Interpretation of Miocene Shallow Marine Depositional Environments Using Sedimentary Structures: ABSTRACT

Eleven Neogene outcrops (seven of the Miri Formation and four of the Seria Formation) from Brunei Darussalam are described. Detailed stratigraphic columns are presented with special emphasis on the sedimentary sequences, providing insights into the depositional environments. The rocks are comprised mostly of sandstone, claystone and a mix of both lithologies, and are piled up in cycles of coarsening upward successions, which are here interpreted as parasequences. Most sections are characterized by abundant and diverse sedimentary structures, reworked fossiliferous deposits and organic fragments such as ambers and wood remains. Certain beds are rich in fossils: among the macrofossils, the most common are bivalves, gastropods and followed by fish remains (teeth and otholiths), crustaceans, corals and echninoderms, which are abundant at specific locations. Among the microfossils, the most common are foraminifera, which are mostly dominated by either rotaliids or textulariids; the most common genera are Ammonia, Elphidium and Trochammina. Porcelaneous and planktonic foraminifera are rare. Ostracods are also found. Ichnofossils are quite abundant in all sections but are represented mostly by Ophiomorpha and Thalassinoides. In view of the observations, the sections are interpreted as evidence of shallow-marine conditions, in which wave, fluvial and tidal actions strongly influenced the depositional environment. In a few cases, deposition of sediment seems to reflect the transition from wave-dominated to tide-dominated conditions. Our findings indicate that in such shallow marine deposits, the interpretation of sediment type and sedimentary structures alone cannot indicate one specific sedimentary environment, but such observations should include palaeontological evidence to generate more accurate palaeoenvironmental reconstructions. Lastly, our results are discussed in relation to the sedimentary evolution of the region.

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Facies Evaluation and Depositional Environments of Carbonates of the Bagh Group, Dhar District, Madhya Pradesh, India

Indian Association of Sedimentologists ◽

10.51710/jias.v38i1.154 ◽

2021 ◽

Vol 38 (1) ◽

pp. 33-40

Author(s):

Sreejita Chatterjee ◽

Dhiren Kumar Ruidas

Keyword(s):

Grain Size ◽

Large Scale ◽

Energy Condition ◽

Size Variation ◽

High Energy ◽

Depositional Environments ◽

Small Scale ◽

Peninsular India ◽

Sedimentary Structures ◽

Nodular Limestone

A significant event of marine transgression took place in Central India during Late Turonian-Coniacian. Fossiliferous marine succession of Bagh Group is one of the few carbonate successions exposed in peninsular India which was in focus of the current study for understanding this event. The signatures of this event were identified in the carbonate succession. The carbonates of Bagh Group are composed of two formations: the lower part is represented by Nodular limestone Formation which is overlain by Bryozoan limestone Formation at the top. On the basis of grain size variation and sedimentary structures, the Nodular limestone is divisible into three facies: facies ‘A’, facies ‘B’ and facies ‘C’. A hardground exists between facies B and facies C. Lack of sedimentary structures and high mud content indicates low energy depositional setting for the Nodular limestone Formation. Similarly, Bryozoan limestone Formation is divisible into five facies: facies ‘D’, facies ‘E’, facies ‘F’, facies ‘G’ and facies ‘H’ based on grain size variation and sedimentary structures. All of these five facies are fossiliferous. Glauconites are present within facies ‘G’ and have two modes of occurrence - as infilling within Bryozoan limestone and as altered feldspar. Presence of both small- and large-scale cross-stratification in Bryozoan limestone with lesser mud content are indicative of high energy shallow marine conditions. Large-scale cross-stratifications are possibly representing tidal bars while the small scale cross stratifications are formed in inter bar setting. Presence of reactivation surfaces within facies ‘E’ also supports their tidal origin. Increase in depositional energy condition is also evident from dominated by packstone facies.

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Deciphering tectonic, eustatic and surface controls on the 20 Ma-old Burdigalian transgression recorded in the Upper Marine Molasse in Switzerland

10.5194/se-2019-27 ◽

2019 ◽

Cited By ~ 1

Author(s):

Philippos Garefalakis ◽

Fritz Schlunegger

Keyword(s):

Sea Level ◽

Depositional Environments ◽

Sediment Supply ◽

Sediment Flux ◽

Crustal Material ◽

Molasse Basin ◽

Shallow Marine ◽

Depositional Settings ◽

Stratigraphic Architecture ◽

Aar Massif

Abstract. The stratigraphic architecture of the Swiss Molasse basin reveals crucial information about the basin’s geometry, its evolution and the processes leading to the deposition of the clastic material. Nevertheless, the formation of the Upper Marine Molasse (OMM) and the controls on the related Burdigalian transgression are not fully understood yet. During these times, from c. 20 to 17 Ma, the Swiss Molasse basin was partly flooded by a peripheral shallow marine sea, striking SW – NE. We proceeded through detailed sedimentological and stratigraphic examinations of several sites across the entire Swiss Molasse basin in order to deconvolve the stratigraphic signals related surface and tectonic controls. Surface-related signals include stratigraphic responses to changes in eustatic sea level and sediment fluxes, while the focus on crustal-scale processes lies on the uplift of the Aar-massif at c. 20 Ma. Field examinations show, that the evolution of the Burdigalian seaway was characterized by (i) shifts in the depositional settings, (ii) changes in discharge directions, a deepening and widening of the basin, and (iv) phases of erosion and non-deposition. We relate these changes in the stratigraphic records to a combination of surface and tectonic controls at various scales. In particular, roll-back subduction of the European mantle lithosphere, delamination of crustal material and the associated rise of the Aar-massif most likely explain the widening of the basin particular at distal sites. In addition, the uplift of the Aar-massif was likely to have shifted the patterns of surface loads. These mechanisms could have caused a flexural adjustment of the foreland plate underneath the Molasse basin, which we use as mechanism to explain the establishment of distinct depositional environments and particularly the formation of subtidal-shoals where a lateral bulge is expected. In the Alpine hinterland, these processes occurred simultaneously with a period of fast tectonic exhumation accomplished through slip along the Simplon detachment fault, with the consequence that sediment flux to the basin decreased. It is possible that this reduction in sediment supply contributed to the establishment of marine conditions in the Swiss Molasse basin and thus amplified the effect related to the tectonically controlled widening of the basin. Because of the formation of shallow marine conditions, subtle changes in the eustatic sea level contributed to the occurrence several hiatus that chronicle periods of erosion and non-sedimentation. While these mechanisms are capable of explaining the establishment of the Burdigalian seaway and the formation of distinct sedimentological niches in the Swiss Molasse basin, the drainage reversal during OMM-times possibly requires a change in the tectonic processes at the slab scale. We conclude that sedimentological records can be used to decipher surface controls and lithospheric-scale processes in orogens from the stratigraphic record, provided that a detailed sedimentological and chronological database is available.

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Environmental control on granular clinoforms of ancient carbonate shelves

Geological Magazine ◽

10.1017/s0016756806001749 ◽

2006 ◽

Vol 143 (3) ◽

pp. 343-365 ◽

Cited By ~ 8

Author(s):

A. QUIQUEREZ ◽

G. DROMART

Keyword(s):

Environmental Control ◽

Depositional Environments ◽

Angle Of Repose ◽

Coarse Grained ◽

Carbonate Platforms ◽

Carbonate Sediment ◽

Sediment Grain Size ◽

Sedimentary Structures ◽

Lower Slope ◽

Sediment Fabric

The purpose of this paper is to document the influence of depositional environments on shallow-water, low-relief clinoforms from the description of five ancient carbonate platforms: the Neoproterozoic (Namibia), Middle Jurassic (France), Lower Cretaceous (France), Upper Cretaceous (Oman) and Miocene (Turkey). These examples have been investigated on the basis of field observations. The clinoforms are described with reference to geometric and compositional attributes: declivity, shape, height, sedimentary structures, sediment fabric and components. The results show great variability in stratal geometry, declivity and facies distribution: (1) depositional profiles vary from exponential, to sigmoidal, to oblique; (2) maximal slope angles range from 3 to 25°, most of them being grouped between 10 and 18°; (3) facies differentiation identified from lateral facies successions along beds, and vertical facies successions through beds, is pronounced to subtle. This study documents linkages between depositional environments and clinoform attributes. Proximal/shallow clinoforms display round-edged exponential profiles. Sediment deposition has resulted from unidirectional currents in the upper convex section, and storm-generated oscillatory currents in the lower concave part. The sediment fabric changes gradually along this type of clinoform. There is little vertical facies differentiation through these clinobeds which have formed from a continuous amalgamation of deposits. By contrast, distal clinoforms (shelf break, distally steepened ramp settings) yield a much broader spectrum of profiles and are generally shorter and steeper. Sedimentary structures in gravel-sized deposits of the upper slope indicate pure traction by unidirectional currents. Conversely, marks of oscillatory flows (undular, wavy top bounding surfaces of clinobeds) are common in the lower slope. Intercalation of massive, fine-grained deposits suggests offshore transport of carbonate mud by suspension. Each distal clinobed represents a single flow event. Accordingly, facies differentiation is weak laterally but may be pronounced through the clinobeds. Our study suggests that low-relief forms of proximal/shallow environments, which contain coarse-grained and photo-independently produced debris, record hydrodynamic equilibrium profiles, whereas the higher-relief forms of this setting rather reflect a high differential production rate of carbonate sediment with water depth. The carbonate sediment of the distal clinobeds mainly derives from skeletal production by oligophotic and photo-independent biota of the middle shelf/ramp and upper portion of the clinoforms. The contribution by in situ skeletal biota only becomes significant on the lower slope, indicating that the distal, submerged slopes of carbonate platforms are not organically but hydrodynamically generated. Our compilation shows that the slope angles of shallow marine, low-relief clinoforms do not simply correlate to the sediment grain size and fabric, in contrast to what has been documented for the high, linear slope profiles. This difference stems from the depositional settings, namely the involved transport mechanisms. Low-relief clinoform accretion seems to be dominantly influenced by wave-induced sediment transport, in contrast to linear flanks of high-relief clinoforms that build to the angle of repose, and for which gravity is the primary transport process.

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The significance of large-scale sedimentary structures in the Silurian succession of western Ireland

Geological Magazine ◽

10.1017/s001675680001668x ◽

1987 ◽

Vol 124 (4) ◽

pp. 361-366 ◽

Cited By ~ 4

Author(s):

D. Michael Williams ◽

T. Nealon

Keyword(s):

Large Scale ◽

Tidal Channel ◽

Marine Origin ◽

Shallow Marine ◽

Sedimentary Structures ◽

Shelf Slope ◽

Western Ireland

AbstractLarge-scale sedimentary structures are described from the Lough Muck Formation (Wenlock) of north Galway, Ireland. They consist of bed packages separated by truncation surfaces of varying orientations. They had previously been interpreted as rotational slumps generated on a shelf–slope interface. It is shown that the structures formed in a tidally influenced environment far removed from a slope. They bear strong similarities to structures described from other tidal channel environments and it is proposed that they represent deposition on aggradational margins of such channels. The supposed slope–shelf transition is therefore not present at this level in the Silurian succession and much of the Lough Muck Formation may be of a dominantly shallow-marine origin.

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The Fish River Subgroup in Namibia: stratigraphy, depositional environments and the Proterozoic–Cambrian boundary problem revisited

Geological Magazine ◽

10.1017/s0016756805000956 ◽

2005 ◽

Vol 142 (5) ◽

pp. 465-498 ◽

Cited By ~ 23

Author(s):

G. GEYER

Keyword(s):

Trace Fossils ◽

Global Scale ◽

Depositional Environments ◽

Trace Fossil ◽

Braided River ◽

Shallow Marine ◽

Sequence Stratigraphic ◽

Marine Habitats ◽

Short Period ◽

Distinct Sequence

The Fish River Subgroup of the Nama Group, southern Namibia, is restudied in terms of lithostratigraphy and depositional environment. The study is based on partly fine-scaled sections, particularly of the Nababis and Gross Aub Formation. The results are generally in accordance with earlier studies. However, braided river deposits appear to be less widely distributed in the studied area, and a considerable part of the formations of the middle and upper subgroup apparently were deposited under shallowest marine conditions including upper shore-face. Evidence comes partly from sedimentary features and facies distribution, and partly from trace fossils, particularly Skolithos and the characteristic Trichophycus pedum. Environmental conditions represented by layers with T. pedum suggest that the producer favoured shallow marine habitats and transgressive regimes. The successions represent two deepening-upward sequences, both starting as fluvial (braided river) systems and ending as shallow marine tidally dominated environments. The first sequence includes the traditional Stockdale, Breckhorn and lower Nababis formations (Zamnarib Member). The second sequence includes the upper Nababis (Haribes Member) and Gross Aub formations. As a result, the Nababis and Gross Aub formations require emendation: a new formation including the Haribes and Rosenhof and possibly also the Deurstamp members. In addition, four distinct sequence stratigraphic units are deter-minable for the Fish River Subgroup in the southern part of the basin. The Proterozoic–Cambrian transition in southern Namibia is most probably located as low as the middle Schwarzrand Subgroup. The environmentally controlled occurrence of Trichophycus pedum undermines the local stratigraphic significance of this trace fossil which is eponymous with the lowest Cambrian and Phanerozoic trace fossil assemblage on a global scale. However, occurrences of such trace fossils have to be regarded as positive evidence for Phanerozoic age regardless of co-occurring body fossils. Other suggestions strongly dispute the concept of the formal Proterozoic–Cambrian and Precambrian–Phanerozoic boundary. Carbon isotope excursions and radiometric datings for the Nama Group do not help to calibrate precisely the temporal extent of the Fish River Subgroup. Fossil content, sequence stratigraphy and inferred depositional developments suggest that this subgroup represents only a short period of late orogenic molasse sedimentation during the early sub-trilobitic Early Cambrian.

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Paleogeography and Depositional Environments of the Cambro-Ordovician Shallow-Marine Facies of the North Atlantic

Geological Society of America Bulletin ◽

10.1130/0016-7606(1972)83[3223:padeot]2.0.co;2 ◽

1972 ◽

Vol 83 (11) ◽

pp. 3223 ◽

Cited By ~ 47

Author(s):

KEENE SWETT ◽

DAVID E. SMIT

Keyword(s):

North Atlantic ◽

Depositional Environments ◽

Shallow Marine ◽

The North ◽

Marine Facies ◽

The North Atlantic

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Palaeoecology and depositional environments of the Tendaguru Beds (Late Jurassic to Early Cretaceous, Tanzania)

Fossil Record ◽

10.5194/fr-5-19-2002 ◽

2002 ◽

Vol 5 (1) ◽

pp. 19-44 ◽

Cited By ~ 5

Author(s):

M. Aberhan ◽

R. Bussert ◽

W.-D. Heinrich ◽

E. Schrank ◽

S. Schultka ◽

...

Keyword(s):

Early Cretaceous ◽

Late Jurassic ◽

Tidal Flats ◽

Depositional Environments ◽

Coastal Plains ◽

Fair Weather ◽

Shallow Marine ◽

Plant Fossils ◽

Sand Bar ◽

Formed Part

The Late Jurassic to Early Cretaceous Tendaguru Beds (Tanzania, East Africa) have been well known for nearly a century for their diverse dinosaur assemblages. Here, we present sedimentological and palaeontological data collected by the German-Tanzanian Tendaguru Expedition 2000 in an attempt to reconstruct the palaeo-ecosystems of the Tendaguru Beds at their type locality. Our reconstructions are based on sedimentological data and on a palaeoecological analysis of macroinvertebrates, microvertebrates, plant fossils and microfossils (ostracods, foraminifera, charophytes, palynomorphs). In addition, we included data from previous expeditions, particularly those on the dinosaur assemblages. The environmental model of the Tendaguru Beds presented herein comprises three broad palaeoenvironmental units in a marginal marine setting: (1) Lagoon-like, shallow marine environments above fair weather wave base and with evidence of tides and storms. These formed behind barriers such as ooid bar and siliciclastic sand bar complexes and were generally subject to minor salinity fluctuations. (2) Extended tidal flats and low-relief coastal plains. These include low-energy, brackish coastal lakes and ponds as well as pools and small fluvial channels of coastal plains in which the large dinosaurs were buried. Since these environments apparently were, at best, poorly vegetated, the main feeding grounds of giant sauropods must have been elsewhere. Presumably, tidal flats and coastal plains were visited by dinosaurs primarily during periods of drought. (3) Vegetated hinterland. Vegetation of this environment can only be inferred indirectly from plant material transported into the other depositional environments. Vegetation was dominated by a diverse conifer flora, which apparently formed part of the food source of large herbivorous sauropods. Evidence from various sources suggests a subtropical to tropical palaeoclimate, characterised by seasonal rainfall alternating with a pronounced dry season during the Late Jurassic. In Early Cretaceous times, sedimentological and palaeontological proxies suggest a climatic shift towards more humid conditions. Die Tendaguru-Schichten von Tansania in Ostafrika (Oberjura bis Unterkreide) sind als Lagerstätte oberjurassischer Dinosaurier seit nahezu einem Jahrhundert weltweit bekannt. Anhand von sedimentologischen und paläontologischen Daten, die während der Deutsch-Tansanischen Tendaguru Expedition 2000 im Typus-Gebiet der Tendaguru-Schichten gewonnen wurden, werden Paläo-Ökosysteme rekonstruiert. Grundlage der Rekonstruktionen sind die Auswertung sedimentologischer Daten sowie die paläo-ökologische Analyse von Makroinvertebraten, Mikrovertebraten, pflanzlichen Fossilien und Mikrofossilien (Ostrakoden, Foraminiferen, Charophyten, Palynomorphen). Darüber hinaus werden Informationen über Dinosaurier berücksichtigt, die bei früheren Expeditionen gewonnen wurden. Das hier vorgestellte Ablagerungsmodell der Tendaguru-Schichten umfaßt drei Teilbereiche eines randlich marinen Sedimentationsraumes, die wie folgt gekennzeichnet werden können: (1) Lagunen-artige, marine Flachwasserbereiche, die oberhalb der Schönwetter-Wellenbasis lagen und unter deutlichem Einfluß von Gezeiten und Stürmen standen. Sie waren vom offenen Meer durch Barrieren, wie Ooidbarren und siliziklastischen Sandbarrenkomplexen, getrennt und wiesen einen leicht schwankenden Salzgehalt auf. (2) Ausgedehnte Wattgebiete und flache Küstenebenen. Dort befanden sich niedrig-energetische, brackische Strandseen und Teiche sowie Tümpel und kleinere Flußrinnen, in denen die großen Dinosaurier eingebettet wurden. Da diese Lebensräume bestenfalls dürftig bewachsen waren, müssen die Nahrungsquellen und der eigentliche Lebensraum der riesigen Sauropoden anderswo gelegen haben. Vermutlich wurden die Wattgebiete und Flachküsten von Dinosauriern vorrangig in den Trockenzeiten aufgesucht. (3) Bewachsenes Hinterland. Die Vegetation dieses Lebensraumes kann nur indirekt aus Pflanzenresten erschlossen werden, die in die anderen Ablagerungsraume transportiert wurden. Die Vegetation wurde von einer diversen Koniferenflora dominiert, die zumindest teilweise die Nahrungsgrundlage der großen, herbivoren Sauropoden bildete. Sedimentologische und paläontologische Indikatoren sprechen für ein subtropisches bis tropisches Klima wahrend der späten Jurazeit mit einem jahreszeitlichen Wechsel von Regenfällen und ausgeprägten Trockenzeiten. In der frühen Kreidezeit deutet sich ein Wechsel zu starker humiden Bedingungen an. doi:<a href="http://dx.doi.org/10.1002/mmng.20020050103" target="_blank">10.1002/mmng.20020050103</a>

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