Inventory and identification of geodiversity to support geotourism in the Lenggoksono bay area of South Malang, Indonesia

Lenggoksono Beach Area which is a geomorphological region in the form of karst mountain located in the south of Malang Regency. This beach has beautiful scenery and presents unique and an interesting geosite conditions to be enjoyed. The purpose of this study is to inventory geodiversity data to fulfill the geotourism criteria and assess geodiversity data in the Lenggoksono Bay Area. The research method used was a survey and data collection method with 5 stages: data collection, criteria, assessment, interpretation, and clustering. The Lenggoksono Bay area has 5 landscapes, 4 beaches, islands, hills, and a river estuary. From the survey results, 6 types of rocks were found. Lenggoksono Bay was formed through the process of lifting the seabed containing limestone and coral reefs and igneous rock deposits over millions of years ago. These processes form the morphology and structure that has developed until present. The Lenggoksono Bay area has high value (4.4), where it contains scientific records, specific geological settings or landscapes. This is very meaningful, as an evidence of important geological events, and has special ecological functions that can be utilized for research, education, understanding of geological processes, and conservation. This area includes areas that comply the criteria to become geotourism.


Introduction
Geotourism is a branch of cognitive tourism or adventure tourism that emphasizes geological features, including geological objects (geosites) and recognition of geological processes [1,2]. Geotourism under the umbrella of ecotourism is tourism linked to the geological character in a place or region that has a principle of sustainability [3,4]. Thus Geotourism can be used as a concept of development of the South Malang Karst Area or it can be used as a bridge of development without abandoning the principles of sustainability. Lenggoksono Beach Area which is a geomorphological region in the form of mountains which composed of limestone and karst and located in the South of Malang Regency. It has beautiful scenery and presents unique and interesting geosite conditions to be enjoyed. The Lenggoksono Beach area is one of the seven potential geosites to be developed as a tourism With the development of geotourism in the Lenggoksono Coastal Region, Geopark which has several benefits will be obtained both for regional development and economic improvement. To be able to develop the existing Geotourism in Lenggoksono Bay, it is necessary to inventory and identify the existing Geodiveristy in the area.

Research Location and Date
The implementation of research was conducted from April 2019 to May 2019. The final project will be carried out at Lenggoksono Beach, Purwodadi, Tirtoyudo, Malang, East Java.

Research Method
The implementation of this final project uses the method of literature study, survey and data collection approach. The stages of the study are divided into 5 stages:

Data Collection:
Data sources in this research are primary and secondary data.

Criteria.
The criteria for assessing geodiversity are described as in Table 1:

Interpretation:
Interpretation aims to determine the meaning of Geodiversity from several aspects [5]: 1. Geodiversity is scientific, if it is a record and evidence of the evolution of the earth 2. Geodiversity means aesthetics, if it has a uniqueness and natural beauty 3. Geodiversity means recreation, if it has the potential to support tourism 4. Geodiversity means culture, if it has historical and cultural aspects

Clustering
Clustering aims to establish the function of Geodiversity. There are 4 clusters in geodiversity [5]: 1. As an artifact of earth's history, where geological diversity has the ability to explain the history of the earth, whose information can be used as a basis for geological resource management activities, including predictions of upcoming geological events

Landscape Criteria
Landscape criteria are geotourism criteria of a location consisting of mountains, hills, plains, islands and volcanoes.  According to the data on the Topographic Map (Figure 1) in the Lenggoksono Bay area there are mountains shown on the map namely Cengger and Butak Mountain on the west side of Lenggoksono Beach. For the hilly criteria, it can be seen on the map, the contour shape shows that there are hills in the Lenggoksono Bay Area. One of the hills located between Wedi Awu Beach and Lenggoksono Beach is Bukit Tumpak Wi. There are 2 small islands in the south, i.e. Simun and Kalong Island. In the volcanic landscape criteria, according to the Purwodadi Village Geotourism Map [6], there is a geomorphological type of the Mandalika Formation formed from andesite, basalt, trachts, and andesite breccias as a result of magmatic activity taking place from the age of Eocene to recent of ~45 Ma [7]. There are 4 beaches at Lenggoksono Bay:

Lenggoksono Beach
This beach is included in the Mandalika formation. Lenggoksono Beach Tourism can be used to do activities such as swimming, surfing and snorkeling. Lenggoksono Beach has a beautiful beach length of ± 60 meters surrounded by high cliffs and lush and green trees (Figure 2).

Wedi Awu Beach
Known as one of the good surfing spots in Malang Regency. When entering the dry season or when the full moon the waves at Wedi Awu Beach are quite good and the height can reach 3 meters. For beginner surfers, they can surf at Lenggoksono Beach because the bottom of the beach is sand, so it is relatively safer compared to Wedi Awu Beach which has a rock ( Figure 3).

Bolu-Bolu Beach
Bolu-Bolu Beach has white sand and clear sea water. Bolu-Bolu Beach is also a sunrise attraction. Visitors can also enjoy snorkeling tours underwater beauty of Bolu-Bolu Beach. There have been many tourists who admire going to this beach; local and overseas tourists. Generally, foreign tourists also tour camping here to see the sunrise ( Figure 4).

Banyu Anjlok Beach
Basin-shaped like a bay that is actually part of a cluster of beaches from a larger bay. Banyu Anjlok Beach has a beach with calm waves so it is safe as a swimming destination on Banyu Anjlok Beach. The main destination of this beach is a waterfront beach facing the sea ( Figure 5). Above the waterfall, there is also a freshwater pool This freshwater pool can also be used as a tourist destination for swimming and diving ( Figure 6).
So, from the above data it can be concluded that the landscape criteria, get a score of 5.

Rock Domain Criteria
Rocks found in the hills, valleys and beaches of Lenggoksono Bay are listed as in Figure 7.

Internal and External Process Criteria
Internal processes are shown by the existence of plate activity that has influenced the shape of the island of Java since the Mesozoic age to Cenozoic (~65 Ma). The basement in East Java is part of the crust originating from Western Australia or Gondwana who joined the Sundaland at the end of the Cretaceous [7]. The next tectonic phase is subduction which results in a magmatic arc from Eocene to the present [7,8,9]. Mandalika formation in south of Malang are the result of Miocene magmatic arcs [10]. The Mandalika formation also intruded by diorite, dacite, andesite, and basalt units. The Mandalika tuff formation is deposited unconformably. It was also deposited breccia and lava whose expanse was quite extensive [10]. External processes that occur are shown by the emergence of a phase of transgression that causes sediment associated with deltaic environment, characterized by the formation of Nampol. After the formation of the Nampol, Wonosari formation was also deposited associated with limestone [10]. This limestone can be a clue that the southern part of Malang is a shallow or neritic marine environment in Miocene [11,12]. After that, erosion took place forming a morphology and structure that has developed to present research area. In addition, the alluvium formation was cut off by the presence of a dendritic river [10]. From the above inventory, in this criterion, 4 criteria are met, and the score is 4.

Temporary Evolution Criteria
The Lenggoksono Bay Area is composed of the Mandalika Formation [10]. The andesite lava consists of andesite pyroxene, andesite hornblende, which in some places undergoes hydrothermal alteration in the form of kaolin. Basalt lava generally consists of amygdaloidal basaltic pyroxene whose cavities are filled with secondary minerals of calcite and zeolite. Dacite lava is found in many mineral-pyrite as well as tantrums of iron oxide. Andesite breccias have andesite fragments with scoria. The formation in the study area can be drawn from the age of the Late Oligocene Mandalika Formation to the beginning of the Middle Miocene [10].
Based on the criteria determined in the description above, the geodiversity status of the Lenggoksono Bay Tourism Area can be determined as shown in Table 2.

Conclusion
Based on the research results above, The Lenggoksono Bay area has a high value where it contains scientific records, specific geological settings or landscapes, is meaningful as evidence of important geological events, and has special ecological functions that can be utilized for research, education, understanding of nature, and conservation. This area includes areas that have met the criteria to become geotourism because they have 5 geological destinations that have the potential to become geotourism and can be further developed after this research.