Stratigraphic Correlation Exercise
Dorian Aldrege
You practiced lithostratigraphic correlation in Lab 4 by matching beds and facies between stratigraphic logs, as well as some time-stratigraphic correlation. This lab will focus on time-stratigraphic and biostratigraphic correlation. This requires that you be able to match rocks on one particular range of geological time to others of the same time, even if those other rocks are from a different facies, using fossils or fossil assemblages.
Biostratigraphy is the correlation of stratigraphic units based on fossil content, either through the use of index (guide) fossils or similarities in fossil assemblages. An index fossil is a useful guide for correlation if it possesses the following characteristics:
This is an interval over which the taxon range biozones of two fossils do not overlap (Figure 9.3). This type of biozone can sometimes be hard to determine as the absence of a fossil could just mean that none were preserved, not that they were absent.
This is an expanded version of a concurrent range biozone determined by the presence of multiple fossils, all of which have broad ranges. This grouping, or assemblage, of fossils is biostratigraphically distinguishable from adjacent strata. In the Figure 9.4, the fossil species A to G appear together only during the Permian Period.
The peak biozone is the relative geological period of maximum species abundance. Abundance refers to the number of individuals of a particular taxon in a certain volume of sediment. Recall from Labs 6-8 that most of the phyla you have learned about have periods of peak abundance. Figure 9.5 shows the range biozone of each taxon as a black bar, and the peak biozone is indicated by a thicker segment along the bar. Notice that not all of the taxa in Figure 9.5 have peak biozones.
The wells are divided into three cross sections (X-SEC-A, X-SEC-B, X-SEC-C). Each of these cross sections and the basemap can viewed on electronic media that include PC, Notebook, Tablet, or Pad. Power Point drawing tools are an effective and easy way to handle the objectives of the exercise and a means for collective viewing of results in class. Click on red box for more details. Exercises can also be printed from the .pdf format, reassembled and taped to aid in the correlation (PRINTABLE-X-SEC-A, PRINTABLE-X-SEC-B, PRINTABLE-X-SEC-C).
EXERCISE 1 - Objective: Well log correlation and sequence stratigraphic interpretation
Using SP & RES logs you are provided with a basemap locating three wells (W-1, W-2, W-3). Each well has Spontaneous Potential and Resistivity logs that are used to correlate the wells. You learn how correlation can be based on bounding transgressive surfaces and thelithofacies of parasequences identified in well logs drilled in a clasticshoreline depositional system dissected by regressive high stand beach systemsand incised valleys extending below sea level but formed during a low sea level.
A pdf file containing all wells and a base map can viewed on electronic media that include PC, Notebook, Tablet, or Pad and interpreted with a graphics program like Power Point. Using Power Point drawing tools, in particular curve, in the electronic media is an effective and easy way to handle the objectives of the exercise and a means for collective viewing of results in class. Click on red box for more details. The output can be printed, reassembled and taped (PRINTABLE-EX-1). A reduced pdf file version can be also viewed and or printed (VIEW-EX-1). These well logs are flattened on the top of a major transgressive surface (TS) on the silt marking the contact between the La Pascua below and the overlying Roblecito Formation.
Normally radioactive peaks on gamma ray logs, associated with are more extensive and would have been better correlation surfaces than the transgressive surfaces but gamma ray logs were not available for much of the Guarico Sub Basin. As in the movie above you should use geologic logic to infer the location of the maximum flooding surfaces (mfs) and correlate these on all the well logs.
Make a cross-section tying the silts and shales of all the wells and finally the sand geometries. If you view the above movies and have read in the earlier sections related to the geologic setting of the La Pascua Formation and the introduction to the well log response to the La Pascua Formation. you will know something of the depositional setting of these rocks. You should combine this understanding of the regional geology with your understanding of vertical and lateral facies relationships in near shore clastic settings (eg. shoreline, beach, stacked beaches, tidal flats, deltas) and Walther's Law. You should use these to build a depositional model and a sequence stratigraphic interpretation of the well log section.
This course offers a practical approach to the sequence stratigraphic analysis of well logs. Lectures and exercises introduce the concepts and terminology of sequence stratigraphy and then apply them to the interpretation and correlation of well logs. Exercises are used to identify significant chronostratigraphic surfaces on well logs and then use the surfaces to construct log correlation sections for a variety of depositional settings. The approach allows for subdividing stratigraphic intervals into meaningful genetic packages, in order to interpret depositional histories and build geologically meaningful maps. Participants will develop the skills necessary to identify and predict new prospects and better subdivide reservoirs.
Fundamental. This course is aimed at geoscientists to teach them how to interpret well log data, make well-to-well correlations and generate maps in a sequence stratigraphic framework. The content is also suitable for professionals who work with geoscientists, such as petrophysicists and reservoir engineers.
The purpose of this course is to provide succinct information andinsight into palynological data and techniques through instilling anunderstanding of the main palynomorph groups, their uses, advantagesand disadvantages and what they can and cannot do. This willaid the non-specialist geologist to get the most out of her palynologicaldata. It will do this by providing simple jargon-free informationon palynomorph groups, and real-world case studies of the ways inwhich these have been used in geological problem solving covering the whole of the Phanerozoic and all major palynomorph groups.
The course will be supported by high quality PowerPoint resourcesand a set of open access reports and published papers that illustrateconcepts and techniques. The course will also provide worked throughexamples and simple exercises in palynology in explorationincluding examples of palynology used alongside logs and seismic,palynology calibrated against other fossil groups, palynology calibratedagainst radiometric dates and Sr isotope values, palynologyto create time slices, palynology to fingerprint individual sands andmudstone layers, palynofacies characterisation of mudstone organicmatter, and use of palynological assemblages in paleoenvironmentalinvestigation. These worked examples and simple exercises will besupported by high quality resources including real data, images,photographs and sections.
Prof Mike Stephenson has over 25 years of experience in appliedpalynology with over 100 peer-reviewed papers. Mike began hiscareer with a PhD at Sheffield University on the palynology of theCarboniferous-Permian of Saudi Arabia and Oman focusing on theUnayzah and Al Khlata formations with sample material from SaudiAramco and Petroleum Development Oman. In 2003 Mike alongwith other industry professionals published a palynological biozonationfor the Carboniferous-Permian of Saudi Arabia and Omanwhich is still in use today and which has helped to elucidate manystratigraphic problems across the Middle East establishing new correlationsand relationships within complex glacial and post glacialsequences of a fast-evolving Gondwana region. Following his PhD,Mike worked with all the major companies in the Middle East onsequences from the Ordovician to the Triassic but mainly on theDevonian, Carboniferous and Permian. Mike has published widely quoted reviews of the Permian of the world and is the Vice Chair ofthe Sub-commission on Permian Stratigraphy. He was also the Editor-in-Chief of the Elsevier scientific journal Review of Palaeobotanyand Palynology between 2009 and 2021; has professorships at theuniversities, Milan (Italy) and Nanjing (China); and was the Presidentof the IUGS Deep-time Digital Earth Programme, 2019 to 2021. Foreight years Mike was Director of Science and Technology and thenExecutive Chief Scientist at the British Geological Survey where hegained deep knowledge of a range of applied geology disciplinesincluding CCS, shale, hydrogeology and geological mapping. Hismost recent palynology work focuses on the Permian and Triassic ofIsrael and Jordan. Mike is an experienced trainer with post graduateteaching qualifications. He has taught practical and technical courseson palynology in universities and inhouse in companies, and wasa trainer in the regular AASP masterclass series.
All rights reserved. This course or part hereof may not be reproduced or transmitted in any form or by any means, electronic or mechanical, including recording, or any information storage and retrieval system, without the prior written permission
of the publisher.
All rights reserved. This course or part hereof may not be reproduced or transmitted in any form or by any means, electronic or mechanical, including recording, or any information storage and retrieval system, without the prior written permission of the publisher.
The relationship of paleontology to sedimentologic and stratigraphic modeling can be viewed as dependent, independent, or some combination of the two. Independent paleontologic data are taxonomy based and include standard paleontologic techniques, such as biostratigraphy. Tremendous advances in temporal acuity have resulted from our ability to analyze standard biostratigraphic data bases through the different methodologies of quantitative biostratigraphy. Dependent paleontologic data result from biotic responses to externally mediated physical parameters (e.g., sea level, climate, sediment accumulation rate). Thus, for example, trace-fossil distribution can be used with care as a tool to help discern transgressive-regressive events. In addition, biotic event horizons (epiboles) can be used as indicators of temporal equivalency across complex depositional facies mosaics and thus serve as important markers for regional correlation.
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