Narikel Jinjira is a dumbbell – shaped sedimentary continental island located on an eastern flank of an anticline, which like Chittagong my be part of the Arakan Yoma Naga folded system. The surface area of the island is about 8 squire km depending of tidal level.

The island may be divided into 4 distinct physiographic area 1)Uttarpara; 2) Golachipa; 3)Dakhinpara 4) Cheradie

Uttarpara is the northern part of thfe island with a maximum width ( along the E to W axis) is about 1 km. The topsoil of length along the S to N axis of Uttarpara consists of alluvial sands mixed with marine calcareous deposits. Scattered throughout the area are small clumps of coral colonies many still on growth position. A large shallow lagoon is located in the middle of Uttarpara.The lagoon has been largely converted into agricultural fields, and is connected to the sea at high tide by a narrow tidal channel on the west coast. The remaining flooded part of the lagoon has been largely converted into agricultural fields, and is connected to the sea at high tide by a narrow tidal channel on the west coast. The remaining flooded part of the lagoon has an area of about 0.4 squire km with a depth of 1 m or less.

The southern part of the island is divided into the northern and southern Dakhinpara. Maddhyapara is about 1.2 km long and about 350 m wide, while Dakhinpara is 1.5 km long and about 900m wide. The topsoil of these two areas is similar to that of Uttarpara. Pleistocene calcareous deposits, coined the coquina beds are also found on Dakhinpara.

Uttarpara is separated from Dakhinpara by a narrow neck locally known Golachipa. Golachipa is a beach and dune environment. Extending from the southern part of Dakhinpara in an SSE direction is a rocky reef that is about 1.8 km long and between 50to300m wide. Located on this intertidal rocky reef are 3 vegetated islands locally known as Siradia. Surficial deposits on the Siradea have a high content of molluscan shells when compared to the northern parts of the island.

Almost the entire coastline of Narikel Jinjira is fringed by a unique rocky intertidal. The width of the rocky intertidal at spring low tides varies from 100 to 400m. The rocky intertidal is formed

by smsll and large boulders, which according to Alam and Hassan are genetically related to the bed rocks of the island.In addition, many of the spherical boulders are calcareous concretions . Coral boulders are also present but these are relatively rare and in no place do they form a coherent feature that can be called a coral reef.The presenceof relatively well preserved dead coral colonies in the upper and middle intertidal suggests that the island has been uplifted in relatively recent times.

The recent uplift on Narikel Jinjira is evident from the presence of large Porites microatolls, which are found in the lower intertidal on the north west coast of Uttarpara . The morphology of these microatolls suggests that the relative sea level has dropped by about 15 cm during the last 150 years or so. This rough estimate is based on the size and average growth rates of the microatolls. Clearly this is an exciting area for new research. the s3edimentary boulders, calcareous concretions, sandstone and shale found in the intertidal area extend into the subtidal. The rocky subtidal along the west coast of the island is much wider than along the east coast. A number of offshore rocky reefs along the west coast become exposed during low spring tides. However, island was reported to be encircled by a cluster of smaller islands (Anwar, 1988). There are only 3 vegetated islands on the south coast of Narikel Jinjira, locally known as the Siradia. These three islands can be classified as "vegetated sand islands", since they have developed from the accumulation of both alluvial sands and calcareous littoral deposits, During the low tides, the sand islands are connected with the southern part of Narikel Jinjira by a narrow

sand belt (consisting of alluvial sand and littoral carbonates) which has accumulated on the top of a rocky intertidal reef. A number of non-vegetated rocky outcrops are found on the north wet coast of Uttarpara. These sup0ratidal outcrops are the seaward continuations of the rocky intertidal.

A detailed description of the lithology and stratigraphy of Narikel Jinjira, clearly states that: "Corals do not form a continuous reef but occur as clusters along the eastern, southern, and south-western shore........". Provides the following strait graphic succession of St. Martin Island.

Source: http://www.stmartinsbd.org