Text

Umur batu bara

Pembentukan batu bara memerlukan kondisi-kondisi tertentu dan hanya terjadi pada era-era tertentu sepanjang sejarah geologi. Zaman Karbon, kira-kira 340 juta tahun yang lalu (jtl), adalah masa pembentukan batu bara yang paling produktif dimana hampir seluruh deposit batu bara (black coal) yang ekonomis di belahan bumi bagian utara terbentuk.

Pada Zaman Permian, kira-kira 270 jtl, juga terbentuk endapan-endapan batu bara yang ekonomis di belahan bumi bagian selatan, seperti Australia, dan berlangsung terus hingga ke Zaman Tersier (70 - 13 jtl) di berbagai belahan bumi lain।

Hampir seluruh pembentuk batu bara berasal dari tumbuhan. Jenis-jenis tumbuhan pembentuk batu bara dan umurnya menurut Diessel (1981) adalah sebagai berikut:

Alga, dari Zaman Pre-kambrium hingga Ordovisium dan bersel tunggal. Sangat sedikit endapan batu bara dari perioda ini.
Silofita, dari Zaman Silur hingga Devon Tengah, merupakan turunan dari alga. Sedikit endapan batu bara dari perioda ini.
Pteridofita, umur Devon Atas hingga KArbon Atas. Materi utama pembentuk batu bara berumur Karbon di Eropa dan Amerika Utara. Tetumbuhan tanpa bunga dan biji, berkembang biak dengan spora dan tumbuh di iklim hangat.
Gimnospermae, kurun waktu mulai dari Zaman Permian hingga Kapur Tengah. Tumbuhan heteroseksual, biji terbungkus dalam buah, semisal pinus, mengandung kadar getah (resin) tinggi. Jenis Pteridospermae seperti gangamopteris dan glossopteris adalah penyusun utama batu bara Permian seperti di Australia, India dan Afrika.
Angiospermae, dari Zaman Kapur Atas hingga kini। Jenis tumbuhan modern, buah yang menutupi biji, jantan dan betina dalam satu bunga, kurang bergetah dibanding gimnospermae sehingga, secara umum, kurang dapat terawetkan.

Sabtu, 17 Mei 2014

LEIGHTON HOLDINGS

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Conditional Settlement of Leighton Class Action

16 May 2014 Leighton Holdings Limited announces that it has entered into a conditional agreement to settle the shareholder class action brought against it in relation to... View PDF (1.2 MB) Conditional Settlement of Leighton Class Action (PDF - 1.2 MB)

John Holland awarded $100 million project in Western Australia

16 May 2014 John Holland has been awarded a contract worth approximately $100m for mine infrastructure by Rio Tinto in the Pilbara region of Western Australia. View PDF (680.6 KB) John Holland awarded $100 million project in Western Australia (PDF - 680.6 KB)

Industry Applauds Winner of Australian Construction Achievement Award

9 May 2014 The Australian Constructors Association (ACA) and Engineers Australia (EA) today applauded the John Holland Group, winner of the ... View PDF (1.2 MB) Industry Applauds Winner of Australian Construction Achievement Award (PDF - 1.2 MB)

South West Rail Project Wins National Award

8 May 2014 Minister for Transport Gladys Berejiklian today announced the South West Rail Link project won the 2014 Railway Project of the Year ... View PDF (1.1 MB) South West Rail Project Wins National Award (PDF - 1.1 MB)

Annual General Meeting Webcast

19 May 2014 Watch the live AGM webcast at 10am AEST, Monday 19 May 2014. Test your computer's ability to view the webcast before the event, or access the webcast on the day. Visit Site Annual General Meeting Webcast This external link will open in a new window

Leighton reports 1Q14 NPAT of A$152m, reiterates guidance

6 May 2014 Leighton Holdings Limited today announced its results for the three months to 31 March 2014 ... View PDF (560.7 KB) Leighton reports 1Q14 NPAT of A$152m, reiterates guidance (PDF - 560.7 KB)

Leighton to build Segment 10 of the North Luzon Expressway

1 May 2014 Leighton Asia, India and Offshore has secured an US$201 million contract from Manila North Tollways Corporation (MNTC) to construct Segment 10 of the North Luzon Expressway ... View PDF (471.4 KB) Leighton to build Segment 10 of the North Luzon Expressway (PDF - 471.4 KB)

Leighton awarded contract to build HK-Zhuhai-Macao Passenger Clearance Building

28 April 2014 Leighton Asia, in a joint venture with Hong Kong construction company Chun Wo, has secured a contract worth AU$1.16 billion to construct the Passenger Clearance Building ... View PDF (293.0 KB) Leighton awarded contract to build HK-Zhuhai-Macao Passenger Clearance Building (PDF - 293.0 KB)