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The new knowledge is written on sedimentary rocks – a comment on Shanmugam’s paper “the hyperpycnite problem”

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In a recent contribution G. Shanmugam (2018) discusses and neglects the importance of hyperpycnal flows and hyperpycnites for the understanding of some sediment gravity flow deposits. For him, the hyperpycnal flow paradigm is strictly based on experimental and theoretical concepts, without the supporting empirical data from modern depositional systems. In this discussion I will demonstrate that G. Shanmugam overlooks growing evidences that support the importance of hyperpycnal flows in the accumulation of a huge volume of fossil clastic sediments. Sustained hyperpycnal flows also provide a rational explanation for the origin of well sorted fine-grained massive sandstones with floating clasts, a deposit often wrongly related to sandy debris flows.
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A C A D E M I C D I S C U S S I O N Open Access
The new knowledge is written on
sedimentary rocks a comment on
Shanmugams paper the hyperpycnite
problem
Carlos Zavala
1,2
Abstract
In a recent contribution G. Shanmugam (2018) discusses and neglects the importance of hyperpycnal flows and
hyperpycnites for the understanding of some sediment gravity flow deposits. For him, the hyperpycnal flow
paradigm is strictly based on experimental and theoretical concepts, without the supporting empirical data from
modern depositional systems. In this discussion I will demonstrate that G. Shanmugam overlooks growing
evidences that support the importance of hyperpycnal flows in the accumulation of a huge volume of fossil clastic
sediments. Sustained hyperpycnal flows also provide a rational explanation for the origin of well sorted fine-grained
massive sandstones with floating clasts, a deposit often wrongly related to sandy debris flows.
Keywords: Hyperpycnites, Turbidites, Sediment gravity flows
1 Introduction
In a recent paper G. Shanmugam (2018) relativized the
importance of hyperpycnal flows as an important sedi-
ment transfer mechanism to associated lacustrine and
marine basins. Controversially, hyperpycnal flows were
the first documented land derived sediment gravity flows
in lakes (Forel 1885) and in deep marine settings (Hee-
zen et al. 1964). At present, our understanding of hyper-
pycnal flows and their related deposits (hyperpycnites)
has been deeply improved due to a join effort on the
study of ancient and recent deposits, complemented
with detailed oceanographic observations, flume experi-
ments and mathematical modeling.
Full discussion with Shanmugam (2018) will be the
scope of a forthcoming full paper. The objective of this
short reply is to discuss some points observed by G.
Shanmugam (2018) concerning my recent paper (Zavala
and Arcuri 2016) focused on the recognition and inter-
pretation of ancient hyperpycnites.
2 Comments on Shanmugam (2018) paper The
hyperpycnite problem
2.1 Sand transport to deep waters by hyperpycnal flows
Shanmugam (2018), page 199 right line: There is not a
single documented case of hyperpycnal flow, which is
transporting sand across the continental shelf, and sup-
plying sand beyond the modern shelf break.
There is growing evidences provided by the study of
the discharges of Taiwan rivers (Dadson et al. 2005)es-
pecially SW Taiwan rivers into the Gaoping Canyon (Liu
et al. 2006,2012,2016; Chiang and Yu 2008; Zhang et
al. 2018), the case of the Cap Timiris Canyon (Antobreh
and Krastel 2006), the Rhone fan (Mear 1984; Droz et al.
2001; Tombo et al. 2015), the Var deep sea fan (Mulder
et al. 2001; Khripounoff et al. 2009,2012), the Hueneme
canyon in the Santa Monica Basin (Romans et al. 2009),
the very thick deep water hyperpycnites related to the
Missoula flood (Griggs et al. 1970; Brunner et al. 1999;
Normark and Reid 2003; Reid and Normark 2003), the
Newport canyon in Southern California (Covault et al.
2010), the Geremeas river in the Sardinian southern
margin (Meleddu et al. 2016), the Alsek Sea Valley in Al-
aska (Milliman et al. 1996), the failure of the Malpasset
Dam in the Mediterranean (Mulder et al. 2009), the Eel
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Correspondence: czavala@criba.edu.ar
1
Departamento de Geología, Universidad Nacional del Sur, San Juan 670,
8000 Bahía Blanca, Argentina
2
GCS Argentina SRL, Molina Campos 150, 8000 Bahía Blanca, Argentina
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Zavala Journal of Palaeogeography (2019) 8:23
https://doi.org/10.1186/s42501-019-0037-3
submarine fan in the offshore of northern California
(Paull et al. 2014), the Al Batha hyperpycnal system in
Oman (Bourget et al. 2010), the Santa Barbara Channel
in California (Warrick and Milliman 2003), and the
Zaire (Congo) canyon (Heezen et al. 1964; Khripounoff
et al. 2003; Savoye et al. 2009; Azpiroz-Zabala et al.
2017) among others. Khripounoff et al. (2003) docu-
mented on March 8, 2001, a sediment-laden turbidity
current in the Congo canyon travelling at 121 cm/sec at
4000 m depth, 150 m above the channel floor, transport-
ing quartz-rich well sorted fine-grained sand (150
200 μm) and large plant debris (wood, leaves, roots).
This single flow was sustained for ten days. More re-
cently Azpiroz-Zabala et al. (2017) recognized in the
same turbidity system flows lasting an average of 6.7
days with peak velocities between 80 and 100 cm/sec.
Additionally in their review of recent sinuous
deep-water channels, Wynn et al. (2007) claimed that
Deep-water sinuous channels are dominantly fed by
high-frequency or semi-continuous, low-density turbidity
currents, some of which may be hyperpycnal at times of
peak fluvial discharge. More recently Zhang et al.
(2018) showed the results of monitoring the turbidity
currents in the Gaoping submarine canyon during 3.5
years. The mooring system was located at a water depth
of 2104 m, 146 km far from the canyon head. They re-
corded 20 turbidity currents directly attributed to peak
river discharges during flood periods. The duration of
each individual flow ranged from a week up to a month.
The associated interstitial water had high temperature
and less salinity respect to the ambient water, thus dem-
onstrating that these turbidites were originated directly
from hyperpycnal flow discharges. Zhang et al. (2018)
concluded that These observations strongly suggest that
hyperpycnal flow conditions associated with the river
floods during the typhoon season are the dominant
drivers of sediment redistribution in tectonically active
and climatically disturbed areas such as Taiwan and its
connected submarine canyons, and support the link be-
tween upstream hyperpycnal flows and sustained turbid-
ity currents in the deep sea.
2.2 The origin of hyperpycnal flows
Shanmugam (2018), page 199 right line: Thus far, the
emphasis has been solely on river mouth hyperpycnal
flows (Mulder et al. 2003), thus ignoring density plumes
in other environments, such as open marine settings, far
away from the shoreline.
Of course, the hyperpycnal condition can only be
achieved at the coast. According to Bates (1953) a hyper-
pycnal flow occurs when a subaerial (fluvial) system dis-
charges a mixture of water and sediment with a bulk
density higher than that of the water in the reservoir.
When this situation occurs, the incoming flow sinks
below basin waters forming a hyperpycnal flow which
can travel considerable distances carrying large volumes
of sediment directly supplied from a river in flood. An
underflow can only be considered as hyperpycnal (from
the Greek πέρ (hyper) meaning over, pycnal = density,
from Greek: πυκνός (puknos) meaning dense) if it's
originated on land. The last excluded from the definition
of hyperpycnal flowto all kinds of underflows gener-
ated inside the basin, as the case of mass-transport com-
plexes, intrabasinal turbidites, tempestites, cascadites,
and turbulent flows derived from convective instability
(Parsons et al. 2007) or density stratification. Conse-
quently hyperpycnal flows can only be formed at river
mouths.
2.3 Turbidity currents from plunging rivers
Shanmugam (2018), page 205 right line: No one has
documented the transformation of river currents into tur-
bidity currents at a shallow plunge point in modern mar-
ine environments.
There is a lot of documentation about the hyperpycnal
origin of turbidites, both in shallow and deep waters (see
comments on chapter 2.1 with references there). Add-
itionally, a very nice documentation of the 1954 Bonea
River flood in Italy and its related hyperpycnal flow de-
posits is also available (Budillon et al. 2005; Violante
2009; Sacchi et al. 2009). Recently Katz et al. (2015) pub-
lished a detailed observation of an actual hyperpycnal
discharge in the Gulf of Aqaba (Red Sea). They shared a
very interesting video available online https://www.you-
tube.com/watch?v=4r9ndJ80_1Y
2.4 Hyperpycnal flow deposits and turbidites
Shanmugam (2018), page 205 right line: Hyperpycnal
flows are defined solely on the basis of fluid density.
Therefore, it is misleading to equate turbidity currents
with hyperpycnal flows.
In our paper (Zavala and Arcuri 2016) we follow the
approach of Mutti and Ricci Lucchi (1972), Mutti (1992)
and Mutti et al. (1999), considering as turbidites all
those sediments deposited by sediment gravity flows and
not strictly turbidity currents. According to this defin-
ition, turbidites (intrabasinal or extrabasinal) include a
broad spectrum of deposits ranging from matrixor
clastsupported conglomerates to graded mudstone
beds. We absolutely agree with Muttis point of view,
and we are convinced that this broad definition substan-
tially simplifies the discussion in a field in which sedi-
mentary processes, flow rheology, flow states are in most
cases inferred from the careful analysis of sedimentary
rock bodies. In our paper (Zavala and Arcuri 2016)we
have clarified this topic in page 37 Note that in this ap-
proach, the criterion of Mutti et al. (1999) is followed,
considering as turbidites the deposits of all types of
Zavala Journal of Palaeogeography (2019) 8:23 Page 2 of 8
subaqueous sediment gravity flows independently if they
are related or not to purely turbulent flows. Conse-
quently, in this work, the deposits of both Newtonian
(fluid) and non-Newtonian (plastic) flows are included in
this category. Clearly, we dont equate turbidity currents
(Newtonian turbulent flows) to hyperpycnal flows.
Hyperpycnal flows can originate from different high
density flows, ranging from cohesive debris flows up to
low density turbidity currents (Zavala 2018).
2.5 Coarse-grained deltas and hyperpycnal flows
Shanmugam (2018), page 206 right line At present,
coarse-grained deltas are totally ignored in studying
hyperpycnal flows. As a consequence, all published exam-
ples of hyperpycnal flows are from fine-grained deltas,
such as the Yellow River delta in China.
Not true. Probably G. Shanmugam ignores one of the
best known documentation of coarse- grained hyperpyc-
nal flows of different fan deltas in British Columbia,
Canada (Prior and Bornhold 1990; Bornhold and Prior,
1990). Additionally, several additional examples of re-
cent bedload dominated hyperpycnal flows and their de-
posits are available in Mulder and Chapron (2011).
2.6 Hyperpycnal flows and the inverse to normally-
graded sequence
Shanmugam (2018), page 217 left line Importantly, no
one has reproduced the entire inverse to normally-graded
sequence with internal erosional surface (i.e., the hyper-
pycnite facies model) in laboratory flume experiments;
nor has anyone documented this sequence from modern
settings. The conceptual hyperpycnite model exists only
in theory in publications, not in the real-world sediment-
ary record.
This is not true. Violante (2009), in his Fig. 10, pro-
vided a nice example- of an inverse to normally-graded
interval in recent hyperpycnal flow deposit generated by
the Bonea flood in 1954. Similar inverse to normally-
graded intervals have been documented in recent hyper-
pycnal deposits from the Al Batha lobes by Bourget et
al. (2010), his Fig. 12. Hyperpycnites characterized
by couples of inverse-normal grading were well docu-
mented in the Triassic Yanchang Formation (Ordos
Basin, central China). Hyperpycnites developed not only
in sandstones (Yang et al., 2017a), but also in
fine-grained sediments (Yang et al., 2017b).
2.7 Hyperpycnal flows and the origin of fine-grained
massive sandstones
Shanmugam (2018), page 217 left line Massive sand-
stones, considered to be a recognition criteria for hyper-
pycnites (Steel et al. 2016; Zavala and Arcuri 2016), are
not unique to deposits of hyperpycnal flows. There are
alternative processes that can equally explain the origin
of massive sands.The Ta division has also been attrib-
uted to deposition from sandy debris flows (Shanmugam
1997).
In my paper (Zavala and Arcuri 2016) I dont consider
the occurrence of massive sandstones as a diagnostic cri-
teria for the recognition of hyperpycnites. Although
fine-grained massive sandstones are a very common
product of hyperpycnal flow deposits, only the presence
of entire leaves within fine-grained massive sandstones is
considered a diagnostic feature that allows the recogni-
tion of hyperpycnal flow deposits (Zavala and Arcuri
2016, pp. 46). This is because the existence of entire
leaves proves that extrabasinal materials were trans-
ported together with sand grains within a turbulent sus-
pension, and were then trapped during the progressive
collapse of the suspension cloud.
Of course, the accumulation of massive sandstones
has been for long in the past related to an en masse
accumulation but this origin was largely speculative,
since most arguments were supported in the lack of
sedimentary structures and the observation of floating
clasts which were considered as supported by an in-
ternal flow cohesion.
In his discussion about the validity of the high density
turbidity current paradigm, G. Shanmugam (1996) intro-
duces the concept of sandy debris flows for cohesive to
cohesionless debris flows supported by matrix strength,
dispersive pressure and buoyant lift. G. Shanmugam also
pointed out that these sandy debris flows are common
in fine-grained sands with low to moderate mud content.
According to G. Shanmugams point of view: (I) almost
all kinds of massive or inversely graded clastic deposits
should be interpreted as accumulated by sandy debris
flows; (2) deposits containing floating outsized clasts can
be produced only by debris flows; and (3) a traction car-
pet developed beneath a turbulent flow should be
regarded as a debris flow (Sohn 1997).
G. Shanmugam (2015) proposed a sandy debris flow
origin for fine-grained massive sandstones based on
flume experiments carried out by Marr et al. (2001).
These experiments were conducted in a 10 m long glass
flume with a slope ranging from 4.6° to 0°. Experimental
sediment gravity flows were primarily composed of clay,
well sorted fine-grained silica sand (110 μm), tap water,
and a siliceous material produced as a residue from
burning coal. These experiments show that, for these
considered slopes, the generation of coherent gravity
flows with water contents ranging from 25 to 40 wt% re-
quire the addition of some clay. The experiments were
carried out with bentonite (0.7 to 5 wt%) and kaolinite (7
to 25 wt%). No experiments were performed to analyze
the requirement of other common clays in lacustrine
and marine settings, like chlorite, illite and smectite. Of
course the final deposit was well sorted because they use
Zavala Journal of Palaeogeography (2019) 8:23 Page 3 of 8
well sorted sand in the experiment. Nevertheless, flows
having a matrix strength can transport different grain
size materials which are deposited en masseby cohe-
sive freezing, giving the typical poorly sorted characteris-
tic of debris flow deposits.
G. Shanmugam (2015) in his Fig. 15 (here reproduced
in Fig. 1), provides an example of a core photograph of
massive fine-grained sandstone showing a large floating
mudstone clast with a planar clast fabric (Fig. 1), a typ-
ical bi-modal deposit. According to him these evi-
dencessuggest a deposition from a laminar sandy
debris flow. The occurrence of mudstone clasts of differ-
ent sizes and the sharp and irregular upper bedding con-
tact are interpreted as indicative of flow strength and
deposition from cohesive freezing in a laminar plastic
flow. According to me, this interpretation is absolutely
wrong.
Sohn (1997, p. 507) strongly criticizes the point of
view of G. Shanmugam about the deposition of
fine-grained massive sandstones and floating clay clasts:
.. large floating clasts cannot be foolproof evidence of
debris flows because they can be produced under turbu-
lent flow conditions as long as the deposition of large
clasts lags behind in a traction carpet.
Main evidences that are against the interpretation
of a sandy debris flow origin for the example shown
in Fig. 1include:
1) The deposit is clearly bimodal, suggesting the join
occurrence of two different depositional processes,
A) gradual collapse of suspended load (massive well
sorted fine-grained sands and silt) transported within
a diluted sustained turbulent flow as a consequence
of a progressive loss of flow capacity and B) bedload
(large and occasionally rounded clay clasts) of large
clast dragged by shear forces provided by the
overpassing long lived turbulent flow over the rising
deposit-flow interface.
2) Texture, sorting and sedimentary structures dont
support a debris flow origin for this interval. The
deposit is mainly composed of well sorted fine-
grained sandstones, which suggest a highly selective
Fig. 1 Core photograph showing a typical example of a sandy debris flow deposit according to G. Shanmugam. Note the imbrication in the
small clay clasts located close to the top. From Shanmugam (2015)
Zavala Journal of Palaeogeography (2019) 8:23 Page 4 of 8
transportation mechanism like suspension of sand
grains in a long lasting low density turbulent flow.
Dispersive pressure in very fine grained sands is
not an efficient support mechanism because of
the negligible inertia of very small sand grains.
Additionally there is no evidence of escaping
pore fluid.
3) The evident low clay matrix of the deposit is also
against the interpretation of a debris flow origin.
4) The imbrication of the small clay clasts at the top
indicates a flow moving from left to right. Imbrication
is very important since it suggest that clasts were
transported as bedload at the base of a sustained
turbulent flow. Once again, not a debris flow.
The above evidences suggest for these fine-grained
massive sandstones a gradual accumulation (Sanders
1965) from sustained low density turbidity currents with
associated bedload.
Shanmugam (2012,2015), p 138 considered that Deb-
ris flows are capable of transporting gravel and
coarse-grained sand because of their inherent strength. In
contrast, turbidity currents cannot transport coarse sand
and gravel in turbulent suspension. The assumption
that turbidity current cannot transport clasts can result
in dangerous oversimplifications.
Floating clasts in turbidites are not only possible but
very common, because they are transported as bedload
(mostly creep and rolling) above a progressively raising
depositional surface (Postma et al. 1988; Kneller and Bran-
ney 1995; Sohn 1997; Branney and Kokelaar 2002;Man-
ville and White 2003). Flume experiments performed by
Banerjee (1977), Arnott and Hand (1989) and Sumner et
al. (2008) demonstrated that the accumulation of massive
sandstones occur by the collapse of suspended load from
waning dilute turbulent suspensions (12vol%ofparti-
cles) at bed aggradation rates in excess of 0.44 mm/s.
As a conclusion, the interpretation of fine-grained
massive sandstones as accumulated by sandy debris
flows creates more problems than it solves, because:
1) Almost all thick fine-grained massive sandstones are
relatively well sorted and have very little or no clay
content (Zavala and Pan 2018, their Fig. 12).
2) Slopes in inner shelf and in lakes usually are less than
0.5°, which will not favor the movement of cohesive
or poorly cohesive debris flows characterized by
matrix strength.
3) An accumulation from sandy debris flows cannot
adequately explain the facies recurrence between
massive and laminated sandstones commonly
observed in the field (Zavala and Pan 2018, their
Fig. 15), and also the common association of
massive sandstones with low angle cross bedding.
4) Massive fine-grained sandstones are commonly
associated with levels of similar composition and
grain size, showing planar lamination and climbing
ripples. The last suggests a common origin to these
deposits related to traction plus fallout of fine-grained
sand sediments from a turbulent suspension, under
different velocity and rates of sediment fallout (Zavala
and Pan 2018, their Fig. 15).
5) Sandy debris flows cannot explain clast imbrication
within massive sandstones, since this structure
suggests that clasts were free to roll as bedload at
the base of a progressively aggrading depositional
surface (Zavala and Pan 2018, their Fig. 5)
2.8 Lofting rhythmites
Shanmugam (2018), page 217 right line: Zavala and
Arcuri (2016, their Fig. 18), in justifying their criteria for
recognizing hyperpycnites, presented a core photograph
showing rhythmites, which they called lofting rhyth-
mites. The core photograph is from the modern Orinoco
Fan, off Orinoco Delta in Eastern Venezuela (their
Fig. 15). Such rhythmites are common in deep-water
tidal deposits (Cowan et al. 1998; Shanmugam 2003).
The deep watertidal rhythmites studied by Cowan et
al. (1998) are from the Muir Inlet, a macrotidal fjord in
Alaska. These rhythmites are not equivalent to those de-
scribed in our case studies, since they were described in
a core recovered from a water depth of 241 m, located
less than 1 km far from the coast (Cowan et al. 1998,
their Fig. 1). These rhythmites are composed of silt-clay
couplets accumulated by a tide modulated suspension
settling from turbid plumes originating from meltwater
discharges, where black intervals are plankton (no plant
remains were recognized). The example from the Ori-
noco Fan is located at a water depth of 1994 m, more
than 300 km far from the Orinoco littoral delta. In all
case studies shown in our paper, lofting rhythmites are
never associated with sedimentary structures indicative
of tidal action like sigmoidal cross bedding, and are
always associated with massive and cross-bedded sand-
stones suggesting an origin associated with sediment
gravity flows. The analysis of thin sections allows to tract
step by step the origin of this structure (Zavala et al.
2008,2012), and conveniently explains the occurrence of
plant remains and mica at the surface lamina.
2.9 Intrabasinal and extrabasinal turbidites
Shanmugam (2018), page 220 left line: Intrabasinal tur-
bidites are those with sediments derived locally from ad-
jacent shelf and got transported into the basin by
classicturbidity currents. In contrast, extrabasinal tur-
bidites are those with sediments derived from distant
land and delta and got transported into the basin by
flood-triggeredturbidity currents or hyperpycnal flows
Zavala Journal of Palaeogeography (2019) 8:23 Page 5 of 8
(Fig. 16). In other words, large river-delta fed submar-
ine fans on passive continental margins, such as the
Mississippi Fan and the Amazon Fan, would be
classified as extrabasinal turbidite.
This is not true. The distinction between intrabasinal
and extrabasinal turbidites applies for single flows and
should not be generalized for entire systems. A deep sea
fan can be internally composed of both intrabasinal and
extrabasinal turbidites. Intrabasinal and extrabasinal
turbidites display diagnostic characteristics that allow a
clear differentiation between them (Zavala and Arcuri
2016).
2.10 Sand and gravel transport by hyperpycnal flows
Shanmugam (2018), page 221 left line: However, hyper-
pycnal flows cannot be responsible for transporting gravel
and sand from the land, carrying them 10100 km/s1
across the shelf, and delivering them to the deep sea. For
example, no one has ever documented by direct measure-
ments or observations of transport of gravel and sand by
hyperpycnal flows in suspension from the shoreline to the
deep sea in modern settings.
This is not true. The existence of deep water gravel
and pebbly sandstone deposits related to hyperpycnal
discharges of the Columbia river has been clearly docu-
mented in the Cascadia Channel (Zuffa et al. 2000)in
cores located 200 km far from the coast and at a water
depth of 3820 m (Griggs et al. 1970; Normark and Reid
2003). Individual pebbles are rounded to subrounded
with diameters up to 4 cm. These gravel deposits contain
a mixture of intrabasinal and extrabasinal components
like molluscan shells, wood fragments, and different
water depth foraminifera.
3 Concluding remarks
The discovery of hyperpycnal flows and their related de-
posits (both in coarse and fine-grained successions) con-
stitutes one of the most important and genuine recent
advances in clastic sedimentology. Current understand-
ing in this field was possible from the decadal joint effort
of a multi-disciplinary global community of recognized
geoscientists. Of course too much work will be necessary
in the future to achieve a more comprehensive
understanding of these flows and their related deposits.
G. Shanmugams claims that this research branch is a
hype specially designed for the petroleum industry
sounds, at least, offensive.
In his paper G. Shanmugam (2018) tries to minimize
the importance of hyperpycnal flows claiming that the
recognition of these flows and their related deposits is
based strictly on experimental or theoretical basis, with-
out the supporting empirical data from modern deposi-
tional systems. Although this is not absolutely true,
when G. Shanmugam (2018) generalizes the case of the
Yellow River, he over enhanced the role of present depo-
sitional processes both in their characteristics and mag-
nitudes to try to explain the sedimentary rock record.
The fact is that the application of a strict uniformitar-
ianismto the understanding of fossil sedimentary
successions can lead to serious mistakes, since it con-
strains past geologic rates and conditions to those of the
present. For a stratigrapher, its important to understand
if certain geological phenomena were possible in the
geological record, and not only if these conditions are
achieved nowadays. The key point resides in carefully
describing, reading, and interpreting sedimentary rocks
in the field, since only the stratigraphic record contains
both present and future knowledge. Somewhere,
something incredible is waiting to be knownCarl Sagan
(19341996).
Abbreviations
cm: centimeter; cm/sec: centimeters for second; et al.: et alii; Fig: Figure;
Km: kilometer; m: meter; mm/s: millimeters for second; vol%: volume
percent; wt%: weight percent; μm: micrometer
Acknowledgements
The author deeply acknowledges the comments and suggestions provided
by the Editor-in-Chief, Feng Zengzhao and two anonymous reviewers, which
substantially help in performing this manuscript.
Authors contributions
The author read and approved the final manuscript.
Competing interests
The author declares that he has no competing interests.
PublishersNote
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
Received: 26 September 2018 Accepted: 23 April 2019
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... C) BH reservoir types in core and corresponding porosity-permeability distribution. D) Representative core photos of the three most common reservoir facies in the basin (after Konar et.al, 2018, Dasgupta and Mukherjee, 2017, 2019 VIJAYA AND VANDANA FIELD (V&V) Vijaya and Vandana (V&V) Field is located west and down structure from the eastern basin bounding fault and 5km southeast of Aishwariya field ( Figure 1B). V&V is a stratigraphic trap formed by pore-throat seals and large-scale turbidite facies pinchouts down-dip of the Aishwariya structure. ...
... The BH-10 has a more aggradational pattern with a higher net to gross ratio. The package is comprised by floodinduced hyperpycnal flows (Zavala, 2019;Zavala et al., 2012). Laterally migrating channel networks dominate a lacustrine slope apron similar to the one described by Cunlei et al. 2016). ...
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... This conforms well with the evidence of tectonics and sedimentation from many Precambrian diamictites worldwide, which also could help explain stepwise oxygenation of the Earth´s atmosphere resulting from tectonics (Eyles, 1993;Eguchi et al., 2020). The origin of the basal "tillite" is interpreted to be "the missing fan facies" and to have been deposited by cohesive debris flows, possibly as hyperpycnal flows which may be deposited as a full spectrum of gravity flows including cohesive debris flows and rhythmites (Zavala & Arcuri, 2016;Shanmugam, 2019;Zavala, 2019Zavala, , 2020. ...
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Fine-grained sediments from the Late Triassic Yanchang Fm. in the Ordos Basin (central China) were studied by core analysis and geophysical logging. Part of the mudstones in this formation are stratified, part of them are unstratified; the various mudstones can be subdivided into eight types on the basis of their structures and textures. They represent a variety of environments, ranging from delta fronts and subaqueous fans to deep-water environments. Part of the sediments were reworked and became eventually deposited from subaqueous gravity flows, such as mud flows, turbidity currents and hyperpycnal flows that easily developed on the clay-rich deltaic slopes. The sediments deposited by such gravity flows show abundant soft-sediment deformation structures. Understanding of such structures and recognition of fine-grained sediments as gravity-flow deposits is significant for the exploration of potential hydrocarbon occurrences. Because fine-grained deposits become increasingly important for hydrocarbon exploration, and because the sediments in the lacustrine Yanchang Formation were deposited by exactly the same processes that play a role in the accumulation of deltaic and prodeltaic fine-grained sediments, the sedimentological analysis provided here is not only important for the understanding of deep lacustrine sediments like the Yanchang Formation, but also for a better insight into the accumulation of fine-grained prodeltaic deep-marine sediments and their potential as hydrocarbon source rocks and reservoir rocks.
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The Triassic Yanchang Formation contains the main oil-bearing strata in the Ordos Basin, central China. But the sedimentology of the Upper Triassic is still under debate, and flood-generated, hyperpycnal-flow deposits and their implications for unconventional petroleum development have long been overlooked. Our study indicates that hyperpycnites are well developed in the seventh oil member of the Yanchang Formation. They are characterized by couplets of upward-coarsening intervals and upward-fining intervals , separated by microscale erosion surfaces. The origination of hyperpycnal flows was controlled mainly by episodic tectonic movements and the humid climate. The deposits extend from distributary estuaries into the deep lake, have intercalations of dark shales and tuffs, and coexist with debrites and turbidites as a result of the progradation of subaqueous fans. The hyperpycnites have implications for unconventional petroleum reservoirs, because the flows supplied not only large amounts of coarse grains and organic material to the deep-water, fine-grained central lake sediments but also affected the ecosystems, resulting in a higher total organic carbon content in the sediments.
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