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.

CALCAREOUS NANNOFOSSILS BIOSTRATIGRAPHY OF NGALANG RIVER SECTION, SOUTHERN MOUNTAIN AREA, GUNUNG KIDUL, YOGYAKARTA

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

CALCAREOUS NANNOFOSSILS BIOSTRATIGRAPHY
OF NGALANG RIVER SECTION, SOUTHERN MOUNTAIN AREA, GUNUNG KIDUL, YOGYAKARTA

Akmaluddin^', T. Susio^', and W. Rahardjo^'
'Department of Geology, Gadjah Mada University
ABSTRACT

Total of 46 samples were collected from Miocene age of Ngalang River section. Those samples yield abundant calcareous nannofossils contents which belong to Sambibitu and Oyo Formation. Biozonation were done based on standard procedure of first and last occurrences of taxa which are widely known as standard zone indicators. The result of this study shows that there are 59 taxa known on Sambipitu and Oyo Formation and can be sub-divided into seven interval zone and one range zone.

Sambipitu formation shows 5 zones (NN2-NN6) which equals to Early Miocene to Middle Miocene while Oyo Formation shows 3 zone (NN8-NN10) which are equals to Middle Miocene to Late Miocene. These results indicated that there is a gap between Sambipitu and Oyo Formation with the absence of NN7 not founded. That means there is an unconformity between of them. Based on nannofossils date, it appears that all of the formations show younger age than which has been dated previously.

DIAGENETIC ALTERATION IN LATE MIOCENE CARBONATE OF TACIPI AREA, SOUTH CELEBES.

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

DIAGENETIC ALTERATION IN LATE MIOCENE CARBONATE OF TACIPI AREA, SOUTH CELEBES.

Andri Slamet Subandrio^'

^'Dept. of Geology, Faculty of Earth Science and Mineral Technology, Institut Teknologi Bandung,
Jl. Ganesha No. 10 Bandung 40132, Email : andri@gc.itb.ac.id

ABSTRACT

The Tacipi carbonate platform is a part of Neogene East and West Sengkang Basin that are located in the south part of Sulawesi, precisely in western of Bone city. The limestones of this area, outcropping mainly on the north-south oriented hills such as Temapole, Anadara, Tamping, Lappa, etc., are the best reef example in the Tacipi area, as the reef itself, its debris and detritus can be distinguished in the field. Throughout the ridges and pinnacle in Tacipi field the limestones are predominantly homogenous boundstones on the top and detrital bioclastic packstones with local grainstones, and wackestones at the bottom. Bioclasts are mainly of branching finger-like corals, bivalves and calcareous algae with gastropods, foram and echinoderms. Generally the size of bioclast varies from fine to coarse grained and large coral fragments are common. Calcareous algae and corals in growth position is abundant, embedded in a micritic cements which are partly altered to sparry calcite due freshwater cementation. This reef debris facies occur in the lower part of ridge or pinnacle as inter-reef between the ridges. It is characterized by a changeable facies of rudstones-packstones, wacke stone and mudstones. There are four major reef zonation indentified pacth reef, barrier reef, fore reef and lagoon. The extensive freshwater leaching of fossil fragments and calcareous cement give the preservation of biomouldic and vug pore spaces.

THE OCCURRENCE OF A NEWLY FOUND EOCENE TECTONIC MELANGE IN KARANGSAMBUNG AREA, CENTRAL JAVA

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

THE OCCURRENCE OF A NEWLY FOUND EOCENE TECTONIC MELANGE IN KARANGSAMBUNG AREA, CENTRAL JAVA

C. Prasetyadi ¹ , E.R. Suparka ² , A.H. Harsolumakso ² , B. Sapiie ² .

¹ Jurusan Teknik Geologi, FTM-UPNV, Jalan Lingkar Utara, Condongcatur, Jogjakarta.
² Department of Geology, FIKTM- ITB, Jalan Ganesha No.10, Bandung.

ABSTRACT

Based on the 2004-2005 field work in the northern part of Karangsambung area this study presents new evidences for the occurrence of Eocene tectonic melange in the area. Previous studies have mapped the northern area of Karangsambung as part of the Cretaceous Luk Ulo Melange Complex. In this area, especially in the Larangan area, the present study discovered for the first time Middle Eocene Asterocyclina-bearing limestone blocks within the tectonic melange. The occurrence of Middle Eocene limestone blocks indicates the age of tectonic melange rock in this area is no longer of Cretaceous but at least of Late Eocene. If Luk Ulo melange complex indicates the presence of Cretaceous-Paleocene northwestward-plunging subduction zone then it is expected to the north we should find the older part of the melange. The presence of Eocene tectonic melange to the north of the Cretaceous-Paleocene subduction melange does not fit with this model and indicates that deformation phases responsible for both melanges are different. Based on our field work we propose a new model for the tectonic evolution of the area that the shifting of NE-SW trend of Cretaceous subduction to E-W trending in the Oligocene time has occurred due to collision of a micro-continent. It is concluded that the Late Cretaceous to Paleocene subduction occurred in the subduction zone where the Luk Ulo Mélange Complex was formed. The sub-sequence overlying Paleogene (Eocene) series were deposited, following by collision in the Late Eocene – Early Oligocene as indicated by the occurrence of Eocene tectonised rocks prior to the onset of the OAF (Old Andesite Formation) new subduction-related volkanism.

WEATHERING OF SOME SELECTED ROCK TYPES AND THEIR STRENGTH DEGRADATION OBTAINED FROM SCHMIDT HAMMER

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

WEATHERING OF SOME SELECTED ROCK TYPES AND THEIR STRENGTH DEGRADATION OBTAINED FROM SCHMIDT HAMMER

Imam A. Sadisun ¹, Andri S. Subandrio ¹, Asep Nurjamil ¹, Prihananto Setiadji ²

¹ Research Division on Applied Geology , Faculty of Earth Science and Mineral Technology,
Bandung Institute of Technology, Bandung.

² Department of Mineral Technology , Faculty of Engineering, Cendrawasih University, Papua

ABSTRACT

Weathering generally develops in irregular depth and intensity controlled by some very complex factors, whether from internal or external factors of the rock, such as climatic condition, topography/morphology, groundwater, and organism activity. Differences in result of weathering are almost gradual and often reflected by regular patterns in weathering profile. Due to similarity of weathering products, it is possible to establish a classification scheme and systematic description of weathered rock.

In this study, an effort was made to know some sequences of changes in different degree of weathering of selected rock types, which are andesite, diorite, limestone, claystone and tuff. In addition, the influence of weathering in weakening of the rocks was assessed based on the data obtained from a Schmidt hammer test. Site-specific classification schemes have been developed for each rock type. The correlations between weathering grade (WG) and Schmidt hammer value (SHV) have been derived. It is very clear that weathering will lead to a significant reduction in rock strength.

Keywords: rock, weathering, weathering grade, strength, Schmidt hammer