THE GEOLOGICAL EXPRESSION OF EUSTACY IN THE EARLY TERTIARY OF THE GIPPSLAND BASIN

1976 ◽  
Vol 16 (1) ◽  
pp. 73 ◽  
Author(s):  
A. D. Partridge
Keyword(s):  
Sea Level ◽  
Time Interval ◽  
Marine Environments ◽  
Fine Grained ◽  
Sedimentary Sequences ◽  
Seismic Records ◽  
Basin Morphology ◽  
The Times ◽  
Sequence Boundaries ◽  
Gippsland Basin

In the non-marine to marginal marine environments of the Latrobe Group, distinct sedimentary sequences are recognised on seismic records and these sequences are often expressed in wells by palynological zones, changes in E-log character and lithology.The succession of sequences represents variations in sea level, many of which are interpreted aseustatic. Eustatic falls are represented by unconformities and channel formation along the seaward margin and by hiatuses (frequently with dolomite cementation of underlying sands) landward in deltaic and non-marine sections. Eustatic rises are represented by dinoflagellate ingressions over truncated surfaces at sequence boundaries, followed by outbuilding of deltaic environments at the stillstand towards the end of each cycle.During the Paleocene and Eocene very little sediment was deposited beyond the limits of the marginal marine environments except within channels where the Flounder and Turrum Formations are found. In this time interval they was an overall landward encroachment of successive sequences reflecting an overall sea level rise. The interaction of rising sea level and limited deposition beyond the marginal marine edge meant that successive sequences became more restricted seaward such that within the marine environment the area of non-deposition increased. The surface thus defined, modified locally by channel erosion, constitutes the unconformity at the top of the Latrobe Group. This unconformity surface was preserved when deposition of fine-grained open marine sediments of the Lakes Entrance Formation commenced in the Oligocene.In the Tasman Sea a succession of terrigenous silts and clays present in the Deep Sea Drilling Project (DSDP) Site 283 can be correlated with periods when fine-grained sediments bypassed the Gippsland shelf. The stratigraphy of this site can be interpreted as a record of availability of sediment from the southeastern Australian continental shelf. The times of commencement and termination of stratigraphic units and disconformities at Site 283 correlate with timing of eustatic cycles. Thus the stratigraphy of Site 283 is a record, as is the Latrobe Group, of how eustacy interacts with basin morphology to modify distribution of sediments.

TECTONOSTRATIGRAPHIC EVOLUTION OF THE SOUTH-EAST GIPPSLAND BASIN

1991 ◽  
Vol 31 (1) ◽  
pp. 116 ◽  
Author(s):  
B.A. Duff ◽  
N.G. Groilman ◽  
D.J. Mason ◽  
J.M. Questiaux ◽  
D.S. Ormerod ◽  
...  
Keyword(s):  
Sea Level ◽  
Normal Faults ◽  
Plate Boundaries ◽  
Sea Level Changes ◽  
The South ◽  
Seismic Sequences ◽  
Controlled Deposition ◽  
Global Sea Level ◽  
Sequence Boundaries ◽  
Gippsland Basin

Evolution of the south-east Gippsland Basin since ca. 96 Ma has been governed by the interaction of three distinct processes:re-organisation of regional plate boundaries at 96, 80 and 50 Ma, registered as major angular unconformities or megasequence boundaries;intra-basin response of cover to basement-controlled deformational phases, registered as the sequence boundaries within these megasequences; andthe more subtle balance between regressive sedimentation associated with these phases and the transgressive deposition associated with longer-term eustatic sea level rises.The Golden Beach Megasequence (seismic sequences UK1 and UK2) accumulated syntectonically in an extensional setting characterised by an orthogonal array of north-northeast trending transfer faults and associated normal faults. Major compressional tectonism at ca. 80 Ma terminated this regime, initiating a modified mosaic of stratotectonic domains which controlled deposition of the Latrobe Megasequence.The seismic sequences within this megasequence display two types of cyclicity distinguishing intra-Campanian to Top Maastrichtian sequences (UK3-UK5) from early Tertiary sequences (PL1, PL2 and EO1). The sequence boundaries are considered to be the expression of recurrent compressive deformational phases. They are demonstrable as angular unconformities in transpressional and pull-apart structures in domains within which deformation was focused over the older extensional grain.The ca. 50 Ma Top Latrobe megasequence boundary appears to mark the transition from a basement-coupled deformational style characteristic of the Latrobe Megasequence, to a basement-decoupled inversion style of deformation during deposition of the Seaspray Megasequence (post-50 Ma).Seismic sequence boundaries, at least within basins such as the Gippsland, are therefore the stratigraphic expression of deformational phases rather than signatures of global sea-level changes. Eustacy is not invariably a shorter-term process than basin tectonism, nor is it the sole or main determinant of depositional style.

Sea-level changes and ammonite faunal turnover during the Lias/Dogger transition in the western Tethys

2002 ◽  
Vol 173 (1) ◽  
pp. 57-66 ◽  
Author(s):  
José Sandoval ◽  
Luis O’Dogherty ◽  
Juan Antonio Vera ◽  
Jean Guex
Keyword(s):  
Sea Level ◽  
Time Interval ◽  
Sea Level Changes ◽  
Western Tethys ◽  
Faunal Turnover ◽  
Faunal Diversity ◽  
Minor Sequence ◽  
Sequence Boundaries ◽  
Extinction Events ◽  
Major Sequence

Abstract The aim of this paper was to investigate the possible connections between ammonite faunal turnover and the eustatic events recorded in Tethyan sequences during the middle Toarcian/early Bajocian time interval. For this we have analysed the biostratigraphic ranges, at the subzone level, of approximately 600 ammonite species belonging to 160 genera from several selected sections of the western Tethys (Mediterranean and Submediterranean provinces). The analysis of taxon ranges enabled us to plot curves for ammonite faunal turnovers, inter-subzonal distance, and diversity. Comparing the mentioned curves with Tethyan sequences [Hardenbol et al., 1998], we find that sea-level changes correlate well with origination and extinction events and faunal diversity. Most of the faunal turnovers correlate with stratigraphic events. Extinction events with their corresponding decrease in diversity correlate with regressive intervals and with major or minor sequence boundaries. Origination events and their corresponding increase in diversity were clearly connected with transgressions in Tethyan sequences. In several cases, the major sequence boundary and the subsequent transgressive phase correlate with major ammonite faunal turnover, whereas minor or medium sequence boundaries generally gave rise to minor or medium turnovers.

Palynology and paleoenvironments of a Pliocene carbonate platform: the Clino core, Bahamas

1999 ◽  
Vol 73 (1) ◽  
pp. 1-25 ◽  
Author(s):  
Martin J. Head ◽  
Hildegard Westphal
Keyword(s):  
New Species ◽  
Sea Level ◽  
Carbonate Platform ◽  
Marine Environments ◽  
Terrestrial Vegetation ◽  
Carbonate Platforms ◽  
Late Pliocene ◽  
Great Bahama Bank ◽  
Fine Grained ◽  
Two Phases

Neritic dinoflagellates from periplatform (slope) carbonates of the Clino borehole, located on the western, leeward margin of the Great Bahama Bank, record environmental fluctuations on the platform top. A lower Pliocene interval (3.6–4.2 Ma) contains platform-top sediments shed onto the lower slope when the platform was open and ramplike. Despite this open topography, abundantPolysphaeridium zoharyiindicate the presence of restricted marine environments on the platform top. Terrestrial palynomorphs are rare throughout this interval and imply a mostly or fully submergent platform top.By late Pliocene times (about 2.1–2.3 Ma) the platform had become flat-topped and steep-sided, with the Clino site located on its upper slope. Samples characteristic of sea-level highstands and lowstands were selected for analysis.Polysphaeridium zoharyiis abundant only in lowstand samples and may have thrived in proximity to terrestrial vegetation. In highstand samplesLingulodinium machaerophorumreplacesP. zoharyi, perhaps in response to less restricted marine environments on the platform top. This change in assemblages, along with apparent variations in cyst influx, reflects a fluctuating history of currents and salinities over the platform top in the late Pliocene. Upper Pliocene lowstand samples contain anomalously high proportions of terrestrial palynomorphs, allowing the identification of two phases of emergence and vegetation of the platform top. Palynology therefore appears to be a sensitive indicator of short-term (4th-order) sea-level change on carbonate platforms.Dinoflagellate concentrations correlate positively with carbonate compaction, and infer that compacted layers have undergone dissolution of their metastable constituents. Dinoflagellate concentrations therefore can be useful in the often difficult task of assessing compaction and dissolution in fine-grained limestones where other indicators are absent.The following dinoflagellate species are formally proposed:Operculodinium bahamenseHead new species,Operculodinium?megagranumHead new species, andSpiniferites rhizophorusHead new species.

Planktic foraminiferal biostratigraphy and 87Sr/86Sr isotopic stratigraphy of the Oligocene-to-Pleistocene sedimentary sequence in the southeastern Calabrian microplate, southern Italy

1995 ◽  
Vol 69 (1) ◽  
pp. 7-20 ◽  
Author(s):  
R. Timothy Patterson ◽  
John Blenkinsop ◽  
William Cavazza
Keyword(s):  
Time Interval ◽  
Sedimentary Sequence ◽  
Sequence Stratigraphic ◽  
Fine Grained ◽  
Marine Deposits ◽  
Sedimentary Sequences ◽  
Continental Block ◽  
Isotope Stratigraphy ◽  
Physical Stratigraphy ◽  
Foraminiferal Biostratigraphy

Integration of foraminiferal biostratigraphy, 87Sr/86Sr isotope stratigraphy, and traditional physical stratigraphy has provided a refined age control of a poorly known Oligocene-to-Pleistocene sedimentary sequence nonconformably covering the crystalline basement complex of the Calabrian microplate, a continental block which rifted off the southern margin of the European plate during Neogene time. In spite of the fossil-poor content of the sequence, the simultaneous use of paleontological and geochemical techniques have resulted in the following conclusions. 1) The age of an unnamed, thin calcarenite unit locally present at the base of the sequence, previously considered Rupelian to early Aquitanian in age, has been refined to Chattian (27.8–24.8 Ma). This calcarenite was considered a basal, conformable member of the overlying Stilo-Capo d'Orlando Formation. However, this study indicates that it is separated from the Stilo-Capo d'Orlando Formation either by an angular unconformity or by a disconformity representing a significant time interval. 2) The Stilo-Capo d'Orlando Formation has a latest Chattian–earliest Aquitanian to Burdigalian age. Previously published reports suggested deposition over a much longer time span, ranging from late Rupelian to Langhian. 3) An unnamed deep-marine siliciclastic unit mostly composed of conglomerate and sandstone and previously considered Tortonian in age is, in fact, Serravallian to Tortonian. 4) The depositional interval of the “trubi,” fine-grained marine deposits, has been independently confirmed to span the Pliocene-Pleistocene.The results of this study provide a framework for future sequence–stratigraphic and paleotectonic studies in the area, and prove the effectiveness of an integrated paleontological and geochemical (87Sr/86Sr) approach in the study of fossil-poor sedimentary sequences.

scholarly journals Late Albian, Cenomanian and Turonian Natih Supersequence of Oman: Type section for Orbiton 7 (103.6–89.0 Ma)

GeoArabia ◽  
2010 ◽  
Vol 15 (4) ◽  
pp. 125-142 ◽  
Author(s):  
Moujahed I. Al-Husseini
Keyword(s):  
Sea Level ◽  
Time Scale ◽  
Structural Deformation ◽  
Arabian Plate ◽  
Time Interval ◽  
Geological Time ◽  
Geological Time Scale ◽  
Type Section ◽  
Subaerial Exposure ◽  
Sequence Boundaries

ABSTRACT The Upper Albian, Cenomanian and Turonian Natih Formation in Oman was interpreted by previous authors in terms of the regional Natih I to V depositional sequences comprising 34 higher-order subsequences (referred to as the Adopted Interpretation in this paper). It mainly consists of limestones, and is separated from the underlying Albian shales of the Nahr Umr Formation by the Natih Sequence Boundary. The interpreted position of the Cenomanian Stage within the formation differs substantially depending on carbon-isotope and/or biostratigraphic data (ammonite, microfaunal and nannofossil). The top of the Natih Formation is a regional subaerial exposure surface (incised by channels with depths reaching 150–200 m) that was transgressed by Lower Coniacian marine shales (Muti Formation at outcrop, and Shargi Member of the Fiqa Formation in subsurface; Fiqa Transgression above the Fiqa Sequence Boundary). Over paleohighs the lower part of the Fiqa, Natih and older formations are eroded by the Campanian angular Intra-Fiqa Unconformity that is attributed to far-field compressional tectonism along the margins of the Arabian Plate. The paper tunes the 34 Natih subsequences (each named a Straton) at 405 Ky/cycle: the period of the long-eccentricity signal of the Earth’s orbit. They are dated using a time scale that is based on an orbital-forcing model of glacioeustasy, which consists of ca. 14.58 My (36 stratons) repeating, orbital cycles named orbitons. Orbitons are predicted to be separated by major glacio-eustatic lowstands (regional sequence boundary), with Orbiton 1 spanning ca. 16.1 to 1.5 Ma. The Natih Formation completely falls within Orbiton 7 (ca. 103.6–89.0 Ma) in the Late Albian – Turonian time interval of the Geological Time Scale of the International Commission on Stratigraphy (GTS). The Formation consists of only 34 subsequences (compared to the 36 predicted for a complete orbiton). This implies two stratons are represented by a hiatus (ca. 810 Ky) between ca. 89.8–89.0 Ma near the end of Orbiton 7 and the Turonian/Coniacian boundary (88.6 Ma in GTS). The hiatus corresponds to a Late Turonian – ?earliest Coniacian biostratigraphic break at the Sub-Fiqa Unconformity and is correlated to a model-predicted major polar glaciation and sea-level lowstand. The hiatus is unrelated to the structural deformation in Interior Oman (First Alpine Event), which started some 10 My later in Campanian time. Orbiton 7 (ca. 103.6–89.0 Ma) correlates by architecture (sequence boundaries and maximum flooding surfaces) and age to the global Late Albian – Turonian UZA 2 Supersequence inclusive of the shortlived 100+ m sea-level drop in latest Turonian (ca. 102.5–88.6 Ma in empirical time scale). The Formation is proposed as the Natih Supersequence and the type section of Orbiton 7.

SOME CONCEPTS OF SEISMIC STRATIGRAPHY WITH APPLICATION TO THE GIPPSLAND BASIN

1976 ◽  
Vol 16 (1) ◽  
pp. 67 ◽  
Author(s):  
R.J. Steele
Keyword(s):  
Sea Level ◽  
Seismic Data ◽  
Sedimentary Basins ◽  
Building Blocks ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Sea Level Fluctuations ◽  
Seismic Sequences ◽  
Sequence Boundaries ◽  
Gippsland Basin

One approach to the problem of extracting stratigraphic information from seismic data is through the concept of sequences which are defined as time-stratigraphic units that are bounded by unconformities or their correlative conformities. These sequences are distinct depositional units that may be thought of as the building blocks of sedimentary basins. Sequence boundaries can be recognized on good quality seismic data by offlapping, onlapping and truncated patterns of cycle terminations. These sequence boundaries can be mapped to determine the configuration and lateral extent of each sequence and to provide a time-stratigraphic framework for analysing a basin. In addition, the logical lateral variations of environment and lithofacies that may be expected within each sequence provide a basis for rational extrapolation of lithological trends beyond the well control.Seismic sequences can also be used to recognize and measure relative sea level fluctuations. The amount of coastal onlap shown by sequences can be used to measure the magnitude and timing of relative sea level rises, and similarly, basinward shifts in deposition across sequence boundaries can be used to document sea level falls. Using these principles, graphs can be constructed that show detailed relative sea level fluctuations within a basin as a function of geological time.A relative sea level chart has been constructed for the Gippsland Basin by integrating seismic sequences with palaeontological data. When the Gippsland chart is compared with high resolution charts derived from seismic sequences in other areas it is found that many synchronous sea level fluctuations occur in widely spaced basins. These synchronous fluctuations are considered to be due to eustatic variations which contrast with other fluctuations that result from local tectonic movements.As detailed relative sea level charts from many areas become available a more complete picture of ecstatic variations should emerge. Such a eustatic framework should assist in inter-regional correlations and also allow the geologist to distinguish between the effects of local tectonism and world-wide sea level changes.

scholarly journals Sensitivity Analysis of Sentinel-1 Backscatter to Oil Palm Plantations at Pluriannual Scale: A Case Study in Gabon, Africa

2021 ◽  
Vol 13 (11) ◽  
pp. 2075
Author(s):  
J. David Ballester-Berman ◽  
Maria Rastoll-Gimenez
Keyword(s):  
Time Series ◽  
Sensitivity Analysis ◽  
Oil Palm ◽  
Time Interval ◽  
Potential Candidate ◽  
Initial Growth ◽  
Natural Forests ◽  
Wet Season ◽  
Radar Signatures ◽  
The Times

The present paper focuses on a sensitivity analysis of Sentinel-1 backscattering signatures from oil palm canopies cultivated in Gabon, Africa. We employed one Sentinel-1 image per year during the 2015–2021 period creating two separated time series for both the wet and dry seasons. The first images were almost simultaneously acquired to the initial growth stage of oil palm plants. The VH and VV backscattering signatures were analysed in terms of their corresponding statistics for each date and compared to the ones corresponding to tropical forests. The times series for the wet season showed that, in a time interval of 2–3 years after oil palm plantation, the VV/VH ratio in oil palm parcels increases above the one for forests. Backscattering and VV/VH ratio time series for the dry season exhibit similar patterns as for the wet season but with a more stable behaviour. The separability of oil palm and forest classes was also quantitatively addressed by means of the Jeffries–Matusita distance, which seems to point to the C-band VV/VH ratio as a potential candidate for discrimination between oil palms and natural forests, although further analysis must still be carried out. In addition, issues related to the effect of the number of samples in this particular scenario were also analysed. Overall, the outcomes presented here can contribute to the understanding of the radar signatures from this scenario and to potentially improve the accuracy of mapping techniques for this type of ecosystems by using remote sensing. Nevertheless, further research is still to be done as no classification method was performed due to the lack of the required geocoded reference map. In particular, a statistical assessment of the radar signatures should be carried out to statistically characterise the observed trends.

scholarly journals Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) Since the Last Glacial Maximum

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 155
Author(s):  
Fiorenza Torricella ◽  
Romana Melis ◽  
Elisa Malinverno ◽  
Giorgio Fontolan ◽  
Mauro Bussi ◽  
...  
Keyword(s):  
Continental Margin ◽  
Ross Sea ◽  
Time Interval ◽  
Central Basin ◽  
Ice Shelf ◽  
Last Glacial ◽  
Ross Ice Shelf ◽  
Sedimentary Sequences ◽  
Ash Layer ◽  
The Last Glacial

The continental margin is a key area for studying the sedimentary processes related to the advance and retreat of the Ross Ice Shelf (Antarctica); nevertheless, much remains to be investigated. The aim of this study is to increase the knowledge of the last glacial/deglacial dynamics in the Central Basin slope–basin system using a multidisciplinary approach, including integrated sedimentological, micropaleontological and tephrochronological information. The analyses carried out on three box cores highlighted sedimentary sequences characterised by tree stratigraphic units. Collected sediments represent a time interval from 24 ka Before Present (BP) to the present time. Grain size clustering and data on the sortable silt component, together with diatom, silicoflagellate and foraminifera assemblages indicate the influence of the ice shelf calving zone (Unit 1, 24–17 ka BP), progressive receding due to Circumpolar Deep Water inflow (Unit 2, 17–10.2 ka BP) and (Unit 3, 10.2 ka BP–present) the establishment of seasonal sea ice with a strengthening of bottom currents. The dominant and persistent process is a sedimentation controlled by contour currents, which tend to modulate intensity in time and space. A primary volcanic ash layer dated back at around 22 ka BP is correlated with the explosive activity of Mount Rittmann.

Dating Late Pleistocene Pluvial Events and Tephras by Correlating Paleomagnetic Secular Variation Records from the Western Great Basin

1992 ◽  
Vol 38 (1) ◽  
pp. 46-59 ◽  
Author(s):  
Robert M. Negrini ◽  
Jonathan O. Davis
Keyword(s):  
Great Basin ◽  
Secular Variation ◽  
Hot Springs ◽  
Time Interval ◽  
Lake Basin ◽  
Lake Surface ◽  
Surface Level ◽  
Sedimentary Sequences ◽  
Tephra Layers ◽  
Geologic Record

AbstractPaleomagnetic records are used to correlate sedimentary sequences from pluvial Lakes Chewaucan and Russell in the western Great Basin. This correlation is the basis for age control in the relatively poorly dated sequence from Lake Chewaucan. The resulting chronology supports a lack of sedimentation in Lake Chewaucan during the interval 27,400 to 23,200 yr B.P., an assertion supported by the presence of a lag deposit at the corresponding stratigraphic horizon. Because the Lake Chewaucan outcrop (near Summer Lake, Oregon) is near the bottom of the lake basin, we conclude that Lake Chewaucan was at a lowstand during this time interval. The Chewaucan lowstand is coeval with the lowstand accompanying the Wizard's Beach Recession (isotope stage 3) previously seen in the geologic record from nearby pluvial Lake Lahontan. The ages of six tephra layers, including the Trego Hot Springs tephra, were also estimated using the paleomagnetic correlation. Together, the new age of the Trego Hot Springs tephra (21,800 yr B.P.) and the lake surface level prehistory of Lake Chewaucan imply a revised model for the lake surface level prehistory of Lake Lahontan. The revised model includes a longer duration for the Wizard's Beach Recession and the occurrence of a younger lowstand of short duration soon after the lowstand corresponding to the Wizard's Beach Recession.

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