Sedimentary facies refer to rock or sediment bodies that are distinguished by their composition, texture, structures and other features related to the depositional environment. Key aspects of facies include grain size, sorting, fossils and bedding. Individual facies represent specific depositional conditions. Multiple genetically-related facies comprise a facies association representing a depositional system. Facies successions occur at different scales from individual systems to basin-scale sequences reflecting changes in sea level over time.
Boundary problems between :-
Precambrian/Cambrian
Permian/Triassic
Cretaceous/Tertiary
Neogene/Quaternary
Stratigraphic boundaries are determined by one or more of geological events such as volcanic activity, sedimentation, tectonism, paleo-environments & evolution of life.
Faunal records have played major role in determining the boundaries of the Phanerozoic units.
The other geological events are dated on the evidence of fossil records.
CLASSIFICATION OF ORE DEPOSITS
The Mixture of ore minerals are gangue minerals form an Ore deposit. The ore
deposits are generally found enclosed within the country rocks. The ore deposits
are formed in many different ways. Depending upon the process that may
operate to produce them, the ore deposits may be classified as follow:
Magmatic ore deposits.
Sublimation ore deposits.
Pegmatitic ore deposits.
Contact metasomatic ore deposits.
Hydrothermal ore deposits
Cavity filling deposits.
Replacement deposits.
Sedimentation ore deposits.
Evaporation ore deposits.
Residual and mechanical concentration deposits
Metamorphic ore deposits.
MAGMATIC ORE DEPOSITS:
The magmatic ore deposits are the magmatic products which crystallize from
magmas. The magmatic ore deposits are classified as follows:
o Early magmatic deposits
o Late magmatic deposits
Early magmatic deposits:
Early magmatic deposits are formed during the
early stage of the magmatic period. In this case the
ore minerals crystallize earlier than the rock
silicates. The Minerals of Nickel, Chromium, and
Platinum are usually found as early magmatic
deposits. The early magmatic deposits can be sub
divided into two groups:
o Dissemination deposits
o Segregation deposits
Dissemination deposits:
When magma crystallizes
conditions, a granular igneous rock is formed. In
such a rock early formed crystals of
may occur in dissemination.
Segregation deposits:
Magmatic segregation deposits are
formed as a result of gravitative
crystallization differentiation. In
case, the ore mineral which crystallize
early, get ocean-trated on a particular
part of igneous part. The ore deposits
thus formed are known as “Segregation
deposits”.
rly under seated
ore minerals
such
Late Magmatic Deposits:
The ore deposits which are formed to
called late magmatic deposits. The late magmatic deposits contain those ore
minerals which have crystallized at rather low temperature from the residual
magma. The magma which is left after crystallization of early for
is called residual magma. This magma frequently contains many ore minerals. The
late magmatic deposits include most of the magmatic deposits of iron and
titanium ores, these deposits are almost always associated with mafic igneous
rocks.
SUBLIMATION DEPOSITS:
Sublimation is a very minor process of formation of ore deposits. Sublimation
deposits contain only those minerals which have been volatilized by hear and
subsequently redeposit in the same form at low temperature and pressure. The
sublimation deposits are found associated with Volcanoes and Fumaroles. Sulfur
of this origin has been mined in Japan, Italy, and Mexico.
Sedimentary basins are the depressions in the earth's crust where loose particles accumulate and finally lithified to form sedimentary rocks. Basins are particularly attractive to geoscientists from time immemorial due to the wealth hidden here in the form of oil, gas, coal etc. In this document you will find the types of basins, basin-fill types, methods of basin analysis and so on.
Historical geology Is the branch which deals with the history of the rocks of the earth’s crust with special emphasis on their approximate time of formation and the climate changes they have undergone since their formation.
ELEMENTS OF CORRELATION, STRUCTURAL FEATURES, METHOD OF STRATIGRAPHIC CORRELATION ,
Three principle kinds of correlations
This is my presentation on the tectonic control of sediments.
It includes the effects of tectonics either direct or indirect on sediments and sedimentation.
Sedimentation along various plate boundaries.
Few examples as evidence from Pakistan (the Siwalik Group) and Argentina (Fiambala Basin)
The current ppt discusses the different types of lineations formed due to deformation.
Lineations are genetically related to the foliation planes on which they occur, particularly where both are shaped by mineral orientations. Therefore, the planar and linear fabrics are both together aspects of the same three-dimensional geometry, which is related to the shape of the finite strain ellipsoid or,
more important still, to the history of incremental strains.
Boundary problems between :-
Precambrian/Cambrian
Permian/Triassic
Cretaceous/Tertiary
Neogene/Quaternary
Stratigraphic boundaries are determined by one or more of geological events such as volcanic activity, sedimentation, tectonism, paleo-environments & evolution of life.
Faunal records have played major role in determining the boundaries of the Phanerozoic units.
The other geological events are dated on the evidence of fossil records.
CLASSIFICATION OF ORE DEPOSITS
The Mixture of ore minerals are gangue minerals form an Ore deposit. The ore
deposits are generally found enclosed within the country rocks. The ore deposits
are formed in many different ways. Depending upon the process that may
operate to produce them, the ore deposits may be classified as follow:
Magmatic ore deposits.
Sublimation ore deposits.
Pegmatitic ore deposits.
Contact metasomatic ore deposits.
Hydrothermal ore deposits
Cavity filling deposits.
Replacement deposits.
Sedimentation ore deposits.
Evaporation ore deposits.
Residual and mechanical concentration deposits
Metamorphic ore deposits.
MAGMATIC ORE DEPOSITS:
The magmatic ore deposits are the magmatic products which crystallize from
magmas. The magmatic ore deposits are classified as follows:
o Early magmatic deposits
o Late magmatic deposits
Early magmatic deposits:
Early magmatic deposits are formed during the
early stage of the magmatic period. In this case the
ore minerals crystallize earlier than the rock
silicates. The Minerals of Nickel, Chromium, and
Platinum are usually found as early magmatic
deposits. The early magmatic deposits can be sub
divided into two groups:
o Dissemination deposits
o Segregation deposits
Dissemination deposits:
When magma crystallizes
conditions, a granular igneous rock is formed. In
such a rock early formed crystals of
may occur in dissemination.
Segregation deposits:
Magmatic segregation deposits are
formed as a result of gravitative
crystallization differentiation. In
case, the ore mineral which crystallize
early, get ocean-trated on a particular
part of igneous part. The ore deposits
thus formed are known as “Segregation
deposits”.
rly under seated
ore minerals
such
Late Magmatic Deposits:
The ore deposits which are formed to
called late magmatic deposits. The late magmatic deposits contain those ore
minerals which have crystallized at rather low temperature from the residual
magma. The magma which is left after crystallization of early for
is called residual magma. This magma frequently contains many ore minerals. The
late magmatic deposits include most of the magmatic deposits of iron and
titanium ores, these deposits are almost always associated with mafic igneous
rocks.
SUBLIMATION DEPOSITS:
Sublimation is a very minor process of formation of ore deposits. Sublimation
deposits contain only those minerals which have been volatilized by hear and
subsequently redeposit in the same form at low temperature and pressure. The
sublimation deposits are found associated with Volcanoes and Fumaroles. Sulfur
of this origin has been mined in Japan, Italy, and Mexico.
Sedimentary basins are the depressions in the earth's crust where loose particles accumulate and finally lithified to form sedimentary rocks. Basins are particularly attractive to geoscientists from time immemorial due to the wealth hidden here in the form of oil, gas, coal etc. In this document you will find the types of basins, basin-fill types, methods of basin analysis and so on.
Historical geology Is the branch which deals with the history of the rocks of the earth’s crust with special emphasis on their approximate time of formation and the climate changes they have undergone since their formation.
ELEMENTS OF CORRELATION, STRUCTURAL FEATURES, METHOD OF STRATIGRAPHIC CORRELATION ,
Three principle kinds of correlations
This is my presentation on the tectonic control of sediments.
It includes the effects of tectonics either direct or indirect on sediments and sedimentation.
Sedimentation along various plate boundaries.
Few examples as evidence from Pakistan (the Siwalik Group) and Argentina (Fiambala Basin)
The current ppt discusses the different types of lineations formed due to deformation.
Lineations are genetically related to the foliation planes on which they occur, particularly where both are shaped by mineral orientations. Therefore, the planar and linear fabrics are both together aspects of the same three-dimensional geometry, which is related to the shape of the finite strain ellipsoid or,
more important still, to the history of incremental strains.
Lithofacies and palaeoenvironmental reconstruction new microsoft office word ...DrRalimonglaYaden
In the present investigation, an attempt has been made to elucidate the sedimentary facies and depositional environment of tertiary succession of Changki valley comprising of Barail Group, Changki Formation and Tipam Sandstone Formation.
Interpretation and recognition of depositional systems using seismic dataDiego Timoteo
ABSTRACT
The interpretation and recognition of Depositional Systems using seismic data require a strong knowledge in stratigraphy, structural geology, tectonics, biostratigraphy, sedimentology and geophysics; even when a geoscientist doesn’t be a specialist of one of these. The mentioned disciplines interact and complement each other in different stages of study and exploration of hydrocarbon basins. Five stages have been proposed and studied in Interpreting Depositional Systems. (1) Review of basic concepts used in the definition of Depositional Sequences and Systems Tracts within the context of sequence stratigraphy. (2) The deepening in the physical foundations of rocks, that allows to obtain images of the subsurface through the application of seismic reflection method. It also is indicated how to tie the seismic data with well data through the synthetic seismogram. (3) The seismic stratigraphic interpretation, describes how Depositional Sequences and their Systems Tracts are interpreted in the well and seismic data. (4) The recognition of Depositional Systems, describes how the seismic facies analysis is more accurate on the interpretation, because of the association of particular Systems Tracts with particular deposition processes. The Depositional Sequences and Systems Tracts have predictable stratal patterns and lithofacies; thus, they provide a new way to establish a chronostratigraphic correlation framework based on physical criteria. (5) The advanced seismic interpretation allows geoscientists extract more information from seismic data and their applications include hydrocarbon play evaluation, prospect identification, risk analysis and reservoir characterization.
Keywords: depositional systems, seismic stratigraphy, sequence stratigraphy, seismic sequence, seismic facies, potential reservoir rocks.
LGC field course in the Book Cliffs, UT: Presentation 14 of 14 (Thompson Cany...William W. Little
Preview presentation on the Desert Member of the Blackhawk Formation and the Castigate Sandstone in Thompson Canyon for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 13 of 14 (Blue Castle B...William W. Little
Preview presentation on the Kenilworth through Desert Members of the Blackhawk Formation and the Castlegate Sandstone from the Blue Castle Butte area to Gunnison Butte for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 11 of 14 (Woodside Cany...William W. Little
Preview presentation on the Sunnyside Member of the Blackhawk Formation in Woodside Canyon for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 10 of 14 (Woodside Cany...William W. Little
Preview presentation on the Kenilworth Member of the Blackhawk Formation in Woodside Canyon for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 9 of 14 (Coal Creek & S...William W. Little
Preview presentation on the Aberdeen Member of the Blackhawk Formation in Coal Creek and Soldier Canyons for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 7 of 14 (Spring Canyon ...William W. Little
Preview presentation on the Spring Canyon Member of the Blackhawk Formation in Spring Canyon and Sowbelly Gulch for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 5 of 14 (Gentile Wash -...William W. Little
Preview presentation on the Storrs Member of the Star Point Sandstone in Spring Canyon and the Spring Canyon Member of the Blackhawk Formation for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 4 of 14 (Spring Canyon ...William W. Little
Preview presentation on the Panther Tongue of the Star Point Sandstone in Spring Canyon for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 3 of 14 (Gentile Wash -...William W. Little
Preview presentation on the Panther Tongue of the Star Point Sandstone in Gentile Wash for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 2 of 14 (Stratigraphic ...William W. Little
Stratigraphic overview for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
LGC field course in the Book Cliffs, UT: Presentation 1 of 14 (Principles of ...William W. Little
Introductory presentation for a professional field course titled: THE BOOK CLIFFS: A CASE STUDY IN COASTAL SEQUENCE STRATIGRAPHY, offered annually through W.W. LITTLE GEOLOGICAL CONSULTING (also offered by SCA). See details at: HTTP://LITTLEWW.WORDPRESS.COM.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
1. Sedimentary Facies (Lithofacies)
A lithofacies is a body of sediment/rock distinguished by a specified
combination of characteristics (composition, texture, sedimentary
structures) related to a specific set of physical, biological, and chemical
processes.
2. Aspects of Lithofacies
• Composition
• Texture (grain size, sorting, rounding)
• Sedimentary structures
• Bedding (thickness, geometry, nature of contacts)
• Fossil content (types, abundance)
Example: Well-sorted, coarse- to fine-grained, trough cross-bedded
quartz arenite that fines upward as cross-bed sets decrease in thickness.
3. Sedimentary Facies &
Depositional Environments
The unique characteristics of a lithofacies represent deposition under the
very specific conditions of a single environment. For example, the facies
of the previous slide suggests flood stage deposition on a point bar of a
meandering stream.
4. Separation of data (facies) and
interpretation (environment)
In science, it is critical to distinguish between data (what’s there - lithofacies) and
interpretations (how you think it got there – depositional environment). There is not
complete agreement upon use of the term facies. Many use it in conjuction with the
interpreted environment (e.g. point bar facies). I consider this as a misuse of the term.
Data
Interpretation
5. Lithofacies Codes
Some attempts have been made to devise
abbreviations for commonly found
lithofacies. These typically employ a
capitol letter for the major clast size (i.e.
G for gravel, S for sand, and F for fine-
grained) followed by lower case letters
denoting the major structure (i.e. t for
trough cross-bedding and p for planar
cross-bedding).
6. Facies Associations/Assemblages
Facies association: a collection of multiple, genetically-related facies
formed within a single depositional system.
Example: Non-stratified
gravel overlain by well-
sorted coarse- to fine-
grained, trough cross-
bedded sand that fines
upward as cross-bed sets
decrease in thickness
overlain by ripple-bedded
sandstone. Succession
grades laterally to
laminated mudstone that
contains thin lenses of
sandstone.
7. Common Facies Associations
Some facies associations are found repetitively in the stratigraphic record and, therefore, have
informally been given names, such as the “Point bar succession” or the “Bouma (turbidite)
sequence.”
Point bar succession Bouma sequence
9. Facies Associations and Depositional
Systems
A depositional system consists of genetically-related, contemporaneous
depositional environments. Vertical changes in facies associations can
reflect either lateral migration of environments within a system or
fluctuation in base-level.
10. Facies Models/Architecture
Facies models are based on facies associations and are designed to show
the three-dimensional relationships (architecture) between individual
facies (architectural elements) for a depositional system. Models can be
taylored to a specific stratigraphic unit or can be generalized to show an
“average” of characteristics for a “typical” depositional system.
Generalized
model for a
“typical”
meandering
stream system
11. Subsurface Facies Models
Subsurface facies models have the same components as those based on
outcrop but, typically, with less detail; although, recent advances in 3-D
seismic is narrowing that gap.
Fluvial model based on well logs Fluvial model based on 3-D seismic
13. Systems Tracts
A systems tract consists of contemporaneous depositional systems.
Vertical changes in systems tracts reflects changes in sea-level.
14. Vertical Facies Successions
Facies successions occur on three scales: 1) facies assemblage associated
with a depositional system, 2) larger-scale stacking of adjacent systems
within a systems tract; and 3) long-term basin fill successions.
Idealized meandering
stream vertical profile
Idealized deltaic
succession
Stacked Cretaceous systems
tracts in the Book Cliffs
15. Walther’s Law
WaltherWalther’s Law (1894) states that facies found superimposed on one’s Law (1894) states that facies found superimposed on one
another and not separated by an unconformity, must have beenanother and not separated by an unconformity, must have been
deposited adjacent to each other at a given point in timedeposited adjacent to each other at a given point in time
Floodplain
Levee
Point Bar
Photo by W. W. Little
16. Walther’s Law & Systems Tracts
Most systems tracts are preserved in the stratigraphic record as
progradational successions.
Prograding beach Prograding tidal flat
17.
18. Transgressive/Regresssive Cycles
(Sequences)
Walther’s Law was developed to explain vertical changes in facies associated with
changes in sea-level. Sea-level cycles were once drawn as symmetrical wedges
showing smooth transitions and equal preservation of both transgressive and regressive
deposits. We now term these cycles sequences and interpret them as pulses of
progradational deposits that step landward (retrogradational), vertically (aggradational),
or basinward (progradational). Each step is a parasequence.
Old T/R cycle
Parasequence
sets