A Paleoenvironmental Interpretation of the Pukenui Limestone and Hautotara Formation, Southeastern Wairarapa, New Zealand

<p>Two sections from the northern part of the Nga-Waka-A-Kupe Range have been documented in detail. Both sections were expected to cut through sediments of Pleistocene age which at the southern end of the range have been attributed to the Greycliffs Formation, Pukenui Limestone, Hautotara and Te Muna Formations. The Longbush Road section only included the upper Pukenui Limestone to Hautotara Formation. The Hinakura Road section was as expected and included the entire Pukenui Limestone and Hautotara Formation. Previous works in the Popes Head area have recognised the same sequence there. However, only a few correlations can confidently be made between the two areas. This is largely due to the Pukenui Limestone at Popes Head exhibiting a markedly different set of facies to the section in the southern part of the range – its type section. The facies analysis on the two sections here reveals that the depositional environment for the Pukenui Limestone in the Popes Head area is of a near-coastal environment close to the discharge of a large river, where the nearby type section is interpreted as representing deeper marine conditions. The differences in environments could be due to shallowing section or increased discharge from the river in the Popes Head area. More likely, however, it is a combination of these two factors that result in a shallow-water facies.</p>

A Paleoenvironmental Interpretation of the Pukenui Limestone and Hautotara Formation, Southeastern Wairarapa, New Zealand

<p>Two sections from the northern part of the Nga-Waka-A-Kupe Range have been documented in detail. Both sections were expected to cut through sediments of Pleistocene age which at the southern end of the range have been attributed to the Greycliffs Formation, Pukenui Limestone, Hautotara and Te Muna Formations. The Longbush Road section only included the upper Pukenui Limestone to Hautotara Formation. The Hinakura Road section was as expected and included the entire Pukenui Limestone and Hautotara Formation. Previous works in the Popes Head area have recognised the same sequence there. However, only a few correlations can confidently be made between the two areas. This is largely due to the Pukenui Limestone at Popes Head exhibiting a markedly different set of facies to the section in the southern part of the range – its type section. The facies analysis on the two sections here reveals that the depositional environment for the Pukenui Limestone in the Popes Head area is of a near-coastal environment close to the discharge of a large river, where the nearby type section is interpreted as representing deeper marine conditions. The differences in environments could be due to shallowing section or increased discharge from the river in the Popes Head area. More likely, however, it is a combination of these two factors that result in a shallow-water facies.</p>

QFL AND LITHO FACIES: PREDICTING RESERVOIR QUALITY OF THE MIDDLE MIOCENE DEEP-WATER FACIES AT KUTEI AND NORTH MAKASSAR BASINS

As we may all be aware the oil and gas wellbores offshore Kutei and North Makassar have not optimally penetrated the objective strata, which is the Middle Miocene’s deep-water reservoirs. Therefore, evaluating the quality of these reservoirs with onshore dataset then comparing them with the proven Late Miocene’s deep-water producing reservoirs had been very fundamental. The study focuses on the assessment of QFL and sandstones litho-facies based on the rock samples from conventional-core and side-wall core, and well-logs data from forty wells onshore and offshore. These rock samples are bounded by the key biostratigraphy intervals of M40M33, M45M40, M50M45 (Middle Miocene), and M65M50, M66M65, M70M66, M80M70 (Late Miocene). Subdivisions of the reservoirs considered the sandstone litho facies, NTG ratio, sorting, and grain size, to come up with five groups in the Middle Miocene deltaic facies: FLU_SX, DC_SX, DC_SM, DC_SM, and DF_SC; and four groups in the Late Miocene deep-water facies: SSWS, MSWS, SSPS, and MSPS. Core-based porosity and permeability further explain the relationship between the reservoir quality with the sandstones’ composition and litho facies, and concluded that high-energy depositional system is mainly associated with the FLU_SX, DC_SX, SSWS and MSWS being the reservoir with best quality. Oppositely, the DF_SC, SSPS, and MSPS are classified the reservoir with worst to none quality. A cross plot between core-based porosity and maximum burial depth is able to postulate the relational trend of decreasing reservoir quality with deeper depth.

The Late Jurassic–Palaeogene Carbonate Platforms in the Outer Western Carpathian Tethys—A Regional Overview

The present work focuses on palaeogeographic reconstruction of shallow-water carbonate deposition in the Outer Western Carpathian Tethys. Platform deposits are preserved only as a component of turbidites and olistostromes, and reconstructions of these platforms are based on clastic material redistributed into slopes and deep basins and occurring among the Outer Carpathian nappes. Similar platforms were also present on the Tethys margins. These reconstructions were performed using the global models of plate tectonics. Several ridges covered by carbonate platforms developed in that area during the latest Jurassic–Palaeogene times. Three main shallow-water facies associations—Štramberk, Urgonian, and Lithothamnion–bryozoan—could be distinguished. The Tithonian–lowermost Cretaceous Štramberk facies is related to early, synrift–postrift stage of the development of the Silesian Domain. Facies that are diversified, narrow, shallow-water platforms, rich in corals, sponges, green algae, echinoderms, foraminifera, microencrusters, and microbes are typical of this stage. The Urgonian facies developed mainly on the south margin of the Outer Carpathian basins and is characterised by organodetritic limestones built of bivalves (including rudists), larger benthic foraminifera, crinoids, echinoids, and corals. Since the Paleocene, in all the Western Outer Carpathian sedimentary areas, Lithothamnion–bryozoan facies developed and adapted to unstable conditions. Algae–bryozoan covers originating on the siliciclastic substrate are typical of these facies. This type of deposition was preserved practically until the final stage in the evolution of the Outer Carpathian basins.

Mudrock Microstructure: A Technique for Distinguishing between Deep-Water Fine-Grained Sediments

Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is impacted by the natural heterogeneity of the system caused by bioturbation. Based on the microfabric analysis, there is a disparate pattern observed among the sedimentary facies; turbidites are generally bedding parallel due to strong currents resulting in shear flow, contourites are random to semi-random as they are impacted by a weak current, while hemipelagites are random to oblique since they are impacted by bioturbation.

Carbonate shelf development and early Paleozoic benthic diversity in Baltica: a hierarchical diversity partitioning approach using brachiopod data

The Ordovician–Silurian (~485–419 Ma) was a time of considerable evolutionary upheaval, encompassing both great evolutionary diversification and one of the first major mass extinctions. The Ordovician diversification coincided with global climatic cooling and paleocontinental collision, the ecological impacts of which were mediated by region-specific processes including substrate changes, biotic invasions, and tectonic movements. From the Sandbian–Katian (~453 Ma) onward, an extensive carbonate shelf developed in the eastern Baltic paleobasin in response to a tectonic shift to tropical latitudes and an increase in the abundance of calcareous macroorganisms. We quantify the contributions of environmental differentiation and temporal turnover to regional diversity through the Ordovician and Silurian, using brachiopod occurrences from the more shallow-water facies belts of the eastern Baltic paleobasin, an epicontinental sea on the Baltica paleocontinent. The results are consistent with carbonate shelf development as a driver of Ordovician regional diversification, both by enhancing broadscale differentiation between shallow- and deep-marine environments and by generating heterogeneous carbonate environments that allowed increasing numbers of brachiopod genera to coexist. However, temporal turnover also contributed significantly to apparent regional diversity, particularly in the Middle–Late Ordovician.

Carboniferous conodont biostratigraphy

Carboniferous conodont biostratigraphy comprises regional zonations that reflect the paleogeographic distribution of taxa and distinct shallow-water and deep-water conodont biofacies. Some species have a global distribution and can effect high quality correlations. These taxa are incorporated into definitions of global Carboniferous chronostratigraphic units. A standard global Carboniferous zonation has not been developed. The lowermost Mississippian is zoned by Siphonodella species, except in shallow-water facies, where other polygnathids are used. Gnathodus species radiated during the Tournaisian and are used to define many Mississippian zones. A late Tournaisian maximum in diversity, characterized by short-lived genera, was followed by lower diversity faunas of Gnathodus species and carminate genera through the Viséan and Serpukhovian. By the late Viséan and Serpukhovian, Lochriea provides better biostratigraphic resolution. Shallow-water zonations based on Cavusgnathus and Mestognathus are difficult to correlate. An extinction event near the base of the Pennsylvanian was followed by the appearance of new gnathodid genera: Rhachistognathus, Declinognathodus, Neognathodus, Idiognathoides, and Idiognathodus. By the middle of the Moscovian, few genera remained: Idiognathodus, Neognathodus and Swadelina. During the middle Kasimovian and Gzhelian, only Idiognathodus and Streptognathodus species were common. Near the end of the Gzhelian, a rediversification of Streptognathodus species extended into the Cisuralian.

Devonian-Carboniferous boundary sections in Iran

Many sections are known from Iran which exhibit sediments across the Devonian-Carboniferous (D-C) boundary. In contrast to the majority of published D-C sections worldwide from pelagic/hemipelagic environments, successions in Iran are mainly composed of shallow-water sediments. Correlation with hemipelagic or pelagic palaeoenvironments remains difficult due to biostratigraphic uncertainties in most sections and/or hiatuses. On the other hand, a limited number of sections dealing with shallow-water facies settings in Iran at this particular time period are known and further research is necessary. Several sections in the Alborz Mountains provide an excellent opportunity to study successions across the D-C boundary in shallow-water facies. In Iran, protognathoids are represented by Protognathodus meischneri and Protognathodus collinsoni. The two biostratigraphically important protognathoids (Protognathodus kuehni and Protognathodus kockeli) were not reported or did not occur for the first time in the Late Tournaisian. Early siphonodellids were described instead. In the frame of an Iranian/German research project, we study different palaeoenvironments to reduce serious palaeoenvironmental and palaeogeographical sampling bias which may limit our knowledge on the Hangenberg Event particularly in shallow-water facies. We present a summary on published D-C sections in Iran (Ghale-Kalaghu, Howz-e-Dorah 1, Howz-e-Dorah 2 and Shahmirzad) and sections which are under study (Mighan, Chelcheli and Khoshyeilagh) at the time of this writing.