Introduction stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering (stratification). Stratigraphy, from Latin stratum + Greek graphia, is the description of all rock bodies forming the Earth's crust and their organization into distinctive, useful, mappable units based on their inherent properties or attributes in order to establish their distribution and relationship in space and their succession in time, and to interpret geologic history. Stratum (plural=strata) is layer of rock characterized by particular lithologic properties and attributes that distinguish it from adjacent layers.

History of stratigraphy begin by Avicenna (Ibn Sina) with studied rock layer and wrote The Book of Healing in 1027. He was the first to outline the law of superposition of strata:^[1] "It is also possible that the sea may have happened to flow little by little over the land consisting of both plain and mountain, and then have ebbed away from it. ... It is possible that each time the land was exposed by the ebbing of the sea a layer was left, since we see that some mountains appear to have been piled up layer by layer, and it is therefore likely that the clay from which they were formed was itself at one time arranged in layers. One layer was formed first, then at a different period, a further was formed and piled, upon the first, and so on. Over each layer there spread a substance of differenti material, which formed a partition between it and the next layer; but when petrification took place something occurred to the partition which caused it to break up and disintegrate from between the layers (possibly referring to unconformity). ... As to the beginning of the sea, its clay is either sedimentary or primeval, the latter not being sedimentary. It is probable that the sedimantary clay was formed by the disintegration of the strata of mountains. Such is the formation of mountains."

The theoretical basis for the subject was established by Nicholas Steno who re-introduced the law of superposition and introduced the principle of original horizontality and principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment.

The first practical large scale application of stratigraphy was by William Smith in the 1790s and early 1800s. Smith, known as the Father of English Geology, created the first geologic map of England, and first recognized the significance of strata or rock layering, and the importance of fossil markers for correlating strata. Another influential application of stratigraphy in the early 1800s was a study by Georges Cuvier and Alexandre Brongniart of the geology of the region around Paris.

In the stratigraphy you can find term of

- Stratigraphic classification. The systematic organization of the Earth's rock bodies, as they are found in their original relationships, into units based on any of the properties or attributes that may be useful in stratigraphic work.

- Stratigraphic unit. A body of rock established as a distinct entity in the classification of the Earth's rocks, based on any of the properties or attributes or combinations thereof that rocks possess. Stratigraphic units based on one property will not necessarily coincide with those based on another.

- Stratigraphic terminology. The total of unit-terms used in stratigraphic classification.It may be either formal or informal.

- Stratigraphic nomenclature. The system of proper names given to specific stratigraphic units.

- Zone.Minor body of rock in many different categories of stratigraphic classification. The type of zone indicated is made clear by a prefix, e.g., lithozone, biozone, chronozone.

- Horizon. An interface indicative of a particular position in a stratigraphic sequence. The type of horizon is indicated by a prefix, e.g., lithohorizon, biohorizon, chronohorizon.

- Correlation. A demonstration of correspondence in character and/or stratigraphic position. The type of correlation is indicated by a prefix, e.g., lithocorrelation, biocorrelation, chronocorrelation.

- Geochronology. The science of dating and determining the time sequence of the events in the history of the Earth.

- Geochronologic unit. A subdivision of geologic time.

- Geochronometry. A branch of geochronology that deals with the quantitative (numerical)measurement of geologic time. The abbreviations ka for thousand (103), Ma for million (106), and Ga for billion (milliard of thousand million, 109) years are used.

- Facies. The term "facies" originally meant the lateral change in lithologic aspect of a stratigraphic unit. Its meaning has been broadened to express a wide range of geologic concepts: environment of deposition, lithologic composition, geographic, climatic or tectonic association, etc.

- Caution against preempting general terms for special meanings. The preempting of general terms for special restricted meanings has been a source of much confusion.

GEOSTATISTIC RESERVOIR CHARACTERIZATION (USAGE OF STATISTICAL METHODS TO DISTINGUISH THE QUANTITATIVE SPATIAL RESERVOIR CONTINUITY TO OPTIMIZES RESERVOIR DEVELOPMENT)

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

GEOSTATISTIC RESERVOIR CHARACTERIZATION
(USAGE OF STATISTICAL METHODS TO DISTINGUISH
THE QUANTITATIVE SPATIAL RESERVOIR CONTINUITY
TO OPTIMIZES RESERVOIR DEVELOPMENT)

IGP. Oka Ariyasa

ABSTRACT

Within the Oil Industry, Reservoir Characterization is carried out to understand reservoir heterogeneity at various scales. It includes the interpretation of depositional environments, facies distributions, and properties distributions. Though the data are quantitative in nature, in practice, the interpretation results are used in a qualitative manner. Most data are presented graphically that shows the external qualitative reservoir description, and insight into the nature of the reservoir framework. For sustainable reservoir development, detail reservoir characterization not only requires the qualitative data but also the quantitative descriptions.

For many reservoir applications, quantitative descriptions are required for proper analysis as a part of reservoir management. Geostatistic is increasingly being used for reservoir quantitative descriptions, mainly to predict values at unsampled locations. These statistical methods give a sense of quantitative description to the geologic and reservoir property conditions both vertically, laterally, to understand spatial distributions and correlations between the data. Geostatistics also provides quantitative methods for collecting, organizing, summarizing and analyzing data as well as for drawing conclusions.

Common statistical methods used are cross-plots, histograms and variograms. Variograms are a spatial statistical analysis that measures dissimilarity as a function of separation distance, and usually applied to porosity, permeability and saturation. Variograms reflect the geometry and continuity of facies and petrophysical properties.

Examples will be shared to demonstrate how the methods have been practically applied to characterize several reservoirs of Duri Field. They address the internal reservoir variabilities quantify the maximum and minimum ranges of property distribution, direction of continuity, property trends, cyclicity that have given better reservoir assessment on predicted flow behavior, and consequent reservoir decisions for further development.

GEOTOURISM DEVELOPMENT IN MINING AND SOURROUNDING AREA OF PT. NEWMONT NUSA TENGGARA WEST NUSA TENGGARA PROVINCE

PROCEEDINGS PIT IAGI RIAU 2006
The 35th IAGI Annual Convention and Exhibition
Pekanbaru - Riau, 21-22 November 2006

GEOTOURISM DEVELOPMENT IN MINING AND SOURROUNDING AREA OF
PT. NEWMONT NUSA TENGGARA WEST NUSA TENGGARA PROVINCE

¹Heryadi Rachmat, ²Indyo Pratomo, ³Adi Maryono

¹The Regional IAGI Nusa Tenggara
²The Regional IAGI Jawa Barat-Banten.
³The Regional IAGI Nusa Tenggara.

ABSTRACT

West Nusa Tenggara Province has geological and mining condition to be developed as ”a geotourism” as well as other existed tourism areas. Geotourism is one form of alternative tourism that involves traveling to natural areas with the specific objective of studying, admiring, and enjoying the scenery, the volcano, caves, water fall, hot spring, mining, etc., as well as any existing geological manifestations found in these areas.

The term alternative tourism has two meanings, namely: firstly a certain form of tourism which was developed as a reaction to the negative impacts of conventional tourism development; and secondly a different form of tourism which was developed to support enviromental conservation and/or community development.

The development should consider efforts of improvments, among others to improve the quality and values of tourism products, the region’s image as a safe and pleasant tourist destination area, quality of the human resources, cross-sectoral coordination, tourism awareness of the people, activities in arts, as well as regulations for the tourism industry.

Regarding to the planning of the geotourism program in the PT. Newmont Nusa Tenggara mining area so far I know, is “a new paradigm” in the development to discover about tourism object in generall.

By optimizing geology tourism potential and mining based environment, it is expected in the future West Nusa Tenggara can be one of the model for geology potensial use and mining activity that always concerning to the environment.

ROCK FRACTURE DENSITY CHARACTERIZING TO DEFINE DIFFICULTIES OF MINING IN SOROWAKO AREA, SOUTH SULAWESI

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

ROCK FRACTURE DENSITY CHARACTERIZING TO DEFINE DIFFICULTIES OF
MINING IN SOROWAKO AREA, SOUTH SULAWESI

Fatrial Bahesti & Gde Handojo Tutuko^'
'Exploration and Mine Development, PT INCO,Tbk
ABSTRACT

The abundance of shear fractures is described through the evaluation of fracture density. Fracture density can be measured in a number of ways; average spacing of fractures; number of fractures in given area; total cumulative length of fractures; and surface area of all fractures within a given volume of rock. Local geology structure and geomechanics approach is used to deal with outlining rock type boundary for estimating geologic framework; fracture density (FD) and rock quality designation (RQD) which related to weathered rock boulder in lateritic mass.

Knowledge of rock fracture properties allows us to define difficulties of mine and laterite development. Highly rock fractured will increase weathering degree because of larger surface of rock. Thus, fracture is related to boulder forming that enriched by economic mineral as well as laterite development. The result of these studies addressed rock fractured classification which controlled by area with low (type 1), medium (type 2) and highly (type 3) fractured in specified Sorowako mining area. These would reveal us to have an even more define of mining difficulties to reach maximum ore recovery.

MODEL OF REEF DEVELOPMENT IN RESPONSE TO SEA LEVEL FLUCTUATION AND ISOTOPE STRATIGRAPHY OF PACIRAN FORMATION, EAST–JAVA

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

MODEL OF REEF DEVELOPMENT IN RESPONSE TO SEA LEVEL FLUCTUATION
AND ISOTOPE STRATIGRAPHY OF PACIRAN FORMATION, EAST–JAVA

Premonowati ¹, Koesoemadinata, R.P. ² , Pringgoprawiro, H. 2 &
Hantoro, W, S.³.

¹ Department of Geological Engineering, FTM, UPN Yogyakarta,
E-mail: premonowati_geo@yahoo.com
² Prof. Emiritus – Dept. of Geo. Engineering. - Institut Teknologi Bandung, Indonesia.
³ Puslitbang Geoteknologi LIPI, Indonesia.

ABSTRACT

25 samples have been choose on non deformed calcite and analyzed by (oxygen and carbon) stable isotope. It used to validizing a sea level changes during Reef 1 to Reef 12 formation (since 4 Ma to Recent) from Paciran formation with sea surface temperature (SST).

On early forming of Reef 1 to Reef 3 (since 4 – 2.88 Ma), sea level occurred marine flooding surface or temperature warmer. Since Reef 4 formation (2.59 Ma) to Reef 8 formation (1.4 Ma) occurred stagnant temperature and almost to warmer condition. Then, δ¹⁸O drop drastically to 5‰ and shows warmer condition to reef 8 formation or sea level rise, even to Reef 10 formation (0.7 Ma). The temperature have been fluctuated between 0.5^o and 1^oC until Reef 12 forming (Early Holocene) and continue to Reef 12 formation at 2^oC based on the rapidity sampling of Porites sp.

Wholly, curve of oxygen stable isotope shows decreasing or cooler condition since Reef 7 and Reef 8 formation. Recently, a curve of oxygen isotope reveals warmer drastically or sea level have been arisen.

CHARACTERISTICS OF THE ROOT OF Cu-Au PORPYRY SYSTEM: RESULTS OF STUDY FROM BATU HIJAU Cu-Au PORPHYRY DEPOSIT

PROCEEDINGS PIT IAGI RIAU 2006
The 35^th IAGI Annual Convention and Exhibition
Pekanbaru – Riau, 21 – 22 November 2006

CHARACTERISTICS OF THE ROOT OF Cu-Au PORPYRY SYSTEM: RESULTS OF STUDY FROM BATU HIJAU Cu-Au PORPHYRY DEPOSIT

Setyandhaka, D. & Arif, J.
Mine Geology Department, PT Newmont Nusa Tenggara, NTB - Indonesia.
ABSTRACT

Batu Hijau shares many similar characteristics to porphyry copper-gold deposits and the geology of Batu Hijau is an example of classic Cu-Au porphyry system. Compared to many typical porphyry deposits; it has very minor overprints of later alteration and mineralization. Copper and gold mineralization is directly related to quartz veining and wall rock alteration that developed with multiple tonalite porphyry intrusion.

Detailed geological logging, petrography analyses and assays results of the diamond drill cores from the upper level to the deep portion of world class Batu Hijau porphyry copper-gold system shows the high grade ores containing both copper and gold in deep portion are occupied within the host rock intrusion body of tonalites associated igneous breccia, and wall rocks of volcanics and quartz diorite. The ores from the bottom zone containe approximately 1% Cu and 2 g/t Au which are present consistently down to -600 m elevation. Hydrothermal alteration and mineralization in deeper parts show that the quartz veins are dominantly early A-veins and B-veins with the density ranges from 8-15 percent and bornite ± chalcopyrite mineralization.

Below the -600 m elevation, the mineralization is almost barren even though the quartz veins consistently are high in density (>5%) and consisted of B and D type veins. The total sulfide content of barren ore at depth is significantly decreased and it is dominated by pyrite-magnetite with trace of chalcopyrite. The magnetite and quartz grains tend to have coarser grain at barren ores.

This paper describes the characteristics of the root of Cu-Au porphyry system at Batu Hijau deposit and examined the distinction of geological characteristics in deep and shallow parts of the porphyry system by detail geological logging, petrography analyses, thin section and assays results work of the diamond drill cores.