The key difference between stromatolites and thrombolites is that stromatolites are layered sedimentary formations generated by cyanobacteria, while thrombolites are non-layered sedimentary formations generated by cyanobacteria.
Stromatolites and thrombolites are both organosedimetary formations that have fascinated scientists over the past years. Stromatolites have a layered structure, while thrombolites have clotted or clustered structures. Modern stromatolites are mainly found in hypersaline lakes and lagoons. Thrombolites are typically found in areas of groundwater discharge that have a high concentration of nutrients and organic acids. Stromatolites and thrombolites both have great importance because they contain the oldest evidence of life on earth.
CONTENTS
1. Overview and Key Difference
2. What are Stromatolites
3. What are Thrombolites
4. Similarities – Stromatolites and Thrombolites
5. Stromatolites vs Thrombolites in Tabular Form
6. Summary – Stromatolites vs Thrombolites
What are Stromatolites?
Stromatolites are layered sedimentary formations generated by cyanobacteria. They are layered rocks or microbial reefs that are created by photosynthetic cyanobacteria. The formation of stromatolites is due to sediment trapping, binding, and precipitation activities of microbial communities. These structures normally build up very slowly. A single 1 m structure can be 2000 to 3000 years old. Very interestingly, tiny microbes that produce modern stromatolites are very similar to those that existed 3.5 billion years ago.
Figure 01: Stromatolites
Stromatolites have active microbes on the surface layer. The underlying part is a lithified remnant of former microbial surface communities. Therefore, stromatolites can be used as trace fossils. Stromatolites are one of the reasons why people are alive today. Before the existence of cyanobacteria in stromatolites, the atmosphere had only 1 % oxygen. Then the photosynthetic cyanobacteria in stromatolites pumped oxygen into oceans. When the oceans were saturated with oxygen, the oxygen was released into the atmosphere. Today, there is around 20 % oxygen in the air, so live organisms are able to flourish and evolve. Even today, stromatolites that are under the water release oxygen to the atmosphere.
What are Thrombolites?
Thrombolites are non-layered sedimentary formations generated by cyanobacteria. They are clotted accretionary structures or formations that are created due to the trapping, binding, and cementation processes of biofilms of microorganisms, especially cyanobacteria. Thrombolites have a clotted structure. Each clot within thrombolites has a separate cyanobacterial colony. The clots are millimetres to centimetres in size. The clots are also interspersed with sand, mud, or sparry carbonate. These clots that make up thrombolites are called thromboids. Moreover, each clot has a complex internal structure of cells and rimmed lobes that are primarily due to the calcification of the cyanobacterial colony.
Figure 02: Thrombolites
There are two types of thrombolites: calcified microbe thrombolites and coarse agglutinated thrombolites. Thrombolites can be distinguished from microbialites or stromatolites due to their massive size. Calcified microbe thrombolites occurred in sedimentary rocks during the Neoproterozoic and Palaeozoic eras. Therefore, they can be used as ancient fossil records.
What are the Similarities Between Stromatolites and Thrombolites?
- Stromatolites and thrombolites are both organosedimetary formations.
- They are both very old structures.
- Cyanobacteria are the microbial communities found in both structures.
- Stromatolites and thrombolites both have great importance because they contain the oldest evidence of life on earth.
- They can be used as ancient fossil records.
- Both are very important to earth as they release oxygen to the atmosphere.
What is the Difference Between Stromatolites and Thrombolites?
Stromatolites are layered sedimentary formations that are generated by cyanobacteria, while thrombolites are non-layered sedimentary formations that are generated by cyanobacteria. Thus, this is the main difference between stromatolites and thrombolites. Furthermore, stromatolites are not massive in size, while thrombolites are massive in size.
The below infographic lists the differences between stromatolites and thrombolites in tabular form for side by side comparison.
Summary – Stromatolites vs Thrombolites
Stromatolites and thrombolites are organosedimetary structures that show great importance as ancient fossil records. Stromatolites are layered sedimentary formations generated by cyanobacteria. Thrombolites are non-layered sedimentary formations generated by cyanobacteria. So, this is the key difference between stromatolites and thrombolites.
Reference:
1. “Stromatolites: The Earth’s Oldest Living Lifeforms.” BBC Travel, BBC.
2. “Thrombolite.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Red-caps-australia-stromatolite” (CC0) via Pixabay
2. “Lake Clifton SMC 2008” By SeanMack – Own work (CC BY 3.0) via Commons Wikimedia