124

139

127

105

86

75

69

56

484

6.13

84

83

60

57

51

48

46

28

FO Discoaster quinqueramus/berggrenii? 8.29

6.91

> 72.74> 72.75

64.25

61.04

54.75

27.88

Start small Reticulofenestra event

LO Globorotalia lenguaensis

FO Nicklithus amplificus

LO Globoquadrina dehiscens

5.92

FO Globorotalia tumida

5.59

5.53
5.57

FO Sphaeroidinella dehiscens

LO Discoaster quinqueramus

3.85
3.85

LO Globorotalia margaritae

LO Globorotalia margaritae

3.54

3.7

3.47
3.47

LO Dentoglobigerina altispira

LO Dentoglobigerina altispira

LO Reticulofenestra pseudoumbilicus

3.33

LO Sphenolithus abies

2.39

LO Globorotalia limbata

2.39

FO Globigerinoides fistulosus

LO Globorotalia limbata

LO Discoaster pentaradiatus

1.88

1.93

LO Globigerinoides fistulosus

LO Discoaster brouweri

1.88

1.6

LO Calcidiscus macintyrei

72.3

64.2

54.7

45.3

15.2

35.9

6.1

6.1

6.1

1.7

34.87

68.83

54.26554.265

130.4

77.2

50

49.7

43.4

43.4

34.5

24.7

6.3

6.3

1.1

20.1

9.1

3.95

2.34

649.08467

409.8

292.79280.17247.2

126.65

133.2

139.6

117.39114.13

88.64

97.5

85.52

87.4

74.59

71.19

63.9

41.1

21.63
39

17

12

8

0.61

10

10

3

17.59

10.68

3.57

3.57

0.61

LO Globigerinoides fistulosus

1.24

Start small Gephyrocapsa event

LO Globorotalia tosaensis

LO Globorotalia tosaensis

LO Pseudoemiliania lacunosa

0.12

0.29

LO Globigerinoides ruber pink

FO Emiliania huxleyi

0.12

225.5

133.6

76

66.7

66.7

47.9

57.1

47.9

47.9

9.9

9.9

9.9

2.6

Nannofossil Foraminifer Site U1465
Site U1466
Site U1467 depth (mbsf) Site U1468
Site U1469
Site U1470
Site U1471
Site U1472
age
age
depth (mbsf) depth (mbsf)
depth (mbsf) depth (mbsf) depth (mbsf) depth (mbsf) depth (mbsf)

LO Globigerinoides ruber pink

Event

Table 1 Calcareous nannoplankton and planktonic foraminiferal events at sites cored during IODP Exp. 359

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5
Page 8 of 18

13.28

17.71

FO Sphenolithus heteromorphus

19.03

19.72

LO Sphenolithus pseudoheteromorphus

FO Sphenolithus belemnos

FO Sphenolithus pseudoheteromorphus

24.04

27.27

LO Sphenolithus ciperoensis

LO Sphenolithus distentus

FO Paragloborotalia kugleri

22.82

FO Sphenolithus delphix

LO Paragloborotalia kugleri

17.95

18.75

LO Sphenolithus belemnos

FO Orbulina suturalis

13.53

LO Sphenolithus heteromorphus

FO Fohsella fohsi

12.12

LO Coronocycus nitescens

LCO Cyclicargolithus floridanus

10.55

10.55

FO Discoaster hamatus

22.96

21.12

15.1

13.41

10.46

801

769

679

635

593

446

393

315

114

> 707.92> 707.92674

597> 846.7

806.9

774.6

702.9

649.2

634.2

624.3

542.9

492.4

470.7

485.6

424.1

937.1

923.67

928.7

651.6

658.1

631.98Nannofossil Foraminifer Site U1465
Site U1466
Site U1467 depth (mbsf) Site U1468
Site U1469
Site U1470
Site U1471
Site U1472
age
age
depth (mbsf) depth (mbsf)
depth (mbsf) depth (mbsf) depth (mbsf) depth (mbsf) depth (mbsf)

FO Discoaster hamatus

LO Paragloborotalia mayeri

Event

Table 1 Calcareous nannoplankton and planktonic foraminiferal events at sites cored during IODP Exp. 359 (Continued)

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5
Page 9 of 18

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Page 10 of 18

Table 2 Depths and ages of sequence boundaries at sites cored during IODP Exp. 359. Positions of these horizons are shown in
Figs. 4 and 5
Site U1465

Site U1466

Site U1467

Site U1468

Site U1469

Site U1470

Site U1471

Site U1472

(Ma)

(Ma)

(Ma)

(mbsf)(Ma)(mbsf)(Ma)(mbsf)(mbsf)(Ma)(mbsf)(Ma)(mbsf)(Ma)(mbsf)

DS10

1.45

29

1.50

28

1.50

52.5

22.5

25

1.55

31

1.40

53

1.35

33.5

DS9

2.15

40.5

2.00

38

2.10

78

43

38

2.30

49

2.10

90

2.15

54

DS8

2.85

52.5

3.60

60

3.90

157.5

64.5

3.65

78

4.00

166

4.00

100

70

4.10

65

4.20

181.5

77.5

4.35

93

4.60

198

5.30

135

5.60

81

5.50

295.5

93

135

5.50

242.5

6.60

168

5.80

337

107.5

5.80

261.5

6.90

176

8.80

223

DS7
DS6
DS5

(mbsf)

DS4

8.80

535

55

DS3

10.50

603

65

DS2
DS1
PS11

12.70
142

94

11.70

656.5

11.30

191

310

13.00

711

13.00

430

12.85

336

13.10

438

PS10

13.10

380

13.20

457

PS09

14.2

435

14.2

505

PS08

15.1

490

15.1

535

PS07

15.60

525

16.10

573

PS06

17.00

625

17.50

626

PS05

18.50

709

662

PS04

18.60

712

682

141.5

8.80

471.5

148.5

10.60

667

198

12.00

804.5

217

12.90

898

324.5

PS03
PS02
PS01
O/M

20.10

770

21.30

710

21.80

730

25.65

854.7

(Figs. 6b, c). Planktonic and benthic foraminifers, echinoid fragments, and other bioclasts are common, and thematrix contains calcareous nannofossils and aragonite
needles. Darker intervals contain organic matter and noclays. The NGR (gamma ray counts on wholeround cores)
intensity of the sediment varies with the organic content,
and organic-rich intervals have a higher gamma radiationcompared to organic-poor sedimentary intervals.
Bioturbation is pervasive, resulting in a completely
mottled appearance. At Site U1468, two convoluted intervals were recovered in the cores at 641.3 and 700.2
mbsf. Other soft-sediment deformation features andgraded layers with sharp bases occur at Site U1466 at a
depth of 731.4 mbsf (Fig. 6b). Deposits rich in large
benthic foraminifers (Operculina sp., Lepidocyclina [Eulepidina] sp., Heterostegina sp., and Nummulites sp.) occur
at 760 mbsf and are overlain by convoluted layers and avery coarse grained to gravel rudstone (50R-1, 17–19 cm).
The rudstone contains abundant large benthic andplanktonic foraminifers, Halimeda, red algae, fragmented gastropods, and bivalves. Common (at least two
species present) coral fragments up to 1 cm in size
were identified.

The outer platform zone of the Oligocene platform
was recovered at Site U1468. Deposits are wackestones
to floatstone with large benthic foraminifers and planktonic foraminifers.
Basinal and pelagic facies

A pelagic facies in the lower part of the sedimentary successions at Site U1466 and U1468 includes black,organic-rich (up to 8% TOC) planktonic foraminifer, andnannofossil chalks (mudstone–wackestone) with a faintlamination (Fig. 6d). These organic-rich sediments occur
as dark 1–25 cm thick intervals which are intercalatedwith white calcareous nannoplankton and planktonic
foraminifer chalks (mudstones–wackestones) with somebioturbation.
Submarine dunes and drift facies

Submarine dunes were penetrated in the upper part ofthe sedimentary succession at Sites U1465, U1466,
U1468, U1469, and U1470 (Figs. 4 and 5). Deposits havea packstone to grainstone texture and contain abundant
planktonic and benthic foraminifers together with

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Page 11 of 18

Fig. 6 Core photographs of the drift and carbonate platform facies
discussed in the text. a Shallow water limestone with red algal debris
and bioclasts (Core 359-U1465B-4R-1, 18–34 cm). b Slope deposits withslumped layers (Core 359-U1466B-52R-3, 0–150 cm). c Distal slope tobasin deposits characterized by intervals with higher platform export(lighter color) and intervals with reduced platform export (darker color)(Core 359-U1471E-43R-1. 0–150 cm). d Pelagic chalks with dark TOCrich intervals (Core U1466B-56R-1, 0–150 cm). e Drift fan deposits withan alternation of coarser and finer grained bioclastic sands (CoreU1468A-17F-1, 46.5–68.9 cm). f Sheeted drifts deposited in areas of aquiet hydrodynamic regime (Core U1467B-44H-4A, 48.3–81.7 cm)

lithoclasts and shallow water components such as Halimeda flakes (Fig. 6e).
Drift fan deposits were recovered at Sites U1466,
U1468, U1471, and U1472 (Figs. 4 and 5). Sediments
show a textural variation from wackestone to rudstone.
At Sites U1466 and U1468, the drift fan successions
show a fining-upward trend in the lower part of the depositional package followed by a coarsening-upward
trend in its upper part. Wackestones and packstones
within the drift fan are bioclastic with benthic andplanktonic foraminifers. The main components of thegrainstones and rudstones are large benthic foraminifers(Amphistegina, Lepidocyclina, Miogypsinoides, Heterostegina, Operculina, and Sphaerogypsina) together withechinoid spines, red algae, mollusk fragments, bryozoans, Halimeda plates, and aggregate grains.
Sheeted and plastered drift deposits range from wackestones to grainstones at Sites U1467, U1470, U1471,
and U1472 (Fig. 3). Coarser sediments were recovered at
the western end of Kardiva Channel, while at Site
U1467, i.e., in a more current-protected area, the succession are dominated by wackestone. Sheeted drift sediments are bioturbated throughout and contain abundant
planktonic and benthic foraminifers together with bioclasts (Fig. 6f ).
The gamma ray log record of the major sedimentarychanges

Downhole, gamma ray logs in general show low values
with maxima around 80 gAPI (Figs. 4 and 5). Variations
in gamma ray log are controlled by the uranium content
of the sediments and, therefore, trace variations of organic content (Betzler et al. 2017). At Site U1468, thegamma ray log is subdivided into two intervals. The
boundary between these intervals correlates with thebase of the drift sequences, i.e., DS1 (Fig. 4).
The lower interval shows high log values either in theorganic-rich deposits of the restricted basin facies or ataround sequence boundaries (Fig. 4). Above DS1, thegamma ray log values in general show a lower variability
than the values of the platform sequences. The drift deposits, which were logged at Sites U1466, U1467, andU1471 (Figs. 4 and 5), display variable log signatures that

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

do not to follow sequence stratigraphic surfaces or show
any change at these surfaces.
Age model

The sedimentary successions contain variable amountsof age diagnostic microfossils and in some intervals diagenesis obliterate diagnostic characteristics. The dense
set of cores along the two transects, however, provide arobust biostratigraphic framework for age determinationby planktonic foraminifers and nannofossils (Table 1).
Here, an overview is given of the best sites and the challenges in others.
The most useful sequence of biostratigraphic events isfound in the cores from Sites U1471 and U1472 (Betzler
et al. 2017). They allow a clear age model.
At Site U1466, most of the late Miocene interval is absent from the sedimentary record, and a hiatus is inferred between 12.12 and 5.92 Ma. However, thesuccession recovered at Site U1467 is characterized bywell-constrained events (Table 1). In addition, magnetostratigraphy shows reliable results from ~ 100 to 200
mbsf. Data commence with a long reversed interval that,when compared to the biostratigraphic data, was confidently identified as the Gauss magnetochron, C2Ar. Following from this, a succession of subchrons wasPage 12 of 18

identified within Chron C3n. In the lower part of thesection, assemblages of both nannofossils and planktonic
foraminifers are sufficiently well preserved to state withconfidence that the base of the section is younger than
13.3–13.4 Ma.
At Site U1468, the age model for the upper part of thesuccession is poorly constrained because most nannofossil zonal markers are missing (Table 1). Below a hiatus of~ 8 My (Fig. 7), both the nannofossils and planktonic
foraminifers are very poorly preserved and/or diluted
throughout, hampering assignment of zonal boundaries
and/or reliable datum levels. Preservation and abundance of planktonic microfossils increase abruptly below~ 440 mbsf, which coincides with the base of the drift
deposits. In the lower part of the succession, preservation and abundance of planktonic calcareous microfossils are variable, but many samples yielded welldeveloped assemblages. Therefore, several reliable eventswere placed. By extrapolating the linear trend of theaverage sedimentation rate to the base of the interval, an
age of ~ 26 Ma was estimated for the bottom of theinterval.
At Sites U1465 and U1469, the shallow water limestone below sequence boundary DS1 contains large benthic foraminifera of the genus Miogypsinoides, which

Fig. 7 Age-depth curves for the IODP Expedition 359 sites with age of sequence boundaries. Note that PS3 and PS5 are merged with the underlying
boundaries so that individual ages cannot be discriminated for these horizons

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

indicates that these deposits are Early Serravalian orolder in age (Adams 1984).
Timing of sequence boundaries

Depths of the seismic sequence boundaries with lithology, age, mineralogy, and physical properties (gamma
ray log) are shown in Figs. 4 and 5, whereas theirdepths and ages are given in Table 2. The lowermost
seismic reflection traced, i.e., the sequence boundary
O/M, is the first turning point of the Maldives evolution with pelagic deposits overlying neritic limestones.
Its age of ~ 25.7 Ma lies within the Upper Oligocene.
For platform sequence boundary PS1, the second turning point of platform growth, the age assignment is
21.80–22 Ma. Sequence boundary PS2 appears to havean age of ~ 21.3 Ma. Sequence boundary PS3 is amalgamated with PS2 at Sites U1466 and U1468 at seismic
scale and, therefore, no age attribution is possible forthis horizon. The same applies for PS5, which is the third
turning point of platform growth, at 18.5–18.6 Ma.
Sequence boundaries PS6 to PS11 could be unequivocally determined at both Site U1466 and Site U1468(Table 2). The fourth turning point in platform growth,which is defined at PS8 by a change from aggradation toprogradation, has an age of 15.1 Ma. Sequence boundary
DS1, which is the base of the drift succession, is dated as
12.9–13 Ma. The drift sequences were drilled at morethan two sites (Figs. 3, 4, and 5, Table 2). Sequenceboundary DS8, which marks the youngest turning pointof the platform evolution, has an age range of about 2.85
to 4 Ma when ages from all drilling sites are considered.
However, the youngest age for DS8 results from Site
U1465, a location where the seismic facies is indicativeof a high energy hydrodynamic event. We therefore discard this age, which places DS8 into a time interval of
3.6–4.0 Ma.

Discussion
Reflooding of the archipelago and the deposition ofsapropel-like sediments (late Oligocene–early Miocene)

Seismic horizon O/M was interpreted as a drowning unconformity in previous work (Aubert and Droxler 1992,
1996), based on industrial seismic lines displaying a reflection which could be traced regionally. Wells ARI-1(Inner Sea) and NMA-1 (North Malé Atoll) recorded achange from neritic to upper bathyal deposits above thelevel of this horizon (Aubert and Droxler 1996; Purdy
and Betram 1993; Belopolsky and Droxler 2004a, 2004b).
This regional deepening event compares well to thefining-upward trend registered in the succession recovered at Site U1468, where neritic limestones are overlain
by wackestones and floatstones with large benthic foraminifers, and finally followed by mudstones and wackestones with planktonic foraminifers and calcareousPage 13 of 18

nannoplankton (Fig. 4). This lithological succession,
however, indicates a gradual deepening sequence, which
culminated with the deposition of pelagic limestone.
This is in contrast to the reported sedimentary evolution
in well ARI-1, where the Paleogene–Neogene transition
appears to correspond to an abrupt shift from shallow
inner neritic conditions to deeper, outer neritic-upper
bathyal conditions (Aubert and Droxler 1996). In any
case, the new data from Site U1468, which is located
115 km north of well ARI-1 and 79 km northwest ofwell NMA-1, provide additional proof that large parts of
the Maldives area underwent a substantial deepening
during the time interval between 22 and 24 Ma.
The upward-deepening sequences that follow the first
turning point of platform evolution corresponded with awidening of the Inner Sea area through backstepping of
the shallow water parts of the platform towards theouter margins and edges of the ridge (Fig. 2, Purdy andBertram 1993, Aubert and Droxler 1996). The corresponding platform interval below PS1 displays a lowrelief ramp-like profile of the sea floor dipping towards
the Inner Sea (Fig. 2). Multiple sapropel-like intervals inthe basinal part of these sequences indicate that thebasin episodically had conditions which allowed deposition and preservation of an organic-rich sediments inthe late Oligocene and early Miocene. A global sea-level
rise of approximately 50 m following a late Oligocene
sea-level lowstand is reported at the Oligocene–Miocenetransition (Miller et al. 2011, Fig. 8). Such an amplitudeof sea-level rise, however, seems insufficient to trigger anoxygen deficiency within the basin lacking steep margins, or to shut off the neritic carbonate factory at positions of all wells in the Maldives, including at NMA-1,
and to induce pelagic sedimentation all over the known
parts of the platform.
Upwelling and resultant high rates of organic matterproduction could theoretically be responsible for theformation of the sapropel-like layers. Today, the open
Indian Ocean primary upwelling region is located in offequatorial regions at 5°–10° S where the thermocline isshallow (Schott et al. 2009). IODP Sites U1466 andU1468 are located at 4°56′ N but the Indian Plate
crossed the equator at about 20 Ma during its northward
drift (van Hinsbergen et al. 2015). Because the tectonic
plate configuration was different at the Oligocene–Miocene transition, the Indian Ocean circulation pattern forthis time cannot be ascertained in detail. However, there
is a possibility that the site locations during this timeinterval passed the zone of upwelling near the equator.
Such high-nutrient input in the shallow-water realm
would also reduce the growth potential of the neritic
carbonate factories in particular reefs (Hallock andSchlager 1986). This would reconcile the occurrence ofthe sapropel deposits forming on a relatively openBetzler et al. Progress in Earth and Planetary Science (2018) 5:5

Page 14 of 18

Fig. 8 Oligocene to Miocene evolution of the Maldives carbonate platform with ages of the sequence boundaries and key intervals representingchanges of platform configuration. The global sea level curve is from Miller et al. (2005). The intensity of the South Asian Monsoon (SAM) and the
expansion of the Oxygen Minimum Zone (OMZ) are after Betzler et al. (2016a). The global oxygen record is taken from Zachos et al. (2001). MCO
Miocene Climate Optimum (after Holbourn et al. 2005, 2015), EAIS East Antarctic Ice Sheet expansion (after Holbourn et al. 2005), BOM Backstepping of
the outer margin. Numbers in circles denominate turning points of the platform evolution; see text for discussion

carbonate bank. Alternatively, the sapropels could haveformed during a period of stable water mass stratification in the Inner Sea basin. Additional research isneeded to determine what mechanism ultimately triggered the formation of organic carbon rich deposits in
the Inner Sea.
Steepening of the ramp and sea-level controlled platform
growth (early to middle Miocene)

The second turning point of the platform evolution is
the steepening of the carbonate ramp that started above
sequence boundary PS1 at about 22 Ma (Table 2, Figs. 2
and 8, Aubert and Droxler 1992, 1996). The continuous
steeping resulted in a well-defined bank edge on top of
sequence ps3 (Fig. 2). This geometrical turnover is also
observed in several seismic lines located more than
150 km further south (Aubert and Droxler 1996). The
evolution of ramp depositional system into an aggrading
pattern established during the early Miocene indicates arising sea level culminating in a highstand. This growth
pattern is in concert with the global sea-level behavior in
the early Miocene (Fig. 8). In particular, the aggrading
growth pattern of this ramp system correlates well withthe eustatic sea-level high determined in this time interval
at around 20 Ma (Fig. 8). The global sea-level lowering ataround 19.5 Ma corresponds with the progradational
geometry of sequence ps4 (Figs. 2 and 8).
Sequence boundary PS5, i.e., the third turning point of
the platform evolution, correlates to a eustatic sea-levellowstand at about 18.5 Ma, but the overlying aggradational succession was deposited during at a time of a
global sea-level highstand during the Miocene Climate
Optimum (Fig. 8). This highstand is punctuated by two
high-amplitude sea-level lowstands (Miller et al. 2005).
Sequence boundaries PS6 and PS7 date these lowstands
as 17 and 15.6 Ma, respectively. The fourth turning
point in the platform growth evolution to an episode ofprogradation at 15.1 Ma is in concert with an eustatic
sea-level lowering at this time. Sequence boundaries PS9and PS10 again formed at geological times of global sea
level lowstands at 14.2 and 13.1 Ma, respectively.
The early and middle Miocene sequence boundaries,
in addition to representing facies changes, correlate withelevated gamma ray values in the downhole logs. Suchelevated values are related to elevated organic content in
the sediment (Betzler et al. 2016a, 2017). The higher organic content of the sediment around sequence boundaries is likely the consequence of reduced sedimentexport from the platform. The organic content is probably diluted by elevated sediment export from the platform during highstands (Schlager et al. 1994).
The early to middle Miocene aggrading package formed
mostly at the time of the MCO (Fig. 8), which lasted between 17 and 14.7 Ma and was characterized by global
annual mean temperatures ~ 3–8 °C higher than preindustrial levels (Holbourn et al. 2015). Atmospheric
pCO2 reconstructions indicate values reaching ~ 500 ppm(Foster et al. 2012, Zhang et al. 2013). The high-growthBetzler et al. Progress in Earth and Planetary Science (2018) 5:5

potential of the Maldives neritic carbonate platform coincides with a period of global warmth that had higher temperatures than today. This coral growth during such warm
periods adds a new facet to the ongoing discussion about
the reaction of neritic carbonate factories, in particular
reefs, to global warming. The Maldives carbonate succession is the most appropriate location for further drilling toaddress the unanswered question about replacement of
the neritic carbonate producers, i.e., the decline of corals
and the dominance of red algae which has been related to
global oceanographic changes (Bourrouilh-Le Jan andHottinger 1988; Halfar and Mutti 2005).
The cooling of global climate, which began at 13.9 Ma(Holbourn et al. 2005), seems to be out of phase byroughly 1.2 My from an eustatic sea-level lowering at
15.1 Ma (Miller et al. 2005, 2011; Fig. 8). The turning
point 4 (PS8) of the Maldives carbonate edifice evolution
correlates very well to this sea level lowering and trendof overall low sea level.
The change to current-controlled sedimentation (middle
Miocene –Pleistocene)

The good correlation between eustatic changes and thestratigraphic packaging of the Maldives’ sedimentary
succession terminates at 13 Ma (turning point 5) whencurrents start to control the sedimentation in the Inner
Sea. The turning point of this platform evolution coincides with formation of DS1 at the base of the first drift
sequence (Fig. 8). The base of the drift succession correlates with a partial drowning of the Maldives carbonatebanks but does not correspond to a particular sea-levelstand. It coincides with a minor sea-level highstand witha global sea-level position lying in the same range as thepreceding sea-level highstands. A higher amplitude sealevel highstand occurs about 1 My after the partial
drowning of the platform (Fig. 8). Only one of the drift
sequence boundaries, DS3, appears to correlate with aparticular sea-level lowstand. The onset of current influence coincides with initial platform drowning but the sequence of drowning steps ended with DS8, i.e., turning
point 6 at ~ 3.8 Ma, under conditions of a gradual eustatic lowering (Fig. 8; Betzler et al. (2009, 2013a); Lüdmann et al. (2013).
The reconstruction of this evolution of the Maldivessystem, whose ages are now well-constrained, provides
strong evidence for the hypothesis of the monsoontriggered turnover of the Maldives evolution (Betzler et
al. 2009). These authors proposed that the adverse effectof the monsoonal currents and topographically induced
upwelling injected nutrients into surface waters of the
carbonate banks. The current and upwelling processes
are well-documented in the cores recovered during Expedition 359. The drift deposits were deposited under
accelerated currents, and the expansion of the IndianPage 15 of 18

Ocean Oxygen Minimum Zone into the Maldives at
13 Ma is indicated by increased Mn concentration in thesediment Betzler et al. 2016a. The timing of this evolution is in-line with other Indian Ocean records of theonset of the SAM. Gupta et al. (2015), based on stable
isotope records at ODP sites in the Arabian Sea, proposed an onset of the modern monsoon system at
12.9 Ma, and the Bengal fan at Site U1451 at the sametime registered an increase in sedimentation rate
(France-Lanord et al. 2016).
Carbonate platform controlled by sea level and currents

It has been hypothesized that the Maldives carbonate
platform edifice is subjected to two major controlling
factors: sea-level changes and ocean currents (Betzler et
al. 2013a). The relative impact of these factors on thestratigraphic stacking pattern of the carbonate platform
are now elucidated by the correlation of the uppermost
Oligocene to Miocene seismic facies to the cores andthe downhole logs acquired at eight sites during IODP
Expedition 359.
These data prove that a complete shift of the dominating controlling factor can occur in the evolution of acarbonate platform. A system, which is controlled bysea-level changes at a certain time, later can be controlled mainly by ocean currents. The Maldives example
clearly depict that the possibility of such a scenario has
to be considered, for example, when interpreting depositional geometries in seismic data sets.
Published data from elsewhere show that the Maldivesis not a singular case with respect to an interaction ofcarbonate platform growth and ocean currents. Platforms in the Bahamas (Caribbean), the Marion Plateau(Australia), and the South China Sea show similar patterns of sudden increase of current control on the platform basin system (Anselmetti et al. 2000; Isern et al.
2004; Eberli et al. 2004, 2010). In the Bahamas and the
Marion platforms, currents began shaping the carbonate
platforms at 12.5 and 11.1, respectively. In the case of theSouth China Sea, monsoon wind-driven currents andtopographically induced upwelling impinged on carbonate
platforms beginning at ~ 13 Ma (Shao et al. 2017).
It appears clear that the current imprint is a process
restricted to icehouse episodes, when the world’s oceans
host a system of vigorous currents. It is expected thatgreenhouse carbonate platforms do not show such acurrent control. Last but not least, relevance of the newdata from the Maldives is that drifts around carbonate
platforms are not necessarily developing because currents are accelerated around an obstacle at the sea floor,i.e., the carbonate platform, but that the currents actively
shape the platform and control stratigraphy.
The Maldives bear a record of two episodes of partialbank drowning. The first was at the Oligocene–Miocene

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

transition. Following this episode, the platform fully recovered and later flourished and expanded. The second
phase of partial drowning was definitive and only relict
platforms survived. The first phase can be linked to a
combination of high sea level and high paleoproductivity, but the second case is linked to the onset of acurrent system. The thick drift successions located on
the downcurrent side of the drowned banks and thecoarse grain size of some of the components in thesesediments prove that these currents were vigorous. It istherefore proposed that, in this case, platform drowning
was not only triggered by high nutrient injection into
the shallow water, but also by the physical effects ofocean currents.

Conclusions
During the Neogene, Earth’s climate has continuously
reached thresholds that pushed the environment into
new directions. While trends, such as the Miocene Climate Optimum and the subsequent overall cooling, arevisible in the proxy record, threshold steps are ingrainedin the sedimentary record. In carbonate platforms, such
steps are sequence boundaries and stratigraphic packages with distinct sediment accumulation patterns. The
Maldives sedimentary and seismic stratigraphic succession preserves a unique marine record, which conclusively demonstrates this context. Turning points in theplatform growth patterns, such as the change from aggradation to progradation, are linked to overall trends ofsea-level highstands and lowstands and sequence boundaries develop during short-termed sea-level lowstands.
These straightforward relationships in the Maldives are,however, only valid for the lower and middle Miocene.
Younger stratal packaging patterns and sequences arerather driven by the ocean circulation which triggers
erosion and redistribution of sediments by currents.
Current control on carbonate platform sedimentationand growth started nearly simultaneously in different
platforms between 14 and 12 Ma, thus indicating that
this mechanism is an important characteristic of icehouse worlds. This may also apply for other comparable
climate conditions in Earth history.
Acknowledgements
This research used samples and data provided by the International Ocean
Discovery Program (IODP). This study would not have been possible without
the dedicated effort of the drilling crew, ship’s crew, and scientific staff ofthe Drillship JOIDES Resolution. The Ministry of Fisheries and Agriculture of
the Republic of the Maldives is thanked for granting the research permit. We
would like to thank two anonymous reviewers and the handling editor Ryuji
Tada for their constructive comments.
Funding
The expedition was funded by the US National Science Foundation (NSF);
the European Consortium for Ocean Research Drilling (ECORD); the Ministryof Education, Culture, Sports, Science and Technology, Japan (MEXT); theMinistry of Science and Technology (People’s Republic of China); the Korea
Institute of Geoscience and Mineral Resources; the Australian Research

Page 16 of 18

Council and the New Zealand Institute for Geological and Nuclear Sciences;and the Ministry of Earth Sciences (India). The German Federal Ministry of
Education and Research is thanked for funding the seismic surveys (03S0405,
03G0236A).
Availability of data and materials
All data are available at http://iodp.tamu.edu/database/Authors’ contributions
All authors were shipboard scientists of IODP Expedition 359. CB and GPE
acted as co-chiefs and wrote the manuscript; DK and JDW were leading thestratigraphic effort; PKS and BNN performed geochemical and sedimentologicalanalyses; CAZ coordinated the work and performed micropaleontologicalresearch; MAG, OMB, CLB, JAG, SH, SH, MI, LG, LL, JCL, ALHM, TL, MN, KN,
LMP, SDP, JJGR, JR, ALS, CRS, XS, ZY, and JRY equally contributed to this workby sedimentological, micropaleontological, geochemical, magnestostratigraphic,
physical property, and downhole logging analyses. All authors discussed theresults and commented on the manuscript. All authors read and approved thefinal manuscript.
Competing interests
The authors declare that they have no competing interests.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.
Author details
1
Institute for Geology, CEN, University of Hamburg, Bundesstrasse 55, 20146
Hamburg, Germany. 2Department of Marine Geosciences, Department ofMarine Geosciences, Rosenstiel School of Marine and Atmospheric Science,
University of Miami, Miami, FL 33149, USA. 3Department of Geology andGeophysics, University of Edinburgh, Grant Institute, The King’s Buildings,
West Mains Road, Edinburgh EH9 3JW, UK. 4College of Petroleum
Engineering and Geosciences, King Fahd University of Petroleum andMinerals, Dhahran 31261, Saudi Arabia. 5Department of Geological Sciences,
Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ
08854-8066, USA. 6Department of Earth Sciences, University College London,
Gower Street, London WC1E 6BT, UK. 7International Ocean Discovery
Program, Texas A&M University, 1000 Discovery Drive, College Station, TX
77845, USA. 8Divisão de Geologia e Georecursos Marinhos, Instituto
Portugues do Mar e da Atmosfera (IPMA), Avenida de Brasilia 6, 1449-006
Lisbon, Portugal. 9Centro de Ciencias do Mar (CCMAR), Universidade do
Algarve, Faro, Portugal. 10Dr. Moses Strauss Department of Marine
Geosciences, The Leon H. Charney School of Marine Sciences, University of
Haifa, 31905 Carmel, Israel. 11Department of Geosciences, Princeton
University, Guyot Hall, Princeton, NJ 08544, USA. 12Department of Geological
Sciences, California State University Bakersfield, 9001 Stockdale Highway,
Bakersfield, CA 93311, USA. 13Physical Properties Specialist, Ecole Nationale
Superieure de Geologie, Universite de Lorraine, 2 rue du Doyen Marcel
Roubault, 54501 Vandoeuvre-les-Nancy, France. 14Petroleum and Marine
Research Division, Korea Institute of Geoscience and Mineral Resources(KIGAM), Gwahang-no 124, Yuseong-gu, Daejeon 305-350, Korea. 15Graduate
School of Natural Science and Technology, Okayama University, 3-1-1
Tsushima-naka, Okayama 700-8530, Japan. 16Instituto Oceanográfico da
Universidade de São Paulo, Praça do Oceanográfico, 191, São Paulo, SP
05508-120, Brazil. 17Istituto di Scienze della Terra, Università di Urbino, Via S.
Chiara 27, 61029 Urbino, Italy. 18Department of Geology and Geophysics,
Texas A&M University, Mail Stop 3115, College Station, TX 77843-3115, USA.
19
Department of Environmental Engineering for Symbiosis, Soka University,
1-236 Tangi-cyo, Hachioji-shi, Tokyo 192-0003, Japan. 20Geological
Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula,
Goa 403004, India. 21Graduate School of Science and Engineering, Yamagata
University, 1-4-12 Kojirakawa-machi, Yamagata City 990-8560, Japan.
22
Environmental Science and Policy Department, George Mason University,
David King Hall Rm 3005, MSN 5F2, 4400 University Drive, Fairfax, VA
22030-4444, USA. 23Department of Geosciences, Geotechnology andMaterials Engineering for Resources, Akita University, 1-1 Teagata-Gakuencho,
Akita 010-8502, Japan. 24Lamont-Doherty Earth Observatory, Columbia
University, Borehole Bldg. 61 Route 9W, Palisades, NY 10964, USA. 25Earth andEnvironmental Sciences, University of Technology Queensland, R-Block 317, 2

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

George Street, Brisbane, QLD 4001, Australia. 26Key Laboratory of Marginal
Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of
Sciences, 164 West Xingang Road, Guangzhou 510301, People’s Republic ofChina. 27Department of Marine Geology, First Institute of Oceanography (FIO)
State Oceanic Administration (SOA), #6 Xian Xia Ling Road, Qingdao 266061,
Shandong Province, People’s Republic of China. 28Laboratory for Marine
Geology, Qingdao National Laboratory for Marine Science and Technology,
Qingdao, People’s Republic of China.
Received: 1 September 2017 Accepted: 17 December 2017

References
Adams CG (1984) Neogene larger foraminifera, evolutionary and geologicalevents in the context of datum planes In: Pacific Neogene Datum Planes:
Contributions to Biostratigraphy and Chronology (Eds N. Ikebe, & and R.
Tsuchi). Univ. Tokyo Press, pp. 47–67.
Anselmetti FS, Eberli GP, Ding Z-D (2000) From the Great Bahama Bank into theStraits of Florida: a margin architecture controlled by sea-level fluctuations
and ocean currents. Geol Soc Am Bull 112:829–844
Aubert O, Droxler AW (1992) General Cenozoic evolution of the Maldivescarbonate system (equatorial Indian Ocean). Bull Centers Rech Explor Prod
Elf-Aquitaine 16:113–136
Aubert O, Droxler AW (1996) Seismic stratigraphy and depositional signatures ofthe Maldive carbonate system (Indian Ocean). Mar Pet Geol 13:503–536
Backman J, Raffi I, Rio D, Fornaciari E, Pälike H (2012) Biozonation andbiochronology of Miocene through Pleistocene calcareous nannofossils from
low and middle latitudes. Newsl Stratigr 45(3):221–244
Bell DB, Jung SJA, Kroon D, Hodell DA, Lourens LJ, Raymo ME. (2015) Atlantic
Deep-water Response to the Early Pliocene Shoaling of the Central American
Seaway. Scientific Reports, 5, 12252.
Belopolsky, A.V., Droxler, A.W., 2004a. Seismic expressions and interpretations ofcarbonate sequences: the Maldives carbonate platform, equatorial Indian
Ocean. Amer. Assoc. Petrol. Geol., Stud. Geol. 49
Belopolsky AV, Droxler AW (2004b) Seismic expressions of prograding carbonate
bank margins: middle Miocene, Maldives, Indian Ocean. In: Eberli GP,
Masaferro JL, Sarg JF (eds) Seismic imaging of carbonate reservoirs andsystems, pp 267–290
Betzler C, Eberli GP, Alvarez Zarikian CA, Alonso-García M, Bialik OM, Blättler CL,
Guo JA, Haffen S, Horozal S, Inoue M, Jovane L, Kroon D, Lanci L, Laya JC,
Ling Hui Mee A, Lüdmann T, Nakakuni M, Nath BN, Niino K, Petruny LM,
Pratiwi SD, Reijmer JJG, Reolid J, Slagle AL, Sloss CR, Su X, Swart PK, Wright
JD, Yao Z, Young JR (2017) Expedition 359 summary. In: Betzler C, Eberli GP,
Alvarez Zarikian CA, the Expedition 359 Scientists, Maldives Monsoon and
Sea Level (eds) Proceedings of the International Ocean Discovery Program,vol 359. International Ocean Discovery Program, College Station https://doi.
org/10.14379/iodp.proc.359.101.2017
Betzler C, Eberli GP, Kroon D, Wright JD, Swart PK, Nath BN, Alvarez-Zarikian CA,
Alonso-García M, Bialik OM, Blättler CL, Guo JA, Haffen S, Horozal S, Inoue M,
Jovane L, Lanci L, Laya JC, Mee ALH, Lüdmann T, Nakakuni M, Niino K,
Petruny LM, Pratiwi SD, Reijmer JJG, Reolid J, Slagle AL, Sloss CR, Su X, Yao Z,
Young JR (2016a) The abrupt onset of the modern South Asian Monsoon
winds. Sci Rep 6:29838
Betzler C, Fürstenau J, Lüdmann T, Hübscher C, Lindhorst S, Paul A, Reijmer JJG,
Droxler AW (2013a) Sea-level and ocean-current control on carbonateplatform growth, Maldives, Indian Ocean. Basin Res 25:172–196
Betzler C, Hübscher C, Lindhorst S, Lüdmann T, Reijmer JJG, Braga J-C (2016b)
Lowstand wedges in carbonate platform slopes (Quaternary, Maldives, Indian
Ocean). Depositional Rec 2:196–207
Betzler C, Hübscher C, Lindhorst S, Reijmer JJG, Römer M, Droxler AW, Fürstenau
J, Lüdmann T (2009) Monsoonal-induced partial carbonate platformdrowning (Maldives, Indian Ocean). Geology 37:867–870
Betzler C, Lüdmann T, Hübscher C, Fürstenau J (2013b) Current and sea-levelsignals in periplatform ooze (Neogene, Maldives, Indian Ocean). Sediment
Geol 290:126–137
Bourrouilh-Le Jan FG, Hottinger LC (1988) Occurence of rhodolites in the tropical
Pacific—a consequence of Mid-Miocene paleo-oceanographic change.
Sediment Geol 60:355–367
Clift PD, Hodges KV, Heslop D, Hannigan, R, Van Long H, Calves G. (2008)
Correlation of Himalayan exhumation rates and Asian monsoon intensity.
Nature Geosc., 1, 875–880.

Page 17 of 18

Cramer BS, Toggweiler JR, Wright JD, Katz ME, Miller KG. (2009) Ocean
overturning since the Late Cretaceous: Inferences from a new benthic
foraminiferal isotope compilation. Paleoceanography, 24, https://doi.org/10.
1029/2008PA001683.
De Vleeschouwer D, Vahlenkamp M, Crucifix M, Pälike H (2017) Alternating
Southern and Northern Hemisphere climate response to astronomical
forcing during the past 35 m.y. Geology 45:375–378
Duncan RA, Hargraves RB (1990) 40Ar/39Ar geochronology of basement rocks from
the Mascarene Plateau, the Chagos Bank, and the Maldives Ridge. In: Duncan RA,
Backman J, Peterson LC et al (eds) Proceedings of the Ocean Drilling Program,
Scientific Results, vol 115. Ocean Drilling Program, College Station, pp 43–51
Eberli GP, Anselmetti F, Betzler C, Bernoulli D, Van Konijnenburg J-H (2004)
Calibration of seismic data from the western margin of Great Bahama Bank
with exposed strata in the Maiella Mountains (Italy). AAPG Mem 81:207–250
Eberli GP, Anselmetti FS, Isern AR, Delius H (2010) Timing of changes in sea level
and currents along Miocene platforms on the Marion Plateau. In: MorganWA, George AD, Harris PM, Kupecz JA, Sarg JF (eds) Cenozoic carbonate
systems of Australasia, pp 219–242
Flower BP, Kennett JP (1994) The middle Miocene climatic transition: East
Antarctic ice sheet development, deep ocean circulation and global carbon
cycling. Palaeogeogr Palaeoclimatol Palaeoecol 108:537–555. https://doi.org/
10.1016/0031 -0182 (94)90251-8
Foster GL, Lear CH, Rae JWB (2012) The evolution of pCO2, ice volume andclimate during the middle Miocene. Earth Planet Sci Lett 341–344:243–254
France-Lanord C, Spiess V, Klaus A, Schwenk T, the Expedition 354 Scientists(2016) Proceedings of the International Ocean Discovery Program, Bengal
Fan, vol 354. International Ocean Discovery Program, College Station https://doi.org/10.14379/iodp.proc.354.2016
Fürstenau J, Lindhorst S, Betzler C, Hübscher C (2010) Submerged reef terraces ofthe Maldives (Indian Ocean). Geo-Mar Lett 30:511–515
Gupta AK, Yuvaraja A, Prakasam M, Clemens SC, Velu A (2015) Evolution of theSouth Asian monsoon wind system since the late Middle Miocene.
Palaeogeogr Palaeoclimatol Palaeoecol 438:160–167
Halfar J, Mutti M (2005) Global dominance of coralline red-algal facies: a response
to Miocene oceanographic events. Geology 33:481–484
Hallock P, Schlager W (1986) Nutrient excess and the demise of coral reefs andcarbonate platform. PALAIOS 1:389–398
Holbourn A, Kuhnt W, Schulz M, Erlenkeuser H (2005) Impacts of orbital forcing
and atmospheric carbon dioxide on Miocene ice-sheet expansion. Nature
438:483–487
Holbourn A, Kuhnt W, Kochhann KGD, Andersen N, Meier KJS (2015) Global
perturbation of the carbon cycle at the onset of the Miocene Climatic
Optimum. Geology:123–126
Isern A, Anselmetti FS, Blum P (2004) A Neogene carbonate platform, slope andshelf edifice shaped by sea level and ocean currents, Marion Plateau (Northeast
Australia). In: Eberli GP, Masaferro JL, Sarg JF (eds) Seismic imaging of carbonate
reservoirs and systems, vol 81. AAPG Memoir, Tulsa, pp 291–307
Kroon D, Steens T, Troelstra SR (1991) Onset of monsoonal related upwelling in
the western Arabian Sea as revealed by planktonic foraminifers. Proc. Ocean
Drill. Proj., Sci. Results, 117, 257–263.
Lisiecki LE and Raymo ME. (2005) A Pliocene-Pleistocene stack of 57 globally
distributed benthic D18O records. Paleoceanography, 20, https://doi.org/10.
1029/2004PA001071.
Lüdmann T, Kalvelage C, Betzler C, Fürstenau J, Hübscher C (2013) The Maldives,a giant isolated carbonate platform dominated by bottom currents. Mar Pet
Geol 43:326–340
Martini E (1971) Standard Tertiary and Quaternary calcareous nannoplankton
zonation. In: Farinacci A (ed) Proceedings of the Second Planktonic
Conference, Roma 1970, vol 2. Edizioni Tecnoscienza, Rome, pp 739–785
Miller KG, Kominz MA, Browning JV, Wright JD, Mountain GS, Katz ME, Sugarman
PJ, Cramer BS, Christie-Blick N, Pekar SF (2005) The Phanerozoic record ofglobal sea-level change. Science 310:1293–1298
Miller KG, Mountain GS, Wright JD, Browning JV (2011) A 180-million-year recordof sea level and ice volume variations from continental margin and deep-sea
isotopic records. Oceanography 24:40–53
Poore HR, Samworth R, White NJ, Jones SM, McCave IN (2006) Neogene overflowof Northern Component Water at the Greenland-Scotland Ridge.
Geochemistry, Geophysics, Geosystems, 7, https://doi.org/10.1029/
2005GC001085.
Purdy EG, Bertram GT (1993) Carbonate concepts from the Maldives, Indian
Ocean, vol 34. AAPG, Stud. Geol, Tulsa, p 56

Betzler et al. Progress in Earth and Planetary Science (2018) 5:5

Raffi I, Backman J, Fornaciari E, Pälike H, Rio D, Lourens L, Hilgen F (2006) A
review of calcareous nannofossil astrobiochronology encompassing the past
25 million years. Quat Sci Rev 25:3113–3137
Rea DK. (1992) Delivery of Himalayan sediment to the northern Indian Ocean andits relation to global climate, sea level, uplift, and seawater strontium. In:
Synthesis of Results from Scientific Drilling in the Indian Ocean. (Ed R.A.
Duncan), Geophys. Monogr. Ser., Washington, DC, 70, 387–402.
Schlager W, Reijmer JJG, Droxler AW (1994) Highstand shedding of carbonate
platforms. J Sediment Res B64:270–281
Schott FA, Xie S-P, McCreary JP (2009) Indian Ocean circulation and climate
variability. Rev Geophys 47. https://doi.org/10.1029/2007RG000245.
Shao L, Li Q, Zhu W, Zhang D, Qiao P, Liu X, You L, Cui Y, Dong X (2017)
Neogene carbonate platform development in the NW South China Sea:
litho-, bio- and chemo-stratigraphic evidence. Mar Geol 385:233–243
Tomczak M, Godfrey JS (2003) Regional oceanography: an introduction. Daya
Publishing House, Delhi, p 390
Van Hinsbergen DJJ, de Groot LV, van Schaik SJ, Spakman W, Bijl PK, Sluijs A,
Langereis CG, Brinkhuis H (2015) A paleolatitude calculator for paleoclimate
studies. PLoS One 10 https://doi.org/10.1371/journal.pone.0126946
Wright JD and Miller KG (1996) Control of North Atlantic Deep Water Circulationby the Greenland-Scotland Ridge. Paleoceanography,
11, 157–170.
Zachos J, Pagani M, Sloan L, Thomas E, Billups K (2001) Trends, rhythms, andaberrations in global climate 65 Ma to present. Science 292:686–693
Zampetti V, Schlager W, van Konijnenburg J-H, Everts AJ (2004) Architecture andgrowth history of a Miocene carbonate platform from 3D seismic reflection
data; Luconia Province, offshore Sarawak, Malaysia. Mar Pet Geol 21:517–534
Zhang YG, Pagani M, Liu Z, Bohaty SM, DeConto R (2013) A 40-million-year
history of atmospheric CO2. Philos Trans R Soc Lond Ser A 371 dx.doi.org/
https://doi.org/10.1098/rsta.2013.0096
Zheng, H., Powell, C.M., Rea, D.K., Wang, J. and Wang, P. (2004) Late Miocene andmid-Pliocene enhancement of the East Asian monsoon as viewed from theland and sea. Glob. Planet. Change, 41:147–155.

Page 18 of 18