MGG Student Seminar – 3/8/11 – 12:00 pm – 1:00 pm CIMAS Conference Room
Indonesian Lake Stromatolites
Irena Andisa Maura
Stromatolites are one of the oldest fossil known, some dating were shown that the age of
stromatolites might reach 3.5 billion years old. Main component of stromatolites are huge
colonies of cyanobacteria and some scientists consider these bacteria to be the earliest life form
on Earth. The cyanobacteria as a main builder of stromatolites create the blocks of life especially
oxygen and the other elements such as carbon and nitrogen. Therefore, in order to study the
mystery of the earth’s life evolution, knowing about stromatolites is worthwhile. Nowadays,
ancient stromatolites are nearly extinct in marine environment and they only can be found in a
few localities worldwide. The reason of why stromatolites only can grow in few places because
stromatolites required very extreme water environment. Thus, modern analogue of the
stromatolites are needed in order to study their characterization. One places in Indonesia where
we can found the modern stromatolites is Satonda Lake, a lake in Indonesia where modern
stromatolites flourished. Satonda Lake is a small remnant volcanic island located to the north of
Sumbawa at the Flores Sea, Indonesia. The island has a crater lake filled with seawater.
Moreover, because the lake has lost all direct connections with the surrounding sea due to
tectono-volcanic events, the lake environment has changed to be extreme with high alkalinity
and salinity. Another reason why studying the stromatolites is important because it’s potential to
become a hydrocarbon reservoir. Hydrocarbon bearing stromatolites are found in Oman,
Montana and New Mexico with the age of stromatolites are in range from Precambrian to Lower
Paleozoic. Although, Indonesian stromatolites are modern and can not be a precise analogue for
Precambrian to Lower Paleozoic stromatolites because of geologic time differences. However,
Satonda Lake stromatolites can also provide lessons for evaluating ancient stromatolites as
objectives of hydrocarbon exploration.
The Ultrasonic Velocity and Pore Shape/Structure
Albertus Ditya
Ultrasonic wave is being used in wide purposes, such as in medical, communication, jewelry
cleaning, food industry, and non destructive testing/evaluation. The ultrasonic is utilized in many
different subject as a proxy to do a non destructive test or evaluation, for example; finding a
cheese melting temperature, knowing optimum firing temperature in the material industry, and
studying acoustic properties of rock as an analog to the seismic data in the earth science. It is
known for a long time that pore structure has influences in the acoustic wave propagation, not
only in geology but also other different fields. In ceramic industry, they found that the pore
shape influences ultrasonic wave velocity. In my thesis, I examine reefal limestone using
ultrasonic wave to better understand the influence of pore structure in ultrasonic wave
propagation. Ongoing result, the complexity of pore has major influence to the
velocity. By adding pore structure as element or variable in velocity - porosity linear regression
analysis, the correlation coefficient of velocity and porosity relationship is improved.