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.

MICROFACIES DEVELOPMENT OF THE SELAYAR LIMESTONE SOUTH SULAWESI

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

MICROFACIES DEVELOPMENT OF THE SELAYAR LIMESTONE SOUTH SULAWESI

A. M. IMRAN ¹
ROMAN KOCH ²

¹ Geological Department, Hasanuddin University, Makassar
² University of Erlangen-Nuernberg, Germany.

ABSTRACT

The Selayar Limestone was mapped as a member of the Walanae Formation and was developed in the southern tip of South Sulawesi during the Late Miocene to the Pliocene (Sukamto & Supriatna 1982). This study, conducted in two areas of eastern Bulukumba, South Sulawesi. The study reveals four reef units of development, which shifted from an older reef formation in the northern part (Bontotiro area) to a younger formation in the southern part (Bira area). The units corresponding to the age of the reefs are the: a) lower Late Miocene B-1 unit. The B-1 Unit of the Bontotiro area is predominantly composed of large foraminiferal limestone, which form knoll-like hills; b) upper Late Miocene to Pliocene B-2 and Upper Terrace Unit. The B-2 Unit in the upper part of the Bontotiro area and the Upper Terrace Unit of the Bira area are considered as the same development unit because they are of the same age; c) Pliocene coralgal reefs of the Middle Terrace Unit. The Middle Terrace Unit is characterized by Halimeda limestone and well-preserved fibrous cements; d) Pleistocene coral reefs of the Lower Terrace. The Lower Terrace Unit is dominated by coral reefs and was formed from reef flank seaward and reef framework leeward.

Keywords: Microfasies, Unit Facies, Terraces, Selayar Limestone.

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

CHATODOLUMINESCENCE MICROSCOPIC ANALYSIS TO INTERPRET THE
REDOX CONDITION DURING THE FORMATION OF CARBONATE VEIN

Warmada, I W.^' & Hartati, R.^'
1Department of Geological Engineering, Gadjah Mada University, Yogyakarta 55281
ABSTRACT

Cathodoluminescence (CL) is generated by an electron gun coupled to an optical microscope. There are two types of chatodoluminescence, i.e., cold CL and hot CL. In the cold cathode microscopic equipment, the electrons are generated by an electric discharge between two electrodes under a low gas pressure, whereas in the hot CL microscope, the electrons are generated by heating a filament (2000-3000°C). In this paper we utilize cold CL combine with electron microprobe analysis (EMPA). The CL microscopy of carbonate shows at least three carbonate generations, i.e., rhodochrosite with dull or no luminescence, Mg-rich calcite with dark red luminescence, manganese-bearing calcite with up to 0.04 wt.% Mn with bright orange luminescence, and pure calcite and Mn-rich calcite (> 0.15 wt.% Mn) with dull or no luminescence. The result also suggests that the luminescence pattern of calcite is controlled by the amount of Mn²⁺. Sectoral zoning and chevron-shape growth zoning exist in some coarse-grained calcite aggregates. The sectorial zoning of calcite as reflected by dull to bright CL color indicated that slightly to more reducing environment during calcite deposition.

Keywords: Chatodoluminescence, rhodochrosite, calcite, sectorial zoning

GRADE CONTROL ACTIVITIES, A METHOD TO DETERMINE Au-Ag GRADE IN TOGURACI GOLD PROJECT

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

GRADE CONTROL ACTIVITIES, A METHOD TO DETERMINE Au-Ag GRADE IN
TOGURACI GOLD PROJECT

Ewa F Rappe^'
'Mine Geology Department, PT. Nusa Halmahera Minerals
ABSTRACT

Toguraci is located in the North Maluku province of Eastern Indonesia, on the north arm of the island of Halmahera. It is a classic example of a volcanic-hosted, low-sulphidation, epithermal quartz vein deposit. Mining at Toguraci commenced in the last quarter of 2003 and has produced >180 KOz per annum since.

Grade control activities include 1:200 scale geologic trench mapping, face sampling, and reverse circulation drill hole sampling. Trench mapping (+/- sampling) is undertaken on each 5 meter bench, face sampling on each 2.5 meter bench, while reverse circulation drilling is completed at each 15 meters bench. Information gathered includes lithology, alteration, mineralization, structure, and quartz percentage which are stored digitally in MS Access and are run under SURPAC software. Data used for the compilations typically comprise over 21,300 m of reverse circulation drill data and 3,000 m of trench mapping data.

Reverse Circulation (RC) drill data is primarily used for reserve calculation for each 15 meter cut. This data is very good for reserve – resource comparison to improve Toguraci deposit model, better exploration understanding through adjacent area, and to help mine engineers to redesign pit boundary if necessary to obtain optimize stripping ratio. Trench, RC drill and face sample data are very crucial for Au-Ag determination.

THE KEY ROLE OF MINERALOGY AND ORE CHEMISTRY IN OPTIMIZING METALLURGICAL PROCESS OF NICKEL LATERITE

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

THE KEY ROLE OF MINERALOGY AND ORE CHEMISTRY IN OPTIMIZING
METALLURGICAL PROCESS OF NICKEL LATERITE

Agus Superiadi^1
1Superintendent of Ore Quality Assurance, PT INCO Sorowako, South Sulawesi

ABSTRACT

PT INCO processing plant requires consistent ore feed to maximize its production capacity. The consistency of the feed is really driven by mineralogy and ore chemistry of the nickel laterite ore. To extract nickel from laterite ore, PT Inco is using a pyrometallurgy process to produce nickel matte (78% nickel content). Most of the constraints in the Processing Plant are on Electrical Furnaces where the smelting processes occur to separate nickel matte and slag. The processing plant must produce on- specification Electrical Furnace Slag and also on-specification Electrical Furnace Matte. Ore blending efforts at the mine must focus on producing: 25-28% Ni in matte, 9-10% S and the balance is Fe and also producing slag with 16-20% Fe and 2.05-2.25 SiO2/MgO ratio. The variability of Fe and SiO2/MgO ratio are playing the most important role in controlling the melting point and viscosity of the slag, which is very critical for electrical furnace operation. The olivine content of the ore for electrical furnace feed must also be controlled at minimum level to prevent smelting problem since olivine has very high melting temperature. The precipitated olivine in the slag-matte contact will reduce the heat transfer from the slag to the matte that may also cause tapping/skimming difficulties.

In summary to maximize process plant throughput, the ore chemistry and mineralogy must be controlled in such a way that the ore would be able to melt easily, the furnace wall would be protected, and electrical furnace matte and slag are produced on desired chemistry specification. To achieve this, complete geological knowledge of the ore body particularly on mineralogy and ore chemistry is really important to manage mining, ore blending, and metallurgical processing of the ore.